Bimodal structure Mg-Zn alloy with high aging response and preparation method thereof

Abstract

The invention discloses a bimodal structure Mg-Zn alloy with high aging response and a preparation method of the bimodal structure Mg-Zn alloy. The method comprises the following steps: 1, preparing an alloy raw material according to a target product; secondly, alloy raw materials are subjected to ultrasonic-assisted smelting and then poured, and cast ingots are obtained; 3, carrying out two-stage homogenization treatment; 4, differential temperature extrusion; and 5, single-stage or double-stage aging treatment. Through smelting-extrusion-aging treatment, a bimodal structure and a high-density nano precipitated phase are constructed in the Mg-Zn alloy, the mechanical property of the Mg-Zn alloy is synergistically improved, the Mg-Zn alloy shows good strength and plasticity matching, the process is simple, the cost is reduced, continuous production of the low-cost and high-performance Mg-Zn alloy is achieved, and the method is suitable for industrial production. The method is suitable for aerospace and military industry fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnesium alloy preparation and processing, and particularly relates to a bimodal microstructure Mg-Zn alloy with high aging response and a preparation method thereof. Background Art

[0002] Magnesium alloys have low density, high specific strength and specific stiffness, and at the same time have good shock absorption and electromagnetic shielding properties. Therefore, they have broad application potential in the fields of national defense, military industry and aerospace. Developing high-performance magnesium alloys has thus become a research hotspot. Compared with rare-earth magnesium alloys, Mg-Zn alloys have the advantage of low cost, and the Zn element has a large solid solubility in the Mg matrix, and the aging strengthening effect is very significant. However, the plasticity of the Mg-Zn alloy after aging treatment usually drops severely, which limits its engineering applications. To expand the application space of Mg-Zn alloys, it is urgent to develop a microstructure control technology for age-treatable Mg-Zn alloys and develop Mg-Zn alloys with good strength and plasticity matching.

[0003] The bimodal microstructure is a typical heterogeneous microstructure. Thanks to the high strength provided by the deformed grains and the high plasticity contributed by the fine recrystallized grains, the strength and elongation of the bimodal microstructure magnesium alloy can be synergistically improved. The patent with publication number CN108642415A discloses a preparation method of a bimodal microstructure ZK21 magnesium alloy with controllable grain distribution. By multi-pass multi-directional forging of a low-alloyed Mg-2Zn-0.45Zr alloy, the mechanical properties of the ZK21 alloy are improved; however, this method requires multi-pass forging, resulting in low production efficiency and inability to achieve continuous industrial production. The patent with publication number CN111197149A discloses a preparation method of a high-performance bimodal grain size microstructure AZ80 magnesium alloy. This method uses equal-channel angular pressing technology (ECAP) to construct bimodal-distributed grains in the AZ80 magnesium alloy, and the tensile strength of the alloy is 376 MPa; due to the limitation of the sample size processed by ECAP, it is difficult to prepare large-sized magnesium alloy deformed materials by this method, so it is also not suitable for the industrial production of magnesium alloys. The patent with publication number CN113755772A discloses a high-strength and high-toughness heterogeneous magnesium alloy and a preparation method thereof. This method uses a hydrostatic extrusion process to realize the construction of a heterogeneous structure in a commercial AZ80 magnesium alloy. From the above patents, for low-alloyed Mg-Zn alloys and commercial AZ80 magnesium alloys, there are already some methods for constructing bimodal microstructures, but it is difficult to achieve the continuous industrial production of bimodal microstructure magnesium alloys by these methods.

[0004] Therefore, developing an age-treatable bimodal microstructure Mg-Zn alloy suitable for industrial continuous production, enabling the alloy to have good strength and plasticity, is of great significance for expanding the application advantages of low-cost Mg-Zn alloys and facilitating the lightweighting of materials in the fields of aerospace and weaponry. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a high-aging-response bimodal-structured Mg-Zn alloy aiming at the deficiencies of the above-mentioned prior art. This method prepares a high-quality Mg-Zn alloy ingot through ultrasonic-assisted melting, then constructs a bimodal structure in the alloy by differential temperature extrusion, and further uses aging treatment to form a high density of nano-precipitates in the alloy. Through the synergistic strengthening effect of the bimodal structure and nano-precipitates, an Mg-Zn alloy with good strength and plasticity performance is prepared, solving the contradiction that it is difficult to match the strength and plasticity of Mg-Zn alloys with high Zn content and the problem that the current alloy bimodal structure construction technology is difficult to adapt to large-scale industrial continuous production.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A preparation method of a high-aging-response bimodal-structured Mg-Zn alloy, characterized in that the method comprises the following steps:

