ZK60 magnesium alloy with heterostructure and preparation method thereof

Abstract

The invention relates to a ZK60 magnesium alloy with a heterostructure and a preparation method thereof, and the preparation method comprises the following steps: homogenization treatment: carrying out heat treatment on a ZK60 magnesium alloy cast ingot sample, then rapidly transferring the sample subjected to heat treatment into room-temperature water, and cooling to room temperature; the sample subjected to homogenization treatment is subjected to heat preservation in a heat treatment furnace, after the heat preservation time is over, the sample is taken out of the furnace to be subjected to hot extrusion, an extruded bar is obtained and then immediately cooled through water cooling, and the ZK60 magnesium alloy with the heterostructure is obtained; wherein the ZK60 magnesium alloy has fine equiaxed recrystallization crystal grains and coarse non-recrystallization crystal grains, the average size of the recrystallization crystal grains is 1-3 microns, the average size of the non-recrystallization crystal grains is 20-50 microns, the maximum tensile strength of the ZK60 magnesium alloy is 319 MPa, the maximum yield strength of the ZK60 magnesium alloy is 291 MPa, and the maximum percentage elongation after fracture of the ZK60 magnesium alloy is 21.7%. The organization structure of the ZK60 magnesium alloy is regulated and controlled through extrusion plastic processing, and the prepared heterostructure magnesium alloy has high strength and high plasticity.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy materials, and particularly to a ZK60 magnesium alloy with a heterogeneous structure and a preparation method thereof. Background Art

[0002] ZK60 magnesium alloy is a common Mg-Zn-Zr series alloy, and is widely used in the fields of aerospace, automotive industry, electronic equipment, etc. due to its excellent strength, plasticity and corrosion resistance.

[0003] However, traditional ZK60 magnesium alloys all show an obvious strength-plasticity inversion relationship, and it is difficult to achieve both high strength and high plasticity at the same time. In recent years, heterogeneous structure materials have received extensive attention due to their unique microstructure and excellent mechanical properties. By regulating the grain size and distribution, heterogeneous structure materials can achieve the synergistic improvement of strength and plasticity. Developing a ZK60 magnesium alloy with a heterogeneous structure has important scientific significance and application value. Therefore, the present invention aims to explore the optimal extrusion process parameters, improve the strength and plasticity of ZK60 magnesium alloy, and provide new ideas for the preparation of high-performance magnesium alloys. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the object of the present invention is to provide a ZK60 magnesium alloy with a heterogeneous structure and a preparation method thereof. Through this preparation method, the synergistic improvement of the strength and plasticity of ZK60 magnesium alloy can be realized under a simple process flow, and the obtained ZK60 magnesium alloy has excellent mechanical properties.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A preparation method of a ZK60 magnesium alloy with a heterogeneous structure, comprising the following steps: Homogenization treatment: performing heat treatment on a ZK60 magnesium alloy ingot sample, and then quickly transferring the heat-treated sample into room-temperature water and cooling it to room temperature; Hot extrusion: insulating the sample after homogenization treatment in a heat treatment furnace, and after the insulation time ends, taking out the sample from the furnace for hot extrusion, and immediately cooling the obtained extrusion bar by water cooling to obtain a ZK60 magnesium alloy with a heterogeneous structure; Among them, the ZK60 magnesium alloy has fine equiaxed recrystallized grains and coarse non-recrystallized grains. The average size of the recrystallized grains is 1-3 μm, and the average size of the non-recrystallized grains is 20-50 μm. The maximum tensile strength of the ZK60 magnesium alloy is 319 MPa, the maximum yield strength is 291 MPa, and the maximum elongation after fracture is 21.7%.

[0006] Further, the chemical composition of the ZK60 magnesium alloy ingot sample is by weight percentage: Zn 5.5 - 5.9%, Zr 0.5 - 0.9%, Mn ≤ 0.006%, Fe ≤ 0.004%, Si ≤ 0.003%, Cu ≤ 0.002%, Al ≤ 0.002%, and the balance is Mg and unavoidable impurities.

[0007] Further, the heat treatment includes placing the ZK60 magnesium alloy ingot sample in a heat treatment furnace and heating it to 400 °C for insulation for 12 h.

[0008] Further, during the heat treatment, the sample is heated in the furnace from room temperature to the predetermined homogenization temperature at a heating rate of 10 °C / min.

