CN111286657A - High-strength Mg-Gd-Zn-Zr-Ag magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy and a preparation method thereof. The magnesium alloy is composed of the following components by mass percentage: Gd: 11-13%, Zn: 0.8-1.2%, Zr: 0.3 to 0.6%, Ag: 0.5 to 1.5, the total amount of unavoidable impurities is less than 0.12%, and the balance is Mg. In the magnesium alloy system of the present invention, adding Ag element can refine the crystal grains during the solidification process to improve the mechanical properties of the alloy; in addition, after extrusion deformation, Ag can also promote the formation of LPSO phase, which greatly improves the alloy's mechanical properties. Mechanical properties; after further aging treatment, the alloy precipitates more precipitation phase β' phase, which promotes the mechanical properties of the alloy to be further improved, and the tensile strength can reach 441MPa, which can meet the needs of the engineering field for light-strength magnesium alloy materials. , has a good application prospect in the aerospace field.

Description

A kind of high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy and preparation method thereof

technical field

The invention relates to the field of metal materials, in particular to a high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy and a preparation method thereof.

Background technique

In recent years, with the widespread interest in reducing _CO2 emissions from automobiles, lightweight structural materials have become a focus of increasing attention. As the lightest metal structural material, magnesium alloy has the advantages of low density, high specific strength and specific stiffness, and has broad application prospects in the fields of aerospace, weapon equipment, automobiles, communications, etc. A clear advantage that is difficult to replace, which can significantly reduce weight and save fuel consumption. However, due to the low strength of pure magnesium, it cannot meet the demand for lightweight and high-strength magnesium alloy materials in the engineering field, which greatly hinders the application of magnesium alloys in structural parts. Therefore, the development of high-strength lightweight magnesium alloys has become very urgent.

At present, commercial magnesium alloys are mainly divided into two types: cast magnesium alloys and wrought magnesium alloys. Cast magnesium alloys have poor performance due to coarse grains and severe component segregation, which cannot meet the needs of daily use. Compared with cast magnesium alloys, wrought magnesium alloys have excellent properties, high strength, plasticity and toughness, and are more suitable for daily diverse needs.

At present, the main method to improve the strength and toughness of magnesium alloys is to add alloying elements. Commonly used alloying elements are the addition of Re, Zn, Zr, Al, Mn, Ag, etc. By adding Re and Zn elements, the Mg-Re-Zn alloy exhibits good mechanical properties, mainly because when the ratio of RE atoms to Zn atoms reaches a certain value, the LPSO phase will be formed in the alloy, which is a hard phase. The strengthening phase can effectively improve the strength of the alloy. For Mg-Re-Zn alloys, the aging sequence is generally SSSS→β"(D019)→β'(bco)→β1(fcc)→β, and the β' phase is perpendicular to the direction of the basal plane and is the main Mg -Aging enhanced phase of RE-Zn alloy. Adding Ag atoms can significantly improve the aging hardening response of the alloy and promote the precipitation of β' phase, which can further promote the strength of the alloy and meet the diversified needs of the future market.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies in the prior art, one of the purposes of the present invention is to provide a high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy; the second purpose of the present invention is to provide a high-strength Mg-Gd-Zn- Preparation method of Zr-Ag magnesium alloy.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

1. A high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy, the magnesium alloy comprising the following components by mass percentage:

11-13% Gd, 0.8-1.2% Zn, 0.3-0.6% Zr: 0.5-1.5% Ag, the total amount is less than 0.12% of inevitable impurities, and the balance is Mg.

Preferably, the Gd uses a Mg-30%Gd master alloy as a raw material, and the Zr uses a Mg-30%Zr master alloy as a raw material.

Preferably, the Mg is made of industrial pure magnesium ingots, the Ag is made of industrial pure silver, and the Zn is made of industrial pure zinc.

2. The preparation method of the above-mentioned high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy, the method comprising the following steps:

1) smelting and casting: select raw materials by proportioning and smelting and casting to obtain Mg-Gd-Zn-Zr-Ag alloy ingot;

2) Heat treatment: the alloy ingot obtained in step 1) is placed in a heat treatment furnace for high temperature homogenization treatment, and then water-cooled to room temperature after completion;

3) Hot extrusion: preheat the ingot cooled in step 2) at 370 to 420° C. for 1 to 2 hours, and then add it to an extruder for extrusion and air cooling to obtain an extruded bar;

4) Machining: the extruded bar described in step 3) is processed to the specified size for use;

5) Aging treatment: Aging treatment is performed on the spared material in step 4) at 200-225° C. for 24-32 h, and then water-cooled to room temperature to obtain a high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy.

