Heat-resistant and corrosion-resistant magnesium alloy and preparation method thereof

Abstract

The invention belongs to the field of magnesium-based alloys, and particularly relates to a heat-resistant and corrosion-resistant magnesium alloy and a preparation method thereof. The heat-resistant and corrosion-resistant magnesium alloy is composed of the following components in percentage by mass: 2.6%-4.6% of Yb, 0.85%-1.65% of Al, 0.8%-1.6% of Sb, 0.2%-1% of Si and the balance of Mg and inevitable impurity elements. According to the invention, the interaction of Yb, Al, Sb, Si and Mg is fully utilized, the maximum tensile strength and elongation of the prepared alloy with optimal components at 300 DEG C are not lower than 322 MPa and 6.62% after solid solution and aging treatment, and the creep strain capacity of the alloy at 275 DEG C / 110 MPa and 100 h is only 0.27%. The heat-resistant and corrosion-resistant magnesium alloy can stably serve for a long time in a high-temperature and corrosion environment, and the technical problems that an existing magnesium alloy is not high in heat resistance, low in creep resistance and not resistant to corrosion are solved.

Description

Technical Field

[0001] The invention belongs to the field of magnesium-based alloys, and in particular relates to a heat-resistant and corrosion-resistant magnesium alloy and a preparation method thereof. Background Art

[0002] As the lightest metal structural material, magnesium alloy has the advantages of high specific strength, vibration resistance, damping performance and electromagnetic shielding performance, and is widely used in aerospace, transportation, medical equipment, electronic communications and other fields. Although magnesium alloy materials have superior and unique properties, magnesium is chemically active, and the strength and creep resistance of magnesium alloys will gradually decrease with the increase of temperature; at the same time, the number of independent slip systems of magnesium alloys at room temperature is limited, so it exhibits poor formability, plasticity and corrosion resistance, which greatly limits its application in automobiles, aerospace, electronics, construction, and manufacturing.

[0003] In order to further expand the application field of magnesium alloys, it is necessary to improve the high temperature resistance and corrosion resistance of magnesium alloys, so as to meet the requirements of long-term stable service of magnesium alloys in high temperature and corrosive environments. The Chinese invention patent with the authorization announcement date of April 19, 2022 and the authorization announcement number of CN 111575564 B discloses a heat-resistant rare earth magnesium alloy, the composition of which is: Gd 4.5-7%, Ce 0.5-1.0%, Zr 0.1-0.5%, Sb 0.2-3%, Al 2-4%, Mn 0.3-0.6%, impurities less than 0.02%, and the balance is magnesium. The high temperature strength, plasticity and creep resistance of magnesium alloy are improved by alloy composition, refinement and thermal strengthening. The room temperature tensile strength reaches 303-313MPa, the tensile strength at 300℃ reaches 259-268MPa, and the creep strain at 300℃ / 50MPa is 0.31-0.37%. The magnesium alloy can be used in high temperature occasions such as engine pistons.

[0004] Although the above-mentioned magnesium alloys have good high-temperature creep resistance, their high-temperature tensile strength still needs to be further improved. At the same time, the corrosion resistance of magnesium alloys is also one of the important properties that affect their service performance. Only by developing magnesium alloys that are both high-temperature resistant (including high-temperature tensile strength and high-temperature creep resistance) and corrosion resistant can the service performance of magnesium alloys in complex environments such as high temperature and corrosion be effectively improved. Summary of the invention

[0005] The purpose of the present invention is to provide a heat-resistant and corrosion-resistant magnesium alloy to solve the problem that the high-temperature tensile strength and corrosion resistance of the existing magnesium alloy need to be further improved.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned heat-resistant and corrosion-resistant magnesium alloy to solve the above-mentioned problems.

[0007] In order to achieve the above first purpose, the technical solution adopted by the present invention is:

[0008] A heat-resistant and corrosion-resistant magnesium alloy is composed of the following components in percentage by mass: 2.6% to 4.6% Yb, 0.85% to 1.65% Al, 0.8% to 1.6% Sb, 0.2% to 1% Si, and the rest being Mg and inevitable impurity elements.