[0007] Step 1: Prepare alloy raw materials according to the designed composition of the target product Mg-Zn alloy;

[0008] Step 2: Melt the alloy raw materials prepared in Step 1, and at the same time perform ultrasonic stirring on the melt formed by melting to promote the uniform diffusion of alloy elements, and then pour to obtain an Mg-Zn alloy ingot;

[0009] Step 3: Perform two-stage homogenization treatment on the Mg-Zn alloy ingot obtained in Step 2;

[0010] Step 4: Perform differential temperature extrusion on the Mg-Zn alloy ingot after two-stage homogenization treatment in Step 3 at a low temperature to obtain an extruded Mg-Zn alloy;

[0011] Step 5: Perform single-stage or two-stage aging treatment on the extruded Mg-Zn alloy obtained in Step 4 to obtain an aged bimodal-structured Mg-Zn alloy.

[0012] Generally, the present invention heats the alloy raw materials in a crucible of a melting device to 710°C to 730°C to melt the alloy raw materials, and after ultrasonic stirring, keeps them at 700°C to 710°C for heat preservation, and then pours and solidifies. Before pouring, the copper casting mold is preheated to 200°C.

[0013] The preparation method of the above-mentioned high-aging-response bimodal-structured Mg-Zn alloy is characterized in that the designed composition of the Mg-Zn alloy in step one includes the following components by mass percentage: 8% - 10% of Zn, 0.2% - 0.5% of Ce or / and Ca, and the balance is Mg. In conventional Mg-Zn alloys, the Zn content is mostly below 6%. However, due to the addition of alloying elements Ce or / and Ca in the Mg-Zn alloy of the present invention to weaken the basal texture of the alloy and improve the plastic deformation ability of the Mg-Zn alloy, and the alloying elements Ce or / and Ca will form a second phase with the Zn element, consuming Zn atoms in the matrix and affecting the subsequent aging precipitation effect. Therefore, the Zn element is increased to 8% - 10%, exceeding the maximum solid solubility of Zn in Mg, to improve the aging response of the alloy.

[0014] The preparation method of the above-mentioned high-aging-response bimodal-structured Mg-Zn alloy is characterized in that the frequency of the ultrasonic stirring in step two is 800 kHz - 1000 kHz, the power is 800 W - 1000 W, and the time is 3 min - 5 min.

[0015] The preparation method of the above-mentioned high-aging-response bimodal-structured Mg-Zn alloy is characterized in that the system of the two-stage homogenization treatment in step three is: the temperature of the first-stage homogenization treatment is 370°C - 380°C, the time is 10 h - 12 h, the temperature of the second-stage homogenization treatment is 400°C - 420°C, and the time is 2 h - 6 h. For the Mg-Zn alloy after composition design, the present invention adopts the two-stage homogenization treatment with the above process parameters to promote the decomposition of the eutectic structure in the Mg-Zn alloy ingot, weaken the deformation resistance of the Mg-Zn alloy, and ensure the smooth progress of subsequent plastic deformation.

[0016] The preparation method of the above-mentioned high-aging-response bimodal-structured Mg-Zn alloy is characterized in that before the differential temperature extrusion in step four, the Mg-Zn alloy ingot after the two-stage homogenization treatment is preheated, the preheating temperature is 300°C - 350°C, the preheating time is 30 min, the temperature of the extrusion die used for the differential temperature extrusion is 150°C - 200°C, the extrusion speed is 2 mm / s - 4 mm / s, and the extrusion ratio is 16 - 25. For the Mg-Zn alloy after composition design, the present invention adopts differential temperature extrusion. By reducing the temperature of the extrusion die, the energy input during the alloy deformation process is reduced, the growth of dynamically recrystallized grains is inhibited, and a high density of dislocations inside the alloy is retained, so that a bimodal structure containing deformed grains with a high density of dislocations and fine dynamically recrystallized grains is formed in the Mg-Zn alloy, thereby improving the strength and plasticity of the Mg-Zn alloy.

[0017] The preparation method of the above-mentioned high-aging-response bimodal-structured Mg-Zn alloy is characterized in that, in step five, the temperature of the single-stage aging treatment is 180°C to 200°C, and the time is 8h to 12h; the regime of the two-stage aging treatment is: the temperature of the first-stage aging treatment is 90°C, the time is 8h, and the temperature of the second-stage aging treatment is 180°C, and the time is 8h to 12h. Compared with the single-stage aging treatment, the two-stage aging treatment makes the precipitation phases in the Mg-Zn alloy more dispersed and uniform, resulting in a stronger precipitation strengthening effect.

