A high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy and its preparation method

Abstract

The present invention discloses a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy, comprising the following components, by mass percentage: Gd: 7.0-8.5%, Y: 1.6-2.3%, Sm: 1.1-2.1%, Zn: 0.9-1.2%, Zr: 0.4-0.5%, with the balance being Mg and unavoidable impurities, wherein the content of the impurities is less than or equal to 0.02%. The ratio of Gd+Y / Sm / Zn is in the range of (9-10):(1.5-2.0):1. The present invention also provides a method for preparing the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy. The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided by the present invention has excellent high-temperature resistance by adding a certain content of Sm element and a specific component ratio, and then subjecting the cast alloy to solid solution strengthening and aging strengthening. It has broad application prospects in fields such as aerospace.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy materials, and in particular relates to a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy and a preparation method thereof. Background Art

[0002] With the gradual reduction of traditional metal mineral reserves and the pursuit of lightweight structural materials in the manufacturing industry, magnesium and magnesium alloys have received widespread attention. Compared with traditional structural materials (such as steel and aluminum alloys), magnesium alloys have the following significant advantages: (1) low density, high specific strength and specific stiffness, with a density of 1.7g / cm 3 Only about aluminum alloy (2.7g / cm 3 ) or 2 / 3 of steel (7.8g / cm 3 ), using magnesium alloy to replace aluminum alloy or steel can significantly reduce the weight of structural parts and bring significant economic benefits.

[0003] Although Mg alloys have many advantages, the AZ and AM alloys, which are currently the most commercialized in the automotive industry, will rapidly lose their strength when the temperature exceeds 125°C, which greatly limits the further application of Mg alloys in automotive power systems and aerospace.

[0004] Research has shown that adding a small amount of Si, RE, Ca, or Sr to Mg-Al alloys can effectively improve the creep resistance of Mg alloys. Representative alloys include AS21, AS41, AE42, AE41, AX53, AXJ, ACM522, MRI153, and AJ52x. These alloys have a heat resistance temperature of up to 200°C and are all die-cast alloys. Adding rare earth (RE) elements to Mg can significantly improve the high-temperature strength and creep resistance of Mg alloys, making their heat resistance temperature higher than 200°C. However, there are still few magnesium alloys that can serve at higher temperatures such as 350°C.

[0005] Sm has a high solid solubility in magnesium. At the eutectic temperature of 542°C, Sm reaches a maximum solid solubility of 5.8 wt% in magnesium. When the temperature is lowered to 200°C, its solid solubility is only 0.4%. As the temperature decreases, the solid solubility of Sm in Mg decreases, forming a supersaturated solid solution. During aging, this supersaturated solid solution decomposes, forming a large number of precipitates. Therefore, Sm has excellent solid solution strengthening and aging strengthening effects in magnesium alloys. Summary of the Invention

[0006] The present invention aims to address, at least to some extent, one of the technical problems in the related art. To this end, the present invention primarily aims to provide a high-strength, heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy that, while reducing the amount of rare earth elements, maintains high yield strength and tensile strength at high temperatures, making it suitable for use in aerospace and other fields.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy, comprising the following components in mass percentage: Gd: 7.0-8.5%, Y: 1.6-2.3%, Sm: 1.1-2.1%, Zn: 0.9-1.2%, Zr: 0.4-0.5%, and the balance is Mg and unavoidable impurities, the content of which is less than / equal to 0.02%; wherein the ratio of Gd+Y / Sm / Zn is (9-10):(1.5-2.0):1.

[0009] In certain specific embodiments, the following components are included in mass percentage: Gd: 8.1%, Y: 2.3%, Sm: 1.1%, Zn: 1.1%, Zr: 0.5%, and the balance is Mg and inevitable impurities.

[0010] In certain specific embodiments, the following components are included in mass percentage: Gd 7.7%, Y: 2.1%, Sm: 2.1%, Zn: 1.2%, Zr: 0.4%, and the balance is Mg and inevitable impurities.

[0011] In certain specific embodiments, the following components are included in mass percentage: Gd: 8.5%, Y: 2.3%, Sm: 1.3%, Zn: 0.9%, Zr: 0.5%, and the balance is Mg and inevitable impurities.

[0012] A method for preparing the aforementioned high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy comprises the following steps:

[0013] 1) uniformly mixing the raw material components, smelting and casting to obtain a cast alloy;

[0014] 2) The as-cast alloy is subjected to solution treatment and aging treatment in sequence to obtain a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy.