[0009] The present invention is a pioneering invention, which uses the heavy rare earth element ytterbium (Yb) as the main added element, and the third main group element aluminum, the metalloid element antimony, and the non-metallic element silicon as the secondary added elements. The composite addition of Yb, Al, Sb, and Si gives full play to the role of each element. The solid solubility of Yb element in magnesium at 500°C is 3.3wt.%, and it decreases significantly with the decrease of temperature. Therefore, Yb added in an amount of 2.6wt.% to 4.6wt.% has good solid solution strengthening and aging strengthening effects in magnesium; at the same time, Yb element also has a good refining effect, which can refine the grains and form a dense nano-precipitation phase, thereby significantly improving the room temperature and high temperature strength of the alloy. In addition, Yb element also has the functions of removing impurities, purifying the melt, and improving casting performance. Yb and Al can significantly reduce the stacking fault energy and significantly improve the plasticity of magnesium alloys. In addition, Al can transfer the charge on the Mg base surface, forming a strong covalent bond between Mg and Al, effectively strengthening the magnesium matrix and thus improving the tensile strength. At the same time, the presence of Al can form a dense protective film on the alloy surface in a corrosive environment, hindering the entry of corrosive media and improving the corrosion resistance of the alloy. Sb and Si have the advantages of low price, small dosage, and simple addition process. They can modify the cast structure of the alloy and generate strengthening phases Mg3Sb2 and Mg2Si, playing a role in all-round alloying of magnesium alloys.

[0010] The heat-resistant and corrosion-resistant magnesium alloy makes full use of the interaction between Yb, Al, Sb, Si and Mg elements. The optimal composition alloy prepared has a maximum tensile strength, yield strength and elongation of not less than 322MPa, 297MPa and 6.62% at 300°C after solution treatment and aging treatment. At 275°C / 110MPa, the creep strain in 100h is only 0.27%, and the steady-state creep rate is only 3.09×10 -9 s -1 The corrosion rate in 3.5% NaCl solution is no higher than 5.92 mg·cm -2 ·h -1 .

[0011] Overall, this heat-resistant and corrosion-resistant magnesium alloy can serve stably for a long time in high temperature and corrosive environments, solving the technical problems of existing magnesium alloys with low heat resistance, low creep resistance and poor corrosion resistance.

[0012] Preferably, the heat-resistant and corrosion-resistant magnesium alloy is composed of the following components in mass percentage: Yb 3.6% to 4.6%, Al 1.25% to 1.65%, Sb 1.2% to 1.6%, Si 0.6% to 1%, and the rest is Mg and unavoidable impurity elements. Further preferably, the mass content of the unavoidable impurity elements does not exceed 0.02%.

[0013] In order to achieve the above second purpose, the technical solution adopted by the present invention is:

[0014] The preparation method of the heat-resistant and corrosion-resistant magnesium alloy comprises the following steps: melting and pouring raw materials according to a proportion to obtain an alloy ingot; and performing a solution treatment and an aging treatment on the alloy ingot.

[0015] Compared with the prior art, the preparation method of the heat-resistant and corrosion-resistant magnesium alloy of the present invention has a simple preparation process, is easy to operate, and has a low production cost; the obtained magnesium alloy has excellent room temperature and high temperature mechanical properties, as well as corrosion resistance, and is suitable for large-scale promotion and application.

[0016] Preferably, the temperature of the solution treatment is 480-500° C., and the time is 10-20 h. The steel is first quenched with hot water at 95-100° C., and then air-cooled to room temperature.

[0017] More preferably, the aging treatment is carried out at a temperature of 180 to 200° C. for 20 to 40 hours, followed by air cooling to room temperature.

[0018] Preferably, the raw material smelting includes melting pure Mg and Mg-Yb master alloy, then heating to 770-790°C, adding Mg-Si master alloy for heat preservation, cooling to 750-770°C, adding pure Al and pure Sb for heat preservation, and obtaining alloy melt.