Preferably, the smelting and casting described in step 1) specifically includes the following steps: first, preheating the Mg, Zn, and Ag raw materials at 150-250° C. for 30-90 min, respectively, preheating the Mg-30% Gd master alloy and Mg-30% The Zr master alloy is preheated at 200～300℃ for 30～60min respectively; then the Mg raw material is heated to 700～720℃ in a protective atmosphere, and the preheated Mg-30%Gd master alloy, Zn raw material and Ag raw material are added in sequence; Then heat up to 730～750℃ and keep for 10～20min, add preheated Mg-30%Zr master alloy and stir to make it evenly mixed; finally let stand for 20～30min and then naturally cool down to 690～720℃, under the protection of atmosphere Cooling in saturated brine to obtain magnesium alloy ingots.

Preferably, the protective atmosphere is a mixed gas formed by CO ₂ and SF ₆ with a volume ratio of 99:1.

Preferably, the specific operation of the high temperature homogenization treatment in step 2) is as follows: first, the Mg-Gd-Zn-Zr-Ag alloy ingot obtained by smelting and casting is covered with graphite, and then the temperature is kept at 500-510 ° C for 10 ~12h, and finally water cooled to room temperature.

Preferably, in the extrusion process in step 3), the temperature of the extrusion cylinder is 370-420° C., the extrusion ratio is 10:1-15:1, and the extrusion speed is 15-25 mm/s.

The beneficial effects of the present invention are:

1. The extruded magnesium alloy prepared by the present invention has good mechanical properties, adding 0.5-1.5% Ag, with the increase of Ag content, the strength of the alloy increases continuously, and the highest strength can be as high as 411MPa, which is higher than the alloy without Ag added. The strength is increased by about 20%; through aging treatment, the alloy precipitates more precipitation phase β' phase, so that the alloy has a strength of up to 441MPa at room temperature, which can meet the needs of the engineering field for lightweight and high-strength magnesium alloy materials. The field has good application prospects.

2. The present invention realizes the high strength of the magnesium alloy by adding alloying elements (Gd, Zn, Zr, Ag) to the magnesium alloy, and then cooperating with the heat treatment process. The present invention can be realized by using conventional general equipment, and has the advantages of simple operation, reasonable process design and short flow. The raw materials used in the alloy system are all conventional elements, and a deformed magnesium alloy with higher strength can be obtained by extrusion and aging heat treatment, which improves the production efficiency and is beneficial to large-scale industrial application.

Description of drawings

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be preferably described in detail below with reference to the accompanying drawings, wherein:

1 is a metallographic microstructure diagram of the magnesium alloy (Mg-12Gd-1Zn-0.5Zr-0.5Ag) prepared in Example 1;

2 is a metallographic microstructure diagram of the magnesium alloy (Mg-12Gd-1Zn-0.5Zr-1.0Ag) prepared in Example 2;

3 is a metallographic microstructure diagram of the magnesium alloy (Mg-12Gd-1Zn-0.5Zr-1.5Ag) prepared in Example 3.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments are only used to illustrate the basic idea of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

Example 1

A high-strength and high-toughness Mg-Gd-Zn-Zr-Ag magnesium alloy is prepared, wherein the raw materials are prepared according to the following mass percentages: 12% Gd (from Mg-30% Gd master alloy), 1.0% Zn (from Mg-30% Gd master alloy) Industrial pure zinc), 0.5% Zr (from Mg-30% Zr master alloy), 0.5% Ag (from industrial pure silver), and impurity elements with a total content of less than 0.12%, the balance is Mg (from In industrial pure magnesium ingot), its preparation method is as follows:

(1) Smelting and casting: Preheat industrial pure magnesium ingots, pure zinc and pure silver at 150°C for 90min respectively according to the corresponding weight percentages, and separate Mg-30%Gd master alloy and Mg-30%Zr master alloy respectively. Preheated at 200 °C for 60 min; then heated the preheated industrial pure magnesium ingot to 700 °C under a protective atmosphere (volume ratio of _CO2 to _SF6 gas 99:1) and added preheated Mg-30% sequentially Gd master alloy, Zn raw material and Ag raw material; then heat up to 730 ℃ for 20 min, add preheated Mg-30% Zr master alloy and stir to mix well; finally let stand for 20 min, and then cool down to 690 ℃ and protect it in the atmosphere The magnesium alloy ingot is obtained after being placed in saturated salt water for cooling;

