Method for preparing dual-phase heterogeneous deformation mechanism tin bronze alloy through stacking fault energy-oriented Sn content regulation and control and alloy

Abstract

The invention discloses a method for preparing a dual-phase heterogeneous deformation mechanism tin bronze alloy through stacking fault energy-oriented Sn content regulation and control and the alloy, and relates to the technical field of metal materials. The method comprises the following steps: determining a critical component window of a low-Sn glide region and a high-Sn twinborn region on the basis of an influence rule of Sn content on an alpha-Cu solid solution stacking fault energy and a deformation mechanism; through the combination of melt instantaneous cooling induced nucleation and a rheological extrusion forming process, the synergistic distribution of two phases on the microscopic scale is realized in the tin bronze alloy. In the plastic deformation process of the obtained tin bronze alloy, dislocation slippage is used as a dominant deformation mechanism in a low-Sn area, mechanical twinning is used as a dominant deformation mechanism in a high-Sn area, and a heterogeneous deformation coordination mechanism is formed. The alloy prepared through the method shows excellent strength and toughness, and therefore a new path is provided for design and preparation of the high-performance copper alloy.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of metal materials, in particular to a method for preparing a tin bronze alloy with a dual-phase heterogeneous deformation mechanism by adjusting the Sn content based on a stacking fault energy and the alloy. BACKGROUND

[0002] Tin bronze alloys have been widely used in friction transmission devices such as shaft sleeves, bearing seats and gears due to their high strength, large rigidity, low friction coefficient and excellent corrosion resistance, and are one of the key materials indispensable in the industrial field. However, high-tin-content tin bronze (such as the typical brand CuSn10P1) has a significant technical pain point during solidification: it is prone to element segregation, with tin easily accumulating in the interdendritic liquid phase and forming interdendritic brittle structures. This problem severely limits the improvement of the plasticity of the alloy and makes it difficult to meet the stringent requirements of modern industry for the comprehensive mechanical properties of materials. To improve the lack of plasticity, traditional methods such as solid solution annealing are often used for optimization, but these methods often sacrifice the strength of the alloy, making it impossible to achieve simultaneous consideration of high strength and high plasticity, forming a technical bottleneck of "strong and brittle, tough and weak".

[0003] Previous studies have shown that when there are two types of phases or regions with different dominant deformation modes in the alloy (for example, one type is mainly deformed by dislocation slip, and the other type is more prone to mechanical twinning), the strength and plasticity can be improved simultaneously. Among them, the stacking fault energy, as a key micro parameter to describe the competition between slip and twinning, can be precisely controlled by adjusting the chemical composition of a certain phase of the alloy. For the Cu-Sn alloy system, the Sn content in the α-Cu solid solution has good adjustability within a certain range, which provides a solid theoretical basis for achieving deformation mechanism division through composition zoning and then achieving stacking fault energy control.

[0004] In the prior art, a semi-solid slurry-homogenization-extrusion forming preparation process for tin bronze (such as CuSn10P1) has been disclosed, and the core idea is to improve the mechanical properties of the alloy by obtaining a low-tin primary phase and a tin-rich phase.

[0005] However, this technical solution has obvious limitations: it mainly focuses on the optimization of specific preparation steps and process windows, and does not systematically construct the stacking fault energy as a core variable for organizational design and performance control, lacking a transferable and generalizable engineering method chain, i.e., it does not form a complete technical system with "Sn content zoning-stacking fault energy zoning-twinning / slip division-strength and toughness coordination" as the main line, which cannot fundamentally solve the core problem of the difficulty in balancing strength and toughness, and has limited applicability.

