Polishing methods and equipment for titanium-nickel alloys

Abstract

This invention relates to the field of precision machining technology for metal materials, and provides a grinding method and apparatus for titanium-nickel alloys. The method includes: pre-treating a titanium-nickel alloy workpiece; placing the pre-treated titanium-nickel alloy workpiece in a rotary machining cavity, the rotary machining cavity rotating around a central axis, causing the titanium-nickel alloy workpiece to rotate and adhere to the inner wall of the cavity, forming a self-stabilized fixed state without mechanical clamping; introducing a first abrasive medium, a second abrasive medium, and a third abrasive medium into the rotary machining cavity in three stages; while the rotary machining cavity remains rotating, adding an electrolyte and applying electricity to the rotary machining cavity, causing the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state. This solution can establish a synergistic relationship between material microstructure stability control and surface leveling efficiency, achieving highly consistent surface quality control while avoiding processing-induced phase transformation.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for metal materials, and in particular to a grinding method and grinding apparatus for titanium-nickel alloys. Background Technology

[0002] Titanium-nickel alloys are functional materials with shape memory effect and superelastic properties, and are widely used in medical devices, precision elastic components, and high-end structural parts. These materials require high surface quality and microstructure stability.

[0003] In existing technologies, the grinding process of titanium-nickel alloys typically involves mechanical clamping followed by grinding or polishing with an abrasive wheel. However, this type of processing method has the following problems: Mechanical clamping can introduce residual stress on the workpiece surface, affecting the hyperelastic properties of the material; Localized high temperatures can easily trigger martensitic / austenitic phase transformation, leading to phase transformation temperature drift. The natural oxide film on the surface of titanium-nickel alloys is dense, resulting in low efficiency in conventional grinding.

[0004] The tip structure is prone to morphological collapse under the combined effect of clamping stress and cutting force; Poor processing consistency makes it difficult to achieve stable mass production.

[0005] Chinese invention patent CN116103743A discloses an electrochemical polishing slurry and polishing method for nickel-titanium alloys. This technical solution uses a specific electrolyte system with the nickel-titanium alloy workpiece as the anode, performing electrochemical dissolution treatment under an applied voltage. According to the patent disclosure, under certain voltage and electrolytic conditions, a gas film or plasma layer can be formed on the workpiece surface, achieving surface leveling through physical and chemical interactions, thereby improving surface finish.

[0006] The aforementioned electrochemical polishing methods are effective in improving surface roughness. However, these techniques primarily rely on electrochemical dissolution mechanisms, typically involving high voltage conditions or specific electrolytic systems, and the description of temperature control during the process is relatively limited. Furthermore, these methods focus on the electrochemical removal process and do not involve multi-stage physical grinding synergy, clamp-free stress control structures, or end-to-end low-temperature control systems tailored to the phase transformation characteristics of titanium-nickel alloys.

[0007] In addition, although some existing centrifugal polishing equipment can achieve mass production, their structural design is mainly geared towards general metal materials and has not been specifically optimized for the stress and temperature sensitivity of titanium-nickel alloys during processing.

[0008] Therefore, there is a need to provide a grinding method and grinding device for titanium-nickel alloys, which can construct a multi-stage low-temperature composite grinding method suitable for titanium-nickel alloys under the premise of avoiding residual stress from mechanical clamping, suppressing resistance changes caused by temperature rise during processing, improving oxide layer removal efficiency, and maintaining the integrity of tip geometry. This method can establish a synergistic relationship between material microstructure stability control and surface leveling efficiency, and achieve highly consistent surface quality control while avoiding processing-induced phase transformation.

[0009] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0010] The main objective of this invention is to overcome the technical problems existing in the surface processing of titanium-nickel alloys, such as the introduction of processing stress, the risk of phase transformation caused by temperature rise, uneven oxide layer removal, and difficulty in maintaining the tip structure. This invention provides a grinding method and apparatus for titanium-nickel alloys that, while avoiding residual stress from mechanical clamping, suppressing resistance changes caused by temperature rise during processing, improving oxide layer removal efficiency, and maintaining the integrity of the tip geometry, constructs a multi-stage low-temperature composite grinding method suitable for titanium-nickel alloys. It establishes a synergistic relationship between material microstructure stability control and surface leveling efficiency, achieving highly consistent surface quality control while avoiding processing-induced phase transformation.

