A heat treatment method for improving precipitation degree and refining precipitated phase

Abstract

A heat treatment method for improving precipitation degree and refining precipitated phase, comprising: cold rolling or cold forging a solid solution state age hardening type alloy, with a deformation amount of 0-30%; determining the optimal age hardening temperature range of the solid solution state age hardening type alloy and the corresponding time and the critical average radius of the precipitated phase in the solid solution state age hardening type alloy during deformation, which is converted from being bypassed by dislocation to being cut through, and determining the required aging time at a specific aging temperature according to 0.5-2 times the critical average radius, then pre-aging the solid solution state age hardening type alloy after cold rolling or cold forging to obtain a pre-aging sample; cold shearing the pre-aging sample to deform, with a deformation amount of 30-60%; and according to the optimal age hardening temperature range of the solid solution state age hardening type alloy, selecting a temperature within 30% of the lower limit of the range for aging treatment to a peak aging state; the present application improves the precipitation degree of the age hardening type alloy and refines the second phase size through a two-stage cold deformation aging process, and realizes a higher comprehensive performance level.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heat treatment, and particularly relates to a heat treatment method for improving precipitation degree and refining precipitated phase. BACKGROUND

[0002] The size and quantity of precipitated phase in age-strengthening alloy are the most important parameters determining the strengthening effect, and it is a hot issue in material research to improve the precipitation degree and refine the size of precipitated phase as much as possible. The current commonly used method is to realize through cold deformation before aging, but the effect is limited, and there is a big problem, that is, a large number of defects generated by cold deformation before aging indeed promote the nucleation density of precipitated phase, and also improve the precipitation degree to a certain extent, but at the same time, the element diffusion speed is also accelerated, so that the precipitated phase is prone to serious coarsening during aging, and therefore the strength, electrical conductivity and plasticity of the material are difficult to be compatible under the condition of large cold deformation.

[0003] An existing cold deformation aging process solves the problem that the precipitation degree and the size of precipitated phase of age-strengthening alloy are difficult to reconcile under the traditional heat treatment method, and the strength, electrical conductivity and plasticity of the material are difficult to be compatible. However, the precipitation degree of the material under the existing pre-cold deformation aging process is limited, and the precipitated phase is prone to rapid coarsening, and the strength, electrical conductivity and plasticity of the alloy are difficult to be compatible.

[0004] In the patent application file with publication number CN112267075B, an age-strengthening alloy and a preparation method thereof are disclosed, and the performance of the age-strengthening type ultra-low carbon alloy steel is improved through a method of combining three different plastic processes with heat treatment, but since the plastic process promotes the nucleation of precipitated phase while promoting the coarsening of precipitated phase, the strength and plasticity are difficult to be compatible. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a heat treatment method for improving the precipitation degree and refining the precipitated phase, which utilizes the interaction behavior of dislocations and precipitated phase of different sizes and the precipitation process characteristics of precipitated phase, and improves the precipitation degree of age-strengthening alloy and refines the size of second phase through a two-stage cold deformation aging process, so as to realize a higher comprehensive performance level.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0007] A heat treatment method for improving the precipitation degree and refining the precipitated phase, comprising the following steps:

[0008] Step 1, cold rolling or cold forging is performed on the solid solution state age-strengthening alloy, and the deformation amount is 0-30%;

[0009] Step 2, determining the optimal aging temperature range of the solid solution state aging strengthening type alloy, corresponding aging time and the critical average radius of the solid solution state aging strengthening type alloy precipitated phase being bypassed by dislocation, determining the required aging time at a specific aging temperature according to 0.5-2 times of the critical average radius, then pre-aging the solid solution state aging strengthening type alloy after cold rolling or cold forging in step 1 to obtain a pre-aging sample;

[0010] Step 3, cold shearing deformation of the pre-aging sample obtained in step 2, deformation amount 30-60%;

[0011] Step 4, according to the optimal aging temperature range of the solid solution state aging strengthening type alloy, selecting a temperature within 30% of the lower limit of the range for aging treatment to the peak aging state.