(2) heat treatment: the obtained magnesium alloy ingot through smelting and casting of step (1) is placed in a heat treatment furnace to carry out high temperature homogenization treatment (first, the magnesium alloy ingot obtained by smelting and casting is covered with graphite, then at 500 Heat preservation at ~510℃ for 10-12h, and finally water-cool to room temperature), set the heating rate to 15℃/min during the treatment process, heat to 500℃, keep warm for 12h, and then water-cool to room temperature after completion;

(3) machining: machining the magnesium alloy ingot obtained through step (2) to obtain a cylinder with a radius of 80 mm and a height of 90 m, for use;

(4) Hot extrusion: after preheating the cylinder machined in step (3) at 370°C for 2 hours, extrude it on the extruder, which means that the temperature of the extrusion cylinder of the extruder is 400°C, The extrusion ratio is 10:1 and the extrusion speed is 25mm/s;

(5) Aging treatment: The hot extrusion product is subjected to aging treatment at 200 ° C for 32 hours, and then water-cooled to room temperature to obtain a high-strength magnesium alloy Mg-12Gd-1Zn-0.5Zr-0.5Ag, which has a microscopic metallographic structure. The organization chart is shown in Figure 1.

Example 2

A high-strength and high-toughness Mg-Gd-Zn-Zr-Ag magnesium alloy is prepared, wherein the raw materials are prepared according to the following mass percentages: 12% Gd (from Mg-30% Gd master alloy), 1.0% Zn (from Mg-30% Gd master alloy) Industrial pure zinc), 0.5% Zr (from Mg-30% Zr master alloy), 1.0% Ag (from industrial pure silver), and impurity elements with a total content of less than 0.12%, the balance is Mg (from industrial pure magnesium ingot), a high-strength magnesium alloy Mg-12Gd-1Zn-0.5Zr-1.0Ag was prepared according to the preparation method in Example 1, and its metallographic microstructure diagram is shown in FIG. 2 .

Example 3

A high-strength and high-toughness Mg-Gd-Zn-Zr-Ag magnesium alloy is prepared, wherein the raw materials are prepared according to the following mass percentages: 12% Gd (from Mg-30% Gd master alloy), 1.0% Zn (from Mg-30% Gd master alloy) Industrial pure zinc), 0.5% Zr (from Mg-30% Zr master alloy), 1.5% Ag (from industrial pure silver), and impurity elements with a total content of less than 0.12%, the balance is Mg (from industrial pure magnesium ingot), a high-strength magnesium alloy Mg-12Gd-1Zn-0.5Zr-1.5Ag was prepared according to the preparation method in Example 1, and its metallographic microstructure diagram is shown in FIG. 3 .

It can be seen from the metallographic microstructure diagrams in Figures 1-3 that during the extrusion process of magnesium alloy preparation, the grains are obviously refined, which is mainly because of dynamic recrystallization during extrusion; and with the increase of Ag content The increase of , the grain refinement is obvious, and the content of LPSO phase increases significantly, mainly because Ag atoms can replace part of Zn atoms and participate in the formation of LPSO phase.

Table 1 shows the test results of mechanical properties before aging treatment of the magnesium alloys prepared in Examples 1, 2 and 3 and the commercial magnesium alloy ZK60A (the difference from Examples 1 to 3 is that it does not contain Gd and Ag):

Table 1 Test results of mechanical properties of different magnesium alloys

According to the performance test analysis of the examples and ZK60A in Table 1 before the aging treatment, it can be known that: before the aging treatment, the tensile strength of the extruded Mg-Gd-Zn-Zr-Ag magnesium alloy prepared in The yield strength has been improved, especially the tensile strength, yield strength and elongation of the extruded Mg-Gd-Zn-Zr-Ag magnesium alloy prepared in Example 1 are higher than those of ZK60A (tensile strength increased by 11.7%). %, yield strength increased by 19.6%, elongation increased by 39%).

Table 2 is the mechanical property test result after the magnesium alloy prepared by embodiment 1, 2, 3 and commercial magnesium alloy ZK60A aging treatment:

Table 2 Aged mechanical properties of different magnesium alloys

According to the mechanical properties test results obtained in Table 2 after the above Examples 1 to 3 and ZK60A aging treatment, it can be seen that after the aging treatment, the magnesium alloys prepared in Examples 1 to 3 have higher strength, and the tensile strength reaches 441MPa at most. , significantly higher than the tensile strength of ZK60A (265MPa). The reason is that: the added Gd element in the magnesium alloy prepared by the present invention has the effect of solid solution strengthening and aging strengthening; the added Ag element has the effect of refining grains and aging precipitation, which can further improve the strength of the alloy; at the same time, through aging After heat treatment, a large amount of β' phase is precipitated, which helps to improve the strength of the alloy. The tensile strength of the high-strength and high-toughness magnesium alloy prepared in this example can reach 430-441 MPa, the yield strength can reach 335-338 MPa, and the elongation is 4.3-6.0%. The mechanical properties of several alloys can meet the actual demand for materials in the fields of electronics, automobiles, aerospace, building decoration materials, etc. In addition, the equipment used in the present invention is simple in process and easy to operate.