[0011] To achieve the above objectives, the first aspect of the present invention provides a method for polishing titanium-nickel alloys, comprising the following steps: S1: Pretreatment of titanium-nickel alloy workpieces; S2: Place the pretreated titanium-nickel alloy workpiece into the rotary machining cavity. The rotary machining cavity rotates around the central axis, causing the titanium-nickel alloy workpiece to rotate against the inner wall of the cavity, forming a self-stabilized fixed state without mechanical clamping. S3: The first abrasive medium, the second abrasive medium, and the third abrasive medium are introduced into the rotary machining cavity in three stages respectively; S4: Retain a portion of the third abrasive medium, and while the rotary machining cavity remains in a rotating state, add electrolyte into the rotary machining cavity and apply electricity to cause the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state.

[0012] According to an exemplary embodiment of the present invention, in step S1, the pretreatment of the titanium-nickel alloy workpiece includes: The titanium-nickel alloy workpiece is placed in the first solution for ultrasonic cleaning. The titanium-nickel alloy workpiece is then placed in the second solution for ultrasonic cleaning. Rinse and dry.

[0013] According to an exemplary embodiment of the present invention, in step S2, when the nickel-titanium alloy workpiece rotates, the centrifugal acceleration is greater than or equal to 20g and less than or equal to 60g.

[0014] According to an exemplary embodiment of the present invention, in step S3, the particle size of the first abrasive medium is 80-120 mesh, the particle size of the second abrasive medium is 240-400 mesh, and the particle size of the third abrasive medium is 800-1200 mesh.

[0015] According to an exemplary embodiment of the present invention, the polishing time for the first stage is 15-25 minutes, the polishing time for the second stage is 20-30 minutes, and the polishing time for the third stage is 20-40 minutes.

[0016] According to an exemplary embodiment of the present invention, in step S4, the electrolyte includes NaNO3, NaCl, and deionized water.

[0017] According to an exemplary embodiment of the present invention, in step S4, dissolving the surface material of the titanium-nickel alloy workpiece by electrolysis includes: A titanium-nickel alloy workpiece is used as the anode; With a current density greater than or equal to 0.5 A / dm 2 And less than or equal to 2.0 A / dm 2 Dissolves the surface material of titanium-nickel alloy workpieces by applying electricity.

[0018] According to an exemplary embodiment of the present invention, in step S4, when the titanium-nickel alloy workpiece undergoes electrochemical dissolution, the electrolyte temperature is controlled within the range of 15°C to 28°C.

[0019] As a second aspect of the present invention, the present invention provides a grinding apparatus for titanium-nickel alloy, comprising: a pretreatment apparatus, a rotating apparatus, a rotating machining cavity, a feeding apparatus, and an electrolysis apparatus; The pretreatment device is used to pretreat titanium-nickel alloy workpieces; The rotating device is used to cause the rotary machining cavity to rotate about the central axis; The rotary machining cavity is used to place the pretreated titanium-nickel alloy workpiece inside the rotary machining cavity. The rotary machining cavity rotates around the central axis, so that the titanium-nickel alloy workpiece is attached to the inner wall of the cavity and rotates, forming a self-stabilized fixed state without mechanical clamping. The feeding device is used to feed the first abrasive medium, the second abrasive medium and the third abrasive medium into the rotary machining cavity in three stages respectively; The electrolysis device is used to electrolyze titanium-nickel alloy workpieces. When electrolyzing titanium-nickel alloy workpieces, a portion of the third abrasive medium is retained. While the rotary machining cavity is in a rotating state, electrolyte is added into the rotary machining cavity and electricity is applied to cause the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state.

[0020] According to an exemplary embodiment of the present invention, the polishing apparatus for the titanium-nickel alloy further includes a cooling device, which includes a temperature sensor and a temperature control module. The temperature sensor is placed in the electrolyte, and the temperature control module is used to adjust the temperature of the electrolyte according to the temperature detected by the temperature sensor.

[0021] The key to this invention lies in constructing a synergistic processing mechanism combining electrochemical and mechanical actions. Electrochemical dissolution provides a selective material removal path, preferentially acting on surface micro-protrusions, while mechanical grinding, through centrifugal force-driven abrasive contact, continuously renews the processing interface and removes reaction products, thereby avoiding localized passivation that occurs during the electrochemical process. Based on this synergistic mechanism, the two removal methods are not simply superimposed but mutually reinforcing, thus significantly improving material removal efficiency and surface leveling capability while reducing processing stress.