[0006] Therefore, there is an urgent need for an innovative solution that can effectively bridge the microscopic mechanism of stacking fault energy to specific process paths, taking the Sn content partition as the core control object for engineering implementation, and stably constructing a microstructure with a high Sn twin dominant region and a low Sn slip dominant region under actual industrial production conditions, ultimately achieving the simultaneous improvement of high strength and high plasticity of tin bronze alloys, and breaking through the limitations of existing technologies. SUMMARY

[0007] The purpose of the present application is to provide a method for preparing a dual-phase heterogeneous deformation mechanism tin bronze alloy guided by stacking fault energy and Sn content control, and an alloy, to solve the problems existing in the prior art.

[0008] To achieve the above-mentioned purpose, the present application provides the following solutions: The present application provides a method for preparing a dual-phase heterogeneous deformation mechanism tin bronze alloy guided by stacking fault energy and Sn content control, comprising the following steps: (1) Based on the regulation of Sn content on the stacking fault energy of α-Cu solid solution, two types of micro-regions with different plastic deformation mechanisms are constructed in the alloy: The first region: dislocation slip is the dominant deformation mechanism; The second region: mechanical twinning is the dominant deformation mechanism; The Sn content of the first region is in the range below the critical value of mechanical twinning activation; The Sn content of the second region is in the range above the dislocation slip dominant threshold; (2) Using a semi-solid forming process induced by instantaneous cooling nucleation, the first region and the second region are formed in a synergistic distribution at the microscale, and the dual-phase heterogeneous deformation mechanism tin bronze alloy is obtained.

[0009] Further, the first region is an α-Cu solid solution region with Sn content of 0-1.4 at.% and not 0 at.%; the second region is an α-Cu solid solution region with Sn content of 6.0-6.9 at.%.

[0010] Further, the tin bronze alloy is CuSn10P1 alloy.

[0011] Further, the semi-solid forming process comprises the following steps: Semi-solid slurry preparation: the tin bronze alloy melt is subjected to melt instantaneous cooling nucleation to induce nucleation, so that the alloy melt precipitates Sn-poor primary α-Cu solid phase and retains Sn-rich residual undercooled liquid phase, and a semi-solid slurry is obtained; Rheological extrusion forming: the semi-solid slurry is subjected to extrusion forming to obtain a dual-phase heterogeneous deformation mechanism tin bronze alloy in which the first region and the second region coexist; The initial temperature of the tin bronze alloy melt during the semi-solid slurry preparation process is 1150±2℃ when the melt is subjected to the melt transient cooling induced nucleation; During the melt transient cooling induced nucleation process, the transient cooling time is 0.3s, and the cooling rate is 330℃ / s.

[0012] Further, the extrusion forming adopts a punch speed of 25-35mm / s and a forming pressure of 130-150MPa.

[0013] Further, the pressure is maintained for 25-35s after the extrusion forming.

[0014] The application also provides a dual-phase heterogeneous deformation mechanism tin bronze alloy prepared by the above method, and the microstructure of the alloy comprises: The first region is dominated by dislocation slip as the deformation mechanism; The second region is dominated by mechanical twinning as the deformation mechanism; The Sn content of the first region is in a range lower than the critical value of mechanical twinning activation; and the Sn content of the second region is in a range higher than the threshold value of dislocation slip dominance.

[0015] The application discloses the following technical effects: The application successfully constructs a low-Sn slip region and a high-Sn twinning region that are cooperatively distributed on a microscale in the tin bronze alloy by the Sn content partition regulation strategy guided by the stacking fault energy, and realizes the organic cooperation of the two plastic deformation mechanisms of dislocation slip and mechanical twinning. The low-Sn region is dominated by dislocation slip due to the high stacking fault energy, and provides good plasticity; the high-Sn region is easy to activate mechanical twinning due to the significantly reduced stacking fault energy, and contributes high strength.

[0016] The dual-phase heterogeneous deformation mechanism effectively breaks through the bottleneck that the strength and plasticity of the traditional single-phase tin bronze are difficult to be considered together, and combines the transient cooling induced nucleation and the rheological extrusion forming process, so that the alloy has high tensile strength and elongation, exhibits excellent synergistic improvement effect of strength and toughness, and provides a new path for the design and preparation of high-performance copper alloys. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0018] Figure 1 The generalized stacking fault energy and twinning tendency evaluation diagram for Cu-Sn solid solution with different Sn contents.

