A method for preparing aluminum-titanium layered composite plates based on critical instability control

Abstract

This invention discloses a method for preparing aluminum-titanium layered composite plates based on critical instability control. The method first determines the constitutive parameters of the aluminum skin and titanium core layer, and calculates the critical reduction rate to suppress macroscopic plastic instability of the core layer. Subsequently, a multi-pass low-reduction rolling process combined with intermediate annealing is employed. For the pure titanium core layer, cold rolling is used for thinning, followed by annealing at 600℃ to achieve near-complete recrystallization and eliminate work hardening. For the titanium alloy core layer, warm rolling at 550-600℃ is used for thinning, followed by annealing at the same temperature to induce a microstructure transformation primarily characterized by recovery softening with secondary local recrystallization. This invention, through theoretical guidance and precise control of deformation and heat treatment regime, effectively solves the problems of necking, wavy buckling, and interface delamination in hard core layers, improving the interfacial bonding quality and mechanical properties of the composite plate, and achieving efficient and stable preparation of lightweight, high-strength metal layered composite materials.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing and composite material preparation technology, and relates to a method for preparing aluminum-titanium layered composite plates based on critical instability control. Background Technology

[0002] Aluminum-titanium layered composite plates possess the advantages of aluminum alloys (low density and high specific strength) and titanium alloys (excellent corrosion resistance and high-temperature performance), demonstrating great application potential in lightweight structural components. Currently, these composite plates are mainly manufactured through a rolling composite method, with core processes including layering and encapsulation, hot rolling to break the film, and multi-pass thinning rolling.

[0003] However, existing technologies face a significant technical bottleneck in actual production: the hard core layer (titanium or titanium alloy) is highly susceptible to macroscopic plastic instability during cold rolling thinning. Because titanium alloys have low work hardening indices and poor room temperature plasticity, while aluminum skin layers have good plasticity and low deformation resistance, their deformation behaviors during rolling are severely incompatible. When the single-pass reduction rate is too high, stress concentration occurs within the hard core layer, easily inducing necking, wavy buckling, or even fracture, leading to severe interface undulations, delamination, or cracking, ultimately resulting in an extremely low product yield.

[0004] To address these issues, traditional processes typically employ two strategies: one is to use a very small single-pass reduction rate for multi-pass rolling, but this leads to low production efficiency and high costs; the other is to increase the intermediate annealing temperature or extend the holding time to fully soften the core layer, but this easily triggers the excessive growth of brittle intermetallic compounds (such as TiAl) at the aluminum / titanium interface, which weakens the interfacial bonding strength and reduces the overall mechanical properties of the composite plate. Furthermore, existing process parameters largely rely on empirical trial and error, lacking theoretical guidance based on material constitutive relationships, making it difficult to precisely control for different thickness ratios or different titanium alloy grades, resulting in a narrow process window and poor stability.

[0005] Therefore, it is necessary to develop a preparation method that can theoretically predict and actively control the plastic instability behavior of the hard core layer, so as to achieve the industrial production of efficient, stable, and high-performance aluminum-titanium layered composite plates while ensuring the quality of interfacial metallurgical bonding. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention proposes a method for preparing aluminum-titanium layered composite plates based on critical instability control.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing an aluminum-titanium layered composite plate based on critical instability control, comprising the following steps: Step S1: Determine the work hardening index of each single-layer material. With strength coefficient Based on the work hardening index The strength coefficient and the preset layer thickness ratio Calculate the critical reduction rate at which the hard core layer of the composite plate undergoes plastic instability during the cold rolling thinning process. ; Step S2: Diffusion welding is performed on the laminated blank consisting of an aluminum skin layer and a titanium alloy core layer to obtain an initial composite blank. Step S3: Perform single-pass hot rolling on the initial composite slab to break up the interface oxide film; Wherein, the reduction rate of the single-pass hot rolling is greater than the critical reduction rate. ; Step S4: Perform cyclic annealing-rolling thinning treatment on the hot-rolled composite plate until the target thickness is achieved; In the cyclic annealing-rolling thinning process, the rolling reduction rate in each pass is less than the critical reduction rate. .

[0008] Specifically, the critical reduction rate is calculated by numerically solving implicit equations. include: Based on the true stress-true strain curves of each monolayer material obtained from uniaxial tensile tests, the work hardening index in its Hollomon constitutive equation was fitted. With strength coefficient ; The work hardening index of the skin layer Strength coefficient The work hardening index of the core layer Strength coefficient and layer thickness ratio Substituting into the following implicit critical strain equation, the critical equivalent strain when the hard core layer undergoes plastic instability can be obtained by numerical iteration. : ; According to the critical equivalent strain The critical reduction rate is determined using the following strain-reduction conversion relationship. : .

[0009] Specifically, when , and When the ratio is in the range of 0.1 to 0.5, the implicit critical strain equation has a unique positive solution in the real number domain.

[0010] Specifically, using a reduction rate exceeding the critical reduction rate The resulting microscopic shear instability in the interface neighborhood breaks the oxide film, while maintaining the macroscopic structural integrity of the core layer. By controlling the rolling reduction rate of each pass to be less than the critical reduction rate This inhibits macroscopic plastic instability in the hard core layer and maintains the macroscopic flatness of the interface.

[0011] Specifically, the cyclic annealing-rolling thinning process further includes: intermediate annealing of the composite plate that has reached a specific deformation amount in a certain pass, wherein the process parameters of the intermediate annealing are determined according to the recovery or recrystallization behavior of the titanium alloy core layer, so as to eliminate or weaken work hardening and suppress the formation of intermetallic compounds at the interface.

[0012] Specifically, when the titanium alloy core layer is a pure titanium layer, the intermediate annealing process parameters are 600℃ at 30℃ for 0.5h to 2h. When the titanium alloy core layer is a titanium-niobium alloy layer, the intermediate annealing process parameters are 600℃ and 30℃ for 0.5h to 2h, so that the titanium-niobium alloy layer undergoes a microstructure transformation mainly characterized by recovery softening and supplemented by local recrystallization.

[0013] Specifically, when the titanium alloy core layer is a pure titanium layer, the critical reduction ratio... The reduction rate of the single-pass hot rolling is 18% to 2%, and the reduction rate of the single-pass hot rolling is 40% to 5%, and the reduction rate of the single-pass rolling is controlled below 15%. When the titanium alloy core layer is a titanium-niobium alloy layer, the critical reduction ratio The reduction rate of the single-pass hot rolling is 40% to 5%, and the reduction rate of the single-pass rolling is controlled below 10%.

