A method and apparatus for preparing nanostructured magnesium alloy bulk materials

Abstract

This invention relates to a method and apparatus for preparing nanostructured magnesium alloy bulk materials. The technical solution utilizes a partially dense, semi-solid magnesium alloy bulk material. Under the influence of electrical pulses and pressure, the partially dense semi-solid magnesium alloy bulk material is repeatedly passed through a titanium mesh. Its internal microstructure is repeatedly cut, achieving nanostructuring. Finally, under specific temperature and pressure conditions, the magnesium alloy bulk material achieves complete densification. Its advantages are: 1. This invention achieves the construction of magnesium alloy bulk material from semi-solid to solid state, and from micron-scale to nanoscale microstructures; 2. The preparation of magnesium alloy bulk material in this invention does not require excessively heavy-duty equipment to achieve intense plastic deformation; 3. During the process, the magnesium alloy bulk material is maintained at a medium to low temperature, avoiding grain growth and improving preparation efficiency.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing nanostructured magnesium alloy bulk materials, belonging to the field of magnesium alloy component manufacturing technology. Background Technology

[0002] Grain refinement is currently the main known method for improving both strength and toughness. There are two main methods for preparing nanocrystals: top-down processes, which aim to refine the grains of conventionally structured materials; and bottom-up processes, which aim to synthesize fine grain structures at the atomic and molecular level. Common preparation methods include rapid solidification, vapor deposition, mechanical alloying, low-temperature metal forming, and intense plastic deformation, among which intense plastic deformation is considered the most suitable for industrial production. Compared to traditional plastic deformation processes, intense plastic deformation technology is designed to maintain the billet's shape essentially unchanged during deformation, thus achieving strain unaffected by the material's shape. Most intense plastic deformation processes are actually cyclic deformation processes, but there are usually changes in the deformation path. Summary of the Invention

[0003] The present invention addresses the aforementioned existing technical situation by providing a method and apparatus for preparing a nanostructured magnesium alloy bulk material. Its purpose is to prepare a magnesium alloy bulk material with a nanoscale microstructure by means of an electric pulse, a titanium mesh, temperature, and pressure, using a semi-solid magnesium alloy bulk material 7 that is not completely dense.

[0004] To achieve the above objectives, the technical solution of this invention is as follows:

[0005] The present invention proposes a method for preparing a nanostructured magnesium alloy bulk material. The method involves repeatedly passing a semi-solid magnesium alloy bulk 7, which is not fully dense, through a titanium mesh 4 under the action of electric pulses and pressure, so that its internal microstructure is repeatedly cut to achieve nano-scale structure. Finally, the magnesium alloy bulk 7 is made completely dense.

[0006] In practice, the titanium mesh 4 is a rigid mesh structure constructed by weaving titanium powder particles onto a substrate formed of iron powder particles. The thickness is 0.1 to 0.5 mm, and the pore size is 100 to 1000 nm.

[0007] In practice, the preparation process of the titanium mesh 4 is as follows: titanium sheets are prepared by 3D printing with a thickness of 0.1 to 0.3 mm. Then, regularly arranged holes are punched into the titanium sheets using a laser. The diameter of the holes is 0.01 to 0.05 mm, and the holes are spaced 0.01 to 0.03 mm apart in the X and Y directions. The above operation is repeated, and the titanium sheets are stacked together until the thickness reaches 1 to 3 mm. The hole depth is consistent with the thickness of the stacked titanium sheets.

[0008] In practice, the density of the partially dense semi-solid magnesium alloy block 7 is 85-90%.

[0009] During implementation, when the partially dense semi-solid magnesium alloy block 7 passes through the titanium mesh 4, the partially dense semi-solid magnesium alloy block 7 is heated to 500-700°C, and the titanium mesh 4 is heated to 200-500°C.

