CN105039816B - A kind of high strength and low cost heat resistance magnesium alloy and preparation method thereof - Google Patents

Abstract

The invention discloses a low-cost high-strength heat-resistant magnesium alloy and a preparation method thereof. The magnesium alloy is composed of the following components in weight percent: 6.2-9.3% Al, 3.5-5.5% Sn, 1.0-1.8% Sb, 0.2- 0.9% Si, 0.1-0.4% Sm, and the balance is Mg. The low-cost high-strength heat-resistant magnesium alloy provided by the present invention uses multi-element microalloying to improve the microstructure of the magnesium alloy, thereby improving its mechanical properties; rationally selecting alloying elements, controlling the content of each alloying element, and making full use of each component The synergistic strengthening effect of the magnesium alloy improves the mechanical properties and heat resistance of the magnesium alloy; the heat-resistant magnesium alloy provided by the invention has a uniform microstructure, high room temperature and high temperature strength, and excellent high temperature creep resistance; On the basis of maintaining high mechanical properties, the cost of the magnesium alloy is greatly reduced, and it is suitable for popularization and application.

Description

A low-cost high-strength heat-resistant magnesium alloy and its preparation method

technical field

The invention belongs to the technical field of metal materials and metallurgy, and in particular relates to a low-cost, high-strength, heat-resistant magnesium alloy and a preparation method thereof.

Background technique

Magnesium and magnesium alloys, as the lightest metal structural materials in engineering applications at the present stage, have low density, high specific strength and specific stiffness, excellent damping and shock absorption performance, and good heat dissipation, and have excellent performance in many fields. Application potential, especially in aerospace, automobiles and motorcycles, high-speed light rail trains and 3C products, it has irreplaceable application advantages.

At present, commercial magnesium alloys are divided into two categories: cast magnesium alloys and wrought magnesium alloys. MgAl series cast magnesium alloys are the most widely used due to their good mechanical properties at room temperature, good flow castability, good machinability, low price and simple casting process, among which AZ91 and AM60/50 series are the most widely used, but there are Defects of poor plasticity and poor high temperature mechanical properties.

In order to meet the needs of the market and expand the application range and fields of magnesium alloys, researchers have conducted a lot of research on the existing MgAl series cast magnesium alloys. Using alloying to improve the mechanical properties of magnesium alloys at room temperature and high temperature is one of the main research directions. The alloying elements used mainly include rare earth elements and alkaline earth elements, as well as other elements such as aluminum, zinc, tin, silicon, antimony, etc., and Mg- Al-Ca, Mg-Al-Si, Mg-Al-RE, Mg-Y-Nd and other series of heat-resistant magnesium alloys, but the above alloys are rarely used in practice due to various reasons. Among them, Mg-Al-Ca series (such as AX51) alloys are limited in casting performance and are prone to hot cracks; Mg-Al-Si series (such as AS41 and AS21) alloys have coarse Chinese character-shaped Mg ₂ Si phases in their structures , which damages its mechanical properties; Mg-Al-RE series (such as AE42) alloys and Mg-Y-Nd series (such as WE43 and WE54), due to the addition of more rare earth elements in the alloy, the cost of the alloy is high and limited It is widely used; the use of cheap elements to improve the mechanical properties of magnesium alloys plays an important role in the application of magnesium alloys in a wider range.

Patent CN101871068B discloses a low-cost, high-strength and high-plastic magnesium alloy containing tin and aluminum and its manufacturing method. The alloy composition and weight percentage are 3-7% Al, 3-6% Sn, and the balance is Mg and Avoid impurities. The alloy has the advantages of high strength and excellent plasticity, no need for heat treatment, and can be used directly. However, in the alloy structure, Sn segregates between dendrites, and the precipitated intermetallic compounds Mg ₁₇ Al ₁₂ and Mg ₂ Sn have coarse grains and uneven distribution, which easily leads to poor mechanical properties and creep resistance when the alloy works at high temperatures. The denaturation becomes worse, thereby affecting the service life of the magnesium alloy.