[0014] Specifically, when the composite plate is an aluminum-titanium-aluminum three-layer structure, the cyclic annealing-rolling thinning treatment involves at least one recrystallization annealing and subsequent cold rolling thinning of the hot-rolled composite plate, wherein the single-pass reduction rate of the cold rolling thinning is controlled at the critical reduction rate. the following; When the composite plate is an aluminum-titanium-niobium alloy-aluminum three-layer structure, the cyclic annealing-rolling thinning treatment specifically involves: performing at least one static recovery annealing and subsequent warm rolling thinning on the hot-rolled composite plate. The rolling temperature for the warm rolling thinning is controlled between 550°C and 600°C, and the single-pass reduction rate is controlled at the critical reduction rate. the following.

[0015] Specifically, a method for preparing an aluminum-titanium layered composite plate based on critical instability control further includes a quality evaluation step on the prepared composite plate, wherein the quality evaluation step includes: Measure the actual thickness of each layer in the composite board; Based on the single-layer tensile strength of each layer of material after undergoing the same heating history treatment as described in the preparation method. and the actual thickness ratio of each layer Calculate the theoretical tensile strength ; The actual tensile strength of the composite plate was obtained through a tensile test. ; Calculate the strength achievement rate The strength achievement rate is used as a quantitative indicator to evaluate the interface flatness and bonding quality of the composite board.

[0016] Specifically, the quality evaluation step further includes: obtaining an interface image of the cross-section of the composite plate by scanning electron microscopy, measuring the maximum vertical distance between the peaks and troughs along the interface contour line, and using it as the interface undulation amplitude, with the interface undulation amplitude not exceeding 10% of the average thickness of the hard core layer as the criterion for judging interface flatness.

[0017] Compared with existing technologies, this invention has the following advantages: First, this invention introduces the Hollomon constitutive model, and by calculating the work hardening index and strength coefficient of aluminum and titanium (or titanium alloy) components, theoretically derives the critical reduction rate for suppressing macroscopic plastic instability of the core layer. This avoids interfacial wavy undulations, necking, and even fracture defects caused by excessive deformation in a single pass, thereby improving the dimensional accuracy and interfacial bonding quality of the product.

[0018] Secondly, by adopting a composite process route of multi-pass small-reduction cold rolling + intermediate recrystallization annealing + final state warm rolling, the deformation coordination is ensured by utilizing the small reduction rate, and the slip system of the difficult-to-deform titanium alloy is activated by warm rolling (550-600℃), thereby reducing the deformation resistance.

[0019] Finally, this control method does not depend on a specific equipment model; the critical process window can be determined solely based on the physical parameters of the material itself. It is applicable to the preparation of aluminum-titanium composite plates with different thickness ratios and different titanium alloy grades (such as pure Ti, TiNb, etc.). Attached Figure Description

[0020] Figure 1 These are comparison images of the interface morphology of Al / Ti / Al composite plates under different process conditions according to the present invention; Figure 2 This is a diagram showing the elemental distribution and line scan analysis of the interface of the Al / TiNb / Al composite plate of the present invention. Figure 3 This is a double logarithmic fitting curve of true stress-true strain in industrial pure aluminum according to the present invention; Figure 4 This is a double logarithmic fitting curve of true stress-true strain for industrial pure titanium according to the present invention; Figure 5 This is a double logarithmic fitting curve of the true stress-true strain of the TiNb alloy of this invention; Figure 6 This is a graph showing the relationship between the Vickers hardness of aluminum plates at different annealing temperatures and time. Figure 7 This is a graph showing the effect of different heat treatment processes on the Vickers hardness of TiNb alloy. Figure 8 This is a comparison diagram of the EBSD grain boundary and dislocation density distribution of the Al / Ti composite plate in the rolled and annealed states of this invention; Figure 9 This invention presents the true stress-true strain curve and strength comparison diagram of the ATA pure cold-rolled composite plate. Figure 10 This invention relates to the true stress-true strain curve and strength comparison diagram of the ATA recrystallized cold-rolled composite plate. Figure 11 This invention relates to the true stress-true strain curve and strength comparison diagram of the ANA recrystallized cold-rolled composite plate. Figure 12 This invention presents the true stress-true strain curves and strength comparison diagrams of the ANA recrystallized warm-rolled composite plate. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figures 1-12 As shown, the technical solution adopted in this invention is as follows: A method for preparing an aluminum-titanium layered composite plate based on critical instability control, comprising the following steps: Step S1: Determine the work hardening index of each single-layer material. With strength coefficient Based on the work hardening index The strength coefficient and the preset layer thickness ratio Calculate the critical reduction rate at which the hard core layer of the composite plate undergoes plastic instability during the cold rolling thinning process. .

[0023] First, the mechanical properties of each single-layer material (including the skin layer material and the core layer material) constituting the composite panel need to be tested to determine its work hardening index. With strength coefficient Among them, the work hardening index The strength coefficient characterizes a material's ability to resist localized necking during plastic deformation; a higher value indicates a stronger ability to deform uniformly. The stress level characterizes the plastic flow of a material; a higher value indicates higher resistance to deformation. Simultaneously, the layer thickness ratio of the composite plate needs to be preset. The thickness ratio of this layer Defined as the ratio of the hard core layer thickness to the total thickness of the composite board. Based on the work hardening index determined above. Strength coefficient and layer thickness ratio The critical reduction rate is calculated using a specific mechanical model. The critical reduction rate It is the threshold of the ultimate deformation amount at which the hard core layer changes from uniform plastic deformation to local plastic instability (i.e., necking or fracture) during the cold rolling thinning process, and it serves as the benchmark for setting subsequent rolling process parameters.

[0024] Specifically, the critical reduction rate is calculated by numerically solving implicit equations. This includes: fitting the work hardening index in the Hollomon constitutive equation of each monolayer material based on the true stress-true strain curves obtained from uniaxial tensile tests. With strength coefficient .

[0025] The work hardening index of the skin layer Strength coefficient The work hardening index of the core layer Strength coefficient and layer thickness ratio Substituting into the implicit critical strain equation shown, the critical equivalent strain when the hard core layer undergoes plastic instability can be obtained by numerical iteration. : .

[0026] According to the critical equivalent strain The critical reduction rate is determined by the strain-reduction ratio conversion relationship shown. : .

[0027] First, uniaxial tensile tests were conducted on standard specimens of each monolayer material, and the load and displacement data were recorded and converted into true stress and true strain data to obtain the true stress-true strain curves for each monolayer material. Then, the Hollomon constitutive equation was used to fit the uniform plastic deformation stage of the true stress-true strain curves.

[0028] The expression for the Hollomon constitutive equation is: ,in True stress, This is the true strain. By taking the logarithm of the equation and linearizing it, i.e. In a log-log coordinate system, the slope of the straight line is the work hardening index. The logarithm of the intercept is the intensity coefficient. This allows for the precise determination of the critical reduction rate used in subsequent operations. Calculated material parameters.