[0010] To achieve the method described in this invention, the technical solution of this invention also proposes an apparatus for preparing nanostructured magnesium alloy bulk materials. The apparatus includes an extrusion cylinder 1, with a titanium mesh 4 placed in the middle of the extrusion cylinder 1, dividing the extrusion cylinder 1 into left and right spaces. The titanium mesh 4 can rotate 10 to 90° along the central axis. A left pressure head 6 and a left pulse current generator 5 connected to the outside of the left side of the titanium mesh 4 are arranged in the left side space. A right pressure head 3 and a right pulse current generator 2 connected to the outside of the right side of the titanium mesh 4 are arranged in the right side space. Both the left pressure head 6 and the right pressure head 3 can move towards the titanium mesh 4 under pressure.

[0011] In practice, the steps for preparing nanostructured magnesium alloy bulk materials using this device are as follows:

[0012] Step 1: Pure -300 to -500 mesh magnesium alloy powder is subjected to hot isostatic pressing at 300 to 700°C. During the hot isostatic pressing process, the magnesium alloy powder is not completely densified by pressure control, and a semi-solid magnesium alloy block 7 with a density of 85 to 90% is obtained. The microstructure of the material of the semi-solid magnesium alloy block 7 has a micron scale.

[0013] Step 2: Start the left pulse current generator 5 and the right pulse current generator 2 to preheat the titanium mesh 4 and maintain it at 200-500℃;

[0014] Step 3: Preheat the partially dense semi-solid magnesium alloy block 7 to a temperature of 600-750℃. After preheating, place the semi-solid magnesium alloy block 7 into the left space of the extrusion cylinder 1. Drive the semi-solid magnesium alloy block 7 to the right with pressure from the left pressure head 6. The moving speed is 1-3 mm / s until the semi-solid magnesium alloy block 7 passes through the titanium mesh 4. At this time, the semi-solid magnesium alloy block 7 enters the right space of the extrusion cylinder 1. Rotate the titanium mesh 4 to the next angle, and then drive the semi-solid magnesium alloy block 7 to the left with pressure from the right pressure head 3. The moving speed is 1-3 mm / s until the semi-solid magnesium alloy block 7 passes through the titanium mesh 4. The whole process is completed within 1 minute.

[0015] Step 4: Repeat the process of Step 3 more than five times. Then, take out the gradually consumed titanium mesh 4 and use the left pressure head 6 and the right pressure head 3 to simultaneously press the semi-solid magnesium alloy block 7 in both directions to obtain a fully dense magnesium alloy block.

[0016] In addition, in step four, the pressing temperature of the left pressure head 6 and the right pressure head 3 is 400-500℃.

[0017] This invention provides a method for preparing nano-sized magnesium alloy bulk materials, which falls between existing top-down and bottom-up processes. The design concept of this method has not been reported domestically or internationally. The invention utilizes a partially dense, semi-solid magnesium alloy bulk material. Under the influence of electrical pulses and pressure, the partially dense semi-solid magnesium alloy bulk material is repeatedly passed through a titanium mesh. Its internal microstructure is repeatedly cut, achieving nano-sized structures. Finally, under specific temperature and pressure conditions, the magnesium alloy bulk material achieves complete densification.

[0018] The beneficial effects of the technical solution of this invention are mainly reflected in:

[0019] 1. Through the present invention, the construction of magnesium alloy bulk materials from semi-solid to solid, and from micron-scale to nano-scale microstructures is realized, and the nano-scale microstructures have dispersibility;

[0020] 2. In the present invention, the preparation of magnesium alloy bulk material does not require equipment with excessive tonnage to achieve severe plastic deformation. During the severe plastic deformation process, the titanium mesh plays a role in refining the microstructure. While cutting the not fully dense magnesium alloy bulk material, there are two refining mechanisms. One is mechanical crushing, where residual magnesium alloy powder particles exist in the not fully dense magnesium alloy bulk material. When passing through the titanium mesh, the residual magnesium alloy powder particles are cut off and nano-sized. The other is recrystallization, where the grain boundaries are reconstructed when the grains pass through the titanium mesh. Under the action of pulsed current, the grain boundaries that are forcibly cut are small-angle grain boundaries. After passing through the titanium mesh, recrystallization occurs rapidly, and no growth occurs at low temperature and in a short time.