[0019] Figure 2 Schematic diagram of the preparation method of the dual-phase heterogeneous deformation mechanism tin bronze alloy.

[0020] Figure 3 Results of microstructure characterization of the CuSn10P1 alloy obtained in Example 1 after tensile deformation at room temperature to 30% true strain.

[0021] Figure 4 Schematic diagram of the strong and tough synergy mechanism based on Sn partitioning and stacking fault energy partitioning matching. DETAILED DESCRIPTION

[0022] A number of exemplary embodiments of the present application are described herein, and those skilled in the art will understand that the application can be practiced with the embodiments and with equivalents thereof without departing from the spirit and scope of the present application. The detailed description of the application is not intended to limit the scope of the application as described in the claims.

[0023] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where particular ranges of values are given, it is intended to include every intervening value between the upper and lower limits of the range. Any smaller ranges between the upper and lower limits are also intended to be included in the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that all

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not an admission that it is prior art with respect to the present application.

[0025] Many modifications and variations of this application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that the application is not limited in scope by the specific embodiments described herein, which are intended for illustrative purposes only, and that the specification and examples are exemplary and do not limit the scope or perimeters of the application.

[0026] It is to be understood that the terms "including", "comprising", "consisting" and "having" and the like are used interchangeably and are meant to be open-ended terms that do not preclude the addition of non-recited, additional elements or steps.

[0027] It should be noted that the present application does not describe in detail the conventional operation means in the art, and is not the focus of the present application.

[0028] The application provides a method for preparing a tin bronze alloy with a dual-phase heterogeneous deformation mechanism by adjusting Sn content based on a stacking fault energy. (1) Based on the regulation of Sn content on the stacking fault energy of the alpha-Cu solid solution, two types of micro-regions with different plastic deformation mechanisms are constructed in the alloy: The first region (low Sn phase): dislocation slip is the dominant deformation mechanism; The second region (high Sn phase): mechanical twinning is the dominant deformation mechanism; The Sn content of the first region is in the range below the mechanical twinning activation threshold; The Sn content of the second region is in the range above the dislocation slip dominant threshold; (2) Using the semi-solid forming process of instantaneous cooling induced nucleation, the first region and the second region are formed in a synergistic distribution at the microscale, and a dual-phase heterogeneous deformation mechanism tin bronze alloy is obtained.

[0029] The application selects Cu-Sn disordered solid solution models with Sn content of 1.4 at.%, 2.1 at.%, 4.2 at.%, and 6.9 at.% based on the fact that Sn content in the alpha-Cu solid solution can fluctuate in the low Sn range and can be used as a stacking fault energy regulation entry, and calculates the generalized stacking fault energy curve and twinning correlation criterion by using the first principle method. The calculation results show that as the Sn content increases, the generalized stacking fault energy barrier gradually decreases, the twinning tendency parameters T and τ a increase, and high Sn solid solution is more likely to activate twinning, while low Sn solid solution is more inclined to deform through dislocation slip. Among them, T is the ratio of the stress intensity factor required by the trailing part and the twinning part of the deformation twinning ability of the crack tip, and τa is the measure of the twinning ability in the FCC metal.

[0030] Table 1 Twinning criteria T and τ of Cu-Sn solid solution with different Sn content a According to the results shown in Table 1, in order to ensure that the low Sn phase and the high Sn phase have obvious differences in plastic deformation mode, the Cu-Sn solid solution with Sn content of 0~1.4 at.% and not 0 at.% is defined as the low Sn phase, and the Cu-Sn solid solution with Sn content of 6.0~6.9 at.% is defined as the high Sn phase.

[0031] Figure 1 The generalized stacking fault energy and twinning tendency evaluation diagram for Cu-Sn solid solution with different Sn content.

