Semi-solid alloying method for preparing metal alloy material

Abstract

The invention relates to a semi-solid alloying method for preparing a metal alloy material. The method comprises the following steps: firstly, obtaining a solid-liquid coexistence temperature interval suitable for treatment based on a phase diagram and thermodynamics calculation; then selecting metal raw materials forming the target component, and assembling the metal raw materials into an original blank with a close contact interface; and in the semi-solid temperature interval, a heat-force coupling process is adopted, a solid-liquid coexisting semi-solid structure is formed through local liquefaction induced by diffusion / mass transfer, and macroscopic flow mixing and microstructure reconstruction of the material are enhanced under the shear deformation or stirring effect, so that uniform alloying and structure refinement of the target alloy material are achieved. Compared with the prior art, the method has the advantages that uniform alloying and structure refinement of the alloy material can be realized under the condition that the traditional multi-step series connection of smelting, casting, heat treatment, deformation processing and the like is not needed, the alloy material with uniform components, fine matrix structure and uniformly distributed second phase is obtained, the process flow is simplified, and the energy consumption is low.

Description

Technical Field

[0001] This invention relates to the field of metal alloying and microstructure control technology, and in particular to a semi-solid alloying method for preparing metal alloy materials. Background Technology

[0002] Traditional metal alloying methods mainly include liquid alloying and solid alloying. Liquid alloying (such as casting) requires the complete melting of the metal raw materials, which is energy-intensive, and often results in problems such as coarse dendrites, element segregation, porosity, and cracks during solidification. Solid alloying (such as mechanical alloying or intense plastic deformation techniques) relies entirely on element diffusion under solid conditions. Although it can avoid solidification defects, the solid diffusion rate is extremely low, usually requires long-term heat holding, is energy-intensive, and it is difficult to achieve macroscopic mixing uniformity.

[0003] Semi-solid metals exist in the temperature range between the solidus and liquidus, exhibiting a microstructure characteristic of solid-liquid coexistence. Their rheological properties are thixotropic, meaning their viscosity decreases significantly under applied shear, exhibiting liquid-like flow behavior. This property has been applied in semi-solid forming processes, such as the semi-solid forming of aluminum and magnesium alloy parts. However, current semi-solid technologies are only used in the "forming" stage, lacking methods to actively promote element diffusion and alloying by utilizing the properties of semi-solid metals.

[0004] Chinese invention CN110202109A discloses a semi-solid thixotropic-plastic composite multi-stage forming process. This process prepares semi-solid molded parts through the following steps: 1) Obtaining the recrystallization temperature, solidus temperature, and liquidus temperature of the material to be formed; 2) Heating the alloy billet to the preparation temperature of the semi-solid billet and holding it at that temperature for 2060 s to obtain the semi-solid billet; 3) Preheating the upper and lower molds, placing the semi-solid billet into the lower mold, and pressing down on the upper mold to partially fill the mold cavity with the semi-solid billet for semi-solid thixotropic forming; controlling the strain rate and true strain throughout the semi-solid thixotropic forming process; 4) Cooling the obtained preform to the plastic forming temperature range determined in step 1), and performing plastic forming to achieve complete filling of the mold by the metal billet, thus obtaining the part. This preparation process can produce parts with uniform microstructure and improve their mechanical properties, thus broadening the industrial application of semi-solid forming technology. However, this invention is aimed at steel billets with a fixed composition, and its purpose is to achieve part forming and cavity filling through "semi-solid thixotropic forming + subsequent solid plastic forming". It does not establish an evaluation-repetitive processing approach for alloy homogenization.