Example 4

A high-strength and high-toughness Mg-Gd-Zn-Zr-Ag magnesium alloy is prepared, wherein the raw materials are prepared according to the following mass percentages: 11% Gd (from Mg-30% Gd master alloy), 0.8% Zn (from Mg-30% Gd master alloy) Industrial pure zinc), 0.3% Zr (from Mg-30% Zr master alloy), 0.5% Ag (from industrial pure silver), and impurity elements with a total content of less than 0.12%, the balance is Mg (from In industrial pure magnesium ingot), its preparation method is as follows:

(1) Smelting and casting: Preheat industrial pure magnesium ingots, pure zinc and pure silver at 250°C for 30min according to the corresponding weight percentages. Preheated at ℃ for 30min; then heated the preheated industrial pure magnesium ingot to 720℃ in a protective atmosphere (the volume ratio of _CO2 to _SF6 gas was 99:1) and added the preheated Mg-30%Gd intermediate Alloy, Zn raw material and Ag raw material; then heat up to 750 ℃ for 10 minutes, add preheated Mg-30% Zr master alloy and stir to make it fully mixed; finally let stand for 30 minutes, and put it under atmosphere protection after cooling to 720 ℃ After cooling in saturated brine, magnesium alloy ingots are obtained;

(2) heat treatment: the obtained magnesium alloy ingot through smelting and casting of step (1) is placed in a heat treatment furnace to carry out high temperature homogenization treatment (first, the magnesium alloy ingot obtained by smelting and casting is covered with graphite, then at 500 ℃ for 12h, and finally water-cooled to room temperature), set the heating rate to 15°C/min during the treatment process, heat to 500°C, hold for 12h, and then water-cool to room temperature after completion;

(3) machining: machining the magnesium alloy ingot obtained through step (2) to obtain a cylinder with a radius of 80 mm and a height of 90 m, for use;

(4) Hot extrusion: after preheating the cylinder machined in step (3) at 420°C for 1 hour, extrude it on the extruder, which means that the temperature of the extrusion cylinder of the extruder is 420°C, The extrusion ratio is 15:1 and the extrusion speed is 15mm/s;

(5) Aging treatment: The product after hot extrusion is subjected to aging treatment at 225 ° C for 24 hours, and then water-cooled to room temperature to obtain a high-strength magnesium alloy Mg-11Gd-0.8Zn-0.3Zr-0.5Ag.

Example 5

A high-strength and high-toughness Mg-Gd-Zn-Zr-Ag magnesium alloy is prepared, wherein the raw materials are prepared according to the following mass percentages: 13% Gd (from Mg-30% Gd master alloy), 1.2% Zn (from Mg-30% Gd master alloy) Industrial pure zinc), 0.6% Zr (from Mg-30% Zr master alloy), 1.5% Ag (from industrial pure silver), and impurity elements with a total content of less than 0.12%, the balance is Mg (from In industrial pure magnesium ingot), its preparation method is as follows:

(1) Smelting and casting: Preheat industrial pure magnesium ingots, pure zinc and pure silver at 200°C for 60 minutes according to the corresponding weight percentages, and mix Mg-30% Gd master alloy and Mg-30% Zr master alloy at 250 Preheated at ℃ for 40min; then heated the preheated industrial pure magnesium ingot to 710℃ in a protective atmosphere (the volume ratio of _CO2 to _SF6 gas was 99:1) and sequentially added the preheated Mg-30%Gd intermediate Alloy, Zn raw material and Ag raw material; then heat up to 740 ℃ for 15 minutes, add preheated Mg-30% Zr master alloy and stir to make it fully mixed; finally let stand for 25 minutes, after cooling to 700 ℃, put it under atmosphere protection After cooling in saturated brine, magnesium alloy ingots are obtained;

(2) heat treatment: the obtained magnesium alloy ingot through smelting and casting of step (1) is placed in a heat treatment furnace to carry out high temperature homogenization treatment (first, the magnesium alloy ingot obtained by smelting and casting is covered with graphite, and then at 510 ℃ for 10h, and finally water-cooled to room temperature), during the treatment process, set the heating rate to 15℃/min, heat to 510℃, hold for 10h, and then water-cool to room temperature after completion;