[0018] Meanwhile, the present invention also discloses a high-aging-response bimodal-structured Mg-Zn alloy, which is characterized in that it is prepared by the above method, and the tensile strength of the aged bimodal-structured Mg-Zn alloy is above 375 MPa, and the elongation is above 8%.

[0019] The present invention has the following advantages compared with the prior art:

[0020] 1. First, the present invention prepares a Mg-Zn alloy ingot by ultrasonic-assisted melting, and then performs two-stage homogenization treatment and differential temperature extrusion on the ingot, so that a bimodal structure in which fine recrystallized grains and high-density dislocation-deformed grains coexist is formed in the obtained extruded Mg-Zn alloy, and its strength and plasticity are both improved. Then, aging treatment is carried out, and the high Zn content enables the Mg-Zn alloy to have a good aging response level, so that a high density of nano-precipitation phases are formed in the Mg-Zn alloy. The formation of the bimodal structure and the high density of nano-precipitation phases synergistically improve the mechanical properties of the Mg-Zn alloy, making the Mg-Zn alloy exhibit a good strength and plasticity match.

[0021] 2. The present invention prepares a Mg-Zn alloy profile with excellent comprehensive performance. The tensile strength of the aged bimodal-structured Mg-Zn alloy can reach above 375 MPa, and the elongation can reach above 8%. It has both good strength and plasticity, and even exceeds some magnesium alloys with high rare earth content, and can replace some rare earth magnesium alloys in the aerospace and military fields.

[0022] 3. The element ratio of the high-aging-response bimodal-structured Mg-Zn alloy of the present invention is simple, and the costs of elements such as Zn, Ca and Ce are lower than those of heavy rare earth elements such as Gd and Y, having a significant low-cost advantage.

[0023] 4. The present invention prepares a Mg-Zn alloy by melting-extrusion-aging treatment, which not only has a simple process, but also can realize the industrial continuous production of large-size high-performance Mg-Zn alloy plates, bars, etc. of different specifications, having broad industrial application prospects.

[0024] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Brief Description of the Drawings

[0025] Figure 1 Macrograph of the extruded Mg-Zn alloy bars prepared in Examples 1 to 3 of the present invention.

[0026] Figure 2 EBSD microstructure diagram of the extruded Mg-9Zn-0.5Ce alloy bar prepared in Example 1 of the present invention.

[0027] Figure 3 TEM microstructure diagram of the aged bimodal microstructure Mg-9Zn-0.5Ce alloy prepared in Example 1 of the present invention.

[0028] Figure 4 EBSD microstructure diagram of the extruded Mg-9Zn-0.5Ce alloy bar prepared in Example 2 of the present invention.

[0029] Figure 5 TEM microstructure diagram of the aged bimodal microstructure Mg-9Zn-0.5Ce alloy prepared in Example 2 of the present invention.

[0030] Figure 6 EBSD microstructure diagram of the extruded Mg-9Zn-0.5Ce alloy bar prepared in Example 3 of the present invention.

[0031] Figure 7 TEM microstructure diagram of the aged bimodal microstructure Mg-9Zn-0.5Ce alloy prepared in Example 3 of the present invention. Detailed Description of the Invention

[0032] Example 1

[0033] This example includes the following steps:

[0034] Step 1: According to the designed composition Mg-9Zn-0.5Ce of the target product Mg-Zn alloy, weigh magnesium ingots, Zn and Mg-30% Ce master alloy as alloy raw materials respectively;

[0035] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then, put the magnesium ingots weighed in Step 1 into a crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and keep it warm for 50 min. After all the magnesium ingots are melted, put the Zn and Mg-30% Ce master alloy weighed in Step 1 and continue to keep it warm at 730 °C for 20 min;

[0036] After all alloy raw materials are melted, an ultrasonic stirring rod is used to ultrasonically stir the melt formed by smelting to promote uniform diffusion of alloying elements. The frequency of ultrasonic stirring is 800 kHz, the power is 800 W, and the time is 3 min. Then, the furnace temperature is reduced to 700 °C and held for 15 min. Subsequently, the melt is skimmed and poured into a copper mold to obtain a Mg-9Zn-0.5Ce alloy ingot;

[0037] Step 3: Perform a two-stage homogenization treatment on the Mg-9Zn-0.5Ce alloy ingot obtained in Step 2; the regime of the two-stage homogenization treatment is: the temperature of the first-stage homogenization treatment is 380 °C and the time is 10 h, and the temperature of the second-stage homogenization treatment is 420 °C and the time is 2 h;

[0038] Step 4: Preheat the Mg-9Zn-0.5Ce alloy ingot after the two-stage homogenization treatment in Step 3. The preheating temperature is 300 °C and the preheating time is 30 min. Then, differential temperature extrusion is carried out. The temperature of the extrusion die used for differential temperature extrusion is 150 °C, the extrusion speed is 4 mm / s, and the extrusion ratio is 25 to obtain an extruded Mg-9Zn-0.5Ce alloy rod with a diameter of 10 mm, as Figure 1 shown;

[0039] Step 5: Perform a single-stage aging treatment on the extruded Mg-9Zn-0.5Ce alloy rod obtained in Step 4 to obtain an aged bimodal microstructure Mg-9Zn-0.5Ce alloy; the temperature of the single-stage aging treatment is 180 °C and the time is 12 h.