[0022] The advantages of this invention are: This solution eliminates the source of residual stress from mechanical clamping through a centrifugal self-stabilizing structure; achieves rapid removal of the oxide layer and gradual surface leveling through a multi-stage abrasive system; reduces processing time and improves leveling efficiency through an electrochemical-physical synergistic mechanism; and suppresses the risk of processing-induced phase transformation through low-temperature closed-loop control throughout the process. Ultimately, this solution enables titanium-nickel alloys to achieve low roughness and high consistency in surface processing while maintaining microstructure stability and tip structure integrity, making it suitable for machining precision functional components that are sensitive to material properties. Attached Figure Description

[0023] The above and other objects, features, and advantages of this application will become more apparent from the detailed description of exemplary embodiments with reference to the accompanying drawings. The drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0024] Figure 1 The diagram illustrates the steps of a polishing method for titanium-nickel alloys. Detailed Implementation

[0025] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted.

[0026] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0027] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0028] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0029] It should be understood that although the terms first, second, third, etc., may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this application. As used herein, the term "and / or" includes all combinations of any one and more of the associated listed items.

[0030] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily essential for implementing this application, and therefore cannot be used to limit the scope of protection of this application.

[0031] According to a first specific embodiment of the present invention, the present invention provides a grinding device for titanium-nickel alloy, comprising: a pretreatment device, a rotating device, a rotating machining cavity, a feeding device, an electrolysis device, and a cooling device.

[0032] The pretreatment device is used to pretreat titanium-nickel alloy workpieces.

[0033] The rotary device is used to rotate the rotary machining cavity about its central axis.

[0034] The rotary machining cavity is a cylindrical hollow structure with a wear-resistant lining on its inner wall. It is used to place the pre-treated titanium-nickel alloy workpiece in the rotary machining cavity. The rotary machining cavity rotates around its central axis, causing the titanium-nickel alloy workpiece to rotate while adhering to the inner wall of the cavity, forming a self-stabilized fixed state without mechanical clamping.

[0035] The feeding device is used to feed the first abrasive medium, the second abrasive medium and the third abrasive medium into the rotary machining cavity in three stages respectively; The electrolysis device is used to electrolyze titanium-nickel alloy workpieces. When electrolyzing titanium-nickel alloy workpieces, a portion of the third abrasive medium is retained. While the rotary machining cavity is in a rotating state, electrolyte is added into the rotary machining cavity and electricity is applied to cause the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state.

[0036] The cooling device includes a temperature sensor and a temperature control module. The temperature sensor is placed in the electrolyte, and the temperature control module is used to adjust the temperature of the electrolyte according to the temperature detected by the temperature sensor.

[0037] According to a second embodiment of the present invention, the present invention provides a method for polishing titanium-nickel alloys, employing the titanium-nickel alloy polishing apparatus of the first embodiment, such as... Figure 1 As shown, it includes the following steps: S1: Pre-treatment of titanium-nickel alloy workpieces.

[0038] The pretreatment step is used to remove organic contaminants and natural oxide films from the workpiece surface, thereby reducing the initial resistance of subsequent mechanical grinding and improving the uniformity of material removal.

[0039] This solution is applicable to nickel-titanium alloy workpieces that are wires or slender structural components, with characteristic dimensions of: diameter 0.2mm to 2.0mm, length 5mm to 200mm, preferably 10mm to 100mm, and aspect ratio of 5 to 200. A higher aspect ratio structure has a larger specific surface area and greater flexibility, which is beneficial for achieving stable adhesion in a centrifugal field and improving the uniformity of the electrochemical reaction.

[0040] Pretreatment of titanium-nickel alloy workpieces using a pretreatment device includes: S11: Place the titanium-nickel alloy workpiece in the first solution for ultrasonic cleaning.

[0041] The first solution used is acetone, and the ultrasonic cleaning time is 5-10 minutes to remove surface oil and grease contaminants.

[0042] S12: Then place the titanium-nickel alloy workpiece in the second solution for ultrasonic cleaning.

[0043] The second solution used was anhydrous ethanol, and the ultrasonic cleaning time was 5 minutes.

[0044] S13: Rinse and dry.

[0045] Rinse with deionized water for 3-5 minutes.

[0046] The drying environment should not exceed 40℃ to avoid the influence of high temperature on the material structure.

[0047] Testing revealed that a 2-5 μm thick oxide layer formed on the surface of the pretreated nickel-titanium alloy workpiece. Due to the non-uniform spatial distribution of this oxide layer, the surface exhibited significant micro-undulations, with an initial surface roughness Ra of 1.20-1.50 μm. This surface roughness primarily stemmed from the non-uniform distribution and localized accumulation of the oxide layer.