[0029] It is necessary to clearly distinguish the material parameters of the skin layer and the core layer: the work hardening index of the skin layer... Strength coefficient of the skin layer and the work hardening index of the core layer Strength coefficient of the core layer Together with the preset layer thickness ratio Substitute these values ​​into the implicit critical strain equation. Since this equation relates to the critical equivalent strain... Since this is a nonlinear implicit equation, it cannot be solved analytically directly. Therefore, a numerical iterative method (such as the Newton-Raphson method or the bisection method) must be used to solve it. The objective value obtained from the solution is the critical equivalent strain. The critical equivalent change Physically, it represents the ultimate equivalent strain value when the hard core layer undergoes plastic instability under the constraint of the composite plate.

[0030] The specific mathematical expression of the implicit critical strain equation is as follows: ; In this equation, The critical equivalent strain to be determined; The work hardening index of the core layer; This refers to the layer thickness ratio; The strength coefficient of the skin layer; The strength coefficient of the core layer; The work hardening index of the skin layer is given by this equation, which establishes the critical equivalent strain. With material constitutive parameters ( and geometric parameters The quantitative relationship between them reflects the control effect of soft and hard layer matching on unstable strain.

[0031] The critical equivalent strain when the hard core layer undergoes plastic instability was obtained. Next, calculations are performed using the physical conversion relationship between strain and reduction rate. This conversion relationship, based on the assumption of constant volume and plane strain conditions, maps the equivalent strain to an engineering-controllable thickness reduction rate. The value determined through this step is the critical reduction rate. The critical reduction rate This will serve as the direct basis for setting the reduction amount in subsequent hot rolling film breaking and cold rolling thinning processes.

[0032] The specific mathematical expression for the strain-reduction ratio conversion relationship is as follows: ; In this formula, Critical reduction ratio, representing the percentage decrease in thickness; The critical equivalent strain obtained from the previous steps; It is a natural exponential function; a constant. This is the conversion factor between equivalent strain and principal strain under plane strain conditions based on the Mises yield criterion. This formula clarifies the critical reduction rate. Changes with critical equivalent effect The increasing nonlinear relationship ensures the accurate correspondence between the theoretical instability criterion and the engineering rolling parameters.

[0033] Specifically, when , and When the ratio is in the range of 0.1 to 0.5, the implicit critical strain equation has a unique positive solution in the real number domain.

[0034] When the work hardening index of the skin layer With the work hardening index of the core layer All values ​​are within the range of greater than 0 and less than 0.5, and the strength coefficient of the skin layer... Strength coefficient of the core layer ratio When the value is within the range of 0.1 to 0.5, it is mathematically guaranteed that the implicit critical strain equation has a unique positive real solution in the real number domain. This condition defines the material parameter space applicable to this preparation method and ensures the critical equivalent strain. The mathematical convergence and physical validity of the calculations avoid the situation of no solution or multiple solutions caused by parameter mismatch.

[0035] Step S2 involves diffusion welding and encapsulating the laminated blank consisting of an aluminum skin layer and a titanium alloy core layer to obtain an initial composite blank.

[0036] First, aluminum is selected as the aluminum skin layer, and a titanium alloy is selected as the titanium alloy core layer. The aluminum skin layer primarily serves to provide plastic flow, transmit rolling force, and constrain the deformation of the titanium alloy core layer during subsequent rolling. The titanium alloy core layer, as the hard core layer, represents the critical reduction rate calculated in the previous steps. The main controlled object. The aluminum skin layer and the titanium alloy core layer are combined according to a preset layer thickness ratio. The materials are physically stacked to form a laminated blank. Subsequently, the laminated blank is subjected to diffusion soldering encapsulation.

[0037] Diffusion bonding is a solid-state joining process. It typically involves placing the laminated billet in a vacuum or inert gas environment and applying specific high temperatures and pressures. Under the combined effects of high temperature and pressure, atomic interdiffusion occurs at the interface between the aluminum skin layer and the titanium alloy core layer, forming preliminary metallurgical bonding points. This imparts a certain initial bonding strength to the laminated billet, preventing interlayer slippage or delamination during subsequent large deformation rolling. Simultaneously, the bonding process (such as perimeter welding) isolates the external environment, preventing re-oxidation of the interface at high temperatures. After diffusion bonding, an initial composite slab is obtained. This initial composite slab possesses a complete geometric shape and preliminary interfacial bonding capability, serving as the direct input for subsequent single-pass hot rolling delamination.

[0038] Step S3: Perform single-pass hot rolling on the initial composite slab to break up the interface oxide film; Wherein, the reduction rate of the single-pass hot rolling is greater than the critical reduction rate. .

[0039] The input object is the initial composite slab obtained in the previous step S2. A single-pass hot rolling process is then performed on this initial composite slab. Single-pass hot rolling refers to heating the initial composite slab to above the recrystallization temperature of the higher melting point materials in the aluminum skin layer and titanium alloy core layer (typical engineering experimental values: for the aluminum-titanium system, the heating temperature range is usually 400℃ to 550℃, set in conjunction with the requirement to suppress aluminum-titanium diffusion reaction), and then passing the initial composite slab through the mill roll gap, undergoing only one rolling deformation stroke.

[0040] The primary function of this single-pass hot rolling process is to generate significant normal compressive stress and shear deformation, which act on the interface between the aluminum skin layer and the titanium alloy core layer. Under the combined mechanical action of this normal compressive stress and shear deformation, the interfacial oxide film between the aluminum skin layer and the titanium alloy core layer undergoes brittle fracture, breaks up, and is extruded from the interfacial region, thereby exposing a fresh metal surface and creating the physical conditions for a direct metallurgical bond between the aluminum skin layer and the titanium alloy core layer.

[0041] When performing the above-mentioned single-pass hot rolling, the reduction rate of the single-pass hot rolling (defined as the ratio of the thickness difference before and after rolling to the thickness before rolling) must be strictly greater than the critical reduction rate calculated in the previous steps. The Boolean logic expression of this constraint is: if the reduction rate of a single hot rolling pass is critical reduction rate... If necessary, the process parameters will not be executed or will be adjusted until the reduction rate of a single hot rolling pass exceeds the critical reduction rate. Only when the reduction rate of a single hot rolling pass is greater than the critical reduction rate. Only when the time is right will the single-pass hot rolling operation be performed.