Contents of the invention

The purpose of the present invention is to provide a low-cost high-strength heat-resistant magnesium alloy, on the basis of controlling the cost of the alloy, improve the mechanical properties of the magnesium alloy at room temperature and high temperature, and endow the alloy with excellent creep resistance at high temperature, Expand the scope of application of magnesium alloys.

The second object of the present invention is to provide the above-mentioned low-cost, high-strength, heat-resistant magnesium alloy preparation method.

In order to achieve the above object, the technical solution adopted in the present invention is:

A low-cost, high-strength, heat-resistant magnesium alloy is composed of the following components in weight percent: 6.2-9.3% Al, 3.5-5.5% Sn, 1.0-1.8% Sb, 0.2-0.9% Si, 0.1-0.4% Sm, and The amount is Mg.

In the low-cost high-strength heat-resistant magnesium alloy provided by the present invention, Al is an important alloying element in magnesium alloy, has a very large solid solubility in magnesium, and has obvious strengthening effect, and its strengthening effect surface has two aspects, one is through The second phase strengthening is the formation of Mg ₁₇ Al ₁₂ intermetallic compounds, and the second is solid solution strengthening through the formation of solid solutions by Al atoms in the magnesium matrix. In order to avoid a large amount of Mg ₁₇ Al ₁₂ phases with poor thermal stability, the content of Al in magnesium-aluminum alloys is generally controlled below 9%, but too low Al content will damage the casting performance of magnesium alloys, especially the fluidity of alloys Generally, the Al content of the cast magnesium alloy should not be lower than 6%, and the Al content in the magnesium alloy of the present invention is 6.2-9.3%. Adding Sn element can improve the fluidity of magnesium alloy and reduce the hot cracking sensitivity of magnesium alloy. The Mg ₂ Sn phase formed by Sn and Mg has a strengthening effect and helps to improve the strength and toughness of the alloy; a small amount of samarium in the raw material composition can purify Alloy liquid, refine alloy structure, improve the morphology and distribution of Mg ₁₇ Al ₁₂ phase, improve mechanical properties; add appropriate amount of antimony and silicon alloy elements, which is beneficial to the grain boundary of Mg-Al or Mg-Al-Sn matrix The intermetallic phases with good high temperature resistance are precipitated, and these intermetallic phases prevent the grains from sliding under high temperature stress conditions, so that the alloy exhibits excellent high temperature creep resistance.

The low-cost high-strength heat-resistant magnesium alloy provided by the invention has an alloy composition of Mg-Al-Sn-Sb-Si-Sm, and uses multi-element microalloying to improve the microstructure of the magnesium alloy, thereby improving its mechanical properties; rationally selecting the alloy Alloying elements, controlling the content of each alloying element, exerted the synergistic strengthening effect of each component, and improved the mechanical properties and heat resistance of magnesium alloys.

The preparation method of the above-mentioned low-cost high-strength heat-resistant magnesium alloy comprises the following steps:

1) Melting raw materials magnesium, aluminum, tin and antimony under the protection of mixed gas to form alloy melt A;

2) When the alloy melt A obtained in step 1) is heated to 710-730°C, the intermediate alloy Mg-Sm and the intermediate alloy Mg-Si are added, and after the alloy is completely melted, the temperature is raised to 740-750°C and stirred evenly to obtain the alloy Melt B;

3) reducing the temperature of the alloy melt B obtained in step 2) to 680-700° C., leaving it to stand, and casting it into a mold to obtain an as-cast alloy;

4) heat-treating the as-cast alloy obtained in step 3).

The raw materials magnesium, aluminum, tin, antimony, master alloy Mg-Sm and master alloy Mg-Si are preheated before use. The raw materials are preheated, which helps the subsequent smelting and casting process to proceed uniformly and stably; the temperature of the preheating is 170-200°C, and the preheating time is not less than 2h; the preheating condition is further preferably 180°C 3h.

Step 1) The mixed gas is CO ₂ and SF ₆ .

Step 3) The mold is preheated before casting. The temperature of the mold preheating treatment is 280-320°C; more preferably, the mold preheating temperature is 300°C.