[0015] In some specific embodiments, in step 1), the smelting and casting are: under the protection of an inert atmosphere, first heating to 720-780°C to melt all the materials, then using a low-carbon steel stirring rod to mechanically stir for 2-4 minutes, and then standing for 5-10 minutes to obtain a preliminary alloy melt; then cooling to 720-740°C and standing for 15-30 minutes before pouring to obtain a cast magnesium alloy.

[0016] In some specific embodiments, in step 1), after obtaining the preliminary alloy melt, the temperature is lowered to 760° C., and a No. 5 refining agent is added to perform a refining treatment on the preliminary alloy melt.

[0017] In some specific embodiments, in step 2), the solution treatment is performed at a temperature of 480-510° C. and a time of 8-12 h to obtain a solid solution magnesium alloy.

[0018] In some specific embodiments, in step 2), the aging treatment step is: first aging treatment at an aging temperature of 195-205° C. for 45-51 hours, and then aging treatment at an aging temperature of 220-230° C. for 8-10 hours to obtain an aged magnesium alloy.

[0019] In some specific embodiments, the raw materials are pure magnesium ingots, pure zinc particles, Mg-Gd master alloy, Mg-Sm master alloy, Mg-Y master alloy, and Mg-Zr master alloy.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] 1) The high-strength, heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided by the present invention has excellent high-temperature resistance by adding a certain amount of Sm element and a specific component ratio, and then subjecting the cast alloy to solid solution strengthening and aging strengthening. When the Sm element content is controlled at 1.1wt%, the magnesium alloy has a tensile strength of 258MPa and a yield strength of 203MPa at a high temperature of 350°C; when the Sm element content is controlled at 2.1wt%, the magnesium alloy has a tensile strength of 231MPa and a yield strength of 186MPa at a high temperature of 350°C. The high-strength, heat-resistant magnesium alloy of the present invention still has a high tensile strength at an ultra-high temperature of 350°C. The high-strength, heat-resistant magnesium alloy of the present invention has broad application prospects in fields such as aerospace.

[0022] 2) The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided in the present application, the addition of the Sm element, the volume fraction of the LPSO precipitate phase during the solid solution process of the magnesium alloy, and the precipitation of the high-temperature resistant β' phase within the grain and the grain boundary β phase during the aging process, can pin the grain boundaries at high temperatures and hinder grain boundary sliding; in the process of preparing the alloy, on the basis of controlling the alloy composition, by performing solid solution treatment and aging treatment on the cast alloy, an alloy containing lamellar LPSO phase, Mg5(RE,Zn) and Gd and Y-rich square phase, with dense β' phase within the grain and dense continuous β phase at the grain boundaries is obtained, and finally a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy is obtained;

[0023] 3) The high-strength and heat-resistant magnesium alloy components of the present invention are Mg-Gd-Y-Sm-Zn-Zr. Compared with the Mg-Gd-Y-Zn-Zr alloy materials in the prior art, the present invention reduces the content of rare earth elements (Gd+Y) while improving the high-temperature tensile strength and / or yield strength by adding Sm, which is less expensive than Gd and Y elements. This reduces the material preparation cost and protects the environment, thus having great economic and social benefits. In addition, the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy of the present invention can be obtained by solution treatment and aging treatment of the cast alloy to obtain an alloy material with high strength and heat resistance, which is suitable for the preparation of materials for large components. The preparation method has a simple preparation process and is easy to industrialize. The present invention greatly saves costs while meeting the high-temperature performance requirements. The high-temperature resistant magnesium alloy of the present invention still has high tensile strength and yield strength at ultra-high temperatures of 350°C, and has broad application prospects in the fields of aerospace, automotive industry, electronic information, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.

[0025] Figure 1 This is an SEM image of the LPSO phase, Mg5(RE,Zn), Gd-rich, and Y-block phases in the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared in Example 1 of the present invention;

[0026] Figure 2 This is a SEM image of the LPSO phase, Mg5(RE,Zn), Gd-rich, and Y-block phases in the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared in Example 2 of the present invention;

[0027] Figure 3 This is a SEM image of β and β' phases in the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared in Example 2 of the present invention;

[0028] Figure 4 This is a SEM image of the LPSO phase, Mg5(RE,Zn), Gd-rich, and Y-block phase in the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared in Comparative Example 1 of the present invention;

[0029] Figure 5 This is a SEM image of the β and β' phases in the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples are merely illustrative and non-restrictive, and should not be used to limit the scope of protection of the present invention.