[0042] The reduction rate for single-pass hot rolling is set to be greater than the critical reduction rate. The technical basis lies in: critical reduction rate This is the theoretical threshold for plastic instability in the hard core layer; when the actual deformation exceeds this critical reduction rate... At this point, the internal stress state of the material will induce a local shear instability mechanism. This mechanism, exceeding the critical reduction rate, can be utilized. The induced strong shear deformation effect can maximize the fragmentation efficiency of the interfacial oxide film, ensuring that the interfacial oxide film is fully broken down and removed. If the reduction rate of a single hot rolling pass is less than or equal to the critical reduction rate... If the deformation is within the uniform plastic deformation range and the shear effect is insufficient, it may lead to incomplete breakage of the interface oxide film, thereby affecting the bonding quality between the aluminum skin layer and the titanium alloy core layer.

[0043] Step S4: Perform cyclic annealing-rolling thinning treatment on the hot-rolled composite plate until the target thickness is achieved; In the cyclic annealing-rolling thinning process, the rolling reduction rate in each pass is less than the critical reduction rate. .

[0044] The input object is a composite plate after a single-pass hot rolling process. This composite plate undergoes a cyclic annealing-rolling thinning treatment. Cyclic annealing-rolling thinning refers to a process cycle that alternates between rolling thinning and intermediate annealing: first, the composite plate is rolled with a certain amount of deformation; when the accumulated deformation causes the material's work hardening to reach a preset threshold, rolling is paused and intermediate annealing is performed, followed by the next round of rolling. This cycle is repeated until the total thickness of the composite plate is reduced to a preset target thickness. This target thickness is a specific value required according to the final product specifications. The purpose of cyclic annealing-rolling thinning is to gradually reduce the thickness of the composite plate while ensuring the quality of the interface bonding, avoiding cracking or delamination caused by a single large deformation.

[0045] In each independent rolling pass of the above-described cyclic annealing-rolling thinning process, the single-pass rolling reduction rate (defined as the ratio of the thickness difference before and after the rolling in that pass to the thickness before the rolling in that pass) must be strictly less than the critical reduction rate calculated in the previous steps. The Boolean logic expression of this constraint is: for any _th ... In single-pass rolling, if the reduction rate is... Critical reduction rate If the process parameters are not up to standard, the rolling procedure needs to be adjusted. <Critical reduction ratio Only when the single-pass rolling reduction rate of all passes meets the requirement... <Critical reduction ratio Then, the cyclic annealing-rolling thinning process is performed. The single-pass rolling reduction rate is set to be less than the critical reduction rate. The purpose is to ensure that the hard core layer is always in a uniform plastic deformation stage, and to avoid local necking or fracture.

[0046] Specifically, using a reduction rate exceeding the critical reduction rate The resulting microscopic shear instability in the interface neighborhood breaks the oxide film, while maintaining the macroscopic structural integrity of the core layer. By controlling the rolling reduction rate of each pass to be less than the critical reduction rate This inhibits macroscopic plastic instability in the hard core layer and maintains the macroscopic flatness of the interface.

[0047] By setting the reduction rate of single-pass hot rolling to be greater than the critical reduction rate Microscale shear instability is induced in the neighborhood of the interface between the aluminum skin layer and the titanium alloy core layer. The high shear stress concentration effect generated by this microscale shear instability is sufficient to cause the brittle interfacial oxide film to break, fracture, and be extruded from the interface, thereby achieving direct contact and metallurgical bonding of the fresh metal.

[0048] At the same time, due to the geometric constraints of the skin layer and the locality of deformation, this instability is confined to the micro-region of the interface and does not extend to the entire core cross-section, thus maintaining the macroscopic structural integrity of the titanium alloy core layer and avoiding defects such as macroscopic cracks, delamination or severe waviness in the core layer.

[0049] In the cyclic annealing-rolling thinning process, the reduction rate of each rolling pass is strictly controlled to be less than the critical reduction rate. This ensures that the stress state within the hard core layer remains below the critical threshold for macroscopic plastic instability (such as diffusion necking or shear band penetration). Within this safe deformation range, the hard core layer exhibits uniform plastic flow, preventing drastic thickness fluctuations, core layer fracture, or severe interface undulations caused by localized instability. This control strategy effectively maintains the macroscopic flatness of the composite panel interface, meaning the interface profile remains smooth on a macroscopic scale, and the vertical distance between peaks and troughs is controlled within allowable limits, providing a uniform geometric basis for subsequent possible solid-state reaction synthesis or final application.

[0050] The cyclic annealing-rolling thinning process further includes: intermediate annealing of the composite plate that has reached a specific deformation amount in a certain pass, wherein the process parameters of the intermediate annealing are determined according to the recovery or recrystallization behavior of the titanium alloy core layer, so as to eliminate or weaken work hardening and suppress the formation of intermetallic compounds at the interface.

[0051] During the cycle, when the composite plate accumulates a certain amount of deformation in a specific pass (this specific amount of deformation usually corresponds to a significant decrease in the material's work hardening index or a critical point where the deformation resistance rises to the equipment limit), an intermediate annealing operation is performed. The process parameters for intermediate annealing (mainly including annealing temperature and holding time) are determined based on the recovery or recrystallization behavior of the titanium alloy core layer.

[0052] The specific logic is as follows: if the titanium alloy core layer mainly exhibits recovery behavior, the intermediate annealing process parameters are set to promote dislocation rearrangement and annihilation at the appropriate temperature and time; if the titanium alloy core layer mainly exhibits recrystallization behavior, the intermediate annealing process parameters are set to promote the nucleation and growth of new grains at the appropriate temperature and time. The intermediate annealing has a dual functional objective: first, to eliminate or weaken the work hardening accumulated from previous rolling processes, restoring the plastic deformation capacity of the titanium alloy core layer for subsequent rolling passes; second, to strictly control the upper limits of temperature and time to suppress the diffusion reaction between aluminum and titanium (or titanium-niobium) elements at the interface, generating excessive brittle intermetallic compounds (such as TiAl₂ phase), thus avoiding deterioration of interfacial bonding and mechanical properties.

[0053] When the titanium alloy core layer is a pure titanium layer, the intermediate annealing process parameters are 600℃ at 30℃ for 0.5h to 2h. When the titanium alloy core layer is a titanium-niobium alloy layer, the intermediate annealing process parameters are 600℃ and 30℃ for 0.5h to 2h, so that the titanium-niobium alloy layer undergoes a microstructure transformation mainly characterized by recovery softening and supplemented by local recrystallization.

[0054] If the titanium alloy core material is pure titanium, the intermediate annealing temperature is set to 600℃-30℃ (i.e., the range of 570℃ to 630℃), and the holding time is set to 0.5 hours to 2 hours. This temperature range is determined based on typical engineering experimental values ​​and falls within the recrystallization temperature range of pure titanium (usually 500℃-650℃), which can promote sufficient recrystallization of the pure titanium layer, reducing hardness and deformation resistance. This holding time range is sufficient to complete the recrystallization process. At the same time, because the temperature is controlled at around 600℃ and the time is relatively short (2 hours), it can effectively limit the excessive growth of intermetallic compounds at the Al-Ti interface, balancing the softening requirement and interface stability.