[0021] 3. During the implementation of this invention, the magnesium alloy bulk material is kept at a medium to low temperature, which avoids grain growth and improves the preparation efficiency;

[0022] 4. In the present invention, the titanium mesh is not a single piece in the thickness direction, but rather several layers are stacked together. This design can significantly reduce the impact of magnesium alloy block material on the titanium mesh when it passes through, indirectly improving the rigidity of the titanium mesh and preventing it from aging prematurely. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the device described in the technical solution of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0025] See appendix Figure 1 As shown, the apparatus for preparing the nanostructured magnesium alloy bulk material of the present invention includes an extrusion cylinder 1, a titanium mesh 4 placed in the middle of the extrusion cylinder 1, dividing the extrusion cylinder 1 into left and right spaces. The titanium mesh 4 can rotate 10 to 90° along the central axis. A left pressure head 6 and a left pulse current generator 5 connected to the outside of it are arranged in the left space of the titanium mesh 4. A right pressure head 3 and a right pulse current generator 2 connected to the outside of it are arranged in the right space of the titanium mesh 4. Both the left pressure head 6 and the right pressure head 3 can move towards the titanium mesh 4 under pressure.

[0026] The steps for preparing nanostructured magnesium alloy bulk materials using this device are as follows:

[0027] Step 1: Pure -300 to -500 mesh magnesium alloy powder is subjected to hot isostatic pressing at 300 to 700°C. During the hot isostatic pressing process, the magnesium alloy powder is not completely densified by pressure control, and a semi-solid magnesium alloy block 7 with a density of 85 to 90% is obtained. The microstructure of the material of the semi-solid magnesium alloy block 7 has a micron scale.

[0028] Step 2: Start the left pulse current generator 5 and the right pulse current generator 2 to preheat the titanium mesh 4 and maintain it at 200-500℃;

[0029] Step 3: Preheat the partially dense semi-solid magnesium alloy block 7 to a temperature of 600-750℃. After preheating, place the semi-solid magnesium alloy block 7 into the left space of the extrusion cylinder 1. Drive the semi-solid magnesium alloy block 7 to the right with pressure from the left pressure head 6. The moving speed is 1-3 mm / s until the semi-solid magnesium alloy block 7 passes through the titanium mesh 4. At this time, the semi-solid magnesium alloy block 7 enters the right space of the extrusion cylinder 1. Rotate the titanium mesh 4 to the next angle, and then drive the semi-solid magnesium alloy block 7 to the left with pressure from the right pressure head 3. The moving speed is 1-3 mm / s until the semi-solid magnesium alloy block 7 passes through the titanium mesh 4. The whole process is completed within 1 minute.

[0030] Step 4: Repeat the process of Step 3 more than five times. Then, take out the titanium mesh 4 that has been gradually consumed. Use the left pressure head 6 and the right pressure head 3 to simultaneously press the semi-solid magnesium alloy block 7 in both directions. The pressing temperature of the left pressure head 6 and the right pressure head 3 is 400-500℃ to obtain a fully dense magnesium alloy block.

Claims

1. A method for preparing a nanostructured magnesium alloy bulk material, characterized in that, Pure -300 to -500 mesh magnesium alloy powder is subjected to hot isostatic pressing at 300 to 700°C. During the hot isostatic pressing process, the magnesium alloy powder is not completely densified by pressure control, and a semi-solid magnesium alloy block (7) with a density of 85 to 90% is obtained. The microstructure of the semi-solid magnesium alloy block (7) has a micron scale. The semi-solid magnesium alloy block (7) is repeatedly passed through a titanium mesh (4) under the action of pulse current and pressure, so that its internal microstructure is repeatedly cut to achieve nano-scale. Finally, the magnesium alloy block (7) is completely densified. When the semi-solid magnesium alloy block (7) is passed through the titanium mesh (4), the semi-solid magnesium alloy block (7) is heated to 500 to 700°C, and the titanium mesh (4) is heated to 200 to 500°C.