[0048] S2: Place the pretreated titanium-nickel alloy workpiece into the rotary machining cavity. The rotary machining cavity rotates around the central axis, causing the titanium-nickel alloy workpiece to rotate against the inner wall of the cavity, forming a self-stabilized fixed state without mechanical clamping.

[0049] When a titanium-nickel alloy workpiece is in a self-stabilizing fixed state without mechanical clamping, the centrifugal acceleration 'a' experienced by the titanium-nickel alloy workpiece satisfies the following relationship: A=ω 2 r; Where ω represents angular velocity in rad / s, and r is the radial distance from the nickel-titanium alloy workpiece (rotating within the machining cavity) to the center of rotation in meters. Under this centrifugal acceleration condition, the workpiece can achieve a stable stress state without mechanical clamps, thereby avoiding stress concentration and microstructural disturbances caused by localized clamping.

[0050] When a nickel-titanium alloy workpiece rotates, the centrifugal acceleration should be greater than or equal to 20g and less than or equal to 60g, preferably greater than or equal to 30g and less than or equal to 50g, and most preferably 40g. This range ensures stable adhesion while avoiding excessive centrifugal load from affecting the workpiece's geometry. Experiments have verified that when the acceleration is below 20g, workpiece adhesion is unstable; when it exceeds 60g, the contact pressure increases, potentially increasing the risk of localized plastic deformation. Within this range, the workpiece adhesion is stable, and no significant localized plastic deformation occurs. Finite element analysis results show that under centrifugal adhesion, the contact stress distribution on the workpiece surface is uniform, with stress fluctuations controlled within ±8%, significantly reducing stress concentration compared to traditional clamping methods. This provides conditions for reducing residual stress in subsequent processing.

[0051] S3: The first abrasive medium, the second abrasive medium, and the third abrasive medium are introduced into the rotary machining cavity in three stages.

[0052] In this embodiment, the contents of the rotary machining cavity mainly include a titanium-nickel alloy workpiece and abrasive media, with an electrolyte further introduced as a reaction medium during the electrochemical machining stage. The titanium-nickel alloy workpiece comprises 5%–15% of the total volume, the abrasive media comprises 40%–65% of the total volume, and the remainder consists of voids and fluid media space.

[0053] In the first stage, the first abrasive medium is alumina abrasive with a particle size of 80-120 mesh, with a volume fraction of 40% to 60% (relative to the effective volume of the rotary machining cavity), and the grinding time is 15-25 minutes, used to remove the oxide layer. This step is the coarse grinding step, using a multi-particle-size alumina abrasive system for primary material removal (in some embodiments, the abrasive can also be diamond abrasive or other high-hardness abrasives, but the particle size and processing parameters need to be controlled to avoid generating excessive processing stress on the titanium-nickel alloy); large-particle-size particles are used to quickly break the surface oxide layer, while small-particle-size particles are used to fill the grinding gaps and inhibit the formation of deep grooves, thereby constructing a multi-scale synergistic removal mechanism; by adjusting the particle size ratio, the material removal rate and surface damage control are balanced.

[0054] In the second stage, the second abrasive medium is an abrasive with a particle size of 240-400 mesh, with a volume fraction of 30% to 50%, and the grinding time is 20-30 minutes, used to eliminate machining marks.

[0055] The abrasive media in the first and second stages are completely discharged after their respective processing is completed to avoid adverse effects on the surfaces processed subsequently.

[0056] In the third stage, the third abrasive medium is a fine abrasive with a particle size of 800-1200 mesh, with a volume fraction of 20% to 40%, and the grinding time is 20 to 40 minutes, used to refine the surface structure.

[0057] The second and third stages are medium and fine grinding steps, which use small-diameter abrasives to gradually level the surface, thereby reducing the surface roughness and eliminating the scratches generated in the coarse grinding stage, providing a uniform interface foundation for the subsequent fine polishing stage.

[0058] The material removal rate Δh is related to the contact pressure P and processing time t by the following relationship: △h = k1 × P × t; Where k1 is an empirical constant related to the properties of the abrasive, Δh is the amount of material removed, P is the contact pressure formed between the workpiece and the inner wall of the cavity under centrifugal force, and t is the processing time. Tests showed that under a centrifugal acceleration of 40g, after three stages of grinding, the oxide layer removal rate could reach over 95%.

