Magnesium alloy sheet having gradient texture and method of manufacturing same, pre-compression die

Abstract

The application provides a magnesium alloy plate with gradient texture and a preparation method and a pre-compression mold thereof. The preparation method comprises the following steps: S1, uniformly treating an AZ31 magnesium alloy cylindrical ingot and then water quenching the ingot to room temperature, and then obtaining an AZ31 plate through extrusion; S2, cutting and processing the AZ31 plate into a to-be-compressed plate; S3, placing the to-be-compressed plate into the pre-compression mold for compression, and then annealing the to-be-compressed plate after compression, and water quenching the to-be-compressed plate to room temperature to obtain a magnesium alloy plate with gradient texture distribution. The application combines the size design of the compressed blank with the gradient structural design of the pre-compression mold, and constructs the gradient texture of the magnesium alloy plate in the thickness direction through the pre-compression combined with the annealing mode, so that the room temperature three-point bending forming capacity of the magnesium alloy plate is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of metal material modification technology, specifically to a magnesium alloy sheet with gradient texture, its preparation method, and a pre-compression mold. Background Technology

[0002] Magnesium alloys possess numerous advantages, including low density, high specific strength, good damping performance, and environmental friendliness, making them promising candidates for applications in the automotive, aerospace, rail transportation, military, and electronic communications industries. However, due to their close-packed hexagonal structure, magnesium alloys have few open slip systems at room temperature, resulting in poor room-temperature deformation capabilities. Furthermore, for wrought magnesium alloy sheets with promising applications, the initial forming process, such as hot extrusion or hot rolling, often results in a strong c-axis∥ND type basal texture, further limiting the deep processing or secondary forming capabilities of these sheets. The strong c-axis∥ND type basal texture of conventionally wrought magnesium alloy sheets typically cannot effectively coordinate the complex stress and strain on the inner and outer sides during secondary bending forming, leading to poor room-temperature bending forming performance.

[0003] Therefore, how to improve the room temperature deformation capacity and bending forming performance of magnesium alloys remains an urgent problem to be solved. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a magnesium alloy sheet with gradient texture, its preparation method, and a pre-compression mold, thus solving the problems mentioned in the background art.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] According to a first aspect of the present invention, a pre-compression mold is provided for constructing a gradient texture in a magnesium alloy sheet, comprising a lower mold and an upper mold, the lower mold comprising a left fixed plate and a right fixed plate, the inner side of the left fixed plate being provided with a first rectangular groove, the inner side of the right fixed plate being provided with a second rectangular groove, the length of the first rectangular groove being greater than the length of the second rectangular groove;

[0009] The upper mold includes a first pressing part and a second pressing part connected together, wherein the height of the first pressing part is less than the height of the second pressing part;

[0010] The first pressing part contacts the left fixing plate, and the second pressing part contacts the right fixing plate.

[0011] Preferably, the length, width, and height of the first rectangular groove are 65mm × 50mm × 5mm;

[0012] The length, width, and height of the second rectangular groove are 45mm × 50mm × 5mm.

[0013] Preferably, the length, width, and height of the first pressing part are 50mm × 5mm × 8mm;

[0014] The second clamping part has dimensions of 50mm × 5mm × 28mm.

[0015] Preferably, the materials of the lower mold and the upper mold are independently selected from No. 45 steel.

[0016] Preferably, the left and right fixing plates are provided with corresponding bolt holes on both sides.

[0017] According to a second aspect of the present invention, a method for preparing a magnesium alloy sheet with a gradient texture is provided, employing the aforementioned pre-compression mold, comprising the following steps:

[0018] S1. First, the AZ31 magnesium alloy cylindrical ingot is homogenized and then water-quenched to room temperature, and then AZ31 sheet is obtained by extrusion.

[0019] S2. The AZ31 sheet is cut into a sheet to be compressed. The sheet to be compressed includes a left sheet of 60mm×50mm×5mm and a right sheet of 20mm×50mm×5mm located in the middle of the left sheet. The left sheet and the right sheet are integrated.

[0020] S3. The sheet material to be compressed is placed in the pre-compression mold for compression, and then the compressed sheet material is annealed and water-quenched to room temperature to obtain a magnesium alloy sheet with a gradient texture distribution.

[0021] Preferably, in step S1, the homogenization treatment conditions are: temperature 400-500℃, time 8-12h;

[0022] The extrusion conditions are: extrusion at 380-400℃ and an extrusion speed of 1-5 mm / min.

[0023] Preferably, in step S3, the annealing conditions are as follows: the compressed sheet material to be compressed is wrapped with tin foil and annealed at 200-250°C for 10-15 hours.

[0024] Preferably, in step S3, the compression amount is 1.5 to 2 mm;

[0025] And / or, the compressive strain of the left plate is less than the compressive strain of the right plate.