[0031] When expressing a certain amount, concentration or other value or parameter in the form of a range, preferred range, or preferred upper and lower numerical limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper range limits or preferred numerical values ​​with any lower range limit or preferred numerical value, without considering whether the range is specifically disclosed. Unless otherwise indicated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within the range.

[0032] Unless otherwise indicated, all percentages, parts, ratios, etc. herein are by weight.

[0033] The materials, methods, and examples herein are illustrative and, unless otherwise indicated, are not to be construed as limiting.

[0034] In the following examples, the mechanical properties of the prepared high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy were tested. The test method was as follows: the high-strength and heat-resistant magnesium alloy obtained in Examples 1-2 was processed into a standard round rod-shaped high-temperature tensile specimen in accordance with the national standard (GB4338-2006). The specimen dimensions were 12 mm in length at the clamping end, 10 mm in diameter, 25 mm in gauge length, and 5 mm in gauge section diameter. The specimens were stretched on a high-temperature tensile testing machine CMT5305. The tensile conditions were as follows: the surface of the specimen was polished with sandpaper, kept at the stretching temperature for 25 min, and then stretched at a rate of 1.5 mm / min, with a strain rate of 10 -3 m / s.

[0035] Example 1

[0036] The preparation method of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided by the present invention comprises the following steps:

[0037] 1) Ingredients: The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy of this embodiment is composed of the following components (raw materials) in percentage by mass: Gd: 8.1%, Y: 2.3%, Sm: 1.1%, Zn: 1.1%, Zr: 0.5%, the total amount of impurity elements Si and Fe is less than 0.02%, and the balance is Mg, wherein the ratio of Gd + Y / Sm / Zn is in the range of 9:1.5:1;

[0038] 2) Raw material impurity removal: First, use a grinding wheel grinder to remove the surface oxide layer of the material; then place the pure magnesium ingot, pure Zn particles, and Mg-Gd master alloy, Mg-Y master alloy, Mg-Sm master alloy, and Mg-Zr master alloy in a drying oven at 250°C and preheat for 30 minutes to remove moisture;

[0039] 3) Preheat the melting furnace at 500°C for 60 minutes; prepare a solution of boron nitride and alcohol in a mass ratio of 1:2, apply it evenly to the inner wall of a low-carbon steel crucible with a brush, and dry it in a drying oven; place the dehydrated pure magnesium ingot in an air-dried iron crucible, and raise the melting furnace temperature to 730°C under the protection of a CO2+SF6 (100:1) mixed gas. After the pure magnesium ingot is melted, add the master alloys Mg-Gd master alloy, Mg-Y master alloy, Mg-Sm master alloy, and pure Zn particles in sequence at 730°C;

[0040] 4) Under the protection of CO2+SF6 (100:1) mixed gas, raise the melting furnace to 780℃, add the master alloy Mg-Zr master alloy, and keep it warm for 10-15 minutes;

[0041] 5) Melt purification: Use a mixed solution of boron nitride and alcohol to evenly coat the inner and outer surfaces of a long-handled low-carbon steel spoon with a slag-removing spoon. After all materials are melted, use the above-mentioned steel spoon to remove the slag on the surface of the melt to obtain a preliminary alloy melt; reduce the temperature of the preliminary alloy melt to 760°C, and use a No. 5 refining agent to refine the preliminary alloy melt; the amount of the No. 5 refining agent is 2% of the total mass of the preliminary alloy melt, and the No. 5 refining agent is placed in a 250°C pit furnace for drying for 30 minutes in advance; the refining operation uses a long-handled low-carbon steel spoon to deliver the No. 5 refining agent to the lower part of the alloy melt, and start stirring up and down for 2 minutes to ensure that the No. 5 refining agent enters the interior of the alloy melt; then rotate and stir for 3 minutes to ensure that the No. 5 refining agent is fully in contact with the preliminary alloy melt. After the refining is completed, an alloy melt is obtained; the alloy melt is fully slag-removed, and then the temperature of the alloy melt is reduced to 740°C, and the alloy melt is kept warm and allowed to stand for 30 minutes before pouring;

[0042] 6) Casting: Evenly coat the inner wall of the permanent metal mold with a mixed solution of boron nitride and alcohol to facilitate cooling and demoulding. Preheat the permanent metal mold in a 250°C pit furnace for 1 hour. After the mold is heated and allowed to stand for 1 hour, pour the mold. Demold the mold after 1 hour and cool it to room temperature in air to obtain the cast magnesium alloy.