[0032] The application provides a method for preparing a tin bronze alloy with a dual-phase heterogeneous deformation mechanism by adjusting Sn content based on a stacking fault energy. (1) melt transiently cools the tin bronze alloy melt to induce nucleation, so that the alloy melt preferentially precipitates a primary α-Cu solid phase with a low Sn content (the Sn content is 0-1.4 at.%, and is not 0 at.%) at the initial stage of solidification, while retaining a residual Sn-rich undercooled liquid phase, thereby obtaining a semi-solid slurry coexisting with a low-Sn solid phase and a high-Sn liquid phase; (2) the semi-solid slurry is placed in a forming die for rheological extrusion forming, and the residual liquid phase is non-equilibrium solidified into a high-Sn α-Cu solid solution (the Sn content is 6.0-6.9 at.%) after the forming for 30 s, so as to finally obtain a dual-phase microstructure with a synergistic distribution on a microscale; wherein, the low-Sn region is mainly subjected to dislocation slip during plastic deformation, and the high-Sn region is mainly subjected to mechanical twinning, thereby forming a synergistic effect of heterogeneous deformation mechanisms.

[0033] In step (1), the melt temperature for melt transiently cooling to induce nucleation is 1150±2℃, and the cooling rate is 330℃ / s.

[0034] In step (2), the punch speed used is 30 mm / s, and the forming pressure is 140 MPa.

[0035] During plastic deformation of the alloy material, the low-Sn region is coordinated in deformation through dislocation slip, and the high-Sn region is coordinated in deformation through mechanical twinning, and the two regions cooperate with each other in space, so as to realize a synergistic improvement of strength and plasticity.

[0036] The application further provides a dual-phase heterogeneous deformation mechanism tin bronze alloy prepared by the above method; and the microstructure of the dual-phase heterogeneous deformation mechanism tin bronze alloy comprises: a first region (low-Sn phase) mainly subjected to dislocation slip as a dominant deformation mechanism, and a second region (high-Sn phase) mainly subjected to mechanical twinning as a dominant deformation mechanism. The Sn content of the first region is in a range lower than a critical value of mechanical twinning activation; and the Sn content of the second region is in a range higher than a threshold value of dislocation slip dominance.

[0037] Further, the first region is an α-Cu solid solution region with a Sn content of 0-1.4 at.% and not 0 at.%; and the second region is an α-Cu solid solution region with a Sn content of 6.0-6.9 at.%.

[0038] Figure 2 It is shown in the accompanying drawings that the application is a preparation method of a dual-phase heterogeneous deformation mechanism tin bronze alloy.

[0039] The technical solutions of the application will be further described in combination with specific embodiments, so as to embody the technical effects achieved in practical applications: Example 1 The embodiment provides a method for preparing a dual-phase heterogeneous deformation mechanism tin bronze alloy (CuSn10P1) by controlling Sn content based on a stacking fault energy, and specifically comprises the following steps. (1) Preheating treatment of the mold: after the mold is opened, the surface oxide of the mold cavity is cleaned, and a mold release agent containing boron nitride is uniformly sprayed; the upper mold and the lower mold are heated by resistance heating rods, so that the temperature of the mold is increased to 430 DEG C ± 5 DEG C, and the temperature is kept for 4h, so as to ensure the stability of the temperature field of the mold.