[0026] According to a third aspect of the present invention, a magnesium alloy sheet is provided, which has a gradient texture, obtained by the above-described method for preparing a magnesium alloy sheet with a gradient texture.

[0027] (III) Beneficial Effects

[0028] This invention provides a magnesium alloy sheet with a gradient texture, its preparation method, and a pre-compression mold. It has the following beneficial effects:

[0029] 1. The method for preparing magnesium alloy sheet with gradient texture provided in this solution combines the size design of the compressed billet with the gradient structure design of the pre-compression mold, and constructs a gradient texture in the thickness direction of the magnesium alloy sheet by combining pre-compression with retraction, which significantly improves the room temperature three-point bending forming capability of the magnesium alloy sheet.

[0030] 2. The magnesium alloy sheet with gradient texture provided by this solution has a bimodal texture distributed along the extrusion direction in the outer region, which can activate basal slip to effectively coordinate tensile strain, and the inner region retains a typical c-axis∥ND type strong basal texture, which can activate tensile twins to effectively coordinate compressive strain. Attached Figure Description

[0031] Figure 1 A schematic diagram of the upper mold of the pre-compression mold provided by the present invention;

[0032] Figure 2 A schematic diagram of the lower mold of the pre-compression mold provided by the present invention;

[0033] Figure 3 An isometric side view of the sheet metal to be compressed provided by the present invention;

[0034] Figure 4 This is a schematic diagram of the gradient texture in the magnesium alloy sheet provided by the present invention;

[0035] Figure 5 This is a schematic diagram of the pre-compression deformation process of the magnesium alloy sheet in Example 3 of the present invention, provided by the present invention.

[0036] Figure 6 A schematic diagram comparing the microstructure of the magnesium alloy sheet in Example 3 of this invention, after initial AZ31 and partial pre-compression treatment, and its room temperature three-point bending forming capability.

[0037] In the figure, 1 is the lower mold; 2 is the upper mold; 3 is the bolt hole; 101 is the left fixing plate; 102 is the right fixing plate; 1011 is the first rectangular groove; 1021 is the second rectangular groove; 201 is the first pressing part; 202 is the second pressing part. Detailed Implementation

[0038] To better illustrate the content of this invention, the following description is provided in conjunction with specific embodiments.

[0039] Example 1

[0040] A pre-compression mold, combined with Figure 1 and Figure 2 As shown, the device includes a lower mold 1 and an upper mold 2, both made of 45# steel. The lower mold 1 includes a left fixed plate 101 and a right fixed plate 102. The inner side of the left fixed plate 101 has a first rectangular groove 1011, and the inner side of the right fixed plate 102 has a second rectangular groove 1021. The length of the first rectangular groove 1011 is greater than the length of the second rectangular groove 1021. The length, width, and height of the first rectangular groove are 65mm × 50mm × 5mm, and the length of the second rectangular groove is... The dimensions are 45mm×50mm×5mm; the upper mold 2 includes a first pressing part 201 and a second pressing part 202 connected together. The height of the first pressing part 201 is less than the height of the second pressing part 202. The length, width and height of the first pressing part 201 are 50mm×5mm×8mm, and the length, width and height of the second pressing part 202 are 50mm×5mm×28mm. The first pressing part 201 is in contact with the left fixing plate 101, and the second pressing part 202 is in contact with the right fixing plate 102.

[0041] The left fixing plate 101 and the right fixing plate 102 are provided with corresponding bolt holes 3 on both sides, and the bolts are passed through the bolt holes 3 to fix the left fixing plate 101 and the right fixing plate 102.

[0042] Example 2

[0043] A method for preparing magnesium alloy sheet with gradient texture, using a pre-compression mold, includes the following steps:

[0044] Step 1: The commercially available as-cast AZ31 magnesium alloy cylindrical ingot with a diameter of 80mm and a length of 60mm is homogenized at 400℃ for 8 hours, water-quenched to room temperature, and then extruded at 380℃ at an extrusion speed of 1mm / min into a plate with a thickness of 10mm and a width of 56mm.

[0045] Step Two: The sheet material prepared in Step One is then cut using wire electrical discharge machining to obtain the sheet material to be compressed. The sheet material to be compressed is as follows: Figure 3 As shown, it includes a left panel measuring 60mm×50mm×5mm and a right panel measuring 20mm×50mm×5mm located in the middle of the left panel, and the left panel and the right panel are integrated.