[0040] The mechanical properties of the aged bimodal microstructure Mg-9Zn-0.5Ce alloy prepared in this example were tested. The results showed that: the tensile strength was 390 MPa, the yield strength was 363 MPa, and the elongation was 12.5%.

[0041] Figure 2 is the EBSD microstructure diagram of the extruded Mg-9Zn-0.5Ce alloy rod prepared in this example. From Figure 2 it can be seen that a bimodal microstructure in which recrystallized grains and deformed grains coexist is formed in the extruded Mg-9Zn-0.5Ce alloy rod. The orientation of the recrystallized grains is relatively random, making the alloy have high strength and plasticity. The deformed grains are mainly basal plane oriented, which improves the strength of the alloy, so that the alloy has a good strength-plasticity match.

[0042] Figure 3 is the TEM microstructure diagram of the aged bimodal microstructure Mg-9Zn-0.5Ce alloy prepared in this example. From Figure 3It can be seen that a large number of nanoscale rod-shaped precipitate phases have precipitated in the alloy. These precipitate phases are mainly Mg-Zn phases precipitated along the prism planes of the magnesium matrix, effectively hindering the slip of basal plane dislocations, thereby improving the mechanical properties of the alloy.

[0043] Example 2

[0044] This example includes the following steps:

[0045] Step 1: According to the designed composition Mg-9Zn-0.5Ca of the target product Mg-Zn alloy, weigh magnesium ingots, Zn, and Mg-30% Ca master alloy as alloy raw materials respectively;

[0046] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then place the magnesium ingots weighed in Step 1 into a crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and hold for 45 min. After all the magnesium ingots are melted, put the weighed Zn and Mg-Ca master alloy in Step 1 and continue to hold at 730 °C for 20 min;

[0047] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed by melting to promote the uniform diffusion of alloying elements. The frequency of ultrasonic stirring is 800 kHz, the power is 800 W, and the time is 5 min. Then lower the furnace temperature to 700 °C and hold for 10 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain a Mg-9Zn-0.5Ca alloy ingot;

[0048] Step 3: Perform a two-stage homogenization treatment on the Mg-9Zn-0.5Ca alloy ingot obtained in Step 2; the system of the two-stage homogenization treatment is: the first-stage homogenization treatment temperature is 370 °C and the time is 12 h, and the second-stage homogenization treatment temperature is 400 °C and the time is 4 h;

[0049] Step 4: Preheat the Mg-9Zn-0.5Ca alloy ingot after the two-stage homogenization treatment in Step 3. The preheating temperature is 300 °C and the preheating time is 30 min. Then perform differential temperature extrusion. The temperature of the extrusion die used for differential temperature extrusion is 200 °C, the extrusion speed is 3 mm / s, and the extrusion ratio is 25 to obtain an extruded Mg-9Zn-0.5Ca alloy rod with a diameter of 10 mm, as Figure 1 shown;

[0050] Step 5: Perform a single-stage aging treatment on the extruded Mg-9Zn-0.5Ca alloy rod obtained in Step 4 to obtain an aged double-peak microstructure Mg-9Zn-0.5Ca alloy; the temperature of the single-stage aging treatment is 200 °C and the time is 8 h.

[0051] The mechanical properties of the aged bimodal microstructure Mg-9Zn-0.5Ca alloy prepared in this example were tested, and the results showed that: the tensile strength was 384 MPa, the yield strength was 367 MPa, and the elongation was 14.0%.

[0052] Figure 4 This is the EBSD microstructure diagram of the extruded Mg-9Zn-0.5Ca alloy bar prepared in this example. From Figure 4 it can be seen that a bimodal microstructure was also formed in the extruded Mg-9Zn-0.5Ca alloy bar, in which the deformed grains were elongated along the extrusion direction, and the dynamically recrystallized grains had random orientations.

