A method for solid-phase regeneration to prepare a high-strength and high-toughness magnesium alloy with LPSO structure

Abstract

The present invention discloses a method for preparing a high-strength and high-toughness magnesium alloy with an LPSO structure by solid-phase recycling. Using magnesium alloy scraps Mg-9Gd-0.5Zr and ZK60 generated in industrial production, through the steps of turning-milling and mixing chips-spark plasma sintering-extrusion into plates, a high-strength and high-toughness solid-phase recycled magnesium alloy with an LPSO structure is prepared by the solid-phase recycling method; under the process conditions of the present invention, the high-strength and heat-resistant magnesium alloy contains elements such as Gd and Zn, and long-period stacking order phases (abbreviated as LPSO) will be formed in the alloy, thereby improving the strength and toughness of the alloy; the ZK60 alloy also contains the element Zr, which can further improve the solid solution strengthening and age hardening of the alloy while refining the alloy grains, and further improve the mechanical properties of the alloy at room temperature and high temperature.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of magnesium alloy materials, and particularly relates to a method for preparing a high-strength and high-toughness magnesium alloy with an LPSO structure by solid-phase recycling. Background Art

[0002] In recent years, problems such as global environmental pollution and energy shortage have become increasingly prominent. In order to achieve energy conservation and emission reduction, many new lightweight structural materials have been applied to industrial production, especially in the fields of aerospace, transportation, etc., where lightweight structural materials are more widely used. Magnesium and magnesium alloys, with their abundant reserves, high specific strength, environmental friendliness and easy recyclability, are widely used in various industrial fields, becoming important structural engineering materials in industrial production, and having important application value and broad application prospects.

[0003] With the continuous improvement of the application technology of magnesium alloys, the consumption of magnesium and magnesium alloys in various industries is increasing day by day. The recycling and utilization of waste magnesium and waste magnesium alloys have created a huge demand space, which is of great significance for the recycling of magnesium alloys and has become an outstanding issue.

[0004] Solid-phase recycling is considered a new type of magnesium alloy recycling technology, and the specific process is spark plasma sintering or hot pressing. During the recycling process, magnesium alloy chips undergo phenomena such as crushing, biting, and atomic diffusion under the action of temperature and pressure, forming a small number of new bonding surfaces. Solid-phase recycling of magnesium alloys has many advantages: it is formed by extrusion technology, with simple operation and safety; the processing temperature is relatively low, without the need for melting, reducing the oxidation and combustion of magnesium alloys, saving energy and protecting the environment, and the alloy recovery rate is high (more than 90%), which is a low-cost and high-yield process method for recycling waste materials.

[0005] The long-period stacking ordered (LPSO) phase is a unique periodically changing structure in magnesium alloys. Adding a certain amount of elements such as zinc, copper, nickel, etc. to rare-earth magnesium alloys will cause the appearance of the LPSO phase. Because the internal organizational structures of rare-earth metals Gd and Y are similar to that of Mg, and adding these two elements to magnesium alloys will result in a relatively high solubility, the prospects of Mg-Gd and Mg-Y alloys are broad at present. Therefore, the research on magnesium alloys containing the LPSO phase mainly focuses on alloy systems such as Mg-Y-TM, Mg-Gd-TM, and Mg-Y-Gd-TM.

[0006] Based on the above theoretical basis, the present invention aims to solve the problem of how to use the Mg-9Gd-0.5Zr and ZK60 magnesium alloy waste materials generated in industrial production to prepare a high-strength and high-toughness magnesium alloy with an LPSO structure through solid-phase recycling technology, promote the recycling of magnesium alloy waste materials, reduce production costs, and improve production efficiency. Summary of the Invention

[0007] In view of this, one of the objectives of the present invention is to provide a method for preparing a high-strength and high-toughness magnesium alloy containing LPSO structure by solid-phase regeneration. Using magnesium alloy scraps Mg-9Gd-0.5Zr and ZK60 generated in industrial production, through the steps of turning - ball milling and mixing chips - spark plasma sintering - extrusion into plates, a high-strength and high-toughness solid-phase regenerated magnesium alloy containing LPSO structure is prepared by the solid-phase regeneration method; the second objective of the present invention is to provide a high-strength and high-toughness magnesium alloy product containing LPSO structure prepared by the said method.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] 1. A method for preparing a high-strength and high-toughness magnesium alloy containing LPSO structure by solid-phase regeneration

[0010] Using magnesium alloy scraps Mg-9Gd-0.5Zr and ZK60 generated in industrial production, through the steps of turning - ball milling and mixing chips - spark plasma sintering - extrusion into plates, a high-strength and high-toughness solid-phase regenerated magnesium alloy containing LPSO structure is prepared by the solid-phase regeneration method.