[0005] Chinese invention CN120138555A discloses a production process for a novel copper-based alloy bimetallic synthetic material. The process includes the following steps: selecting a copper-nickel alloy as the substrate and a titanium alloy as the functional layer; optimizing the stress distribution of the bonding layer through gradient composition distribution design; preparing a copper-nickel alloy liquid using vacuum induction melting; fixing the mandrel with three-point support; controlling the temperature and flow rate during casting to form a fused crystal; cleaning the substrate surface using sandblasting; coating a CuTi nano-coating using PVD technology to form a nanoscale uneven structure; constructing mathematical models of the temperature field and composition diffusion field; optimizing the temperature distribution and diffusion behavior of the bonding region through simulation analysis; eliminating residual stress and promoting diffusion through gradient temperature-controlled annealing; evaluating the bonding performance using shear strength and microhardness tests; and dividing the production process based on modular design. This technology can be widely applied in industrial fields requiring high temperature, high strength, and corrosion resistance. However, its technical approach mainly achieves metallurgical bonding through vacuum induction melting and casting to form intergrowth crystals, and enhances the performance and stability of the bonding layer by means of coating, simulation optimization, and gradient annealing to promote diffusion. This belongs to the interface bonding process route of "melting and casting + annealing and diffusion". This invention does not involve the technical concept and means of starting with the assembly of multiple metal raw materials, inducing local liquefaction through cross-interface diffusion to form a semi-solid structure, and further applying shear deformation in the semi-solid region to induce thixotropic flow to promote macroscopic mixing and synergistic reconstruction of the structure, thereby achieving alloying and homogenization of a single alloy material.

[0006] Therefore, there is an urgent need for a universal method that can achieve element diffusion and microstructure refinement in a semi-solid state to overcome the limitations of existing liquid alloying and solid alloying processes. Summary of the Invention

[0007] The purpose of this invention is to provide a semi-solid alloying method for preparing metal alloy materials in order to solve at least one of the above problems. This method achieves uniform alloying and microstructure refinement in a single process without melting the metal system as a whole, through element diffusion, thixotropic flow and dynamic recrystallization in a solid-liquid coexistence state. It overcomes the limitations of traditional liquid alloying and solid alloying, and forms a set of universal semi-solid alloying design and implementation process.

[0008] The objective of this invention can be achieved through the following technical solutions: A semi-solid alloying method for preparing metallic alloy materials includes the following steps: (1) Determine the target alloy composition: Determine the target alloy system and the range of chemical composition of the target alloy to obtain the nominal composition of the target alloy; (2) Determine the semi-solid temperature range: Based on the solidus temperature and liquidus temperature corresponding to the nominal composition of the target alloy, determine the temperature range suitable for semi-solid alloying treatment so that the target alloy system is in a solid-liquid coexistence state within this temperature range. (3) Material assembly: Based on the nominal composition of the target alloy, select two or more metal raw materials that constitute the composition to assemble the original billet, so that metals with different compositions form a close contact interface on a macroscopic scale; (4) Semi-solid thermo-mechanical coupling treatment: The thermo-mechanical coupling process is used to alloy the original billet obtained in step (3), so that the original metal or pre-made billet is heated in the semi-solid temperature range determined in step (2) and simultaneously subjected to shear deformation and / or stirring mechanical action, thereby realizing element diffusion, macro-mixing and alloying in a solid-liquid coexistence state. (5) Evaluation of structure and performance and iterative optimization: Test the uniformity of microstructure and performance of alloy material obtained in step (4); if the preset target requirements are not met, repeat steps (4) and (5) until the set target requirements are met.

[0009] Furthermore, the target alloy system in step (1) is a metal alloy system with an identifiable semi-solid phase region, including binary or multi-component alloy systems based on Zn, Mg, Al, Cu, Fe or Ti.

[0010] Further, in step (2), the solidus temperature and liquidus temperature corresponding to the nominal composition of the target alloy are determined by existing phase diagram databases or thermodynamic calculation software. When determining the semi-solid temperature range, the phase diagram database or thermodynamic calculation software uses the CALPHAD thermodynamic evaluation method to query or calculate the phase equilibrium relationship of the target alloy system to obtain the solidus temperature and liquidus temperature.

[0011] Furthermore, the method of assembling the metal raw materials into the original billet in step (3) includes assembling the metal raw materials into the original billet by means of layering, sandwiching, covering, powder pressing into billet or a combination thereof.