Step 4) The heat treatment is to perform solution treatment and aging treatment on the as-cast alloy in sequence.

The temperature of the solution treatment is 415-430° C., and the treatment time is 10-14 hours; the solution treatment conditions are more preferably, the temperature is 425° C., and the treatment time is 11 hours; after the solution treatment, the hot water is quenched to room temperature. The temperature of the hot water used is 75-90°C.

The temperature of the aging treatment is 200-250° C., and the treatment time is 14-18 hours; the aging treatment conditions are more preferably, the temperature is 220° C., and the treatment time is 16 hours; air cooling to room temperature after the aging treatment.

The solid solution treatment is carried out under the cover of magnesium oxide powder.

The preparation method of the low-cost high-strength heat-resistant magnesium alloy provided by the present invention uses magnesium, aluminum, tin, antimony, master alloy Mg-Sm and master alloy Mg-Si as raw materials for melting and casting and heat treatment, and the microstructure of the obtained magnesium alloy is uniform , has high strength at room temperature and high temperature, and has excellent creep resistance under high temperature conditions; the raw materials used are cheap and easy to obtain, the difficulty of smelting and casting is low, the process is easy to control, and the production cost is greatly reduced. The process is simple and the operation Convenient and suitable for large-scale industrial production.

The heat-resistant magnesium alloy prepared by this method has uniform microstructure, the tensile strength at room temperature can reach 285MPa, and the tensile strength at 200°C can reach 192MPa, which has high room temperature and high temperature strength; After creeping for 100 hours, the minimum strain is 0.36%, and the steady-state creep rate is as low as 1.21×10 ^-8 s ^-1 , which has good high temperature creep resistance; the main components of the alloy are cheap elements, and the On the basis of higher mechanical properties, the cost of the magnesium alloy is greatly reduced, and it is suitable for popularization and application.

detailed description

The present invention will be further described below in conjunction with specific examples. The raw materials magnesium (Mg), aluminum (Al), tin (Sn), antimony (Sb), master alloy Mg-Sm and master alloy Mg-Si involved in each embodiment are all commercially available products.

Example 1

The low-cost high-strength heat-resistant magnesium alloy of this embodiment is composed of the following components in weight percentage: 6.2% Al, 4.9% Sn, 1.8% Sb, 0.7% Si, 0.4% Sm, and the balance is Mg.

The preparation method of the low-cost high-strength heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Place the raw materials of pure magnesium ingot, pure aluminum ingot, pure tin grain, pure antimony, Mg-Sm master alloy and Mg-Si master alloy in a drying oven for drying and preheating. The preheating temperature is 180°C and the preheating time is 3 hours; melt the preheated pure magnesium ingots, pure aluminum ingots, pure tin grains, and pure antimony under the protection of CO ₂ +SF ₆ mixed gas to form alloy melt A;

2) When the alloy melt A obtained in step 1) is heated to 720°C, add the master alloy Mg-Sm and master alloy Mg-Si, keep it warm for 10 minutes, remove the surface scum after the alloy is completely melted, continue to heat up to 740°C and stop Raise the temperature and stir evenly to obtain alloy melt B;

3) Reduce the temperature of the alloy melt B obtained in step 2) to 700°C, let it stand for 5 minutes, and then cast it into a preheated metal mold (the preheating temperature of the metal mold is 300°C) to obtain the cast state alloy;

4) The as-cast alloy obtained in step 3) is subjected to solution treatment and aging treatment sequentially, the solution treatment is carried out under the cover of magnesium oxide powder, the treatment temperature is 425 ° C, the treatment time is 11 h, 80 ° C hot water quenching to room temperature; aging The treatment temperature is 220° C., the treatment time is 16 hours, and air-cooled to room temperature.

Example 2

The low-cost, high-strength, heat-resistant magnesium alloy of this embodiment is composed of the following components by weight percentage: 7.4% Al, 5.5% Sn, 1.5% Sb, 0.9% Si, 0.2% Sm, and the balance is Mg.