(3) machining: machining the magnesium alloy ingot obtained through step (2) to obtain a cylinder with a radius of 80 mm and a height of 90 m, for use;

(4) Hot extrusion: after preheating the cylinder machined in step (3) at 420°C for 1 hour, extrude it on the extruder, which means that the temperature of the extrusion cylinder of the extruder is 420°C, The extrusion ratio is 15:1 and the extrusion speed is 15mm/s;

(5) Aging treatment: The hot extrusion product is subjected to aging treatment at 225° C. for 24 hours, and then water-cooled to room temperature to obtain a high-strength magnesium alloy Mg-13Gd-1.2Zn-0.6Zr-1.5Ag.

The magnesium alloys prepared by the methods of Examples 4 and 5 have been tested and found that their gold tensile strength can still reach 430-441 MPa, yield strength can reach 335-338 MPa, and elongation is 4.3-6.0%, which further illustrates the preparation of the present invention. The magnesium alloy prepared by the method can indeed improve the properties of the original magnesium alloy to a certain extent, and can promote its further application and promotion.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent replacements, without departing from the spirit and scope of the technical solution, should all be included in the scope of the claims of the present invention.

Claims (8)

1. The high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy is characterized by comprising the following components in percentage by mass: 11-13% of Gd, 0.8-1.2% of Zn, 0.3-0.6% of Zr: 0.5-1.5% of Ag, less than 0.12% of unavoidable impurities in total, and the balance of Mg.

2. The high strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to claim 1, wherein said Gd is fed from Mg-30% Gd master alloy and said Zr is fed from Mg-30% Zr master alloy.

3. The high strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to claim 1, wherein said Mg is from an industrial pure magnesium ingot, said Ag is from an industrial pure silver, and said Zn is from an industrial pure zinc.

4. A method for preparing a high strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to any one of claims 1 to 3, characterized in that the method comprises the steps of:

1) smelting and casting: selecting raw materials according to the proportion, and smelting and casting to obtain Mg-Gd-Zn-Zr-Ag alloy cast ingots;

2) and (3) heat treatment: placing the alloy ingot obtained in the step 1) in a heat treatment furnace for high-temperature homogenization treatment, and then cooling the alloy ingot to room temperature by water;

3) hot extrusion: preheating the cast ingot cooled in the step 2) at 370-420 ℃ for 1-2 h, and then adding the cast ingot into an extruder for extrusion and air cooling to obtain an extruded bar;

4) machining: processing the extruded bar in the step 3) to a specified size for later use;

5) aging treatment: aging the material prepared in the step 4) at 200-225 ℃ for 24-32 h, and then cooling to room temperature by water to obtain the high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy.

5. The method for preparing the high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to claim 4, wherein the smelting and casting in the step 1) specifically comprises the following steps: firstly, preheating Mg, Zn and Ag raw materials at 150-250 ℃ for 30-90 min respectively, and preheating a Mg-30% Gd intermediate alloy and a Mg-30% Zr intermediate alloy at 200-300 ℃ for 30-60 min respectively; then heating the Mg raw material to 700-720 ℃ under a protective atmosphere, and sequentially adding a preheated Mg-30% Gd intermediate alloy, a Zn raw material and an Ag raw material; then heating to 730-750 ℃, preserving heat for 10-20 min, adding preheated Mg-30% Zr intermediate alloy, and stirring to uniformly mix; and finally standing for 20-30 min, naturally cooling to 690-720 ℃, and placing in saturated salt solution under the protection of atmosphere for cooling to obtain the magnesium alloy ingot.

6. The method for preparing the high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to claim 5, wherein the protective atmosphere is CO with a volume ratio of 99:1₂And SF₆The resulting mixed gas.

7. The method for preparing the high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to the claim 4, wherein the specific operations of the high temperature homogenization treatment in the step 2) are as follows: firstly, coating graphite outside a Mg-Gd-Zn-Zr-Ag alloy cast ingot obtained by smelting and casting, then preserving heat for 10-12 h at 500-510 ℃, and finally cooling to room temperature by water.

8. The method for preparing the high-strength Mg-Gd-Zn-Zr-Ag magnesium alloy according to claim 4, wherein the temperature of the extrusion cylinder in the extrusion process in the step 3) is 370-420 ℃, the extrusion ratio is 10: 1-15: 1, and the extrusion speed is 15-25 mm/s.

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