[0053] Figure 5 This is the TEM microstructure diagram of the aged bimodal microstructure Mg-9Zn-0.5Ca alloy prepared in this example. From Figure 5 it can be seen that a large number of prismatic precipitates were also precipitated in the alloy. This phase can effectively hinder the basal slip and improve the strength of the alloy.

[0054] Example 3

[0055] This example includes the following steps:

[0056] Step 1: According to the designed composition Mg-9Zn-0.3Ce-0.2Ca of the target product Mg-Zn alloy, weigh magnesium ingots, Zn, Mg-30% Ce master alloy, and Mg-25% Ca master alloy as alloy raw materials respectively;

[0057] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then, put the magnesium ingots weighed in Step 1 into the crucible pre-placed in the melting furnace, heat the furnace temperature to 730 °C and hold for 55 min. After all the magnesium ingots are melted, put the Zn, Mg-30% Ce master alloy, and Mg-25% Ca master alloy weighed in Step 1, and continue to hold at 730 °C for 20 min;

[0058] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed by melting to promote the uniform diffusion of alloy elements. The frequency of ultrasonic stirring is 900 kHz, the power is 1000 W, and the time is 3 min. Then, lower the furnace temperature to 700 °C and hold for 15 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain a Mg-9Zn-0.3Ce-0.2Ca alloy ingot;

[0059] Step 3: Perform a two-stage homogenization treatment on the Mg-9Zn-0.3Ce-0.2Ca alloy ingot obtained in Step 2; the system of the two-stage homogenization treatment is: the first-stage homogenization treatment temperature is 375 °C, the time is 12 h, the second-stage homogenization treatment temperature is 410 °C, and the time is 4 h;

[0060] Step 4: Preheat the Mg-9Zn-0.3Ce-0.2Ca alloy ingot after the double-stage homogenization treatment in Step 3. The preheating temperature is 320 °C and the preheating time is 30 min. Then, perform differential temperature extrusion. The temperature of the extrusion die for differential temperature extrusion is 180 °C, the extrusion speed is 3 mm / s, and the extrusion ratio is 18, to obtain an extruded Mg-9Zn-0.3Ce-0.2Ca alloy rod with a diameter of 7 mm, as Figure 1 shown;

[0061] Step 5: Perform double-stage aging treatment on the extruded Mg-9Zn-0.3Ce-0.2Ca alloy rod obtained in Step 4 to obtain an aged bimodal structure Mg-9Zn-0.3Ce-0.2Ca alloy. The regime of the double-stage aging treatment is as follows: the first-stage aging treatment temperature is 90 °C and the time is 8 h, and the second-stage aging treatment temperature is 180 °C and the time is 8 h.

[0062] Perform mechanical property tests on the aged bimodal structure Mg-9Zn-0.3Ce-0.2Ca alloy prepared in this example. The results show that the tensile strength is 405 MPa, the yield strength is 385 MPa, and the elongation is 8.0%.

[0063] Figure 6 This is the EBSD microstructure diagram of the extruded Mg-9Zn-0.3Ce-0.2Ca alloy rod prepared in this example. From Figure 6 it can be seen that the grain structure in the extruded Mg-9Zn-0.3Ce-0.2Ca alloy rod shows an obvious bimodal state, and this heterogeneous structure effectively improves the strength-ductility matching performance of the alloy.

[0064] Figure 7 This is the TEM microstructure diagram of the aged bimodal structure Mg-9Zn-0.3Ce-0.2Ca alloy prepared in this example. From Figure 7 it can be seen that the precipitates in the alloy after the double-stage aging treatment are short rod-shaped, with smaller size and more dispersed distribution compared with the single-stage aging treatment, so a stronger aging strengthening effect is produced.

[0065] Example 4

[0066] This example includes the following steps:

[0067] Step 1: Weigh magnesium ingots, Zn, and Mg-30%Ce master alloy as alloy raw materials according to the designed composition Mg-8Zn-0.5Ce of the target product Mg-Zn alloy;

[0068] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then, place the magnesium ingot weighed in Step 1 into a crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and hold for 45 min. After the magnesium ingot is completely melted, add the Zn and Mg-30% Ce master alloy weighed in Step 1 and continue to hold at 730 °C for 20 min;

[0069] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed by melting to promote the uniform diffusion of alloy elements. The frequency of ultrasonic stirring is 800 kHz, the power is 1000 W, and the time is 4 min. Then, lower the furnace temperature to 700 °C and hold for 10 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain a Mg-8Zn-0.5Ce alloy ingot;

[0070] Step 3: Perform a two-stage homogenization treatment on the Mg-8Zn-0.5Ce alloy ingot obtained in Step 2; the regime of the two-stage homogenization treatment is: the first-stage homogenization treatment temperature is 370 °C and the time is 10 h, and the second-stage homogenization treatment temperature is 400 °C and the time is 4 h;