[0012] The aging strengthening type alloy in step 1 includes a copper alloy, an aluminum alloy, a magnesium alloy, a precipitation hardening steel, a titanium alloy or a nickel-based alloy.

[0013] The cold shearing deformation of step 3 includes asynchronous rolling, equal channel extrusion or torsion, the direction of asynchronous rolling or equal channel extrusion being consistent or perpendicular to the direction of cold rolling or cold forging in step 1, and the direction of torsion being perpendicular to the direction of cold rolling or cold forging in step 1.

[0014] Compared with the prior art, the present application has the following beneficial effects:

[0015] 1. The present application rationally designs a two-stage cold deformation aging process by utilizing the interaction behavior of dislocations and precipitates of different sizes and the precipitation process characteristics of the precipitates: the first stage, the nucleation density and growth rate of the precipitates are regulated by a certain degree of pre-cold deformation, and the precipitates are controlled to be near the critical conversion radius of dislocation cutting and bypassing by combining different aging temperatures and times; the second stage, the second phase nucleation point is efficiently amplified and the size of the precipitates is reduced by cutting through a high proportion of primary precipitate cores through large shear deformation, thereby destroying the diffusion field of the initial precipitates and generating considerable defect accumulation in the material, and promoting the precipitation of the precipitates in local nucleation rather than long-range diffusion and coarsening. Through the above process, the precipitation degree of the aging strengthening type alloy is improved and the size of the second phase is refined, and a higher comprehensive performance level is achieved.

[0016] 2. The present application can control the size of the precipitates in the alloy near the critical conversion radius of dislocation cutting and bypassing by pre-aging treatment in step 2.

[0017] 3. The present application can efficiently amplify the second phase nucleation point and reduce the size of the precipitates by severe cold shearing deformation in step 3.

[0018] 4. The present application can inhibit the coarsening of the precipitates and thereby reduce their size by lower temperature aging in step 4.

[0019] In summary, the present application, by reasonably regulating the nucleation and growth process of precipitated phase, cooperates with large shear deformation to push dislocation to cut through the initial precipitated phase (and its nucleation point) to realize effective expansion of the number of nucleation points and direct refinement of the size of the precipitated phase in the subsequent precipitation process, destroys the stable diffusion field matched with the initial precipitated phase and further accumulates dislocations, and inhibits the long-range diffusion of elements, promotes the nucleation and growth of the precipitated phase on the high-density dislocations, and effectively inhibits the coarsening thereof. Under the action of the above measures, the precipitation degree is improved and the size of the precipitated phase is refined, and the precipitation strengthening effect is greatly enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application is illustrated in the accompanying drawings, wherein, Figure 1 (a) is a schematic diagram of the primary second phase being cut by dislocation before the present application; Figure 1 (b) is a schematic diagram of the primary second phase being cut by a large number of dislocations after the present application.

[0021] Figure 2 The present application is illustrated in the accompanying drawings, wherein, DETAILED DESCRIPTION

[0022] The present application is illustrated in the accompanying drawings, wherein,

[0023] A heat treatment method for improving the precipitation degree and refining the precipitated phase, comprising the following steps:

[0024] Step 1, cold rolling or cold forging the solution state age hardening type alloy, the deformation amount is 0-30%;

[0025] Step 2, determining the best aging temperature range of the alloy and the corresponding aging time according to the “Heat Treatment Process Specification Data Manual”, combining the coarsening theory and strengthening theory of the precipitated phase to obtain the critical average radius of the precipitated phase being bypassed and cut by dislocation during deformation of the alloy, determining the required aging time at a specific aging temperature according to 0.5-2 times the critical radius, then pre-aging the solution state age hardening type alloy after cold rolling or cold forging in step 1 to obtain a pre-aging sample;

[0026] Step 3, severely cold shearing the pre-aging sample obtained in step 2, the deformation amount is 30-60%;

[0027] Step 4, selecting a temperature within 30% of the lower limit of the best aging temperature range of the alloy given in the “Heat Treatment Process Specification Data Manual” to age to the peak aging state.