The preparation method of the low-cost high-strength heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Place the raw materials of pure magnesium ingot, pure aluminum ingot, pure tin grain, pure antimony, Mg-Sm master alloy and Mg-Si master alloy in a drying oven for drying and preheating. The preheating temperature is 170°C and the preheating time is 4 hours; melt the preheated pure magnesium ingots, pure aluminum ingots, pure tin grains, and pure antimony under the protection of CO ₂ +SF ₆ mixed gas to form alloy melt A;

2) When the alloy melt A obtained in step 1) is heated to 730°C, add the master alloy Mg-Sm and master alloy Mg-Si, keep it warm for 10 minutes, remove the surface scum after the alloy is completely melted, continue to heat up to 740°C and stop Raise the temperature and stir evenly to obtain alloy melt B;

3) Reduce the temperature of the alloy melt B obtained in step 2) to 690°C, let it stand for 5 minutes, and then cast it into a preheated metal mold (the preheating temperature of the metal mold is 300°C) to obtain the cast state alloy;

4) The as-cast alloy obtained in step 3) is subjected to solution treatment and aging treatment sequentially, the solution treatment is carried out under the cover of magnesium oxide powder, the treatment temperature is 420°C, the treatment time is 13h, and the hot water is quenched at 85°C to room temperature; aging The treatment temperature is 220° C., the treatment time is 16 hours, and air-cooled to room temperature.

Example 3

The low-cost, high-strength, heat-resistant magnesium alloy of this embodiment is composed of the following components by weight percentage: 8.6% Al, 4.4% Sn, 1.6% Sb, 0.2% Si, 0.3% Sm, and the balance is Mg.

The preparation method of the low-cost high-strength heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Place the raw materials of pure magnesium ingot, pure aluminum ingot, pure tin grain, pure antimony, Mg-Sm master alloy and Mg-Si master alloy in a drying oven for drying and preheating. The preheating temperature is 200°C and the preheating time is 2 hours; melt the preheated pure magnesium ingots, pure aluminum ingots, pure tin particles, and pure antimony under the protection of CO ₂ +SF ₆ mixed gas to form alloy melt A;

2) When the alloy melt A obtained in step 1) is heated to 720°C, add the master alloy Mg-Sm and master alloy Mg-Si, keep it warm for 10 minutes, remove the surface scum after the alloy is completely melted, continue to heat up to 740°C and stop Raise the temperature and stir evenly to obtain alloy melt B;

3) Reduce the temperature of the alloy melt B obtained in step 2) to 700°C, let it stand for 5 minutes, and then cast it into a preheated metal mold (the preheating temperature of the metal mold is 300°C) to obtain the cast state alloy;

4) The as-cast alloy obtained in step 3) is subjected to solution treatment and aging treatment sequentially, the solution treatment is carried out under the cover of magnesium oxide powder, the treatment temperature is 430°C, the treatment time is 10h, and the hot water is quenched at 90°C to room temperature; aging The treatment temperature is 250° C., the treatment time is 15 hours, and air-cooled to room temperature.

Example 4

The low-cost high-strength heat-resistant magnesium alloy of this embodiment is composed of the following components in weight percentage: 9.3% Al, 3.5% Sn, 1.2% Sb, 0.4% Si, 0.1% Sm, and the balance is Mg.

The preparation method of the low-cost high-strength heat-resistant magnesium alloy of the present embodiment comprises the following steps:

1) Place the raw materials of pure magnesium ingot, pure aluminum ingot, pure tin grain, pure antimony, Mg-Sm master alloy and Mg-Si master alloy in a drying oven for drying and preheating. The preheating temperature is 180°C and the preheating time is 3 hours; melt the preheated pure magnesium ingots, pure aluminum ingots, pure tin grains, and pure antimony under the protection of CO ₂ +SF ₆ mixed gas to form alloy melt A;

2) When the alloy melt A obtained in step 1) is heated to 720°C, add the master alloy Mg-Sm and master alloy Mg-Si, keep it warm for 10 minutes, remove the surface scum after the alloy is completely melted, continue to heat up to 740°C and stop Raise the temperature and stir evenly to obtain alloy melt B;