[0019] More preferably, the holding time after adding the Mg-Si master alloy is 10 to 20 minutes; the holding time after adding pure Al and pure Sb is 5 to 15 minutes.

[0020] Further preferably, the mass content of Yb in the Mg-Yb master alloy is 15-20%; the mass content of Si in the Mg-Si master alloy is 3-5%.

[0021] Preferably, the mold used during the pouring is preheated, and the preheating temperature is 220-240°C. DETAILED DESCRIPTION

[0022] The technical concept of the present invention is to use Yb as the main element, Al, Sb, and Si as the secondary elements, and to use the solid solubility range of Yb in magnesium to add 2.6wt.% to 4.6wt.% to make it play a role in solid solution strengthening and aging strengthening; Yb and Al are used together to reduce the stacking fault energy of magnesium alloy, and the addition amount of Al is 0.85wt.% to 1.65wt.% to improve the tensile strength and corrosion resistance; and further add 0.8wt.% to 1.6wt.% of Sb and 0.2wt.% to 1wt.% of Si to modify the cast structure of the alloy. The entire magnesium alloy formula uses a small amount of alloying elements, and various alloying elements play a synergistic role, effectively improving the room temperature and high temperature tensile strength, creep resistance and corrosion resistance of the magnesium alloy, thereby improving the service performance of the magnesium alloy in complex environments such as high temperature and corrosive media.

[0023] By further optimizing the content of alloying elements such as Yb, Al, Sb, and Si, the above-mentioned high temperature resistance and corrosion resistance of magnesium alloys can be significantly improved, which is conducive to further broadening the application fields of magnesium alloys.

[0024] The implementation process of the present invention is described in detail below in conjunction with specific embodiments.

[0025] 1. Specific embodiments of the heat-resistant and corrosion-resistant magnesium alloy and its preparation method of the present invention

[0026] Example 1

[0027] The heat-resistant and corrosion-resistant magnesium alloy of this embodiment is composed of the following components in percentage by mass: 2.6% Yb, 0.85% Al, 0.8% Sb, 0.2% Si, and the rest are Mg and unavoidable impurity elements, and the content of the impurity elements does not exceed 0.02%.

[0028] The method for preparing the heat-resistant and corrosion-resistant magnesium alloy of this embodiment comprises the following steps:

[0029] 1) descaling the raw materials magnesium, aluminum, antimony, magnesium-ytterbium master alloy (Mg-20Yb, wherein the mass content of Yb is 20%), and magnesium-silicon master alloy (Mg-5Si, wherein the mass content of Si is 5%), and then drying all the raw materials for standby use;

[0030] 2) Putting raw materials magnesium and magnesium-ytterbium master alloy into a crucible in turn, and smelting them in an electromagnetic induction furnace. A mixed protective gas of CO2 and SF6 is used for protection during smelting. The raw materials are melted at 750° C. to form alloy liquid A;

[0031] 3) raising the temperature of alloy liquid A to 770°C, adding magnesium-silicon master alloy, and keeping the temperature for 10 minutes to obtain alloy liquid B;

[0032] 4) lowering the temperature of alloy liquid B to 750°C, adding pure aluminum and pure antimony, and keeping the temperature for 5 minutes to obtain alloy liquid C; pouring alloy liquid C into a metal mold preheated to 240°C to obtain an alloy ingot;

[0033] 5) subjecting the alloy ingot obtained in step 4) to solution treatment and artificial aging treatment; the solution treatment process is solution treatment at 480°C for 20 hours, quenching in 100°C hot water, and air cooling to room temperature; the artificial aging treatment process is aging at 180°C for 40 hours, and air cooling to room temperature after being taken out of the furnace, so as to obtain a heat-resistant and corrosion-resistant magnesium alloy.

