Method for improving strength of AZ-series magnesium alloy through three-dimensional continuous precipitated phase

Abstract

The invention discloses a method for improving the strength of an AZ-series magnesium alloy through a three-dimensional continuous precipitated phase. The method comprises the steps that S1, solution treatment is conducted, specifically, solution treatment is conducted on an AZ-series magnesium alloy extruded plate / rolled plate; s2, primary deformation-aging: loading the magnesium alloy treated in the step S1 along an ED direction or an RD direction, introducing # imgabs0 # stretching twin crystal, inducing magnesium alloy grains to generate full twinning in the ED direction or the RD direction, and then performing primary artificial aging treatment on a twinning sample; s3, secondary deformation-aging: carrying out compression deformation on the magnesium alloy in the TD direction, and carrying out secondary artificial aging treatment; and S4, third-time deformation-aging: carrying out compression deformation on the magnesium alloy in the ND direction, and carrying out third-time artificial aging treatment. The technological process is easy to operate and low in cost, the strength improvement effect on the magnesium alloy is remarkable, the plasticity of the magnesium alloy is synchronously improved, and the application potential of the AZ-series magnesium alloy is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy materials, and in particular to a method for improving the strength of AZ series magnesium alloys through three-dimensional continuous precipitation phases. Background Art

[0002] Magnesium and magnesium alloys are one of the lightest metal structural materials currently used in industrial applications. They have the advantages of low density, good specific elastic modulus, good polishing performance, shock absorption performance, cutting performance, etc. They play an important role in industrial production and are known as "green engineering materials of the 21st century". AZ series magnesium alloys are highly favored among many magnesium alloys due to their low cost, aging hardening, mature preparation process and good comprehensive mechanical properties. However, the poor aging hardening efficiency of AZ series magnesium alloys has seriously hindered their application in aerospace, automotive, military and other fields with high strength requirements.

[0003] The aging strengthening efficiency of the alloy is closely related to its precipitation behavior. The precipitation phase of AZ magnesium alloy is Mg 17 Al 12 , which presents two competing growth mechanisms: continuous precipitation phase (CP) and discontinuous precipitation phase (DP). The CP phase precipitates in the form of laths and particles within the crystal, which can produce an ideal strengthening effect. The DP phase is Mg 17 Al 12 As a result of the cellular growth of the phase alternation layer at the high-angle grain boundary, the coarse discontinuous precipitation phase may induce cracks and reduce the strength and ductility. Therefore, promoting the precipitation of CP phase while inhibiting the growth of DP phase is one of the ways to improve the strengthening efficiency of Mg-Al alloy. 17 Al 12 The phase mainly precipitates along the basal plane of the matrix. The basal plane precipitation phase is difficult to significantly hinder the most common basal plane slip of magnesium alloys, resulting in a relatively low aging strengthening efficiency of Mg-Al alloys. Studies have shown that the cylindrical lamellar phase can effectively pin the basal plane slip, and the basal plane lamellar phase can effectively pin the cylindrical plane slip. If the advantages of the cylindrical precipitated phase and the basal plane precipitated phase can be combined to prepare a three-dimensional precipitation structure, various slip systems in the magnesium alloy can be suppressed at the same time, providing more effective barriers for different tensile twin variants, thereby maximizing the aging strengthening effect.

[0004] Therefore, how to improve the strength of AZ magnesium alloys under the premise of economy and environmental protection is of great significance for expanding its application. Summary of the invention

[0005] The purpose of the present invention is to provide a method for improving the strength of AZ series magnesium alloys by three-dimensional continuous precipitation phases in order to solve the problem of insufficient strength of the alloy system in application fields.

[0006] In order to achieve its purpose, the present invention adopts the following technical solution:

[0007] A method for improving the strength of AZ series magnesium alloy by three-dimensional continuous precipitation phase comprises the following steps:

[0008] S1. Solution treatment: subjecting the AZ series magnesium alloy extruded sheet / rolled sheet to solution treatment at 400-450°C for 2-10 hours, and then subjecting it to quenching treatment;

[0009] S2, primary deformation-aging: The magnesium alloy treated in step S1 is loaded along the ED direction (for extruded plates) or the RD direction (for rolled plates) to introduce Tensile twinning, inducing full twinning of magnesium alloy grains in the ED direction or RD direction, and then the twinned samples are subjected to the first artificial aging treatment;

[0010] S3, secondary deformation-aging: the magnesium alloy that has completed the first deformation-aging treatment is compressed and deformed along the TD direction to induce full twinning of the magnesium alloy grains in the TD direction, and then a second artificial aging treatment is performed;

[0011] S4, three-stage deformation-aging: the magnesium alloy that has completed the second deformation-aging treatment is compressed and deformed along the ND direction to induce full twinning of the magnesium alloy grains in the ND direction, and then the third artificial aging treatment is performed;

[0012] The artificial aging temperature in steps S2, S3 and S4 is 170-210°C, and the aging time is 1-10 hours.