[0028] The age hardening type alloy in step 1 includes a copper alloy, an aluminum alloy, a magnesium alloy, a precipitation hardening steel, a titanium alloy or a nickel-based alloy.

[0029] The severe cold shear deformation in step 3 includes asynchronous rolling, equal channel extrusion or torsion, the direction of asynchronous rolling or equal channel extrusion is consistent with the cold deformation direction in step 1, and the direction of torsion is perpendicular to the cold deformation direction in step 1.

[0030] Embodiment 1

[0031] A heat treatment method for improving precipitation degree and refining precipitate phase, comprising the following steps:

[0032] Step 1, cold rolling Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy, deformation amount 20%;

[0033] Step 2, determining the best aging temperature interval 450-540℃ of the Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy, the cold-rolled 20% alloy is aged at 480℃ for 3h to reach the peak aging state (as shown in Figure 2 The precipitate phase radius is 4.3nm, according to the dislocation cutting and Orowan bypass mechanism, the radius range of dislocation cutting-bypass conversion of the precipitate phase is about 1.5nm when the alloy is deformed, and according to the precipitate phase coarsening theory, the required aging time at 480℃ is about 8min, therefore, the cold-rolled 20% Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy is respectively pre-aged for 2min, 5min, 8min, 18min and 35min, respectively corresponding to precipitate phase sizes of 0.9nm, 1.3nm, 1.5nm, 2.0nm and 2.4nm, to obtain a pre-aged alloy;

[0034] Step 3, asynchronous rolling treatment of the pre-aged alloy obtained in step 2, deformation amount 50%, to obtain an asynchronous rolling alloy;

[0035] Step 4, according to the best aging temperature interval 450-540℃ of the Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy determined in step 2, the asynchronous rolling alloy obtained in step 3 is aged at 450℃ for different times to the peak aging state.

[0036] Embodiment 2

[0037] A heat treatment method for improving precipitation degree and refining precipitate phase, comprising the following steps:

[0038] Step 1, cold rolling Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy, deformation amount 0%;

[0039] Step 2, the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy is determined to have an optimal aging temperature range of 450-540°C, and the alloy with 0% cold rolling is aged at 510°C for 3h to reach a peak aging state (as shown in Figure 2 The alloy is determined to have a radius range of about 1.5nm for dislocation cutting and Orowan bypassing of the precipitated phase during deformation according to the dislocation cutting and Orowan bypassing mechanism, and the alloy is required to be aged at 510°C for about 5min according to the precipitated phase coarsening theory, so the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy with 0% cold rolling is respectively subjected to pre-aging treatment for 0.6min, 2.6min, 5min, 17min and 41min, respectively corresponding to precipitated phase sizes of 0.75nm, 1.2nm, 1.5nm, 2.25nm and 3.0nm, to obtain a pre-aging alloy;

[0040] Step 3, the pre-aging alloy obtained in step 2 is subjected to equal channel extrusion treatment with a deformation of 60% to obtain an equal channel extrusion alloy;

[0041] Step 4, according to the optimal aging temperature range of 450-540°C of the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy determined in step 2, the equal channel extrusion alloy obtained in step 3 is subjected to aging treatment at 470°C for different times to reach a peak aging state.

[0042] Example 3

[0043] A heat treatment method for improving the precipitation degree and refining the precipitated phase, comprising the following steps:

[0044] Step 1, a Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy is cold rolled with a deformation of 30%;

[0045] Step 2, the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy is determined to have an optimal aging temperature range of 450-540°C, and the alloy with 30% cold rolling is aged at 480°C for 3h to reach a peak aging state (as shown in Figure 2The Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy is cold-rolled by 30% to obtain a cold-rolled alloy, and the cold-rolled alloy is aged at 480 ℃ for 3 h to obtain a peak-aged alloy, wherein the cold-rolled alloy is pre-aged at 480 ℃ for 1 min, 4.5 min, 9 min, 30 min and 70 min respectively to obtain a pre-aged alloy, and the pre-aged alloy is twisted to obtain a twisted alloy, and the twisted alloy is aged at 460 ℃ for different times to obtain a peak-aged alloy.