[0011] Preferably, the method of the present invention includes the following specific steps:

[0012] (1) Select Mg-9Gd-0.5Zr and ZK60 alloy ingot scraps, remove the oxide scale of the ingots, and then process them into turning chips. After the turning chips are cleaned, they are dried.

[0013] (2) The cleaned Mg-9Gd-0.5Zr and ZK60 turning chips are ball milled and mixed evenly according to a mass ratio of 10:1 to 4.

[0014] (3) Take 100 g of the evenly mixed turning chips, and perform spark plasma sintering and compaction in a mold with a diameter of 40 mm to obtain a compacted block.

[0015] (4) Put the compacted block into an extrusion mold, place it in a heating furnace, heat it to 300 °C to 450 °C, and keep it warm for 60 min.

[0016] (5) At an extrusion rate of 0.2 mm·s -1 , extrude a high-strength and high-toughness solid-phase regenerated magnesium alloy plate containing LPSO structure with an extrusion ratio of 11:1.

[0017] Preferably, in step (1), no cutting fluid is used during the turning process, and the dry turning process is selected to turn off the oxide scale on the outer layer of the magnesium alloy as-cast blank.

[0018] Preferably, in step (1), the turning chips have a length of 4.0 to 4.2 mm, a width of 2.0 to 2.2 mm, and a thickness of 0.43 mm.

[0019] Preferably, in step (2), the rotation speed of the ball milling is 400 r / min, the ball-to-material ratio is 10:1, and the ball milling time is 4 h.

[0020] Preferably, in step (2), the rotation is stopped for 20 min every 1 h of ball milling to prevent excessive temperature generated by the collision of balls and materials during the ball milling process.

[0021] Preferably, in step (3), the temperature of the spark plasma sintering is 400 °C, the pressure is 30 MPa, and the pressure is maintained for 8 min.

[0022] Preferably, in step (4), during the heating process, the heating rate is 25 °C / min to avoid the growth of alloy grains during the heating process and reduce the mechanical properties of the alloy.

[0023] Preferably, in step (5), during the extrusion process, after the extrusion, the alloy material is air-cooled. The purpose of this is to reduce the cooling rate of the blank and promote the precipitation of the LPSO phase.

[0024] 2. A high-strength and high-toughness magnesium alloy containing an LPSO structure prepared by the method

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

[0026] The present invention combines waste recycling and the long-period stacking ordered phase theory, and proposes a method for solid-phase regeneration to prepare a high-strength and high-toughness solid-phase regenerated magnesium alloy containing an LPSO structure, that is, using recycled magnesium alloy scrap to prepare a high-strength and high-toughness solid-phase regenerated magnesium alloy extrusion sheet; the development and research of this process provide a method basis for the recycling and regeneration of magnesium alloy scrap; in the entire industrial chain, it is of great significance for promoting the development and utilization of magnesium alloys, energy conservation and emission reduction, and realizing green circulation and sustainable development.

[0027] The advantages of the present invention are as follows:

[0028] 1. The present invention makes full use of the waste materials in industrial production, realizes waste utilization, and has a low cost.

[0029] 2. The whole process of the present invention is pollution-free and does not produce waste materials, waste liquids, etc.

[0030] 3. The operation process of the present invention is simple, easy to implement, and the production efficiency is more than 90%.

[0031] 4. The present invention uses LPSO to strengthen the magnesium alloy and improve its mechanical properties.

[0032] 5. The present invention can regulate the mechanical properties of the regenerated alloy by controlling the waste ratio. Description of the Drawings

[0033] To make the objectives, technical solutions and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0034] Figure 1 Flow chart for preparing a high-strength and high-toughness magnesium alloy with an LPSO structure by solid-phase regeneration;

[0035] Figure 2 Magnesium alloy before discharge plasma sintering and after extrusion;

[0036] Figure 3 Magnesium alloy sheet prepared after extrusion;

[0037] Figure 4 LPSO structure inside the alloy sheet with an extrusion ratio of 11;

[0038] Figure 5 Room temperature mechanical properties of the alloy after extrusion of the discharge plasma sintering blank. Detailed implementation manners

[0039] The present invention will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments cited are not intended to limit the present invention.