[0013] The compression deformation in steps S2, S3 and S4 is 8% to 14% and the strain rate is 0.001 to 0.1s -1 ;

[0014] After the artificial aging treatment in steps S2, S3 and S4 is completed, air cooling is performed.

[0015] Preferably, the AZ series deformable magnesium alloy comprises the following components in percentage by mass: aluminum: 6%-9.5%, zinc: 0.3%-0.9%, manganese: 0.05-0.25%, and the remainder is magnesium and unremovable impurity elements.

[0016] Preferably, the AZ series deformable magnesium alloy is a hot extruded AZ80 magnesium alloy.

[0017] Preferably, after the solution treatment in step S1 is completed, rapid quenching is performed by water cooling at room temperature.

[0018] Preferably, in step S1, the solution treatment temperature is 420-450° C. and the treatment time is 2-8 h; preferably, the solution treatment temperature is 430-440° C. and the treatment time is 2-5 h or 2-3 h.

[0019] Preferably, the artificial aging temperature in steps S2, S3 and S4 is 180-210°C, and the aging time is 1-5 hours; preferably, the artificial aging temperature is 190-210°C, and the aging time is 1-3 hours.

[0020] The first artificial aging treatment in step S2 promotes the precipitation of the CP phase to form a primary precipitation phase.

[0021] The second artificial aging treatment in step S3 promotes the precipitation of the CP phase, forming a secondary precipitated phase having a different orientation from the primary precipitated phase.

[0022] The third aging treatment in step S4 promotes the precipitation of the CP phase, forming a tertiary precipitation phase with different orientations from the first two precipitation phases, and obtaining a three-dimensional CP phase precipitation structure.

[0023] The purpose of the room temperature compression deformation in step S2 is to introduce Tensile twinning causes full twinning of the grains, thereby inducing full twinning of the magnesium alloy in the ED direction. After deflection, an aging process is performed to promote the precipitation of the CP phase to form a primary precipitate phase. The purpose of the room temperature compression deformation in step S3 is to induce a second complete deflection of the orientation of the magnesium alloy, induce full twinning of the magnesium alloy in the TD direction, and perform a second aging process after deflection to promote the precipitation of the CP phase, forming a secondary precipitate phase with a different orientation from the primary precipitate phase. The purpose of the room temperature compression deformation in step S4 is to induce a third complete deflection of the orientation of the magnesium alloy, induce full twinning of the magnesium alloy in the ND direction, and perform a third aging process after deflection to promote the precipitation of the CP phase, forming a tertiary precipitate phase with a different orientation from the first two precipitates.

[0024] The present invention utilizes The high-density dislocations within the tensile twins promote the precipitation of the CP phase. At the same time, the tensile twins are continuously used to adjust the matrix orientation during the aging process, which can induce the phase to continuously transform and precipitate in different three-dimensional spaces to obtain a three-dimensional CP phase precipitation structure, further improving its strengthening efficiency.

[0025] The beneficial effects of the present invention are:

[0026] (1) The method of the present invention can utilize the high density dislocations in the tensile twins to promote the precipitation of the CP phase and inhibit the growth of the DP phase, thereby preventing the coarse DP phase from inducing cracks and reducing the strength and ductility.

[0027] (2) The method of the present invention can enable AZ series magnesium alloy to continuously adjust the matrix orientation by using tensile twins during the aging process, and induce the precipitation phase to continuously transform and precipitate in different three-dimensional spaces to obtain a three-dimensional precipitation structure. It can inhibit various slip systems in magnesium alloys and provide more effective barriers for different tensile twin variants, thereby maximizing the aging strengthening effect and providing theoretical value for the preparation of high-strength magnesium alloys.