[0012] Furthermore, the method by which the metal raw materials are assembled into the original billet in step (3) includes at least one of the following: (1) The plates are butted together and a thin metal sheet is sandwiched between the butt joints; (2) Multi-layer stacking assembly of plates / foils; (3) Sheathing or encasing assembly of wire / rod / pipe materials; (4) Mixing metal powders of different compositions and pressing them into dense blanks; (5) Any combination of two or more of the above methods.

[0013] Furthermore, the thermo-mechanical coupling process described in step (4) includes one or more of the following: friction stir processing or friction stir combined processing, extrusion torsion, induction heating and mechanical stirring, electromagnetic stirring, ultrasonic vibration-assisted plastic deformation, laser disturbance, vibration shearing or pulsed current-assisted plastic deformation.

[0014] Furthermore, in the semi-solid thermo-mechanical coupling treatment described in step (4), at least two or more of the following metallurgical phenomena occur simultaneously in the alloy system: (1) Element diffusion within the solid phase region; (2) Selective liquefaction in local areas forms a continuous or discontinuous liquid phase network; (3) Semi-solid thixotropic flow under shearing action mixes with macroscopic components; (4) Dynamic recrystallization and grain refinement in the solid phase region.

[0015] Furthermore, in step (5), the detection of microstructure uniformity is carried out by one or more of the following methods: metallographic or electron microscopy observation, statistical analysis of grain size, second phase size and distribution, and surface scanning analysis of composition uniformity. Performance testing includes mechanical performance testing, fatigue performance testing, corrosion or degradation performance testing, and one or more of the following: optical, electrical, and magnetic properties.

[0016] The present invention also provides a metal alloy material prepared by the method described above.

[0017] The microstructure of the metal alloy material consists of a refined equiaxed crystal matrix, with small and uniformly distributed second-phase particles at grain boundaries and / or within grains, thereby achieving good strength-plasticity combined properties and / or corrosion resistance, degradation resistance, and other functional characteristics.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. Compared to liquid alloying methods, this invention performs alloying within the solid-liquid coexistence range, eliminating the need for complete melting of all metals. The maximum processing temperature is lower than traditional melting temperatures, and the holding time is significantly shortened, thus reducing energy consumption and heat loss. By avoiding the complete "melting-solidification" process, this invention is less prone to the formation of coarse dendrites and severe macroscopic segregation. Fine equiaxed grain structures and uniform composition can be obtained through shear deformation, thixotropic flow, and dynamic recrystallization in a semi-solid state, reducing the need for subsequent long-duration homogenization annealing and multiple plastic processing passes. Simultaneously, the small liquid phase exposure area avoids large-scale casting, reducing the probability of melting-related defects such as oxidation, inclusions, and porosity, resulting in higher material density and reliability.

[0019] 2. The advantages of this invention compared to solid-state alloying are as follows: Solid-state alloying mainly relies on atomic diffusion within the solid phase, which has a small diffusion coefficient, takes a long time, and is difficult to eliminate macroscopic interfaces. This invention introduces a certain volume fraction of liquid phase within the solid-liquid coexistence region through thermo-mechanical coupling. The liquid phase has a high diffusion coefficient and exhibits macroscopic flow under stirring and shearing. Simultaneously, the solid skeleton undergoes dynamic recrystallization under high strain conditions, achieving a synergistic mechanism of "macroscopic mixing + rapid diffusion + grain refinement." Alloying and microstructure refinement can be completed in a shorter time. Furthermore, the flow stress in the semi-solid state is lower than in the fully solid state, reducing the required forming load and widening the process window, making it easier to implement on existing equipment.