[0009] Further, the temperatures of the extrusion nozzle and the die are set to 200 °C and 170 °C respectively, and the extrusion nozzle is kept at the extrusion temperature for 0.5 - 1 h before extrusion.

[0010] Further, the extrusion ratio is 17.36:1.

[0011] Further, the extrusion speed is 0.5 mm / s - 3.0 mm / s.

[0012] Further, the quenching transfer time of the extruded bar is less than 20 s.

[0013] A ZK60 magnesium alloy with a heterogeneous structure is prepared by the above preparation method.

[0014] Generally speaking, the present invention has the following advantages: (1) Through the homogenization and hot extrusion processes, the present invention effectively improves the strength of the ZK60 magnesium alloy, while maintaining a high elongation after fracture, and the process flow is relatively simple. The ZK60 alloy does not contain rare earth elements, reducing the preparation cost of high-performance magnesium alloys.

[0015] (2) By regulating the microstructure of the ZK60 magnesium alloy through extrusion plastic processing, the prepared heterogeneous structure magnesium alloy has both fine recrystallized grains and coarse deformed grains, with high strength and high plasticity, further broadening the application prospects of the ZK60 magnesium alloy in the lightweight field. Description of the Drawings

[0016] Figure 1 is the OM metallographic diagram of the homogeneous ZK60 magnesium alloy; Figure 2 is the SEM scanning electron microscope diagram of the homogeneous ZK60 magnesium alloy; Figure 3 is the OM metallographic diagram of the heterogeneous structure ZK60 magnesium alloy prepared in Example 1; Figure 4SEM micrograph of the heterostructured ZK60 magnesium alloy prepared in Example 1; Figure 5 Engineering stress-strain curves of Example 1, Example 2, and Example 3. Detailed Description of the Invention

[0017] The present invention will be further described in detail below.

[0018] Example 1 This example discloses a method for preparing a high-performance continuously extruded ZK60 magnesium alloy material based on hot extrusion, including the following steps: (1) Homogenization treatment: Place the ZK60 magnesium alloy ingot in a heat treatment furnace and quickly heat it from room temperature to 400 °C at a heating rate of 10 °C / min. After holding for 12 h, then quickly transfer the heat-treated ingot into room-temperature water and cool it to room temperature. The cooling method is water quenching.

[0019] (2) Hot extrusion: Keep the sample after homogenization treatment in the heat treatment furnace. The heating rate in the furnace is 10 °C / min. Heat it to 200 °C and hold at this temperature for 60 min. At the same time, heat the extrusion nozzle and the die to 200 °C and 170 °C respectively and hold for 60 min. After the holding time ends, take out the sample from the furnace and immediately perform hot extrusion. The extrusion ratio is 17.36:1, and the extrusion speed is 0.5 mm / s. Obtain the final extruded bar with a diameter of 12 mm and immediately cool it with water cooling. The water cooling transfer time is less than 20 s.

[0020] The metallographic picture of the heterostructured ZK60 magnesium alloy material is as Figure 3 shown. It can be seen that there are fine equiaxed recrystallized grains and coarse non-recrystallized deformed grains. Its microstructural diagram is as shown in Figure 4 (a) and (b) in. It can be seen that there are granular second phases at the grain boundaries.

[0021] The surface of the prepared heterostructured ZK60 magnesium alloy bar has no obvious cracks. The mechanical properties of the material are tested, and the test results are as follows: the maximum yield strength is 291 MPa, the maximum tensile strength is 319 MPa, and the elongation after fracture is 21.7%.

[0022] Example 2 (1) Homogenization treatment: Place the ZK60 magnesium alloy ingot in a heat treatment furnace and quickly heat it from room temperature to 400 °C at a heating rate of 10 °C / min. After holding for 12 h, then quickly transfer the heat-treated ingot into room-temperature water and cool it to room temperature. The cooling method is water quenching.

[0023] (2)Hot extrusion: The homogenized sample is kept warm in a heat treatment furnace. The heating rate in the furnace is 10 °C / min. It is heated to 200 °C and kept warm at this temperature for 60 min. At the same time, the extrusion nozzle and the die are heated to 200 °C and 170 °C respectively and kept warm for 60 min. After the holding time ends, the sample is taken out of the furnace and immediately subjected to hot extrusion. The extrusion ratio is 17.36:1, and the extrusion speed is 2.0 mm / s. An extruded bar with a final diameter of 12 mm is obtained and immediately cooled by water cooling. The water cooling transfer time is less than 20 s.