[0028] (3) The multi-pass twinning-aging method provided by the present invention is simple to operate, low in cost, and has a significant effect on improving the strength of magnesium alloys, greatly improving the application potential of AZ series magnesium alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a microscopic morphology of the magnesium alloy precipitation phase of Example 1.

[0030] Figure 2 This is the microscopic morphology of the magnesium alloy precipitation phase of Comparative Example 4.

[0031] Figure 3 2 is a room temperature stress-strain curve diagram (compression) of the embodiments of the present invention and the comparative example. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited thereto.

[0033] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0034] The magnesium alloy in each embodiment of the present invention is a hot extruded AZ80 magnesium alloy sheet (commercially available), and its chemical composition is (wt.%): aluminum: 6%-9.5%, zinc: 0.3%-0.9%, manganese: 0.05-0.25%, and the remainder is magnesium and unremovable impurity elements.

[0035] In the embodiment of the present invention, the length direction of the plate is the extrusion direction ED, the width direction is the transverse direction TD, and the thickness direction of the plate is the normal direction ND.

[0036] Example 1: Method of improving the strength of AZ-based magnesium alloys by three-dimensional continuous precipitation phase of the present invention

[0037] Follow these steps:

[0038] S1. Solution treatment: The AZ80 magnesium alloy sheet was solution treated at 435°C for 2 h and then quenched to room temperature.

[0039] S2, primary deformation-aging: After solution treatment, the magnesium alloy is subjected to 8% full twinning compression deformation along the ED direction at room temperature, thereby inducing full twinning of the magnesium alloy grains in the ED direction. The strain rate is 0.001s -1 After the grain orientation is deflected, artificial aging is performed at 200°C for 1 h to promote the precipitation of the CP phase and form a primary CP phase. After the aging treatment, air cooling is performed.

[0040] S3, secondary deformation-aging: then compress and deform 8% along the TD direction, strain rate 0.001s -1, inducing full twinning of magnesium alloy grains in the TD direction, and performing secondary artificial aging after deflection to promote the precipitation of CP phase, forming a secondary precipitation phase with a different orientation from the primary precipitation phase. The artificial aging temperature is 200℃, and the aging time is 1h. After the aging treatment is completed, air cooling is performed.

[0041] S4, three deformation-aging: compress and deform 8% along the ND direction, strain rate 0.001s -1 , inducing full twinning of magnesium alloy in ND direction, and then performing artificial aging three times after deflection to form a tertiary precipitation phase with different orientations from the first two precipitation phases, thereby preparing a three-dimensional CP phase precipitation structure. The artificial aging temperature is 200℃ and the aging time is 1h. After the aging treatment is completed, air cooling is performed.

[0042] Example 2: Method of improving the strength of AZ-based magnesium alloys by three-dimensional continuous precipitation phase of the present invention

[0043] Follow these steps:

[0044] S1. Solution treatment: The AZ80 magnesium alloy sheet was solution treated at 435°C for 2 h and then quenched to room temperature.

[0045] S2, primary deformation-aging: After solution treatment, the magnesium alloy is subjected to 11% full twinning compression deformation along the ED direction at room temperature, thereby inducing full twinning of the magnesium alloy grains in the ED direction. The strain rate is 0.001s -1 After the grain orientation is deflected, artificial aging is performed at 200°C for 1 h to promote the precipitation of the CP phase and form a primary CP phase. After the aging treatment, air cooling is performed.

[0046] S3, secondary deformation-aging: then compress and deform by 11% along the TD direction, with a strain rate of 0.001s -1 , inducing full twinning of magnesium alloy grains in the TD direction, and performing secondary artificial aging after deflection to promote the precipitation of CP phase, forming a secondary precipitation phase with a different orientation from the primary precipitation phase. The artificial aging temperature is 200℃, and the aging time is 1h. After the aging treatment is completed, air cooling is performed.

[0047] S4, three deformation-aging: compression deformation along ND direction 11%, strain rate 0.001s -1 , inducing full twinning of magnesium alloy in ND direction, and then performing artificial aging three times after deflection to form a tertiary precipitation phase with different orientations from the first two precipitation phases, thereby preparing a three-dimensional CP phase precipitation structure. The artificial aging temperature is 200℃ and the aging time is 1h. After the aging treatment is completed, air cooling is performed.