[0071] Step 4: Preheat the Mg-8Zn-0.5Ce alloy ingot after the two-stage homogenization treatment in Step 3. The preheating temperature is 300 °C and the preheating time is 30 min. Then, perform differential temperature extrusion. The temperature of the extrusion die used for differential temperature extrusion is 150 °C, the extrusion speed is 4 mm / s, and the extrusion ratio is 25 to obtain an extruded Mg-8Zn-0.5Ce alloy bar with a diameter of 10 mm;

[0072] Step 5: Perform a single-stage aging treatment on the extruded Mg-8Zn-0.5Ce alloy bar obtained in Step 4 to obtain an aged double-peak microstructure Mg-8Zn-0.5Ce alloy; the temperature of the single-stage aging treatment is 180 °C and the time is 8 h.

[0073] Perform a mechanical property test on the aged double-peak microstructure Mg-8Zn-0.5Ce alloy prepared in this example. The results show that: the tensile strength is 378 MPa, the yield strength is 360 MPa, and the elongation is 15.0%.

[0074] Example 5

[0075] This example includes the following steps:

[0076] Step 1: According to the designed composition Mg-10Zn-0.3Ce-0.5Ca of the target product Mg-Zn alloy, weigh magnesium ingot, Zn, Mg-30% Ce master alloy, and Mg-25% Ca master alloy as alloy raw materials respectively;

[0077] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then, place the magnesium ingots weighed in Step 1 into a crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and hold for 50 min. After all the magnesium ingots are melted, add the Zn, Mg-30% Ce master alloy, and Mg-25% Ca master alloy weighed in Step 1, and continue to hold at 730 °C for 20 min;

[0078] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed by melting to promote the uniform diffusion of alloying elements. The frequency of ultrasonic stirring is 1000 kHz, the power is 1000 W, and the time is 5 min. Then, lower the furnace temperature to 700 °C and hold for 15 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain a Mg-10Zn-0.3Ce-0.5Ca alloy ingot;

[0079] Step 3: Perform a two-stage homogenization treatment on the Mg-10Zn-0.3Ce-0.5Ca alloy ingot obtained in Step 2; the system of the two-stage homogenization treatment is: the temperature of the first-stage homogenization treatment is 380 °C and the time is 12 h, and the temperature of the second-stage homogenization treatment is 420 °C and the time is 6 h;

[0080] Step 4: Preheat the Mg-10Zn-0.3Ce-0.5Ca alloy ingot after the two-stage homogenization treatment in Step 3. The preheating temperature is 350 °C and the preheating time is 30 min. Then, perform differential temperature extrusion. The temperature of the extrusion die used for differential temperature extrusion is 200 °C, the extrusion speed is 2 mm / s, and the extrusion ratio is 25 to obtain an extruded Mg-10Zn-0.3Ce-0.5Ca alloy bar with a diameter of 10 mm;

[0081] Step 5: Perform a two-stage aging treatment on the extruded Mg-10Zn-0.3Ce-0.5Ca alloy bar obtained in Step 4 to obtain an aged bimodal structure Mg-10Zn-0.3Ce-0.5Ca alloy; the system of the two-stage aging treatment is: the temperature of the first-stage aging treatment is 90 °C and the time is 8 h, and the temperature of the second-stage aging treatment is 180 °C and the time is 12 h.

[0082] Perform a mechanical property test on the aged bimodal structure Mg-10Zn-0.3Ce-0.5Ca alloy prepared in this example. The results show that: the tensile strength is 412 MPa, the yield strength is 388 MPa, and the elongation is 8.0%.

[0083] Example 6

[0084] This example includes the following steps:

[0085] Step 1: According to the designed composition of the target product Mg-Zn alloy, i.e., Mg-10Zn-0.2Ce, weigh magnesium ingots, Zn, and Mg-30% Ce master alloy respectively as alloy raw materials;

[0086] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then, put the magnesium ingots weighed in Step 1 into the crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and hold for 45 min. After all the magnesium ingots are melted, put the weighed Zn and Mg-30% Ce master alloy in Step 1 and continue to hold at 730 °C for 20 min;

[0087] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed by melting to promote the uniform diffusion of alloying elements. The frequency of ultrasonic stirring is 900 kHz, the power is 1000 W, and the time is 4 min. Then, lower the furnace temperature to 700 °C and hold for 12 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain a Mg-10Zn-0.2Ce alloy ingot;