[0046] Step 3, the pre-aged alloy obtained in step 2 is twisted to obtain a twisted alloy, and the deformation amount is 30%;

[0047] Step 4, according to the best aging temperature interval 450-540 ℃ of the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy determined in step 2, the twisted alloy obtained in step 3 is aged at 460 ℃ for different times to obtain a peak-aged alloy.

[0048] As shown in the principle diagram shown in Figure 1 , the pre-deformation aging makes the alloy exist in the size range of the dislocation cutting-passage conversion radius of the precipitated phase, as shown in Figure 2 , the hardness curves of the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy cold-rolled by 0% (SS) and 20% (CR20) are aged at different temperatures for 3 h, and the peak-aged alloy is obtained at 510 ℃ and 480 ℃ respectively, and the average radius of the precipitated phase is 4.9 nm and 4.3 nm respectively. Figure 2 The results obtained by the conventional aging can accurately control the pre-aging temperature and time, and can conveniently regulate the interaction mode and proportion of dislocations and the primary precipitated phase during large shear deformation. Among them, the number of the second phase (or its nucleation point) can be directly amplified and the size can be greatly refined by means of dislocation cutting the primary second phase, and the shear deformation has the advantages of destroying the diffusion field of the primary second phase, accumulating a large number of dislocations as subsequent aging nucleation points, etc. Combined with the low-temperature aging process to further limit the element diffusion radius, the present application can improve the nucleation ability and precipitation degree of the second phase in the whole process and limit the coarsening of the second phase, realize the high level of high precipitation degree and fine precipitated phase size, effectively solve the serious problems such as the formation of excessive dislocations around the pre-cold deformation, the easy coarsening of the subsequent second phase and other serious problems caused by the high defect density or the coarse size of the second phase under the traditional cold deformation aging method, and synergistically improve the comprehensive performance such as strength, plasticity and conductivity of the aging strengthening alloy.

[0049] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A heat treatment method for improving precipitation degree and refining precipitated phase, characterized in that, Includes the following steps: Step 1: Cold roll or cold forge the solution-treated age-strengthened alloy with a deformation of 0-30%. Step 2: Determine the optimal aging temperature range, corresponding aging time, and critical average radius of the transformation of the precipitated phase by dislocation bypass-cut-through during deformation of the solid solution aged alloy. Determine the required aging time at a specific aging temperature based on 0.5-2 times the critical average radius. Then, perform pre-aging treatment on the solid solution aged alloy after cold rolling or cold forging in Step 1 to obtain a pre-aged sample. Step 3: Perform cold shear deformation on the pre-aged sample obtained in Step 2, with a deformation amount of 30-60%. Step 4: Based on the optimal aging temperature range of the solution-treated age-strengthened alloy, select a temperature range within 30% of the lower limit of this range to perform temperature aging treatment to the peak aging state.

2. The heat treatment method for improving precipitation degree and refining precipitated phase according to claim 1, characterized in that, The age-hardening alloys in step 1 include copper alloys, aluminum alloys, magnesium alloys, precipitation-hardening steels, titanium alloys, or nickel-based alloys.

3. The heat treatment method for improving precipitation degree and refining precipitated phase according to claim 1, characterized in that, The cold shearing deformation in step 3 includes asynchronous rolling, equal channel extrusion, or torsion. The direction of asynchronous rolling or equal channel extrusion is consistent with or perpendicular to the direction of cold rolling or cold forging in step 1, and the direction of torsion is perpendicular to the direction of cold rolling or cold forging in step 1.