[0055] If the titanium alloy core material is titanium-niobium alloy (TiNb), the intermediate annealing temperature is also set at 600℃-30℃ (i.e., within the range of 570℃ to 630℃), and the holding time is set at 0.5 hours to 2 hours. Due to the solid solution strengthening effect of niobium, the recrystallization temperature of the titanium alloy is increased. Under these temperature and time parameters, the titanium-niobium alloy layer mainly undergoes a recovery process (reduction in dislocation density and subgrain formation), accompanied by local recrystallization. This microstructure transformation, characterized by recovery softening as the primary process and local recrystallization as a secondary process, is sufficient to reduce the deformation resistance of the titanium-niobium alloy layer, improve interlayer deformation coordination, and avoid the grain coarsening or intensified interface reactions that may result from high-temperature, long-time annealing. This represents a preferred process window for thinning TiNb core-layer composite plates.

[0056] When the titanium alloy core layer is a pure titanium layer, the critical reduction ratio The reduction rate of the single-pass hot rolling is 18% to 2%, and the reduction rate of the single-pass hot rolling is 40% to 5%, and the reduction rate of the single-pass rolling is controlled below 15%. When the titanium alloy core layer is a titanium-niobium alloy layer, the critical reduction ratio The reduction rate of the single-pass hot rolling is 40% to 5%, and the reduction rate of the single-pass rolling is controlled below 10%.

[0057] When the core material is pure titanium, based on theoretical calculations and typical engineering experiments, its critical reduction ratio is... The value range is 18% to 2% (i.e., 16% to 20%). Based on this critical reduction rate... The reduction rate for a single hot rolling pass is set at 40% to 5% (i.e., within the range of 35% to 45%), which is greater than the critical reduction rate. The upper limit is set to ensure that interfacial micro-shear instability is fully induced to break the oxide film.

[0058] In cyclic thinning, the reduction rate of a single-pass rolling is strictly controlled below 15%, which is less than the critical reduction rate. The lower limit (16%) is used to ensure that the pure titanium core layer does not experience macroscopic plastic instability in any pass and to maintain interface flatness.

[0059] When the core material is a titanium-niobium alloy, based on theoretical calculations and typical engineering experiments from previous steps, due to the difference in its work hardening characteristics and strength matching relationship, its critical reduction rate... The value range is 10% to 2% (i.e., 8% to 12%). Based on this relatively low critical reduction rate... The reduction rate for single-pass hot rolling is still set at 40% to 5% (i.e., the range of 35% to 45%), which is much higher than the critical reduction rate. The upper limit is sufficient to trigger interfacial microinstability and break the oxide film. In cyclic thinning, the reduction rate of a single pass rolling is strictly controlled below 10% (usually rounded to 10% or lower), which is less than or equal to the critical reduction rate. The upper limit is set to strictly suppress the macroscopic plastic instability of the titanium-niobium alloy core layer and adapt to its narrower stable deformation window.

[0060] When the composite plate is an aluminum-titanium-aluminum three-layer structure, the cyclic annealing-rolling thinning treatment specifically involves: performing at least one recrystallization annealing and subsequent cold rolling thinning on the hot-rolled composite plate, wherein the single-pass reduction rate of the cold rolling thinning is controlled at the critical reduction rate. the following; When the composite plate is an aluminum-titanium-niobium alloy-aluminum three-layer structure, the cyclic annealing-rolling thinning treatment specifically involves: performing at least one static recovery annealing and subsequent warm rolling thinning on the hot-rolled composite plate. The rolling temperature for the warm rolling thinning is controlled between 550°C and 600°C, and the single-pass reduction rate is controlled at the critical reduction rate. the following.

[0061] If the composite plate structure is a three-layer structure of aluminum skin layer - pure titanium core layer - aluminum skin layer, then the cyclic annealing-rolling thinning process is specifically performed as follows: First, the hot-rolled composite plate undergoes at least one recrystallization annealing (usually at around 600℃ to ensure complete recrystallization of the pure titanium core layer), followed by cold rolling thinning (rolling at room temperature). During this cold rolling thinning process, the single-pass reduction rate for each pass must be strictly controlled at the critical reduction rate. The following process route utilizes recrystallization annealing to completely eliminate the work hardening of the pure titanium layer, combined with low-reduction cold rolling, to achieve high flatness in the preparation of ATA composite plates, avoiding cracking of the pure titanium layer at room temperature due to excessively rapid work hardening.

[0062] If the composite plate structure is a three-layer structure of aluminum skin layer - titanium-niobium alloy core layer - aluminum skin layer, then the cyclic annealing-rolling thinning process is specifically implemented as follows: First, the hot-rolled composite plate undergoes at least one static recovery annealing (temperature approximately 600℃, mainly to promote the recovery of the titanium-niobium alloy), followed by warm rolling thinning. Warm rolling thinning refers to rolling the composite plate at a specific temperature range, controlled between 550℃ and 600℃. This temperature range is determined based on typical engineering experimental values ​​and falls within the dynamic recovery temperature range of the titanium-niobium alloy. This utilizes thermal deformation to further promote dynamic recovery and reduce deformation resistance. Simultaneously, the single-pass reduction rate of warm rolling is strictly controlled at the critical reduction rate. The following process route is adapted to the characteristics of TiNb alloy, which has a high recrystallization temperature and poor room temperature plasticity, and solves the problems of interface instability and cracking during the thinning process of ANA composite plates.

[0063] Specifically, a method for preparing an aluminum-titanium layered composite plate based on critical instability control further includes a quality evaluation step on the prepared composite plate, wherein the quality evaluation step includes: Measure the actual thickness of each layer in the composite board.

[0064] Based on the single-layer tensile strength of each layer of material after undergoing the same heating history treatment as described in the preparation method. and the actual thickness ratio of each layer Calculate the theoretical tensile strength .

[0065] The actual tensile strength of the composite plate was obtained through a tensile test. .

[0066] Calculate the strength achievement rate The strength achievement rate is used as a quantitative indicator to evaluate the interface flatness and bonding quality of the composite board.

[0067] After successfully executing the preceding method for preparing aluminum-titanium layered composite plates based on critical instability control and obtaining the composite plates, a quality evaluation step is performed. This quality evaluation step is a comprehensive testing and calculation process. Its function is to quantitatively evaluate the interface flatness and interfacial bonding quality of the aluminum-titanium layered composite plates through joint analysis of macroscopic mechanical property data and microscopic morphology data, thereby verifying the effectiveness of the critical reduction rate control strategy in the preceding preparation process.