[0040] (2) Using an industrial-grade CuSn10P1 alloy (the nominal composition is Sn 10 wt.%, P 0.1 wt.%, and the balance is Cu) as a raw material, the alloy is melted at 1300 DEG C in a medium-frequency induction furnace under the protection of an inert atmosphere, and after keeping for 5 min, the alloy melt is taken out and kept for 30 s to obtain an alloy melt with uniform composition; (3) The alloy melt is treated by a melt instantaneous cooling nucleation process (the initial temperature of the tin bronze alloy melt is 1150±2 DEG C, the instantaneous cooling time is 0.3s, and the cooling rate is 330 DEG C / s), so that the melt is rapidly supercooled under strong chilling conditions, preferentially precipitates Sn content of about 1.4 at.% of primary α-Cu solid phase, and at the same time, retains Sn content of about 6.9 at.% of Sn-rich residual supercooled liquid phase, thereby forming a semi-solid slurry coexisting with low Sn solid phase and high Sn liquid phase; (4) The semi-solid slurry is transferred to the barrel of an extruder, and is formed by rheological extrusion: the punch speed is set to 30 mm / s, the forming pressure is 140 MPa, the extrusion is completed after keeping for 30 s, and the mold is kept for 15 min, and then the mold is cooled to room temperature in the furnace, so that the stable distribution of the high Sn area and the low Sn area is solidified through the rheological extrusion forming process under the controlled thermal-mechanical conditions, and a bulk tin bronze alloy sample (CuSn10P1 product) is obtained.

[0041] In step (3), the instantaneous cooling nucleation semi-solid slurry preparation device makes a large amount of primary α-Cu phase precipitate in the alloy liquid, which is the embryo of the low Sn phase, and the remaining high tin supercooled residual liquid phase prepares for the formation of the high Sn phase; in step (4), the primary α-Cu further grows and continuously discharges Sn in front of the solid / liquid interface, so that the Sn content is further reduced. The solid / liquid interface is solidified by the α-Cu discharging Sn and the remaining high tin supercooled liquid phase, and the high Sn phase is formed under the joint action of the two.

[0042] Comparative Example 1 (CuSn10P1 heat-treated state prepared by traditional liquid casting) In this comparative example, the CuSn10P1 alloy is prepared by a sand casting method, and the specific steps are as follows: (1) Making a sand mold; (2) The same smelting process as in Example 1 was adopted to obtain a CuSn10P1 alloy melt; (3) The melt was injected into a sand mold cavity through a gating system; (4) After the metal liquid was naturally cooled in air, the casting was taken out.

[0043] It was tested that the tensile strength of the as-cast CuSn10P1 alloy was 347.05 MPa, and the elongation was 5.39%. Subsequently, the casting was subjected to stress relief annealing treatment: holding at 260℃ for 4 hours, and then air cooling to room temperature. After heat treatment, the tensile strength of the alloy was reduced to 302.12 MPa, and the elongation was 6.03%.

[0044] Comparative Example 2 (existing semi-solid forming process CuSn10P1) The CuSn10P1 alloy in this comparative example was prepared by using an existing semi-solid forming process, and the parameters were only different from those in Example 1 in that: Semi-solid slurry preparation stage: the initial temperature of the melt was 1210℃, and the cooling rate was 380℃ / s; Rheological extrusion forming stage: the punch speed was 22 mm / s, and the forming pressure was 145 MPa.

[0045] The remaining parameters were the same as in Example 1.

[0046] The CuSn10P1 alloy prepared by this process had a tensile strength of 457.5 MPa and an elongation of 54.56%.

[0047] Table 2 is the energy spectrum analysis (EDS) characterization of the tin bronze alloy in Example 1 after rheological extrusion forming and cooling to room temperature. The alloy sample obtained in Example 1 was subjected to multi-point energy spectrum analysis (EDS), and the Sn content was measured to be 0.8~1.6 at.% in different low Sn phase regions and 6.3~7.1 at.% in different high Sn phase regions, indicating that the alloy formed a clear two-phase structure in the microscale, which was consistent with the theoretical design of Sn content partition target, proving that a clear high / low Sn phase partition can be realized in the actual alloy by the method.

[0048] Table 2 Figure 3 The results of microstructure characterization of the CuSn10P1 alloy obtained in Example 1 after being stretched at room temperature to 30% true strain. Figure 3The low tin phase is in the middle white dotted box, the rest is high tin phase, and the black arrow points to the area where the high Sn phase region appears obvious cross deformation belt and other typical mechanical twinning characteristics, and the low Sn phase region does not observe such structure. The above results verify the mechanism of the "high Sn twinning dominant area" and "low Sn slip dominant area" constructed by the application in the process of plastic deformation.