[0059] S4: Retain a portion of the third abrasive medium, and while the rotary machining cavity remains in a rotating state, add electrolyte into the rotary machining cavity and apply electricity to cause the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state.

[0060] After the third stage of grinding is completed, the third abrasive medium is discharged, and a portion of the third abrasive medium is retained in the rotary machining cavity. The retention amount is 5% to 30% of the initial volume of the third abrasive. When it is less than 5%, the abrasive contact probability is low, the synergistic effect almost disappears, and it degenerates into pure electrochemistry; when it is more than 30%, there is too much abrasive, which blocks the electrode surface and affects the current distribution, or even becomes "mechanically dominant".

[0061] The retained third abrasive acts synchronously with the electrochemical dissolution process during electrochemical machining. By continuously breaking down the passivation film and gas film on the workpiece surface, it maintains the activation state of the electrode interface, thereby achieving synergistic machining through electrochemical and mechanical action.

[0062] The electrolyte consists of NaNO3, NaCl, and deionized water. The mass fraction of NaNO3 is 8%-15%, the mass fraction of NaCl is 3%-8%, and the remainder is deionized water.

[0063] The substances that dissolve on the surface of titanium-nickel alloy workpieces by electric current include: In the electrochemical dissolution process, the cathode material is selected as an inert conductive material that does not undergo significant electrochemical reactions in the electrolyte and has good conductivity. A titanium-nickel alloy workpiece is used as the anode, and a material with good conductivity and electrochemical stability in the electrolyte system is selected as the cathode, preferably a stainless steel plate; the current density is greater than or equal to 0.5 A / dm³. 2 And less than or equal to 2.0 A / dm 2 In a preferred embodiment, the material on the surface of a titanium-nickel alloy workpiece is dissolved by electrolysis, with a current density greater than or equal to 0.8 A / dm³. 2 And less than or equal to 1.5 A / dm 2 The processing time is 10-25 minutes, and the metal dissolution rate v follows Faraday's law: ; Where v represents the metal dissolution rate, η represents the current efficiency, I is the current intensity in A, M represents the molar mass of the metal, n represents the number of electrons transferred, and F is the Faraday constant. This indicates the material density. Experimental results show that at a current density of 1.2 A / dm², the surface micro-protrusions preferentially dissolve, thus achieving a surface smoothing effect.

[0064] At least a portion of the third abrasive medium is retained within the rotary machining cavity, allowing it to contact the titanium-nickel alloy workpiece surface under centrifugal force, thus enabling electrochemical dissolution and mechanical grinding to proceed simultaneously. A small amount of the third abrasive medium is retained during the electrochemical leveling process, ensuring that electrochemical dissolution and mechanical grinding occur concurrently. In this synergistic machining process, electrochemical dissolution preferentially occurs in the micro-protrusion areas of the workpiece surface, resulting in selective dissolution and reducing surface height differences. Simultaneously, the abrasive medium maintains continuous contact with the workpiece surface under centrifugal force, applying micro-cutting action to further remove the surface film layer and residual protrusions generated by the electrochemical reaction.

[0065] Furthermore, electrochemical dissolution reduces the local hardness and removal resistance of the material surface, thereby lowering the force required for mechanical grinding. Simultaneously, mechanical grinding continuously renews the reaction interface, reducing the formation of passivation films during the electrochemical reaction, thus improving the efficiency of electrochemical dissolution. Therefore, a synergistic enhancement mechanism is formed under these conditions: "electrochemicals promote mechanical removal, and mechanical action strengthens the electrochemical reaction." At the same time, under the centrifugal field of the rotating machining cavity, the abrasive maintains stable contact with the workpiece and its distribution stability is maintained under controlled electrolyte flow disturbances, thus providing continuous conditions for electrochemical-mechanical synergistic processing.

[0066] The state of electrochemical-mechanical co-processing satisfies the following relationship: V total =V mech +V elec +V couple ; Among them, V total V represents the total material removal rate. mech V represents the mechanical removal rate. elec V represents the electrochemical removal rate. couple Synergy enhancement item.

[0067] Under the aforementioned synergistic processing mechanism, the material removal process no longer relies solely on electrochemical dissolution or mechanical grinding, but rather forms a coupled enhancement effect. Compared to a single electrochemical leveling method, under the same current density and processing time conditions, the material removal efficiency in this invention is improved by approximately 28%. This is because electrochemical dissolution preferentially removes micro-protrusions, reducing surface roughness, while mechanical grinding continuously removes reaction products and renews the processing interface, thereby avoiding local passivation and improving reaction uniformity, ultimately enhancing the overall removal efficiency.