[0068] The quality evaluation process includes multiple sub-operations, which are performed sequentially: thickness measurement, strength calculation, tensile testing, and morphology observation.

[0069] This step involves acquiring basic data on the geometric parameters of the composite plate. Using a high-precision thickness gauge or metallographic microscope, cross-sectional observations are performed on the composite plate obtained after the previous preparation process, measuring the actual thickness of each layer in both the aluminum skin layer and the titanium alloy core layer. Actual thickness refers to the physical dimension of each individual layer along the thickness direction in the final state of the composite plate. The output data of this measurement operation is the actual thickness value of each layer, which will serve as the basis for subsequent calculations of the percentage of actual thickness in each layer. The accuracy of the data must be ensured during the measurement process.

[0070] First, obtain the single-layer tensile strength of each layer of material. Single-layer tensile strength This refers to the tensile strength value obtained by preparing individual samples of each layer of material constituting the composite plate (such as aluminum, titanium, or titanium-niobium alloy) and subjecting them to the same heating history treatment as the entire composite plate preparation process (including thermal cycles such as diffusion welding temperature, hot rolling temperature, intermediate annealing temperature, and holding time), and then measuring them through a standard tensile test.

[0071] Introducing the condition of undergoing the same heating history treatment as described in the preparation method is to eliminate the influence of heat treatment on the strength of the matrix material itself and to ensure the comparability of benchmark data. Secondly, based on the actual thickness of each layer measured in the previous step, the actual thickness percentage of each layer is calculated. The actual thickness percentage of each layer Defined as the first The ratio of the actual thickness of the layer to the total actual thickness of the composite panel. Finally, the theoretical tensile strength is calculated using the hybridization principle. Theoretical tensile strength The calculation formula is: ; in, This represents the summation over all layers. Theoretical tensile strength. This represents the upper limit of the expected strength of the composite board under ideal interface conditions with no macroscopic defects.

[0072] Standard tensile specimens were cut from the prepared composite plate and subjected to tensile testing on a universal testing machine until the specimens fractured. The maximum load during the tensile process was recorded and divided by the original cross-sectional area of ​​the specimen to obtain the actual tensile strength of the composite plate. Actual tensile strength This reflects the load-bearing capacity of the composite panel under actual conditions, and its value includes the combined effects of interface bonding quality, interface flatness, and the properties of each layer of materials. If there are unbonded areas or severe waviness at the interface, the actual tensile strength will be lower. Below the theoretical tensile strength .

[0073] Based on the actual tensile strength obtained in the previous steps Compared with theoretical tensile strength Calculate the strength achievement rate Strength achievement rate The calculation formula is: ; Strength achievement rate The physical meaning of "strength achievement rate" is the ratio of the actual load-bearing capacity of the composite panel to its ideal theoretical load-bearing capacity. As a quantitative indicator for evaluating the flatness and bonding quality of composite panel interfaces.

[0074] Its evaluation logic is: if the strength achievement rate A value close to 1 (e.g., greater than 95%) indicates good interface bonding and high flatness, with minimal weakening effect of interface defects on strength; if the strength achievement rate... A value below 1 indicates interface delamination, residual oxide film, or stress concentration due to severe macroscopic instability, leading to premature failure of the composite panel. This can be addressed by setting a strength achievement rate. The threshold (such as the typical engineering experimental value set as) (For qualified products), it can realize the quantitative judgment of the quality of composite boards.

[0075] Specifically, the quality evaluation step further includes: obtaining an interface image of the cross-section of the composite plate by scanning electron microscopy, measuring the maximum vertical distance between the peaks and troughs along the interface contour line, and using it as the interface undulation amplitude, with the interface undulation amplitude not exceeding 10% of the average thickness of the hard core layer as the criterion for judging interface flatness.

[0076] As a supplement to the quality assessment steps, high-magnification imaging of the composite plate cross-section was performed using scanning electron microscopy (SEM) to obtain clear interface images. In the interface images, the interface profile between the aluminum skin layer and the titanium alloy core layer was traced, and the maximum vertical distance between the highest point (crest) and the lowest point (trough) on this profile was measured. This maximum vertical distance was defined as the interface undulation amplitude. The interface undulation amplitude visually reflects the degree of wave-like behavior of the interface at the microscale.

[0077] Subsequently, the logic for determining interface flatness is executed: the average thickness of the hard core layer (i.e., the titanium alloy core layer) within the measurement area is obtained, and 10% of the average thickness of the hard core layer is calculated as the judgment threshold. If the interface fluctuation is greater than 10% of the average thickness of the hard core layer, the interface flatness of the composite plate is deemed acceptable; if the interface fluctuation is greater than 10% of the average thickness of the hard core layer, the interface flatness of the composite plate is deemed unacceptable. This judgment standard (10%) is determined based on typical engineering experimental values. In the field of aluminum-titanium layered composite materials, when the interface fluctuation exceeds 10% of the core layer thickness, it is generally considered that macroscopic plastic instability has occurred, which will lead to stress concentration and early failure during subsequent processing or use.

[0078] Example 1: Preparation and performance evaluation of Al / Ti / Al(ATA) three-layer composite plate.

[0079] This embodiment provides a method for preparing aluminum-titanium layered composite plates based on critical instability control, specifically applied to the preparation of composite plates with Al / Ti / Al structure (hereinafter referred to as ATA structure).

[0080] 1. Raw material configuration and process route setting.

[0081] In this embodiment, an industrial pure aluminum plate is selected as the skin layer and an industrial pure titanium plate as the core layer. According to the experimental design, the thickness ratio of the aluminum layer to the titanium layer is set to 1 / 2 / 1. Specifically, an aluminum plate with a thickness of 0.5 mm and a titanium plate with a thickness of 1.0 mm are stacked, resulting in an initial total thickness of 2.0 mm. After pretreatment, the total thickness of the slab entering the formal rolling process is 1.2 mm.

[0082] This embodiment employs a process route combining diffusion welding preheating with hot rolling to break the film and cyclic recrystallization annealing cold rolling. The specific steps are as follows: First, a 1.2mm thick slab undergoes diffusion welding preheating to maintain a constant thickness; then, a single-pass hot rolling process is performed to reduce the thickness to 0.72mm in one go; subsequently, a cyclic processing stage is entered, sequentially undergoing recrystallization annealing and cold rolling processes to gradually reduce the thickness to 0.61mm, 0.52mm, 0.44mm, 0.38mm, and 0.32mm, ultimately reaching the target thickness of 0.30mm. Between each cold rolling pass, a recrystallization annealing treatment at 600℃ is interspersed to eliminate work hardening and restore the material's plasticity.