[0034] Example 2

[0035] The heat-resistant and corrosion-resistant magnesium alloy of this embodiment is composed of the following components in percentage by mass: 3.6% Yb, 1.25% Al, 1.2% Sb, 0.6% Si, and the rest are Mg and unavoidable impurity elements, and the content of the impurity elements does not exceed 0.02%.

[0036] The method for preparing the heat-resistant and corrosion-resistant magnesium alloy of this embodiment comprises the following steps:

[0037] 1) Descaling the raw materials magnesium, aluminum, antimony, magnesium-ytterbium master alloy (Mg-20Yb), and magnesium-silicon master alloy (Mg-5Si), and then drying all the raw materials for standby use;

[0038] 2) Putting raw materials magnesium and magnesium-ytterbium master alloy into a crucible in turn, and smelting them in an electromagnetic induction furnace. A mixed protective gas of CO2 and SF6 is used for protection during smelting. The raw materials are melted at 750° C. to form alloy liquid A;

[0039] 3) raising the temperature of alloy liquid A to 780°C, adding magnesium-silicon master alloy, and keeping the temperature for 15 minutes to obtain alloy liquid B;

[0040] 4) The temperature of alloy liquid B is lowered to 760°C, pure aluminum and pure antimony are added, and the temperature is kept for 10 minutes to obtain alloy liquid C; the alloy liquid C is poured into a metal mold preheated to 230°C to obtain an alloy ingot;

[0041] 5) subjecting the alloy ingot obtained in step 4) to solution treatment and artificial aging treatment; the solution treatment process is solution treatment at 490°C for 15 hours, quenching in 100°C hot water, and air cooling to room temperature; the artificial aging treatment process is aging at 190°C for 30 hours, and air cooling to room temperature after being taken out of the furnace, so as to obtain a heat-resistant and corrosion-resistant magnesium alloy.

[0042] Example 3

[0043] The heat-resistant and corrosion-resistant magnesium alloy of this embodiment is composed of the following components in percentage by mass: 4.6% Yb, 1.65% Al, 1.6% Sb, 1% Si, and the rest are Mg and unavoidable impurity elements, and the content of the impurity elements does not exceed 0.02%.

[0044] The method for preparing the heat-resistant and corrosion-resistant magnesium alloy of this embodiment comprises the following steps:

[0045] 1) Descaling the raw materials magnesium, aluminum, antimony, magnesium-ytterbium master alloy (Mg-20Yb), and magnesium-silicon master alloy (Mg-5Si), and then drying all the raw materials for standby use;

[0046] 2) Putting raw materials magnesium and magnesium-ytterbium master alloy into a crucible in turn, and smelting them in an electromagnetic induction furnace. A mixed protective gas of CO2 and SF6 is used for protection during smelting. The raw materials are melted at 750° C. to form alloy liquid A;

[0047] 3) raising the temperature of alloy liquid A to 790°C, adding magnesium-silicon master alloy, and keeping the temperature for 20 minutes to obtain alloy liquid B;

[0048] 4) The temperature of the alloy liquid B is lowered to 770°C, pure aluminum and pure antimony are added, and the temperature is kept for 15 minutes to obtain the alloy liquid C; the alloy liquid C is poured into a metal mold preheated to 220°C to obtain an alloy ingot;

[0049] 5) subjecting the alloy ingot obtained in step 4) to solution treatment and artificial aging treatment; the solution treatment process is solution treatment at 500°C for 10 hours, quenching in 100°C hot water, and air cooling to room temperature; the artificial aging treatment process is aging at 200°C for 20 hours, and air cooling to room temperature after being taken out of the furnace, so as to obtain a heat-resistant and corrosion-resistant magnesium alloy.

[0050] 2. Comparison

[0051] Comparative Example 1

[0052] The magnesium alloy of this comparative example is composed of the following components in percentage by mass: 2.5% Yb, 1.25% Al, 1.2% Sb, 0.6% Si, and the remainder is Mg and unavoidable impurity elements, and the content of the impurity elements does not exceed 0.02%.