[0068] While electrochemical dissolution is being carried out, the presence of micro-abrasives is maintained, allowing electrochemical dissolution to preferentially act on the micro-protrusion area, while physical micro-grinding simultaneously achieves micro-leveling, thus forming a coupling mechanism between electrochemical selective dissolution and mechanical shaping. This synergistic mode can achieve high surface leveling efficiency under low current density conditions and shorten the overall processing time.

[0069] After using this method, the surface roughness Ra of the polished nickel-titanium alloy workpiece is less than or equal to 0.2μm.

[0070] When dissolving the surface material of a titanium-nickel alloy workpiece by applying electricity, the processing temperature is monitored in real time by arranging temperature sensors in the processing area, and closed-loop heat exchange control is achieved through a coolant circulation system.

[0071] Because the phase transformation behavior of titanium-nickel alloys is a thermally activated process, the phase transformation temperature between austenite and martensite (including characteristic temperatures such as Ms and Af) is highly sensitive to temperature changes; even small temperature fluctuations can cause changes in the phase transformation temperature. During processing, both mechanical grinding and electrochemical reactions generate heat, leading to a localized increase in workpiece temperature, which may alter the phase transformation behavior of the material and cause a phase transformation temperature drift.

[0072] Therefore, the temperature of the processing area is controlled by the coolant circulation system, and the electrolyte temperature is maintained in the range of 15°C to 28°C, preferably 15°C to 22°C. When the monitored temperature exceeds the set threshold, the cooling capacity is automatically enhanced, thereby suppressing the influence of thermal disturbances generated during processing on the phase transformation behavior of titanium-nickel alloy, and keeping the material in a stable phase structure state during processing.

[0073] During the coolant circulation process, the electrolyte flow rate is controlled to keep the electrolyte in a low-disturbance flow state. Under the centrifugal force of the rotating machining cavity, the centrifugal inertial force on the third abrasive medium is greater than the fluid drag force generated by the electrolyte flow, thereby enabling the abrasive to maintain a relatively stable spatial distribution state and avoiding significant migration or loss caused by fluid circulation.

[0074] Based on the comparison between centrifugal force and fluid force, the abrasive distribution is stabilized by controlling the flow rate, thereby ensuring the synergistic effect.

[0075] Within the rotary machining cavity, abrasive particles are subjected to the combined effects of centrifugal force and fluid resistance. To ensure a stable distribution of abrasive particles on the workpiece surface, this solution controls the electrolyte flow rate to ensure that the centrifugal force is greater than or equal to the fluid resistance. Specifically, the following relationship must be satisfied: F c ≥F d ; Among them, centrifugal force F c =m·ω 2 r, fluid resistance Fd =6πμRv; m represents the mass of the abrasive particle, ω represents the angular velocity of rotation, r represents the radius of rotation, μ represents the dynamic viscosity of the electrolyte, R represents the equivalent radius of the abrasive particle, and v represents the flow rate of the electrolyte.

[0076] Therefore, the flow velocity control condition can be obtained as follows: v ≤ (m·ω) 2 r) / (6πμR) Under these conditions, abrasive particles can stably adhere to the processing interface, thereby maintaining the synergistic state of electrochemical and mechanical action.

[0077] In actual processing, the fluid in the processing area is kept in a low-velocity laminar flow state by adjusting the electrolyte circulation flow rate, preferably controlled within the range of 0.1–0.5 m / s. When the flow rate is too high, abrasive particles are easily washed away from the processing interface; when the flow rate is too low, reaction products are difficult to remove in time. Through the above control, a balance can be achieved between abrasive stability and electrochemical reaction efficiency, thereby ensuring stable co-processing.

[0078] The rotating machining chamber also serves as an electrolytic reaction chamber. In the rotating state, an electrochemical reaction is achieved by setting up an electrode structure, thereby enabling simultaneous mechanical grinding and electrochemical dissolution in the same space.

[0079] Compared to conventional metallic materials, titanium-nickel alloys are highly sensitive to temperature and stress during processing, and their surfaces are prone to forming dense oxide films. This invention addresses key technical challenges in the processing of titanium-nickel alloys by employing a clamp-free centrifugal fixing structure to reduce stress introduction, suppressing phase transformation through low-temperature control, and breaking the passivation film through the synergistic effect of electrochemistry and abrasives.