[0020] 3. The difference between this invention and traditional semi-solid forming processes lies in the following: Traditional semi-solid forming generally uses pre-alloyed alloy ingots as raw materials, with the main goal of improving filling performance and forming quality. Essentially, it remains a "forming process" without altering the overall alloy composition. This invention, however, starts with two or more different metal raw materials, assembling billets through plate / foil stacking, butt jointing, overlaying, or powder pressing. Within the semi-solid temperature range, it applies thermo-mechanical coupling processes such as stirring friction, extrusion torsion, and electromagnetic stirring. The semi-solid state serves as a "platform for alloying and microstructure design," enabling synergistic processes of element diffusion, localized liquefaction, semi-solid thixotropic flow, plastic deformation, and microstructure reconstruction. This achieves the alloying and homogenization of the target alloy material, as well as the controllable construction of a fine-grained matrix and a dispersed second phase, rather than primarily serving mold cavity filling. Furthermore, this invention allows for repeated semi-solid treatment of the same material, achieving iterative optimization of "gradual alloying and gradual homogenization," a process feature typically not systematically utilized in traditional semi-solid forming. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a schematic diagram of the raw material assembly in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the processing in Example 1; Figure 4 This is a schematic diagram of the experimental results of Example 1; Figure 5 This is a schematic diagram of the experimental results of Example 2.

[0022] Among them, 1 represents the pure zinc plate in the multi-layer composite structure, 2 represents the pure magnesium foil in the multi-layer composite structure, 3 represents the heat input, 4 represents the force of deformation, 5 represents the solid phase in the semi-solid metal, 6 represents the liquid phase in the semi-solid metal, 7 represents the equiaxed matrix, 8 represents the second phase, 9 represents the pure zinc plate, 10 represents the pure magnesium foil, 11 represents the stirring tool, and 12 represents the processed Zn-0.2Mg alloy rod. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, each point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value, or combined with other lower or upper limits, to form a range not explicitly stated. In the description of this application, it should be noted that, unless otherwise stated, "above" includes the stated number, and "multiple" in "one or more" means two or more.

[0025] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are representative only and should not be construed as exhaustive.

[0026] Numerous details are explored in the following description to provide a more thorough explanation of embodiments of this application; however, it will be apparent to those skilled in the art that embodiments of this application may be practiced without these specific details.

[0027] To further understand the present invention, the following embodiments are provided. It is worth noting that, unless otherwise specified, all raw materials used in the present invention are commercially available; and all methods and equipment employed are common in the art.

[0028] Example 1: This embodiment provides a method for preparing Zn-0.2wt.%Mg alloy by semi-solid alloying based on friction stir processing. The alloy is required to have the following characteristics: fine matrix structure (average grain size less than 10 micrometers), uniform distribution of the second phase, tensile strength exceeding 250 MPa, and uniform elongation greater than 5%.

[0029] Prepare according to the following steps: (1) Raw material pretreatment. Two pieces of pure zinc (>99.99 wt.%) plates, each 500mm*50mm*6mm in size, and one piece of pure magnesium foil (>99.9 wt.%), each 500mm*6mm*0.1mm in size, were selected. The two pieces of pure zinc plates and one piece of pure magnesium foil were pretreated as follows: Ethanol was used as a cleaning agent to remove dust and oil stains from the surface of the raw materials, and then they were dried; 180# to 2000# sandpaper was used to polish the contact surfaces in stages to make them smooth and remove the oxide film on the material surface, so as to facilitate a tighter fit between the raw materials and avoid the introduction of oxides; after polishing, the material surface was cleaned with ethanol and then dried for later use. According to the phase diagram database, the temperature range suitable for the semi-solid alloying preparation of Zn-0.2wt.%Mg alloy is 369-419℃.

[0030] (2) Raw material assembly: The pretreated raw materials are clamped and fixed on the friction stir processing platform, specifically: two pure zinc plates 9 are placed end to end, and then pure magnesium foil 10 is inserted into the mating surface, such as Figure 2 As shown. The plate is fixed to the processing platform by a clamping device to ensure that there is no displacement between the plate and the processing platform.

[0031] (3) Semi-solid friction stir processing: The friction stir processing technology is used to achieve thermo-mechanical coupling processing in the semi-solid range: A stirring tool 11 with threads and three-plane features, with a shoulder diameter of 18 mm, a needle length of 5.4 mm, a needle root diameter of 7 mm, and a needle tip diameter of 4 mm, is used for processing. Based on the temperature range of the semi-solid alloying treatment determined in step (1), the rotation speed of the stirring tool is set to 1800 rpm, the travel speed is 50 mm / min, and the shoulder pressing amount is 0.1 mm. Through the frictional heat generated by the stirring tool and the plate, the processing temperature reaches 392℃, which is within the semi-solid temperature range. At the same time, the mechanical stirring action of the stirring tool will also generate high strain rate shear deformation in the processing area. The processing path is along the mating surface, and the central axis of the stirring tool is on the same plane as the mating surface of the plate.