[0046] Step 3: Lubricate the left and right fixing plates and the upper mold of the compression mold with an oil bath. Fix the sheet material to be compressed in the cavity formed by the upper and lower molds. Compress the upper mold by 1.5 mm using a universal testing machine, taking the elastic strain as 0.5%. The effective compressive strain of the left side of the sheet material to be compressed is 2.0%, and the effective compressive strain of the right side is 7.0%. Then wrap the sheet material to be compressed with tin foil and anneal it at 200℃ for 10 hours. After water quenching to room temperature, a magnesium alloy sheet with a gradient texture distribution is obtained, such as... Figure 4 As shown, the number of {10-12} tensile twins on both sides of the magnesium alloy sheet is significantly different, and the texture types on both sides show significant differences after annealing. Specifically, the left sheet has a typical c-axis∥ND type strong basal surface texture, while the right sheet has a bimodal texture type distributed in the extrusion direction. This can activate basal surface slip to effectively coordinate tensile strain, resulting in a gradient texture distribution in the thickness direction of the magnesium alloy sheet, which has excellent room temperature three-point bending forming performance.

[0047] Example 3

[0048] The difference between this embodiment and embodiment 2 is that in step 3, a universal testing machine is used to compress the upper mold by 3mm.

[0049] The magnesium alloy sheet from step 3 was tested using simulation software, specifically Deform-3D. Figure 5 The deformation process of the above-mentioned local pre-compression is presented. Comparing the initial state and the state after compression of 3 mm, it can be seen that although there is a local stress concentration phenomenon in the distribution of effective stress, the distribution of effective strain and rate during local pre-compression is relatively uniform, which indicates that the gradient structure obtained by the local pre-compression process is guaranteed in terms of uniformity.

[0050] according to Figure 6 As shown, the initial AZ31 has a typical strong basal texture, with extremely poor three-point bending ability at room temperature. Microcracks appear on the outer side, which is attributed to the fact that the grains of the basal texture cannot effectively coordinate the tensile strain in the thickness direction under the tensile strain environment on the outer side.

[0051] The specimens after local pre-compression exhibit a distinct gradient texture distribution. One side retains the typical strong basal surface texture, while the other side evolves into a bimodal type dispersed along the compression direction. Ultimately, under the same room temperature three-point bending forming environment, perfect forming can be achieved, with no obvious cracks appearing on either the inner or outer side. This gradient texture effectively caters to the strain environment of internal compression and external tension during bending, significantly improving the strain coordination between the inner and outer sides.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a magnesium alloy sheet with a gradient texture, characterized in that: S1. First, the AZ31 magnesium alloy cylindrical ingot is homogenized and then water-quenched to room temperature, and then AZ31 sheet is obtained by extrusion. S2. The AZ31 sheet is cut into a sheet to be compressed. The sheet to be compressed includes a left sheet of 60mm×50mm×5mm and a right sheet of 20mm×50mm×5mm located in the middle of the left sheet. The left sheet and the right sheet are integrated. S3. The sheet material to be compressed is placed in a pre-compression mold for compression, and then the compressed sheet material is annealed and water-quenched to room temperature to obtain a magnesium alloy sheet material with a gradient texture distribution. The pre-compression mold includes a lower mold and an upper mold. The lower mold includes a left fixed plate and a right fixed plate. The inner side of the left fixed plate is provided with a first rectangular groove, and the inner side of the right fixed plate is provided with a second rectangular groove. The length of the first rectangular groove is greater than the length of the second rectangular groove. The upper mold includes a first pressing part and a second pressing part connected together, wherein the height of the first pressing part is less than the height of the second pressing part; The first pressing part contacts the left fixing plate, and the second pressing part contacts the right fixing plate; The annealing conditions are as follows: the compressed sheet material is wrapped in tin foil and annealed at 200~250℃ for 10~15h. The compressive strain of the left plate is less than that of the right plate; In step S3, the compression amount is 1.5~2mm.

2. The method for preparing magnesium alloy sheet with gradient texture according to claim 1, characterized in that: The first rectangular groove has dimensions of 65mm × 50mm × 5mm. The length, width, and height of the second rectangular groove are 45 mm × 50 mm × 5 mm.

3. The method for preparing magnesium alloy sheet with gradient texture according to claim 1, characterized in that: The length, width, and height of the first clamping part are 50mm × 5mm × 8mm; The second clamping part has dimensions of 50mm × 5mm × 28mm.

4. The method for preparing magnesium alloy sheet with gradient texture according to claim 1, characterized in that: The materials of the lower mold and the upper mold are independently selected from No. 45 steel.

5. The method for preparing magnesium alloy sheet with gradient texture according to claim 1, characterized in that: The left and right fixing plates are provided with corresponding bolt holes on both sides.

6. The method for preparing magnesium alloy sheet with gradient texture according to claim 1, characterized in that: In step S1, the homogenization treatment conditions are: temperature 400~500℃, time 8~12h; The extrusion conditions are: extrusion at 380~400℃ and an extrusion speed of 1~5 mm / min.

7. A magnesium alloy sheet obtained by the method for preparing a magnesium alloy sheet with a gradient texture according to any one of claims 1 to 6, characterized in that, The magnesium alloy sheet has a gradient texture.

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