[0088] Step 3: Perform a two-stage homogenization treatment on the Mg-10Zn-0.2Ce alloy ingot obtained in Step 2; the system of the two-stage homogenization treatment is: the temperature of the first-stage homogenization treatment is 370 °C and the time is 12 h, and the temperature of the second-stage homogenization treatment is 420 °C and the time is 4 h;

[0089] Step 4: Preheat the Mg-10Zn-0.2Ce alloy ingot after the two-stage homogenization treatment in Step 3. The preheating temperature is 350 °C and the preheating time is 30 min. Then, perform differential temperature extrusion. The temperature of the extrusion die used for differential temperature extrusion is 200 °C, the extrusion speed is 3 mm / s, and the extrusion ratio is 25 to obtain an extruded Mg-10Zn-0.2Ce alloy bar with a diameter of 10 mm;

[0090] Step 5: Perform a two-stage aging treatment on the extruded Mg-10Zn-0.2Ce alloy bar obtained in Step 4 to obtain an aged double-peak structure Mg-10Zn-0.2Ce alloy; the system of the two-stage aging treatment is: the temperature of the first-stage aging treatment is 90 °C and the time is 8 h, and the temperature of the second-stage aging treatment is 180 °C and the time is 10 h.

[0091] Perform a mechanical property test on the aged double-peak structure Mg-10Zn-0.2Ce alloy prepared in this example. The results show that: the tensile strength is 386 MPa, the yield strength is 373 MPa, and the elongation is 12.0%.

[0092] Example 7

[0093] This example includes the following steps:

[0094] Step 1: According to the designed composition of the target product Mg-Zn alloy, Mg-8Zn-0.2Ca, weigh magnesium ingots, Zn, and Mg-25% Ca master alloy as alloy raw materials respectively;

[0095] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then, put the magnesium ingots weighed in Step 1 into a crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and hold for 45 min. After all the magnesium ingots are melted, put the weighed Zn and Mg-25% Ca master alloy in Step 1 and continue to hold at 730 °C for 20 min;

[0096] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed by melting to promote the uniform diffusion of alloying elements. The frequency of ultrasonic stirring is 900 kHz, the power is 900 W, and the time is 3 min. Then, lower the furnace temperature to 700 °C and hold for 12 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain a Mg-8Zn-0.2Ca alloy ingot;

[0097] Step 3: Perform a two-stage homogenization treatment on the Mg-8Zn-0.2Ca alloy ingot obtained in Step 2; the regime of the two-stage homogenization treatment is: the temperature of the first-stage homogenization treatment is 370 °C and the time is 12 h, and the temperature of the second-stage homogenization treatment is 400 °C and the time is 4 h;

[0098] Step 4: Preheat the Mg-8Zn-0.2Ca alloy ingot after the two-stage homogenization treatment in Step 3. The preheating temperature is 350 °C and the preheating time is 30 min. Then, perform differential temperature extrusion. The temperature of the extrusion die used for differential temperature extrusion is 150 °C, the extrusion speed is 3 mm / s, and the extrusion ratio is 16 to obtain an extruded Mg-8Zn-0.2Ca alloy bar with a diameter of 10 mm;

[0099] Step 5: Perform aging treatment on the extruded Mg-8Zn-0.2Ca alloy bar obtained in Step 4 to obtain an aged bimodal structure Mg-8Zn-0.2Ca alloy; the aging treatment temperature is 180 °C and the time is 10 h.

[0100] Perform mechanical property tests on the aged bimodal structure Mg-8Zn-0.2Ca alloy prepared in this example. The results show that: the tensile strength is 376 MPa, the yield strength is 368 MPa, and the elongation is 15.0%.

[0101] Example 8

[0102] This example includes the following steps:

[0103] Step 1: According to the designed composition of the target product Mg-Zn alloy, Mg-9Zn-0.2Ce-0.2Ca, weigh magnesium ingots, Zn, and Mg-30% Ce and Mg-25% Ca master alloys as alloy raw materials respectively;

[0104] Step 2: Heat the melting furnace to 650 °C and continuously introduce argon. Then put the magnesium ingots weighed in Step 1 into a crucible pre-placed in the melting furnace. Raise the furnace temperature to 730 °C and hold for 45 min. After all the magnesium ingots are melted, put the Zn and Mg-30% Ce master alloys weighed in Step 1 and continue to hold at 730 °C for 20 min;

[0105] After all the alloy raw materials are melted, use an ultrasonic stirring rod to ultrasonically stir the melt formed during melting to promote uniform diffusion of alloying elements. The frequency of ultrasonic stirring is 1000 kHz, the power is 1000 W, and the time is 4 min. Then lower the furnace temperature to 700 °C and hold for 12 min. Subsequently, skim the slag from the melt and pour it into a copper mold to obtain Mg-9Zn-0.2Ce-0.2Ca alloy ingots;