[0032] (4) Multi-pass repeated processing: After the first pass of processing is completed, the resulting alloy material is subjected to microstructure analysis using metallographic microscope (OM), electron microscope (SEM) combined with energy dispersive spectroscopy (EDS). A room temperature uniaxial tensile test is performed using a universal testing machine according to ASTM E8 / E8M standards to evaluate mechanical properties (including tensile strength and uniform elongation). When the test results show that the microstructure at different locations in the processing zone (five locations within the cross-section of the stirring zone—upper, lower, middle, forward, and backward sides) exhibits significant uneven distribution of the second phase (e.g., blocky aggregation in the lower part), significant uneven grain size, etc., and the mechanical property test results do not meet the preset target requirements (in this embodiment, the preset target is tensile strength exceeding 250 MPa and uniform elongation greater than 5%), the stirring tool is returned to the starting position, and processing is repeated along the same path direction. In the multi-pass processing, the path length of each pass is reduced by 18 mm to avoid overlap with the keyhole left in the previous pass.

[0033] (5) After four processing passes, the processing area is basically uniformly alloyed. A Zn-Mg alloy bar with dimensions of 400mm*4mm*4mm is cut from the processing area, such as... Figure 3 As shown in the figure. Compositional analysis was performed using inductively coupled plasma atomic emission spectrometry (ICP-AES), revealing a Mg content of 0.2 wt.% in the obtained Zn-Mg alloy. Microstructure analysis of the obtained Zn-Mg alloy was conducted using SEM, and the results are shown in the figure. Figure 4 As shown in the left figure, its microstructure consists of fine, equiaxed matrix grains (average grain size approximately 4 micrometers) and a uniformly distributed second phase. The Zn-Mg alloy obtained from four processing passes was subjected to room temperature uniaxial tensile testing using a universal testing machine. The results are as follows: Figure 4 As shown in the right figure, it has an excellent combination of ultimate tensile strength (255 MPa) and uniform elongation (9%).

[0034] Example 2: This embodiment provides a method for preparing Mg-3.6 wt.%Zn-0.9wt.%Cu alloy by semi-solid alloying based on friction stir processing. The alloy is required to have the following characteristics: fine matrix structure (average grain size less than 10 micrometers), uniform distribution of the second phase, tensile strength exceeding 200 MPa, and uniform elongation greater than 15%.

[0035] It is prepared by the following method: (1) Raw material pretreatment. Two pieces of pure magnesium (>99.99 wt.%) plates, each 500mm*50mm*6mm in size, were selected; one piece of pure zinc foil (>99.99 wt.%), each 500mm*6mm*0.05mm in size, was selected; and one piece of pure copper foil (>99.99 wt.%), each 500mm*6mm*0.01mm in size, was selected. The raw materials were pretreated as follows: Ethanol was used as a cleaning agent to remove dust and oil stains from the surface of the raw materials, and then dried; sandpaper of 180# to 2000# was used to polish the contact surfaces in stages to make them smooth and remove the oxide film on the surface of the materials, so as to facilitate a tighter fit between the raw materials and avoid the introduction of oxides; after polishing, the surface of the materials was cleaned with ethanol and then dried for later use. Thermodynamic calculations using CALPHAD determined that the temperature range suitable for semi-solid alloying treatment was 345-500℃.

[0036] (2) Raw material assembly: The pretreated raw materials are clamped and fixed on the friction stir processing platform. Specifically, two pure magnesium plates are placed end to end, and then pure zinc foil and pure copper foil are inserted into the mating surface together. The plates are fixed on the processing platform by a clamping device to ensure that there is no displacement between the plates and the processing platform.