2. The method for preparing nanostructured magnesium alloy bulk material according to claim 1, characterized in that: The titanium mesh (4) is a rigid mesh structure constructed by weaving titanium powder particles on a substrate formed by iron powder particles. The thickness is 0.1 to 0.5 mm and the pore size is 100 to 1000 nm.

3. The method for preparing nanostructured magnesium alloy bulk material according to claim 1, characterized in that: The preparation process of the titanium mesh (4) is as follows: titanium sheets are prepared by 3D printing with a thickness of 0.1 to 0.15 mm. Then, regular holes are punched out on the titanium sheets using a laser. The diameter of the holes is 0.01 to 0.05 μm and the spacing between the holes in the X and Y directions is 0.01 to 0.03 mm. The above operation is repeated and the titanium sheets are stacked together until the thickness reaches 1 to 3 mm. The hole depth is consistent with the thickness of the stacked titanium sheets.

4. An apparatus for preparing the nanostructured magnesium alloy bulk material according to claim 1, characterized in that: The device includes an extrusion cylinder (1) with a titanium mesh (4) placed in the middle of the extrusion cylinder (1), dividing the extrusion cylinder (1) into left and right spaces. The titanium mesh (4) can rotate 10 to 90 degrees along the central axis. A left pressure head (6) and a left pulse current generator (5) connected to the outside of the titanium mesh (4) are arranged in the left space of the titanium mesh (4). A right pressure head (3) and a right pulse current generator (2) connected to the outside of the titanium mesh (4) are arranged in the right space of the titanium mesh (4). Both the left pressure head (6) and the right pressure head (3) can move towards the titanium mesh (4) under pressure.

5. The apparatus according to claim 4, characterized in that: The steps for preparing nanostructured magnesium alloy bulk materials using this device are as follows: Step 1: The pure -300 to -500 mesh magnesium alloy powder is subjected to hot isostatic pressing at 300 to 700°C. During the hot isostatic pressing process, the magnesium alloy powder is not completely densified by pressure control, and a semi-solid magnesium alloy block (7) with a density of 85 to 90% is obtained. The microstructure of the semi-solid magnesium alloy block (7) has a micron scale. Step 2: Start the left pulse current generator (5) and the right pulse current generator (2) to preheat the titanium mesh (4) and keep it at 200-500℃; Step 3: Preheat the partially dense semi-solid magnesium alloy block (7) to a temperature of 600-750°C. After preheating, place the semi-solid magnesium alloy block (7) into the left space of the extrusion cylinder (1) and drive the left pressure head (6) to move the semi-solid magnesium alloy block (7) to the right at a speed of 1-3 mm / s until the semi-solid magnesium alloy block (7) passes through the titanium mesh (4). At this time, the semi-solid magnesium alloy block (7) enters the right space of the extrusion cylinder (1). Rotate the titanium mesh (4) to the next angle and then drive the right pressure head (3) to move the semi-solid magnesium alloy block (7) to the left at a speed of 1-3 mm / s until the semi-solid magnesium alloy block (7) passes through the titanium mesh (4). The whole process is completed within 1 minute. Step 4: Repeat the process of step 3 more than five times, then take out the gradually consumed titanium mesh (4), and use the left pressure head (6) and the right pressure head (3) to simultaneously press the semi-solid magnesium alloy block (7) in both directions to obtain a fully dense magnesium alloy block.

6. The apparatus according to claim 5, characterized in that: In step four, the pressing temperature of the left pressure head (6) and the right pressure head (3) is 400-500℃.

Images