[0106] Step 3: Perform a two-stage homogenization treatment on the Mg-9Zn-0.2Ce-0.2Ca alloy ingots obtained in Step 2; The regime of the two-stage homogenization treatment is: the temperature of the first-stage homogenization treatment is 370 °C and the time is 12 h, and the temperature of the second-stage homogenization treatment is 420 °C and the time is 4 h;

[0107] Step 4: Preheat the Mg-9Zn-0.2Ce-0.2Ca alloy ingots after the two-stage homogenization treatment in Step 3. The preheating temperature is 350 °C and the preheating time is 30 min. Then perform differential temperature extrusion. The temperature of the extrusion die used for differential temperature extrusion is 200 °C, the extrusion speed is 2 mm / s, and the extrusion ratio is 16 to obtain an extruded Mg-9Zn-0.2Ce-0.2Ca alloy rod with a diameter of 10 mm;

[0108] Step 5: Perform a two-stage aging treatment on the extruded Mg-9Zn-0.2Ce-0.2Ca alloy rod obtained in Step 4 to obtain an aged double-peak structure Mg-9Zn-0.2Ce-0.2Ca alloy; The regime of the two-stage aging treatment is: the temperature of the first-stage aging treatment is 90 °C and the time is 10 h, and the temperature of the second-stage aging treatment is 180 °C and the time is 10 h.

[0109] Perform mechanical property tests on the aged double-peak structure Mg-9Zn-0.2Ce-0.2Ca alloy prepared in this example. The results show that: the tensile strength is 394 MPa, the yield strength is 382 MPa, and the elongation is 12.5%.

[0110] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a bimodal Mg-Zn alloy with high aging response, characterized in that: The method comprises the following steps: Step 1: preparing alloy raw materials according to the designed composition of the target product Mg-Zn alloy; Step 2, smelting the alloy raw material prepared in step 1, and simultaneously performing ultrasonic stirring on the melt formed by smelting to promote uniform diffusion of alloy elements, and then pouring to obtain a Mg-Zn alloy ingot; Step 3, subjecting the Mg-Zn alloy ingot obtained in step 2 to a two-stage homogenization treatment; Step 4: subjecting the Mg-Zn alloy ingot after the double-stage homogenization treatment in step 3 to differential temperature extrusion at low temperature to obtain an extruded Mg-Zn alloy; Step 5: Perform single-stage or double-stage aging treatment on the extruded Mg-Zn alloy obtained in step 4 to obtain an aged bimodal Mg-Zn alloy.

2. The method for preparing a bimodal Mg-Zn alloy with high aging response according to claim 1, characterized in that: The designed composition of the Mg-Zn alloy in step 1 includes the following components in percentage by mass: Zn 8% to 10%, Ce and / or Ca 0.2% to 0.5%, and the balance Mg.

3. The method for preparing a bimodal Mg-Zn alloy with high aging response according to claim 1, characterized in that: The frequency of the ultrasonic stirring in step 2 is 800kHz to 1000kHz, the power is 800W to 1000W, and the time is 3min to 5min.

4. The method for preparing a bimodal Mg-Zn alloy with high aging response according to claim 1, characterized in that: The double-stage homogenization treatment system in step three is: the first-stage homogenization treatment temperature is 370°C to 380°C, the time is 10h to 12h, and the second-stage homogenization treatment temperature is 400°C to 420°C, the time is 2h to 6h.

5. The method for preparing a bimodal Mg-Zn alloy with high aging response according to claim 1, characterized in that: Before the differential temperature extrusion in step 4, the Mg-Zn alloy ingot after the double-stage homogenization treatment is preheated, the preheating temperature is 300°C to 350°C, the preheating time is 30 minutes, the extrusion die temperature used in the differential temperature extrusion is 150°C to 200°C, the extrusion speed is 2mm / s to 4mm / s, and the extrusion ratio is 16 to 25.

6. The method for preparing a bimodal Mg-Zn alloy with high aging response according to claim 1, characterized in that: The temperature of the single-stage aging treatment in step 5 is 180°C to 200°C, and the time is 8h to 12h; the system of the double-stage aging treatment is: the first-stage aging treatment temperature is 90°C, the time is 8h, and the second-stage aging treatment temperature is 180°C, and the time is 8h to 12h.

7. A bimodal Mg-Zn alloy with high aging response, characterized in that: The aged bimodal Mg-Zn alloy is prepared by the method described in any one of claims 1 to 6, and has a tensile strength of more than 375 MPa and an elongation of more than 8%.

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