[0080] According to this scheme, nickel-titanium alloy workpieces are ground. The phase transformation temperature drift comparison shown in Table 1 indicates that the method of this invention has minimal impact on the phase transformation temperature of the nickel-titanium alloy during processing and can effectively suppress phase transformation temperature drift. The comprehensive performance comparison shown in Table 2 demonstrates that the method of this invention is superior to traditional methods in terms of surface roughness, residual stress, phase transformation temperature stability, and processing efficiency.

[0081] Table 1

[0082] Table 2

[0083] Differential scanning calorimetry results show that the change range of austenite termination temperature Af before and after processing is controlled within ±1℃, preferably not exceeding ±0.8℃. In this embodiment, the average drift is 0.3℃, indicating that this method does not cause significant phase transformation temperature drift during processing.

[0084] In summary, the method of the present invention can control the Af drift of titanium-nickel alloy before and after processing within ±1℃, preferably not exceeding ±0.8℃, and the average drift amount in a typical embodiment is 0.3℃.

[0085] Eight hours of continuous operation and three days of continuous processing verification showed that the system operated stably, with good consistency in processing quality and no abnormal fluctuations. These results demonstrate that the proposed method has good industrial feasibility in reducing residual stress, improving surface uniformity, and controlling phase transition temperature stability.

[0086] After completing the single-factor experimental verification, in order to comprehensively evaluate the overall processing stability and measurement reliability of the method of the present invention under actual industrial conditions, batch processing tests were conducted on samples with different combinations of structural parameters, and comprehensive statistical analysis was performed on processing size deviation, surface roughness deviation, residual stress fluctuation and phase transition temperature change, so as to determine the overall measurement accuracy and systematic error level of the present invention.

[0087] Specifically, three groups of titanium-nickel alloy samples with different parameter combinations (no less than 20 pieces in each group) were selected and processed according to the method of the present invention. A precision displacement platform and a dial indicator were used as reference detection devices to compare and measure the dimensional changes after processing. At the same time, a white light interferometer was used to measure the surface roughness, X-ray diffraction was used to detect the residual stress change, and differential scanning calorimetry (DSC) was used to detect the phase transition temperature change.

[0088] Statistical analysis reveals the following: Dimensional measurement error: Within the loading range of 0–100 μm, the maximum deviation between the displacement value calculated by the method of the present invention and the measurement value of the reference instrument is controlled within ±4.85 μm, the average deviation is ±3.12 μm, and the standard deviation is less than 1.05 μm.

[0089] Surface roughness fluctuation range: Surface roughness R after machining a The average value is 0.18 μm, which can be reduced to 0.05 μm under co-optimized parameters. The maximum batch-to-batch variation does not exceed ±0.03 μm.

[0090] Residual stress stability: The residual stress distribution range of samples in the same batch is 18 to 26 MPa, and the deviation between batches does not exceed ±3 MPa.

[0091] Phase transition temperature stability: The variation range of the austenite termination temperature Af before and after processing is controlled within ±1℃, preferably not exceeding ±0.8℃.

[0092] Under continuous operation for 8 hours and batch processing verification for three days, no significant accuracy drift or abnormal fluctuations were observed, indicating that the method of the present invention has good long-term stability and industrial applicability.

[0093] Therefore, it can be confirmed that the clamp-free low-temperature composite grinding method described in this invention meets the engineering application requirements in terms of dimensional control accuracy, surface consistency, and material performance retention.

[0094] As can be seen from the above, this solution is a clamp-free low-temperature composite grinding method for titanium-nickel alloys. It is based on centrifugal self-stabilizing positioning, with multi-stage physical grinding as the main method and electrochemical-physical synergistic polishing as the final leveling method. It also incorporates a complete processing path through a full-process low-temperature control mechanism. It is suitable for precision surface processing of wires, slender rods, or titanium-nickel alloy parts with pointed structures. While avoiding the local stress concentration problem caused by traditional mechanical clamping, it fixes the workpiece through a centrifugal self-stabilizing structure and completes the surface treatment under full-process temperature control by combining graded physical grinding, electrochemical leveling, and synergistic processing mechanisms.

[0095] This solution eliminates the source of residual stress from mechanical clamping through a centrifugal self-stabilizing structure; achieves rapid removal of the oxide layer and gradual surface leveling through a multi-stage abrasive system; reduces processing time and improves leveling efficiency through an electrochemical-physical synergistic mechanism; and suppresses the risk of processing-induced phase transformation through low-temperature closed-loop control throughout the process. Ultimately, this solution enables titanium-nickel alloys to achieve low roughness and high consistency in surface processing while maintaining microstructure stability and tip structure integrity, making it suitable for machining precision functional components that are sensitive to material properties.