[0040] Example 1

[0041] The raw materials of this example are Mg-9Gd-0.5Zr and ZK60 alloy ingot scraps. The composition of the ZK60 magnesium alloy is shown in Table 1; on a lathe, without using any cutting fluid during the turning process, a slow dry turning process is selected to first turn off the oxide skin on the outer layer of the magnesium alloy as-cast blank, and then process it into chips with a length of 4.0 - 4.2 mm, a width of 2.0 - 2.2 mm, and a thickness of 0.43 mm using the same method; use alcohol and acetone solutions to clean the chips and dry them for standby.

[0042] Table 1 Composition table of ZK60 and Mg-9Gd-0.5Zr magnesium alloys (wt.%)

[0043]

[0044] 1. Proportion the raw materials: Weigh Mg-9Gd-0.5Zr and ZK60 chips in a ratio of 10:3, totaling 100 g, where the Mg-9Gd-0.5Zr alloy chips are 76.92 g and the ZK60 alloy chips are 23.08 g.

[0045] 2. Ball milling and mixing: Put the proportioned chips into the ball milling tank, introduce argon for 20 min and then seal it, and mix the chip materials according to the process with a ball milling speed of 400 r / min, a ball-to-material ratio of 10:1, and a ball milling time of 4 h.

[0046] During the ball milling process, the rotation is stopped for 20 minutes every 1 hour of ball milling to prevent excessive temperature generated by the collision of balls and materials during the ball milling process.

[0047] 3. Spark Plasma Sintering Compaction: Clean the mold and apply a lubricant made of graphene and glass water on the inner wall of the mold; after mixing the chips, load the chips into a spark plasma sintering mold with a diameter of 40 mm. Subsequently, the spark plasma sintering temperature is 400 °C, the pressure is 30 MPa, and the pressure is maintained for 8 minutes to compact the chips, obtaining a compacted block.

[0048] The purpose of this step is to increase the bonding force between the two kinds of chips, thereby promoting the wetting and reaction of the two kinds of chips during sintering, and facilitating the formation of a solid-phase recycled magnesium alloy with stronger comprehensive properties.

[0049] The microhardness of the high-strength and high-toughness solid-phase recycled magnesium alloy containing the LPSO structure is measured by using a HVW-1000 micro-Vickers hardness tester for Vickers hardness testing, where the load is 100 g, the loading time is 15 seconds, and the average value is taken after testing each sample 5 times.

[0050] The tensile test of the magnesium alloy containing the LPSO structure is carried out by using a microcomputer-controlled electronic universal testing machine (DNS200) with reference to the national standard of the People's Republic of China GB 6397-86, and the tensile rate is 0.1 mm / min. To reduce the test error, each sample is subjected to 3 tensile tests and the average value is taken.

[0051] The tensile strength of the prepared magnesium alloy sample is 195.1 MPa, the yield strength is 187.6 MPa, and the elongation is 3.5%.

[0052] Example 2

[0053] Prepare the magnesium alloy containing the LPSO structure according to the method described in Example 1. Different from Example 1, the following operations are carried out after step 3:

[0054] 4. Heating of the Compacted Block: The extrusion die is cleaned and lubricant made of graphite and glass water is applied in the same way as the spark plasma sintering die; the compacted block and the extrusion die are placed in a heating furnace and heated to 400 °C at a heating rate of 25 °C / min, and then held for 60 minutes. The purpose of slow heating is to reduce the growth of alloy grains during heating and reduce the mechanical properties of the alloy.

[0055] 5. Extrusion Molding: Place the compacted block and the die on the working table of the extruder at 0.2 mm·s -1At a rate of 11:1 extrusion ratio, it is extruded into a magnesium alloy containing the LPSO structure. After extrusion forming, the alloy material is air-cooled. The purpose of this is to reduce the cooling rate of the blank and promote the smooth precipitation of the LPSO phase.

[0056] The flow chart of preparing a high-strength and high-toughness magnesium alloy containing the LPSO structure by solid-phase recycling is as Figure 1 shown. The magnesium alloy before and after discharge plasma sintering and after extrusion is as Figure 2 shown. The magnesium alloy sheet prepared after extrusion is as Figure 3 shown. The LPSO structure inside the alloy sheet with an extrusion ratio of 11 is as Figure 4 shown. The room-temperature mechanical properties of the alloys prepared by extruding the billets of raw materials with different chip mass ratios after discharge plasma sintering are as Figure 5 shown.

[0057] The room-temperature ultimate tensile strength of the sample after turning - ball milling - discharge plasma sintering - extrusion forming treatment is 304 MPa, the yield strength is 225 MPa, and the elongation is about 16.2%.

[0058] Example 3

[0059] Prepare a magnesium alloy containing the LPSO structure according to the method described in Example 2. The difference from Example 2 is that: according to the ratio of 10:2, weigh Mg-9Gd-0.5Zr and ZK60 chips, totaling 100 g, among which the Mg-9Gd-0.5Zr alloy chips are 83.33 g and the ZK60 alloy chips are 16.67 g.