[0024] The surface of the prepared heterogeneous structure ZK60 magnesium alloy bar has no obvious cracks. The mechanical properties of the material are tested, and the test results are as follows: The maximum yield strength is 245 MPa, the maximum tensile strength is 306 MPa, and the elongation after fracture is 20.8%.

[0025] Example 3 (1)Homogenization treatment: The ZK60 magnesium alloy ingot is placed in a heat treatment furnace and rapidly heated from room temperature to 400 °C at a heating rate of 10 °C / min, then kept warm for 12 h. Subsequently, the heat-treated ingot is quickly transferred into room-temperature water and cooled to room temperature. The cooling method is water quenching.

[0026] (2)Hot extrusion: The homogenized sample is kept warm in a heat treatment furnace. The heating rate in the furnace is 10 °C / min. It is heated to 200 °C and kept warm at this temperature for 60 min. At the same time, the extrusion nozzle and the die are heated to 200 °C and 170 °C respectively and kept warm for 60 min. After the holding time ends, the sample is taken out of the furnace and immediately subjected to hot extrusion. The extrusion ratio is 17.36:1, and the extrusion speed is 3.0 mm / s. An extruded bar with a final diameter of 12 mm is obtained and immediately cooled by water cooling. The water cooling transfer time is less than 20 s.

[0027] The surface of the prepared heterogeneous structure ZK60 magnesium alloy bar has no obvious cracks. The mechanical properties of the material are tested, and the test results are as follows: The maximum yield strength is 235 MPa, the maximum tensile strength is 309 MPa, and the elongation after fracture is 18.7%.

[0028] Table 1 Mechanical property test table of the alloy obtained in the examples of the present invention

[0029] As can be seen from Table 1, the heterogeneous structure ZK60 magnesium alloy material prepared in the examples of the present invention not only has high strength but also maintains good plasticity, further broadening the development prospects of ZK60 magnesium alloy in the lightweight field.

[0030] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of ZK60 magnesium alloy with a heterogeneous structure, characterized in that: It includes the following steps: Homogenization treatment: Heat-treat the ZK60 magnesium alloy ingot sample, and then quickly transfer the heat-treated sample into room-temperature water and cool it to room temperature; Hot extrusion: Keep the sample after homogenization treatment in a heat treatment furnace. After the holding time ends, take out the sample from the furnace for hot extrusion. Immediately cool the obtained extruded bar by water cooling to obtain a ZK60 magnesium alloy with a heterogeneous structure; Among them, the ZK60 magnesium alloy has fine equiaxed recrystallized grains and coarse non-recrystallized grains. The average size of the recrystallized grains is 1-3 μm, and the average size of the non-recrystallized grains is 20-50 μm. The maximum tensile strength of the ZK60 magnesium alloy is 319 MPa, the maximum yield strength is 291 MPa, and the maximum elongation after fracture is 21.7%.

2. The preparation method according to claim 1, characterized in that: The chemical composition of the ZK60 magnesium alloy ingot sample is by weight percentage: Zn 5.5-5.9%, Zr 0.5-0.9%, Mn≤0.006%, Fe≤0.004%, Si≤0.003%, Cu≤0.002%, Al≤0.002%, and the balance is Mg and unavoidable impurities.

3. The preparation method according to claim 1, characterized in that: The heat treatment includes placing the ZK60 magnesium alloy ingot sample in a heat treatment furnace and heating it to 400°C and holding for 12 h.

4. The preparation method according to claim 1, characterized in that: When performing the heat treatment, heat the sample from room temperature to the predetermined homogenization temperature at a heating rate of 10°C / min with the furnace.

5. The preparation method according to claim 1, characterized in that: The temperatures of the extrusion nozzle and the die are set to 200°C and 170°C respectively. The extrusion nozzle is held at the extrusion temperature for 0.5-1 h before extrusion.

6. The preparation method according to claim 1, characterized in that: The extrusion ratio is 17.36:

1.

7. The preparation method according to claim 1, characterized in that: The extrusion speed is 0.5 mm / s - 3.0 mm / s.

8. The preparation method according to claim 1, characterized in that: The quenching transfer time of the extruded bar is less than 20 s.

9. A ZK60 magnesium alloy with a heterogeneous structure, characterized in that: Prepared by the preparation method described in any one of claims 1-8.

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