[0037] (3) Friction Stir Machining: Friction stir machining is used to achieve thermo-mechanical coupling in the semi-solid range. A stirring tool with threads and three-plane features, with a shoulder diameter of 18 mm, a needle length of 5.4 mm, a needle root diameter of 7 mm, and a needle tip diameter of 4 mm, is used for machining. Based on the temperature range of the semi-solid alloying treatment determined in step (1), the rotation speed of the stirring tool is set to 2000 rpm, the travel speed is 100 mm / min, and the shoulder pressing amount is 0.1 mm. Through the frictional heat generated between the stirring tool and the plate, the processing temperature reaches the semi-solid temperature range (~400℃). At the same time, the mechanical stirring action of the stirring tool will also generate high strain rate shear deformation in the processing area. The processing path is along the mating surface, and the central axis of the stirring tool is in the same plane as the mating surface of the plate.

[0038] (4) Multi-pass repeated processing: After the first pass of processing is completed, the processed area is inspected and evaluated, including detecting the alloy element content of multiple sampling points along the length and / or width of the processed area by micro-area X-ray fluorescence spectroscopy (μ-XRF) to assess the deviation of each sampling point from the target nominal composition and its spatial fluctuation; performing microstructure analysis on the grain size distribution, second phase morphology and distribution uniformity at different locations in the processed area by SEM / EDS; and evaluating the compliance and dispersion of strength and plasticity indicators by room temperature tensile testing using a universal testing machine; when any of the above test results fails to meet the preset target requirements or its spatial fluctuation exceeds the preset threshold, the stirring tool is returned to the starting position and the processing is repeated along the same path direction; when the composition, microstructure and properties of the processed area meet the preset target requirements, the repeated processing is stopped. In the multi-pass processing, the path length of each pass is reduced by 18 mm to avoid overlapping with the keyhole left by the previous pass.

[0039] (5) After six processing passes, the processing area achieved basic uniform alloying. Mg-Zn-Cu alloy rods with dimensions of 360mm*4mm*4mm were cut from the processing area. Composition analysis by ICP-AES showed that the Zn content in the obtained Mg-Zn-Cu alloy was 3.6 wt.% and the Cu content was 0.9 wt.%. Microstructure analysis of the obtained Mg-Zn-Cu alloy was performed by SEM, and the results are as follows: Figure 5 As shown in the left figure, its microstructure consists of fine, equiaxed matrix grains (average grain size approximately 8 micrometers) and a uniformly distributed second phase. The Mg-Zn-Cu alloy obtained from six processing passes was subjected to a room-temperature uniaxial tensile test using a universal testing machine. The results are as follows: Figure 5 As shown in the right figure, it has an excellent combination of ultimate tensile strength (approximately 225 MPa) and uniform elongation (approximately 17.5%).

[0040] Comparative Example 1: To compare the effect of the semi-solid alloying method of the present invention, Zn-0.2wt.%Mg alloy was prepared using the traditional smelting-casting process.

[0041] (1) Raw materials and ingredients. High-purity zinc and high-purity magnesium metal ingots were selected as raw materials, with zinc purity of approximately 99.995 wt.% and magnesium purity of approximately 99.95 wt.%. The ingredients were weighed and prepared according to the target composition of Zn-0.2 wt.%Mg for later use.

[0042] (2) Melting and casting. The prepared zinc and magnesium raw materials are loaded into a steel crucible inside a cylindrical steel mold and heated in a resistance furnace at about 500 °C to completely melt all the metals and stir thoroughly to form a melt with a composition close to Zn-0.2wt.%Mg. After the melt temperature and composition stabilize, the molten alloy is poured directly into the preheated cylindrical steel mold and allowed to cool naturally to room temperature to obtain a Zn-0.2wt.%Mg ingot with a diameter of 15 mm and a length of 80 mm.