4. The heat treatment method for improving precipitation degree and refining precipitated phase according to claim 1, characterized in that, Includes the following steps: Step 1: Cold roll the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy with a deformation of 20%. Step 2: The optimal aging temperature range for the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy was determined to be 450-540℃. The 20% cold-rolled alloy reached its peak aging state after aging at 480℃ for 3 hours, corresponding to a precipitate radius of 4.3nm. Based on the dislocation cut-through and Orowan bypass mechanism, the radius range of the dislocation cut-through-bypass transition to the precipitate during alloy deformation was determined to be 1.5nm. According to the precipitate coarsening theory, the required aging time at 480℃ is 8 minutes. The 20% cold-rolled Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy was pre-aged for 2 minutes, 5 minutes, 8 minutes, 18 minutes, and 35 minutes, respectively, resulting in precipitate sizes of 0.9nm, 1.3nm, 1.5nm, 2.0nm, and 2.4nm, respectively, thus obtaining the pre-aged alloy. Step 3: The pre-aged alloy obtained in Step 2 is subjected to asynchronous rolling with a deformation of 50% to obtain an asynchronous rolled alloy; Step 4: Based on the optimal aging temperature range of 450-540℃ for the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy determined in Step 2, the asynchronous rolled alloy obtained in Step 3 is subjected to aging treatment at 450℃ for different times until it reaches the peak aging state.

5. The heat treatment method for improving precipitation degree and refining precipitated phase according to claim 1, characterized in that, Includes the following steps: Step 1: Cold roll the Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy with a deformation of 0%. Step 2: The optimal aging temperature range for the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy was determined to be 450-540℃. The cold-rolled 0% alloy reached its peak aging state after aging at 510℃ for 3 hours, corresponding to a precipitate radius of 4.9nm. Based on the dislocation cut-through and Orowan bypass mechanism, the radius range of the dislocation cut-through-bypass transformation of the precipitate during alloy deformation was determined to be 1.5nm. According to the precipitate coarsening theory, the required aging time at 510℃ is 5min. The cold-rolled 0% Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy was subjected to pre-aging treatments of 0.6min, 2.6min, 5min, 17min, and 41min, respectively, corresponding to precipitate sizes of 0.75nm, 1.2nm, 1.5nm, 2.25nm, and 3.0nm, respectively, to obtain the pre-aged alloy. Step 3: Perform equal channel extrusion treatment on the pre-aged alloy obtained in Step 2, with a deformation amount of 60%, to obtain an equal channel extruded alloy; Step 4: Based on the optimal aging temperature range of 450-540℃ for the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy determined in Step 2, the isochannel extruded alloy obtained in Step 3 is subjected to aging treatment at 470℃ for different times until it reaches the peak aging state.

6. The heat treatment method for improving precipitation degree and refining precipitated phase according to claim 1, characterized in that, Includes the following steps: Step 1: Cold roll the Cu-2.69Ni-1.14Si-0.45Cr (at.%) alloy with a deformation of 30%. Step 2: The optimal aging temperature range for the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy was determined to be 450-540℃. The 30% cold-rolled alloy reached its peak aging state after aging at 480℃ for 3 hours, corresponding to a precipitate radius of 4.1 nm. Based on the dislocation cut-through and Orowan bypass mechanism, the radius range of the dislocation cut-through-bypass transformation of the precipitate during alloy deformation was determined to be 1.5 nm. According to the precipitate coarsening theory, the required aging time at 480℃ is 9 min. The 30% cold-rolled Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy was pre-aged for 1 min, 4.5 min, 9 min, 30 min, and 70 min, respectively, resulting in precipitate sizes of 0.75 nm, 1.2 nm, 1.5 nm, 2.25 nm, and 3.0 nm, respectively, thus obtaining the pre-aged alloy. Step 3: The pre-aged alloy obtained in Step 2 is subjected to torsion treatment with a deformation of 30% to obtain a torsion alloy; Step 4: Based on the optimal aging temperature range of 450-540℃ for the Cu-2.69Ni-1.14Si-0.45Cr(at.%) alloy determined in Step 2, the torsion alloy obtained in Step 3 is subjected to aging treatment at 460℃ for different times until it reaches the peak aging state.

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