[0096] Exemplary embodiments of the present invention have been specifically shown and described above. It should be understood that the present invention is not limited to the detailed structures, arrangements, or implementations described herein; rather, the present invention is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A method for polishing titanium-nickel alloys, characterized in that, Includes the following steps: S1: Pretreatment of titanium-nickel alloy workpieces; S2: Place the pretreated titanium-nickel alloy workpiece into the rotary machining cavity. The rotary machining cavity rotates around the central axis, causing the titanium-nickel alloy workpiece to rotate against the inner wall of the cavity, forming a self-stabilized fixed state without mechanical clamping. S3: The first abrasive medium, the second abrasive medium, and the third abrasive medium are introduced into the rotary machining cavity in three stages respectively; S4: Retain a portion of the third abrasive medium, and while the rotary machining cavity remains in a rotating state, add electrolyte into the rotary machining cavity and apply electricity to cause the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state.

2. The grinding method for titanium-nickel alloy according to claim 1, characterized in that, In step S1, the pretreatment of the titanium-nickel alloy workpiece includes: The titanium-nickel alloy workpiece is placed in the first solution for ultrasonic cleaning. The titanium-nickel alloy workpiece is then placed in the second solution for ultrasonic cleaning. Rinse and dry.

3. The grinding method for titanium-nickel alloy according to claim 1, characterized in that, In step S2, when the nickel-titanium alloy workpiece rotates, the centrifugal acceleration is greater than or equal to 20g and less than or equal to 60g.

4. The grinding method for titanium-nickel alloy according to claim 1, characterized in that, In step S3, the particle size of the first abrasive medium is 80-120 mesh, the particle size of the second abrasive medium is 240-400 mesh, and the particle size of the third abrasive medium is 800-1200 mesh.

5. The grinding method for titanium-nickel alloy according to claim 4, characterized in that, The first stage of sanding takes 15-25 minutes, the second stage takes 20-30 minutes, and the third stage takes 20-40 minutes.

6. The grinding method for titanium-nickel alloy according to claim 1, characterized in that, In step S4, the electrolyte includes NaNO3, NaCl, and deionized water.

7. The polishing method for titanium-nickel alloy according to claim 1, characterized in that, In step S4, the substance on the surface of the titanium-nickel alloy workpiece that is dissolved by electricity includes: A titanium-nickel alloy workpiece is used as the anode; at a current density of greater than or equal to 0.5 A / dm 2 and less than or equal to 2.0 A / dm 2 Dissolving the surface material of the titanium-nickel alloy workpiece by applying electric current.

8. The grinding method for titanium-nickel alloy according to claim 7, characterized in that, In step S4, when the titanium-nickel alloy workpiece undergoes electrochemical dissolution, the electrolyte temperature is controlled within the range of 15°C to 28°C.

9. A grinding device for titanium-nickel alloy, characterized in that, include: Pretreatment device, rotating device, rotating processing chamber, feeding device and electrolysis device; The pretreatment device is used to pretreat titanium-nickel alloy workpieces; The rotating device is used to cause the rotary machining cavity to rotate about the central axis; The rotary machining cavity is used to place the pretreated titanium-nickel alloy workpiece inside the rotary machining cavity. The rotary machining cavity rotates around the central axis, so that the titanium-nickel alloy workpiece is attached to the inner wall of the cavity and rotates, forming a self-stabilized fixed state without mechanical clamping. The feeding device is used to feed the first abrasive medium, the second abrasive medium and the third abrasive medium into the rotary machining cavity in three stages respectively; The electrolysis device is used to electrolyze titanium-nickel alloy workpieces. When electrolyzing titanium-nickel alloy workpieces, a portion of the third abrasive medium is retained. While the rotary machining cavity is in a rotating state, electrolyte is added into the rotary machining cavity and electricity is applied to cause the titanium-nickel alloy workpiece to undergo electrochemical dissolution, thereby forming an electrochemical-mechanical synergistic machining state.

10. The grinding apparatus for titanium-nickel alloy according to claim 9, characterized in that, It also includes a cooling device, which includes a temperature sensor and a temperature control module. The temperature sensor is placed in the electrolyte, and the temperature control module is used to adjust the temperature of the electrolyte according to the temperature detected by the temperature sensor.

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