[0083] 2. Determination of critical reduction rate and process control logic.

[0084] Before rolling, the critical point of plastic instability of the system is first determined based on the constitutive relationship of the material. For a system with a thickness combination of 1 mm titanium layer and 0.5 mm aluminum layer on one side, the theoretical critical reduction rate is determined to be 18.26% through theoretical calculations and experimental corrections. To ensure process stability, the reduction rate of a single rolling pass is controlled below the theoretical critical reduction rate of 18.26%. In this embodiment, 15% is taken as the upper limit of process control.

[0085] In the specific execution process, the following logical controls must be strictly followed: Hot rolling film breaking stage: The reduction in a single hot rolling pass is reduced from 1.2 mm to 0.72 mm, resulting in a calculated reduction rate of 40%. Since the reduction rate (40%) in a single hot rolling pass is significantly greater than the critical reduction rate... (15%) This step successfully induced microscopic shear instability in the interface neighborhood, achieving effective fragmentation of the oxide film and laying the foundation for subsequent metallurgical bonding.

[0086] Cyclic thinning stage: In the subsequent cyclic recrystallization annealing cold rolling process, the reduction rate of each single pass is strictly controlled. For example, the reduction rate from 0.61mm to 0.52mm is approximately 14.8%, and the reduction rate from 0.52mm to 0.44mm is approximately 15.4% (in actual implementation, the deformation is controlled within a safe range by fine-tuning the roll gap).

[0087] The overall strategy is to ensure that the reduction rate in a single rolling pass is always controlled at the critical reduction rate. The intermediate annealing temperature is set near or below the core layer to prevent macroscopic plastic instability. An intermediate annealing temperature of 600℃ is selected, at which the material has moderate and stable hardness, effectively promoting recrystallization and restoring plasticity, while avoiding grain coarsening caused by overheating.

[0088] 3. Quality evaluation and results analysis.

[0089] The cross-sectional morphology of the prepared ATA composite plate was observed and its mechanical properties were tested.

[0090] 3.1 Layer thickness statistics and strength calculation.

[0091] Multi-point measurements were performed on the cross-section of the composite plate using scanning electron microscopy. The results showed that the five sets of measurements for the titanium core layer were 158.26... 121.12 168.39 183.58 and 68.37 The average thickness of the titanium core layer was calculated to be 139.94 mm. The five sets of measurement data for the aluminum skin layer were 73.96. 52.41 32.54 108.2 and 93.41 The average thickness of the aluminum skin layer was calculated to be 72.104 mm. .

[0092] Based on the mechanical properties of each single-layer material and the aforementioned thickness ratio, the theoretical tensile strength of the composite plate was calculated using the mixing principle. It is 251.6 MPa.

[0093] The average thickness of the pure titanium core layer was measured to be The maximum fluctuation range of the interface is . determination: It meets the standard of flushing, where the interface undulation amplitude does not exceed 10% of the average thickness of the hard core layer.

[0094] 3.2 Actual mechanical properties and microstructure.

[0095] Tensile tests were conducted according to national standards to determine the actual tensile strength of the composite board. It is 200.1 MPa. This is compared to the theoretical tensile strength. Compared with actual tensile strength It can be seen that the composite board prepared by this process has good load-bearing capacity and a high strength achievement rate.

[0096] Microscopic morphology observation shows that the composite plate has good interfacial bonding, with no obvious macroscopic delamination between the aluminum and titanium layers. The interface contour is generally straight, without severe wavy undulations, indicating that the reduction rate of single-pass rolling is controlled at the critical reduction rate. The nearby strategy effectively suppressed the macroscopic instability of the hard core layer and ensured the flatness of the interface.

[0097] Example 2: Preparation and performance evaluation of Al / TiNb / Al(ANA) three-layer composite plate.

[0098] This embodiment differs from Embodiment 1 by using TiNb alloy as the core layer to prepare an Al / TiNb / Al structure (hereinafter referred to as ANA structure) composite plate, focusing on demonstrating the process adaptability and improvement scheme under the high-strength alloy core layer.

[0099] 1. Raw material configuration and process route.

[0100] In this embodiment, an industrial pure aluminum plate is selected as the skin layer and a TiNb alloy plate as the core layer. According to the experimental design, the thickness ratio of the aluminum layer to the TiNb layer is set to 1 / 1 / 1. Specifically, aluminum plates and TiNb plates with a thickness of 0.5 mm are stacked together, with an initial total thickness of 1.0 mm.

[0101] This embodiment first attempts to use a process route combining diffusion welding preheating with hot rolling to break the film and cyclic recovery annealing cold rolling. The specific process is as follows: a 1.0 mm thick initial slab is preheated by diffusion welding; a single-pass hot rolling is performed to thin it to 0.6 mm; then a recovery annealing-cold rolling cycle is entered, and the thickness is successively reduced to 0.54 mm, 0.48 mm, 0.43 mm, 0.39 mm, 0.35 mm, and 0.32 mm, finally reaching 0.30 mm.

[0102] 2. Determination of critical reduction rate and process control logic.

[0103] For a system with a thickness combination of 0.5 mm TiNb layer and 0.5 mm aluminum layer on one side, the theoretical critical reduction rate was determined to be 10.30% after theoretical calculation and experimental correction. Given the weak work hardening ability and low plasticity reserve of TiNb alloy, to ensure process stability, the reduction rate of a single rolling pass is controlled below the theoretical critical reduction rate of 10.30%. In this embodiment, 10% is taken as the upper limit for process control.

[0104] In the specific implementation process: Hot rolling film breaking stage: The thickness of a single-pass hot rolling roll is reduced from 1.0 mm to 0.6 mm, with a reduction rate of 40%. This value is much higher than the critical reduction rate. (10%), successfully induced microscopic shear instability to break the oxide film.

[0105] Cyclic thinning stage: During the subsequent recovery annealing-cold rolling process, the reduction rate of each rolling pass is strictly controlled. For example, the first pass reduces the thickness from 0.6 mm to 0.54 mm, with a reduction rate of 10%, which is on the critical edge. Subsequent passes are also strictly controlled within a small deformation range, and recovery annealing at 600℃ is used to restore the material's plasticity.

[0106] 3. Quality evaluation and process improvement verification.

[0107] The composite board produced using the above method was tested, and its actual tensile strength was found to be... Its strength is only 110.992 MPa, while its theoretical tensile strength is... The strength reached as high as 296.1 MPa. The strength achievement rate was low, and the stress-strain curve showed that the material had extremely poor ductility, indicating that the simple cold rolling process caused severe brittle fracture or interface damage in the TiNb core layer.