3) Reduce the temperature of the alloy melt B obtained in step 2) to 700°C, let it stand for 5 minutes, and then cast it into a preheated metal mold (the preheating temperature of the metal mold is 300°C) to obtain the cast state alloy;

4) The as-cast alloy obtained in step 3) is subjected to solution treatment and aging treatment sequentially, the solution treatment is carried out under the cover of magnesium oxide powder, the treatment temperature is 425°C, the treatment time is 11h, and the hot water is quenched at 90°C to room temperature; aging The treatment temperature is 220° C., the treatment time is 16 hours, and air-cooled to room temperature.

Test case

This test example detects the tensile strength, yield strength and high temperature creep resistance of the low-cost high-strength heat-resistant magnesium alloy obtained in Examples 1-4, wherein the creep test test conditions are: creep temperature 200 ° C, stress 70 MPa conditions Under 100 hours. The test results are listed in Table 1. From the test results in Table 1, it can be seen that the low-cost high-strength heat-resistant magnesium alloy prepared by the present invention has high tensile strength, yield strength and creep resistance in the range of room temperature to 200°C, and is suitable for large-scale application.

Table 1 The performance detection results of low-cost high-strength heat-resistant magnesium alloys in Examples 1-4

Claims (10)

1. A low-cost high-strength heat-resistant magnesium alloy is characterized in that it consists of the following components in weight percentage: 6.2-9.3% Al, 3.5-5.5% Sn, 1.0-1.8% Sb, 0.2-0.9% Si, 0.1 ~0.4% Sm, balance Mg. 2. a preparation method of low-cost high-strength heat-resistant magnesium alloy as claimed in claim 1, is characterized in that, comprises the following steps: 1) Melting raw materials magnesium, aluminum, tin and antimony under the protection of mixed gas to form alloy melt A; 2) When the alloy melt A obtained in step 1) is heated to 710-730°C, the intermediate alloy Mg-Sm and the intermediate alloy Mg-Si are added, and after the alloy is completely melted, the temperature is raised to 740-750°C and stirred evenly to obtain the alloy Melt B; 3) reducing the temperature of the alloy melt B obtained in step 2) to 680-700° C., leaving it to stand, and casting it into a mold to obtain an as-cast alloy; 4) heat-treating the as-cast alloy obtained in step 3). 3. the preparation method of low-cost high-strength heat-resistant magnesium alloy as claimed in claim 2 is characterized in that, described raw material magnesium, aluminium, tin, antimony, intermediate alloy Mg-Sm and intermediate alloy Mg-Si are preheated before using deal with. 4. The method for preparing a low-cost high-strength heat-resistant magnesium alloy according to claim 3, characterized in that the temperature of the preheating treatment is 170-200° C., and the preheating time is not less than 2 hours. 5. The method for preparing a low-cost high-strength heat-resistant magnesium alloy according to claim 2, characterized in that the mold in step 3) is preheated before casting. 6. The method for preparing a low-cost high-strength heat-resistant magnesium alloy according to claim 5, characterized in that the preheating temperature of the mold is 280-320°C. 7. The method for preparing a low-cost, high-strength, heat-resistant magnesium alloy according to claim 2, characterized in that the heat treatment in step 4) is to sequentially perform solution treatment and aging treatment on the as-cast alloy. 8. The preparation method of low-cost high-strength heat-resistant magnesium alloy as claimed in claim 7, characterized in that, the temperature of the solution treatment is 415-430°C, the treatment time is 10-14h, and the hot water is quenched to room temperature; The hot water temperature is 75-90°C. 9. The method for preparing a low-cost high-strength heat-resistant magnesium alloy according to claim 7, characterized in that the temperature of the aging treatment is 200-250° C., the treatment time is 14-18 hours, and the aging treatment is air-cooled to room temperature. 10. The method for preparing low-cost high-strength heat-resistant magnesium alloy according to claim 7 or 8, characterized in that the solution treatment is carried out under the cover of magnesium oxide powder.