[0048] Example 3: Method of improving the strength of AZ-based magnesium alloys by three-dimensional continuous precipitation phase of the present invention

[0049] Follow these steps:

[0050] S1. Solution treatment: The AZ80 magnesium alloy sheet was solution treated at 435°C for 2 h and then quenched to room temperature.

[0051] S2, primary deformation-aging: After solution treatment, the magnesium alloy is subjected to 14% full twinning compression deformation along the ED direction at room temperature, thereby inducing full twinning of the magnesium alloy grains in the ED direction. The strain rate is 0.001s -1 After the grain orientation is deflected, artificial aging is performed at 200°C for 1 h to promote the precipitation of the CP phase and form a primary CP phase. After the aging treatment, air cooling is performed.

[0052] S3, secondary deformation-aging: then compress and deform by 14% along the TD direction, with a strain rate of 0.001s -1 , inducing full twinning of magnesium alloy grains in the TD direction, and performing secondary artificial aging after deflection to promote the precipitation of CP phase, forming a secondary precipitation phase with a different orientation from the primary precipitation phase. The artificial aging temperature is 200℃, and the aging time is 1h. After the aging treatment is completed, air cooling is performed.

[0053] S4, three deformation-aging: compress and deform 10% along the ND direction, strain rate 0.001s -1 , inducing full twinning of magnesium alloy in ND direction, and then performing artificial aging three times after deflection to form a tertiary precipitation phase with different orientations from the first two precipitation phases, thereby preparing a three-dimensional CP phase precipitation structure. The artificial aging temperature is 200℃ and the aging time is 1h. After the aging treatment is completed, air cooling is performed.

[0054] Comparative Example 1

[0055] The magnesium alloy sheet was solution treated at 435°C for 2 hours and then quenched to room temperature. After solution treatment, the magnesium alloy was subjected to 8% plastic compression deformation along the ED direction at room temperature with a strain rate of 0.001s -1 , and aged at 200℃ for 1h, and air-cooled. Then the compression deformation was 8% along the TD direction, and the strain rate was 0.001s -1 , and carry out secondary artificial aging, the aging temperature is 200℃, and the aging time is 1h.

[0056] Comparative Example 2

[0057] The magnesium alloy sheet was solution treated at 435°C for 2 hours and then quenched to room temperature. After solution treatment, the magnesium alloy was subjected to 11% plastic compression deformation along the ED direction at room temperature with a strain rate of 0.001s -1 , and aged at 200℃ for 1h, and air cooled. Then the compression deformation was 11% along the TD direction, and the strain rate was 0.001s -1 , and carry out secondary artificial aging, the aging temperature is 200℃, and the aging time is 1h.

[0058] Comparative Example 3

[0059] The magnesium alloy sheet was solution treated at 435°C for 2 hours and then quenched to room temperature. After solution treatment, the magnesium alloy was subjected to 14% plastic compression deformation along the ED direction at room temperature with a strain rate of 0.001s -1 , and aged at 200℃ for 1h, and air cooled. Then the compression deformation was 14% along the TD direction, and the strain rate was 0.001s -1 , and carry out secondary artificial aging, the aging temperature is 200℃, and the aging time is 1h.

[0060] Comparative Example 4

[0061] The magnesium alloy sheet was solution treated at 435℃ for 2h and then quenched to room temperature. The peak aging treatment was performed at 200℃ and the peak aging time was 18h.

[0062] The main process differences between Examples 1-3 and Comparative Examples 1-4 are summarized in Table 1:

[0063] Table 1 Process parameters of examples and comparative examples

[0064]

[0065] The magnesium alloys prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to room temperature compression mechanical property tests along the ED direction. The mechanical property curves are shown in FIG. Figure 3 The microscopic morphology of the magnesium alloy precipitation phase of Example 1 is shown in Figure 1 The microscopic morphology of the magnesium alloy precipitation phase of Comparative Example 4 is shown in Figure 2 The mechanical properties of the products are shown in Table 2.

[0066] Table 2 Mechanical properties test results of magnesium alloys prepared in the examples and comparative examples

[0067] Example Yield strength / MPa Compressive strength / MPa Elongation / % Example 1 273 609 11.4 Example 2 269 573 12.3 Example 3 278 590 13.3 Comparative Example 1 186 556 10.3 Comparative Example 2 168 521 9.1 Comparative Example 3 177 540 10.3 Comparative Example 4 213 524 10.0

[0068] The test results in Table 2 show that compared with conventional solid solution peak aging (Comparative Example 4) and two-pass full twinning-aging (Comparative Examples 1-3), the multi-pass twinning-aging method provided by the present invention not only effectively improves the strength of AZ series magnesium alloys, but also improves their elongation. The strength and plasticity of AZ series magnesium alloys are simultaneously improved. Figure 1 and Figure 2 It can be seen from the comparison that this method can promote the precipitation of CP phase and obviously inhibit the precipitation and growth of DP phase.