[0108] To address the aforementioned issues, this embodiment further implements an improved process route, which replaces the cold rolling in the cycle stage with warm rolling (i.e., recovery annealing combined with warm rolling process).

[0109] Improved process execution: After hot rolling to break the film to 0.6mm, a recovery annealing-warm rolling cycle is used to successively reduce the thickness to 0.54mm, 0.48mm, 0.43mm, 0.39mm, 0.35mm, and 0.32mm, finally reaching 0.30mm. The warm rolling temperature is controlled within the range of 550℃~600℃.

[0110] Evaluation of the improvement effect: Layer thickness statistics: After improvement, the average thickness of the TiNb core layer is 111.78 mm. The average thickness of the aluminum skin layer is 108.82 mm. .

[0111] The average thickness of the titanium-niobium core layer was measured to be The maximum fluctuation range of the interface is . determination: It meets the standard of being flush.

[0112] Strength Enhancement: Theoretical tensile strength calculated based on the new thickness distribution. The actual tensile strength is 311.3 MPa. Increased to 245.627 MPa.

[0113] Conclusion: By replacing cold rolling with warm rolling in the cyclic thinning stage, the deformation resistance of TiNb alloy is reduced, macroscopic plastic instability is suppressed, and the actual tensile strength is improved. Significantly close to theoretical tensile strength This demonstrates the necessity of introducing a warm rolling process for the difficult-to-deform core layer.

[0114] Microscopic morphology observation further confirmed that the composite plate prepared by the improved process route has a denser interface bond, fewer pore defects, and an interface flatness that meets the requirements of engineering applications.

[0115] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing an aluminum-titanium-based layered composite sheet based on critical instability control, characterized by, Includes the following steps: Step S1: Determine the work hardening index of each single-layer material. With strength coefficient Based on the work hardening index The strength coefficient and the preset layer thickness ratio Calculate the critical reduction rate at which the hard core layer of the composite plate undergoes plastic instability during the cold rolling thinning process. ; Step S2: Diffusion welding is performed on the laminated blank consisting of an aluminum skin layer and a titanium alloy core layer to obtain an initial composite blank. Step S3: Perform single-pass hot rolling on the initial composite slab to break up the interface oxide film; In the formula, the reduction ratio of the single hot rolling is greater than the critical reduction ratio ​ Step S4: Perform cyclic annealing-rolling thinning treatment on the hot-rolled composite plate until the target thickness is achieved; In the cyclic annealing-rolling thinning process, the rolling reduction of each pass is less than the critical reduction .

2. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 1, characterized in that, calculating the critical reduction ratio by numerically solving the implicit equation , and specifically comprises: According to the true stress-true strain curves of each single-layer material obtained by uniaxial tensile test, the work hardening index in Hollomon constitutive equation is fitted With the strength coefficient ; The work hardening index of the skin layer , the strength coefficient , the work hardening index of the core layer , the strength coefficient , and the thickness ratio of the layers are substituted into the following implicit critical strain equation to obtain the critical equivalent strain of the hard core layer when plastic instability occurs by a numerical iteration method : ； According to the critical equivalent strain The critical reduction rate is determined using the following strain-reduction rate conversion relationship. : 。 3. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 2, characterized in that, when , and When the ratio is in the range of 0.1 to 0.5, the implicit critical strain equation has a unique positive solution in the real number domain.

4. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 1, characterized in that, Using a reduction rate exceeding the critical reduction ratio The resulting microscopic shear instability in the interface neighborhood breaks the oxide film, while maintaining the macroscopic structural integrity of the core layer. By controlling the rolling reduction rate of each pass to be less than the critical reduction rate This inhibits macroscopic plastic instability in the hard core layer and maintains the macroscopic flatness of the interface.

5. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 1, characterized in that, The cyclic annealing-rolling thinning process further includes: intermediate annealing of the composite plate that has reached a specific deformation amount in a certain pass, wherein the process parameters of the intermediate annealing are determined according to the recovery or recrystallization behavior of the titanium alloy core layer, so as to eliminate or weaken work hardening and suppress the formation of intermetallic compounds at the interface.

6. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 5, characterized in that, When the titanium alloy core layer is a pure titanium layer, the intermediate annealing process parameters are 600℃ at 30℃ for 0.5h to 2h. When the titanium alloy core layer is a titanium-niobium alloy layer, the intermediate annealing process parameters are 600℃ and 30℃ for 0.5h to 2h, so that the titanium-niobium alloy layer undergoes a microstructure transformation mainly characterized by recovery softening and supplemented by local recrystallization.

7. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 1, characterized in that, When the titanium alloy core layer is a pure titanium layer, the critical reduction ratio The reduction rate of the single-pass hot rolling is 18% to 2%, and the reduction rate of the single-pass hot rolling is 40% to 5%, and the reduction rate of the single-pass rolling is controlled below 15%. When the titanium alloy core layer is a titanium-niobium alloy layer, the critical reduction ratio The reduction rate of the single-pass hot rolling is 40% to 5%, and the reduction rate of the single-pass rolling is controlled below 10%.

8. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 1, characterized in that, When the composite plate is an aluminum-titanium-aluminum three-layer structure, the cyclic annealing-rolling thinning treatment specifically involves: performing at least one recrystallization annealing and subsequent cold rolling thinning on the hot-rolled composite plate, wherein the single-pass reduction rate of the cold rolling thinning is controlled at the critical reduction rate. the following; When the composite plate is an aluminum-titanium-niobium alloy-aluminum three-layer structure, the cyclic annealing-rolling thinning treatment specifically involves: performing at least one static recovery annealing and subsequent warm rolling thinning on the hot-rolled composite plate. The rolling temperature for the warm rolling thinning is controlled between 550°C and 600°C, and the single-pass reduction rate is controlled at the critical reduction rate. the following.

9. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 1, characterized in that, It also includes a step of evaluating the quality of the resulting composite board, the quality evaluation step including: Measure the actual thickness of each layer in the composite board; Based on the single-layer tensile strength of each layer of material after undergoing the same heating history treatment as described in the preparation method. and the actual thickness ratio of each layer Calculate the theoretical tensile strength ; The actual tensile strength of the composite plate was obtained through a tensile test. ; Calculate the strength achievement rate The strength achievement rate is used as a quantitative indicator to evaluate the interface flatness and bonding quality of the composite board.

10. The method for preparing an aluminum-titanium layered composite plate based on critical instability control according to claim 9, characterized in that, The quality evaluation steps also include: obtaining an interface image of the cross-section of the composite plate by scanning electron microscopy, measuring the maximum vertical distance between the peaks and troughs along the interface contour line, and using it as the interface undulation amplitude, with the interface undulation amplitude not exceeding 10% of the average thickness of the hard core layer as the criterion for judging interface flatness.

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