[0060] The room-temperature ultimate tensile strength of the sample after turning - ball milling - discharge plasma sintering - extrusion forming treatment is 339 MPa, the yield strength is 280 MPa, and the elongation is about 16.6%.

[0061] Example 4

[0062] Prepare a magnesium alloy containing the LPSO structure according to the method described in Example 2. The difference from Example 2 is that: according to the ratio of 10:3, weigh Mg-9Gd-0.5Zr and ZK60 chips, totaling 100 g, among which the Mg-9Gd-0.5Zr alloy chips are 76.92 g and the ZK60 alloy chips are 23.07 g.

[0063] The room-temperature ultimate tensile strength of the sample after turning - ball milling - discharge plasma sintering - extrusion forming treatment is 343 MPa, the yield strength is 283 MPa, and the elongation is about 15.6%.

[0064] Example 5

[0065] The magnesium alloy containing LPSO structure was prepared according to the method described in Example 2, which was different from Example 2 in that: according to the ratio of 10:4, Mg-9Gd-0.5Zr and ZK60 turnings were weighed, totaling 100 g, among which the Mg-9Gd-0.5Zr alloy turnings were 71.43 g and the ZK60 alloy turnings were 28.57 g.

[0066] The ultimate tensile strength at room temperature of the sample after turning - ball milling - spark plasma sintering - extrusion forming treatment was 313 MPa, the yield strength was 212 MPa, and the elongation was approximately 14.8%.

[0067] The above - described embodiments are only preferred embodiments cited to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the present invention is subject to the claims.

Claims

1. A method for solid-phase recycling to prepare a high-strength and high-toughness magnesium alloy with an LPSO structure, characterized in that: Using the magnesium alloy scraps Mg-9Gd-0.5Zr and ZK60 generated in industrial production, through the steps of turning - ball milling and mixing chips - spark plasma sintering - extrusion into plates, a high-strength and high-toughness solid-phase recycled magnesium alloy with an LPSO structure is prepared by a solid-phase recycling method; the method includes the following specific steps: (1) Select the Mg-9Gd-0.5Zr and ZK60 alloy ingot scraps, remove the oxide scale of the ingots, and then process them into turning chips. After the turning chips are cleaned, they are dried. (2) Mix the cleaned Mg-9Gd-0.5Zr and ZK60 turning chips evenly by ball milling according to a mass ratio of 10:2~3; the rotation speed of the ball milling is 400 r / min, the ball-to-material ratio is 10:1, and the ball milling time is 4 h. (3) Take 100 g of the evenly mixed turning chips, and perform spark plasma sintering and compaction in a mold with a diameter of 40 mm to obtain a compacted block; the temperature of the spark plasma sintering is 400 °C, the pressure is 30 MPa, and the pressure is maintained for 8 min. (4) Put the compacted block into an extrusion mold, place it in a heating furnace, heat it to 300 °C~450 °C at a heating rate of 25 °C / min, and keep it warm for 60 min. (5) At an extrusion rate of 0.2 mm·s -1 extrude a high-strength and high-toughness solid-phase recycled magnesium alloy sheet containing LPSO structure at an extrusion ratio of 11:

1.

2. The method for solid-phase recycling to prepare a high-strength and high-toughness magnesium alloy with an LPSO structure according to claim 1, characterized in that: In step (1), no cutting fluid is used during the turning process, and the dry turning process is selected to turn off the oxide scale on the outer layer of the as-cast magnesium alloy blank.

3. The method for solid-phase recycling to prepare a high-strength and high-toughness magnesium alloy with an LPSO structure according to claim 1, characterized in that: In step (1), the length of the turning chips is 4.0~4.2 mm, the width is 2.0~2.2 mm, and the thickness is 0.43 mm.

4. The method for solid-phase recycling to prepare a high-strength and high-toughness magnesium alloy with an LPSO structure according to claim 1, characterized in that: In step (2), the rotation is stopped for 20 min every 1 h of ball milling to prevent excessive temperature generated by the collision of balls and materials during the ball milling process.

5. The method for solid-phase recycling to prepare a high-strength and high-toughness magnesium alloy with an LPSO structure according to claim 1, characterized in that: In step (5), after extrusion, the alloy material is air-cooled. The purpose of this is to reduce the cooling rate of the blank and promote the precipitation of the LPSO phase.

6. A high-strength and high-toughness magnesium alloy with an LPSO structure prepared by the method according to any one of claims 1~5.

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