[0043] (3) Evaluation of microstructure and mechanical properties in the as-cast state. The microstructure of the as-cast Zn-0.2wt.%Mg alloy mainly consists of coarse primary Zn dendrites (grain size greater than 100 micrometers) and Zn+Mg2Zn distributed between them. 11 Eutectic microstructure composition. Mechanical property testing: The ultimate tensile strength of the as-cast Zn-0.2wt.%Mg alloy is approximately 100 MPa, and the uniform elongation is approximately 1%.

[0044] Example 3 Using the same alloy system as in Example 1, multiple pure zinc plates and multiple pure magnesium foils were semi-solid alloyed through different thermo-mechanical coupling processes, such as... Figure 1 As shown.

[0045] (1) Select pure zinc plates and pure magnesium foils, and stack them according to the target composition ratio to form a multi-layer composite blank with close contact, such as Figure 1 As shown, the pure zinc plate 1 and the pure magnesium foil 2 in the multi-layer composite structure are stacked sequentially.

[0046] (2) Place the multilayer composite blank obtained in step (1) between the upper and lower anvils / dies of the hot pressing-torsion shearing device, and apply heat input by induction heating, resistance heating or heating the die (in this embodiment, upper and lower anvils are used, induction heating is used, and heat input 3 is referred to). Figure 1 The billet is heated to a temperature between the solidus and liquidus of the target alloy system, so that the billet is in a state where the solid and liquid phases coexist (e.g., Figure 1 As shown, the liquid phase 6 in the semi-solid metal is dispersed in the solid phase 5 of the semi-solid metal. Preferably, the liquid phase volume fraction is controlled at 5%–40%, more preferably 10%–25% (in this embodiment, the liquid phase volume fraction is controlled at 20%), to balance the material's shear flowability and shape retention ability.

[0047] (3) While maintaining the above-mentioned semi-solid temperature range, apply axial pressure to the billet and superimpose torsional load (the force of deformation is as follows 4). Figure 1As shown), the billet undergoes shear deformation and thixotropic flow under solid-liquid coexistence conditions. Preferably, the axial pressure is 10–300 MPa (100 MPa in this embodiment, which can be selected according to the alloy system and billet size); the torsional angular velocity is 0.1–60 rpm; the number of torsional rotations is 0.25–20; and the holding / load holding time is 5–600 s (10 rpm in this embodiment; 10 rotations; 10 s). Under torsional shear, the liquid phase preferentially forms and wets at grain boundaries / interfaces and penetrates along the interface, promoting interlayer interface breakage and recombination, achieving macroscopic mixing and element diffusion-mass transfer coupling; simultaneously, solid particles undergo spheroidization, refinement, and redistribution.

[0048] (4) After stopping the torsional shearing, the billet is subjected to controlled cooling or rapid cooling under pressure holding or unloading conditions to solidify the semi-solid structure and suppress segregation, ultimately obtaining a refined equiaxed matrix structure and a uniformly distributed second phase (such as...). Figure 1 As shown, the second phase 8 is uniformly distributed in the equiaxed matrix 7; optionally, the resulting alloy is subjected to subsequent shaping processes (extrusion, rolling, forging, etc.) or heat treatment to further adjust the microstructure and properties.

[0049] This embodiment achieves semi-solid alloying through a thermo-mechanical coupling method of "heating to enter solid-liquid coexistence + axial pressure + torsional shearing". It differs from the stirring friction method, but it also satisfies the basic principle of this invention that "the coupling of heat input and force action causes thixotropic flow and macroscopic mixing of solid-liquid coexisting materials". Therefore, it can be regarded as one of the representative implementation methods of the various thermo-mechanical coupling methods described in the claims.