[0053] The preparation method of the magnesium alloy of this comparative example comprises the following steps:

[0054] 1) Descaling the raw materials magnesium, aluminum, antimony, magnesium-ytterbium master alloy (Mg-20Yb), and magnesium-silicon master alloy (Mg-5Si), and then drying all the raw materials for standby use;

[0055] 2) Putting raw materials magnesium and magnesium-ytterbium master alloy into a crucible in turn, and smelting them in an electromagnetic induction furnace. A mixed protective gas of CO2 and SF6 is used for protection during smelting. The raw materials are melted at 750° C. to form alloy liquid A;

[0056] 3) raising the temperature of alloy liquid A to 790°C, adding magnesium-silicon master alloy, and keeping the temperature for 20 minutes to obtain alloy liquid B;

[0057] 4) The temperature of the alloy liquid B is lowered to 770°C, pure aluminum and pure antimony are added, and the temperature is kept for 15 minutes to obtain the alloy liquid C; the alloy liquid C is poured into a metal mold preheated to 220°C to obtain an alloy ingot;

[0058] 5) subjecting the alloy ingot obtained in step 4) to solution treatment and artificial aging treatment; the solution treatment process is solution treatment at 500°C for 10 hours, quenching in 100°C hot water, and air cooling to room temperature; the artificial aging treatment process is aging at 200°C for 20 hours, and air cooling to room temperature after being taken out of the furnace to obtain a magnesium alloy.

[0059] Comparative Example 2

[0060] The magnesium alloy of this comparative example is composed of the following components in percentage by mass: 3.6% Yb, 3% Al, 2% Sb, 0.6% Si, and the remainder is Mg and unavoidable impurity elements, and the content of the impurity elements does not exceed 0.02%.

[0061] The preparation method of the magnesium alloy of this comparative example comprises the following steps:

[0062] 1) Descaling the raw materials magnesium, aluminum, antimony, magnesium-ytterbium master alloy (Mg-20Yb), and magnesium-silicon master alloy (Mg-5Si), and then drying all the raw materials for standby use;

[0063] 2) Putting raw materials magnesium and magnesium-ytterbium master alloy into a crucible in turn, and smelting them in an electromagnetic induction furnace. A mixed protective gas of CO2 and SF6 is used for protection during smelting. The raw materials are melted at 750° C. to form alloy liquid A;

[0064] 3) raising the temperature of alloy liquid A to 790°C, adding magnesium-silicon master alloy, and keeping the temperature for 20 minutes to obtain alloy liquid B;

[0065] 4) The temperature of the alloy liquid B is lowered to 770°C, pure aluminum and pure antimony are added, and the temperature is kept for 15 minutes to obtain the alloy liquid C; the alloy liquid C is poured into a metal mold preheated to 220°C to obtain an alloy ingot;

[0066] 5) subjecting the alloy ingot obtained in step 4) to solution treatment and artificial aging treatment; the solution treatment process is solution treatment at 500°C for 10 hours, quenching in 100°C hot water, and air cooling to room temperature; the artificial aging treatment process is aging at 200°C for 20 hours, and air cooling to room temperature after being taken out of the furnace to obtain a magnesium alloy.

[0067] 3. Experimental Examples

[0068] This experimental example tests the room temperature and high temperature tensile strength, elongation, high temperature creep resistance and corrosion resistance of the heat-resistant and corrosion-resistant magnesium alloys prepared in Examples 1-3 and Comparative Examples 1-2. The room temperature tensile strength and elongation test method: According to the national standard GB / T228.1-2021 "Metallic Materials-Tensile Test-Part 1: Room Temperature Test Method", the Shimadzu precision universal electronic tensile testing machine is used for testing; the high temperature tensile strength and elongation test method: According to the national standard GB / T228.2-2015 "Metallic Materials-Tensile Test-Part 2: High Temperature Test Method", the Shimadzu precision universal electronic tensile testing machine is used for testing; the high temperature creep resistance test method: According to the national standard GB / T2039-2012 "Metallic Materials-Uniaxial Tensile Creep Test Method", the round rod-shaped creep specimens are processed and tested using the RC-1130 creep endurance tester. The corrosion rate is measured by weight loss experiment, the corrosion environment is 3.5% NaCl solution, and the solution temperature is 20°C. The test results of tensile strength, elongation, high temperature creep resistance and corrosion resistance are shown in Table 1.