[0049] The mechanical property test of the sample of example 1 shows that the tensile strength of the alloy reaches 480 MPa and the elongation rate is as high as 58.9% under the synergistic effect of the dual-phase heterogeneous deformation mechanism organization, which is significantly better than the traditional CuSn10P1 alloy, and the excellent strength and toughness synergistic effect is embodied.

[0050] Figure 4 It is a schematic diagram of the strength and toughness synergy mechanism based on Sn partition and stacking fault energy partition matching. As shown in Figure 4 The application first divides the alpha-Cu solid solution into a low Sn slip dominant area and a high Sn twinning dominant area by Sn content partition. Due to the different stacking fault energy levels of the two areas, the high Sn area is more likely to activate mechanical twinning and provide higher work hardening capacity, while the low Sn area maintains plasticity and continuous deformation capacity by dislocation slip. The two types of areas form a heterogeneous deformation coordination mechanism during loading, thereby realizing the synchronous improvement of tensile strength and elongation rate.

[0051] The above-described examples only describe the preferred mode of the application and do not limit the scope of the application. Without departing from the design spirit of the application, various modifications and improvements to the technical solutions of the application made by those skilled in the art shall fall within the protection scope determined by the claims of the application.

Claims

1. A method for preparing a dual phase hetero-deformation mechanism tin bronze alloy with a guided stacking fault energy and Sn content control, characterized in that, The method comprises the following steps: (1) based on the regulation of Sn content on the stacking fault energy of α-Cu solid solution, two types of micro-regions with different plastic deformation mechanisms are constructed in the alloy: The first region: dislocation slip as the dominant deformation mechanism; The second region: mechanical twinning as the dominant deformation mechanism; The Sn content of the first region is in the range below the critical value of mechanical twinning activation; The Sn content of the second region is in the range above the threshold of dislocation slip dominance; (2) using the semi-solid forming process of instantaneous cooling induced nucleation, the first region and the second region form a synergistic distribution at the microscale to obtain the dual-phase heterogeneous deformation mechanism tin bronze alloy.

2. The method of claim 1, wherein, The first region is the α-Cu solid solution region with Sn content of 0-1.4 at.% and not 0 at.%; the second region is the α-Cu solid solution region with Sn content of 6.0-6.9 at.%.

3. The method of claim 1, wherein, The tin bronze alloy is CuSn10P1 alloy.

4. The method of claim 1, wherein, The semi-solid forming process comprises the following steps: Semi-solid slurry preparation: tin bronze alloy melt is subjected to melt instantaneous cooling induced nucleation to precipitate Sn-poor primary α-Cu solid phase and retain Sn-rich residual undercooled liquid phase, and semi-solid slurry is obtained; Rheological extrusion forming: the semi-solid slurry is subjected to extrusion forming to obtain a dual-phase heterogeneous deformation mechanism tin bronze alloy in which the first region and the second region coexist; In the semi-solid slurry preparation process, the initial temperature of the tin bronze alloy melt during the melt instantaneous cooling induced nucleation is 1150±2℃; In the process of melt instantaneous cooling induced nucleation, the instantaneous cooling time is 0.3s and the cooling rate is 330℃ / s.

5. The method of claim 4, wherein, The extrusion forming adopts a punch speed of 25-35mm / s and a forming pressure of 130-150MPa.

6. A dual phase inhomogeneous deformation mechanism tin bronze alloy characterized by, Prepared by the method of any one of claims 1-5, the microstructure thereof comprises: The first region: dislocation slip as the dominant deformation mechanism; The second region: mechanical twinning as the dominant deformation mechanism; The Sn content of the first region is in the range below the critical value of mechanical twinning activation; the Sn content of the second region is in the range above the threshold of dislocation slip dominance.

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