[0050] The foregoing has shown and described the basic process, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A semi-solid alloying method for preparing metallic alloy materials, characterized in that, Includes the following steps: (1) Determine the target alloy composition: Determine the target alloy system and the range of chemical composition of the target alloy to obtain the nominal composition of the target alloy; (2) Determine the semi-solid temperature range: Based on the solidus temperature and liquidus temperature corresponding to the nominal composition of the target alloy, determine the temperature range suitable for semi-solid alloying treatment so that the target alloy system is in a solid-liquid coexistence state within this temperature range. (3) Material assembly: Based on the nominal composition of the target alloy, select two or more metal raw materials that constitute the composition to assemble the original billet, so that metals with different compositions form a close contact interface on a macroscopic scale; (4) Semi-solid thermo-mechanical coupling treatment: The thermo-mechanical coupling process is used to alloy the original billet obtained in step (3), so that the original metal or pre-made billet is heated in the semi-solid temperature range determined in step (2) and simultaneously subjected to shear deformation and / or stirring mechanical action, thereby realizing element diffusion, macro-mixing and alloying in a solid-liquid coexistence state. (5) Evaluation of structure and performance and iterative optimization: Test the uniformity of microstructure and performance of alloy material obtained in step (4); if the preset target requirements are not met, repeat steps (4) and (5) until the set target requirements are met.

2. The semi-solid alloying method for preparing metal alloy materials according to claim 1, characterized in that, In step (1), the target alloy system is a metal alloy system with an identifiable semi-solid phase region, including binary or multi-component alloy systems based on Zn, Mg, Al, Cu, Fe or Ti.

3. The semi-solid alloying method for preparing metal alloy materials according to claim 1, characterized in that, In step (2), the solidus temperature and liquidus temperature corresponding to the nominal composition of the target alloy are determined by existing phase diagram databases or thermodynamic calculation software. When determining the semi-solid temperature range, the phase diagram database or thermodynamic calculation software uses the CALPHAD thermodynamic evaluation method to query or calculate the phase equilibrium relationship of the target alloy system to obtain the solidus temperature and liquidus temperature.

4. The semi-solid alloying method for preparing metal alloy materials according to claim 1, characterized in that, The method of assembling metal raw materials into original blanks in step (3) includes assembling the metal raw materials into original blanks by means of layering, sandwiching, covering, powder pressing or a combination thereof.

5. A semi-solid alloying method for preparing metallic alloy materials according to claim 1 or 4, characterized in that, The method of assembling the metal raw materials into the original billet in step (3) includes at least one of the following: (1) The plates are butted together and a thin metal sheet is sandwiched between the butt joints; (2) Multi-layer stacking assembly of plates / foils; (3) Sheathing or encasing assembly of wire / rod / pipe materials; (4) Mixing metal powders of different compositions and pressing them into dense blanks; (5) Any combination of two or more of the above methods.

6. The semi-solid alloying method for preparing metal alloy materials according to claim 1, characterized in that, The thermo-mechanical coupling process described in step (4) includes one or more of the following: friction stir processing or friction stir combined processing, extrusion torsion, induction heating and mechanical stirring, electromagnetic stirring, ultrasonic vibration-assisted plastic deformation, laser disturbance, vibration shearing or pulsed current-assisted plastic deformation.

7. The semi-solid alloying method for preparing metal alloy materials according to claim 1, characterized in that, In the semi-solid thermo-mechanical coupling treatment described in step (4), at least two or more of the following metallurgical phenomena occur simultaneously in the alloy system: (1) Element diffusion within the solid phase region; (2) Selective liquefaction in local areas forms a continuous or discontinuous liquid phase network; (3) Semi-solid thixotropic flow under shearing action mixes with macroscopic components; (4) Dynamic recrystallization and grain refinement in the solid phase region.

8. The semi-solid alloying method for preparing metal alloy materials according to claim 1, characterized in that, In step (5), the detection of microstructure uniformity is carried out by one or more of the following methods: metallographic or electron microscopy observation, statistical analysis of grain size, second phase size and distribution, and surface scanning analysis of composition uniformity. Performance testing includes mechanical performance testing, fatigue performance testing, corrosion or degradation performance testing, and one or more of the following: optical, electrical, and magnetic properties.

9. A metal alloy material, characterized in that, It is prepared by any one of the methods described in claims 1-8.

10. A metal alloy material according to claim 9, characterized in that, The microstructure of the metal alloy material consists of a refined equiaxed crystal matrix, with small and uniformly distributed second-phase particles at grain boundaries and / or within grains, thereby achieving good strength-plasticity combined properties and / or corrosion resistance, degradation resistance, and other functional characteristics.

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