[0069] In summary, the present invention utilizes the high-density dislocations in the tensile twins to promote the precipitation of the CP phase and inhibit the growth of the DP phase. Avoid the coarse DP phase from inducing cracks and reducing strength and ductility. During the aging process, the tensile twins are continuously utilized to adjust the matrix orientation, inducing the precipitated phase to continuously transform and precipitate in different three-dimensional spaces to obtain a three-dimensional precipitation structure. Various types of slip systems in magnesium alloys are inhibited, providing more effective barriers for different tensile twin variants, thereby maximizing the aging strengthening effect. The multi-pass twinning-aging method provided is simple to operate and low in cost, and has a significant effect on improving the strength and plasticity of magnesium alloys. The application potential of AZ series magnesium alloys has been greatly improved.

Claims

1. A method for improving the strength of AZ-based magnesium alloys by three-dimensional continuous precipitation phase, characterized in that: The steps include: S1. Solution treatment: subjecting the AZ series magnesium alloy extruded sheet / rolled sheet to solution treatment at 400-450°C for 2-10 hours, and then subjecting it to quenching treatment; S2, primary deformation-aging: The magnesium alloy treated in step S1 is loaded along the ED direction (extruded sheet) or RD direction (rolled sheet) to introduce Tensile twinning, inducing full twinning of magnesium alloy grains in the ED direction (extruded sheet) or RD direction (rolled sheet), and then the twinned samples are subjected to the first artificial aging treatment; S3, secondary deformation-aging: the magnesium alloy that has completed the first deformation-aging treatment is compressed and deformed along the TD direction to induce full twinning of the magnesium alloy grains in the TD direction, and then a second artificial aging treatment is performed; S4, three-stage deformation-aging: the magnesium alloy that has completed the second deformation-aging treatment is compressed and deformed along the ND direction to induce full twinning of the magnesium alloy grains in the ND direction, and then the third artificial aging treatment is performed; The artificial aging temperature in steps S2, S3 and S4 is 170-210°C, and the aging time is 1-10 hours.

2. The method according to claim 1, characterized in that: The compression deformation in steps S2, S3 and S4 is 8% to 14% and the strain rate is 0.001 to 0.1s -1 ; After the artificial aging treatment in steps S2, S3 and S4 is completed, air cooling is performed.

3. The method according to claim 1, characterized in that: The AZ series deformable magnesium alloy includes the following components in percentage by mass: aluminum: 6%-9.5%, zinc: 0.3%-0.9%, manganese: 0.05-0.25%, and the remainder is magnesium and impurity elements that cannot be removed.

4. The method according to claim 3, characterized in that: The AZ series deformable magnesium alloy is a hot extruded AZ80 magnesium alloy.

5. The method according to claim 1, characterized in that: After the solution treatment in step S1 is completed, rapid quenching is performed by water cooling at room temperature.

6. The method according to claim 1, characterized in that: In step S1, the solution treatment temperature is 420-450° C. and the treatment time is 2-8 h; preferably, the solution treatment temperature is 430-440° C. and the treatment time is 2-5 h or 2-3 h.

7. The method according to claim 1, characterized in that: The artificial aging temperature in steps S2, S3 and S4 is 180-210°C, and the aging time is 1-5 hours; preferably, the artificial aging temperature is 190-210°C, and the aging time is 1-3 hours.

8. The method according to claim 1, characterized in that: The first artificial aging treatment in step S2 promotes the precipitation of the CP phase to form a primary precipitation phase.

9. The method according to claim 1, characterized in that: The second artificial aging treatment in step S3 promotes the precipitation of the CP phase, forming a secondary precipitated phase having a different orientation from the primary precipitated phase.

10. The method according to claim 1, characterized in that: The third aging treatment in step S4 promotes the precipitation of the CP phase, forming a tertiary precipitation phase with different orientations from the first two precipitation phases, and obtaining a three-dimensional CP phase precipitation structure.

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