[0069] Table 1 Test results of tensile strength, elongation, creep resistance and corrosion resistance of heat-resistant and corrosion-resistant magnesium alloys of Examples 1-3 and Comparative Examples 1-2

[0070]

[0071] From the experimental results in Table 1, it can be seen that the heat-resistant and corrosion-resistant magnesium alloys of Examples 1-3 not only have excellent room temperature mechanical properties, with a tensile strength of 327-349 MPa and a yield strength of 303-325 MPa, but also have excellent high-temperature mechanical properties and high-temperature creep resistance, with a tensile strength of 294-322 MPa at 300°C and a yield strength of 279-297 MPa at 300°C. The creep strain at 275°C / 110 MPa for 100 h is as low as 0.27%, and the corrosion rate is as low as 5.92 mg·cm -2 ·h -1 , which proves that the magnesium alloy obtained by the present invention has excellent high-temperature mechanical properties, creep resistance and corrosion resistance, and good comprehensive performance.

Claims

1. A heat-resistant and corrosion-resistant magnesium alloy, characterized in that: It is composed of the following components in mass percentage: Yb 2.6% to 4.6%, Al 0.85% to 1.65%, Sb 0.8% to 1.6%, Si 0.2% to 1%, and the rest are Mg and unavoidable impurity elements.

2. The heat-resistant and corrosion-resistant magnesium alloy according to claim 1, characterized in that: It is composed of the following components in mass percentage: Yb 3.6% to 4.6%, Al 1.25% to 1.65%, Sb 1.2% to 1.6%, Si 0.6% to 1%, and the rest are Mg and unavoidable impurity elements.

3. The heat-resistant and corrosion-resistant magnesium alloy according to claim 1 or 2, characterized in that: The mass content of the unavoidable impurity elements does not exceed 0.02%.

4. A method for preparing a heat-resistant and corrosion-resistant magnesium alloy as claimed in any one of claims 1 to 3, characterized in that: The method comprises the following steps: melting and pouring raw materials according to a proportion to obtain an alloy ingot; and performing a solid solution treatment and an aging treatment on the alloy ingot.

5. The method for preparing a heat-resistant and corrosion-resistant magnesium alloy according to claim 4, characterized in that: The temperature of the solution treatment is 480-500° C., and the time is 10-20 hours. The steel is first quenched with hot water at 95-100° C., and then air-cooled to room temperature.

6. The method for preparing a heat-resistant and corrosion-resistant magnesium alloy according to claim 5, characterized in that: The aging treatment is carried out at a temperature of 180 to 200° C. for 20 to 40 hours, followed by air cooling to room temperature.

7. The method for preparing a heat-resistant and corrosion-resistant magnesium alloy according to claim 4, characterized in that: The raw material smelting comprises melting pure Mg and Mg-Yb master alloy, then heating to 770-790° C., adding Mg-Si master alloy for heat preservation, cooling to 750-770° C., adding pure Al and pure Sb for heat preservation, and obtaining alloy melt.

8. The method for preparing a heat-resistant and corrosion-resistant magnesium alloy according to claim 7, characterized in that: The holding time after adding the Mg-Si master alloy is 10 to 20 minutes; the holding time after adding pure Al and pure Sb is 5 to 15 minutes.

9. The method for preparing a heat-resistant and corrosion-resistant magnesium alloy according to claim 7, characterized in that: The mass content of Yb in the Mg-Yb master alloy is 15-20%; the mass content of Si in the Mg-Si master alloy is 3-5%.

10. The method for preparing a heat-resistant and corrosion-resistant magnesium alloy according to claim 4, characterized in that: During the pouring, the mold used is preheated, and the preheating temperature is 220-240°C.

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