[0043] 7) Solution treatment: The alloy obtained in step 6) is subjected to solution treatment at 480° C. for 12 h, and then placed in water at a temperature of about 25° C. and cooled to room temperature to obtain a solid solution magnesium alloy.

[0044] 8) Aging treatment: The alloy obtained in step 7) was first kept at 195°C for 51 hours, then kept at 230°C for 8 hours, and finally placed in water at a temperature of about 25°C and cooled to room temperature to obtain a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy.

[0045] Example 2

[0046] The preparation method of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided by the present invention comprises the following steps:

[0047] 1) Ingredients: The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy of this embodiment is composed of the following components (raw materials) in percentage by mass: Gd: 7.7%, Y: 2.1%, Sm: 2.1%, Zn: 1.2%, Zr: 0.4%, the total amount of impurity elements Si and Fe is less than 0.02%, and the balance is Mg. The ratio of Gd + Y / Sm / Zn is in the range of 9:2.0:1;

[0048] 2) Raw material impurity removal: First, use a grinding wheel grinder to remove the surface oxide layer of the material; then place the pure magnesium ingot, pure Zn particles, and Mg-Gd master alloy, Mg-Y master alloy, Mg-Sm master alloy, and Mg-Zr master alloy in a drying oven at 250°C and preheat for 30 minutes to remove moisture;

[0049] 3) Preheat the melting furnace at 500°C for 60 minutes; prepare a solution of boron nitride and alcohol in a mass ratio of 1:2, apply it evenly to the inner wall of a low-carbon steel crucible with a brush, and dry it in a drying oven; place the dehydrated pure magnesium ingot in an air-dried iron crucible, and raise the melting furnace temperature to 730°C under the protection of a CO2+SF6 (100:1) mixed gas. After the pure magnesium ingot is melted, add the master alloys Mg-Gd master alloy, Mg-Y master alloy, Mg-Sm master alloy, and pure Zn particles in sequence at 730°C;

[0050] 4) Under the protection of CO2+SF6 (100:1) mixed gas, raise the melting furnace to 780℃, add the master alloy Mg-Zr master alloy, and keep it warm for 10-15 minutes;

[0051] 5) Melt purification: Use a mixed solution of boron nitride and alcohol to evenly coat the inner and outer surfaces of a long-handled low-carbon steel spoon with a slag-removing spoon. After all materials are melted, use the above-mentioned steel spoon to remove the slag on the surface of the melt to obtain a preliminary alloy melt; reduce the temperature of the preliminary alloy melt to 760°C, and use a No. 5 refining agent to refine the preliminary alloy melt; the amount of the No. 5 refining agent is 2% of the total mass of the preliminary alloy melt, and the No. 5 refining agent is placed in a 250°C pit furnace for drying for 30 minutes in advance; the refining operation uses a long-handled low-carbon steel spoon to deliver the No. 5 refining agent to the lower part of the alloy melt, and start stirring up and down for 2 minutes to ensure that the No. 5 refining agent enters the interior of the alloy melt; then rotate and stir for 3 minutes to ensure that the No. 5 refining agent is fully in contact with the preliminary alloy melt. After the refining is completed, an alloy melt is obtained; the alloy melt is fully slag-removed, and then the temperature of the alloy melt is reduced to 740°C, and the alloy melt is kept warm and allowed to stand for 30 minutes before pouring;

[0052] 6) Casting: Evenly coat the inner wall of the permanent metal mold with a mixed solution of boron nitride and alcohol to facilitate cooling and demoulding. Preheat the permanent metal mold in a 250°C pit furnace for 1 hour. After the mold is heated and allowed to stand for 1 hour, pour the mold. Demold the mold after 1 hour and cool it to room temperature in air to obtain the cast magnesium alloy.

[0053] 7) Solution treatment: The alloy obtained in step 6) is subjected to solution treatment at 500° C. for 10 h, and then placed in water at a temperature of about 25° C. and cooled to room temperature to obtain a solid solution magnesium alloy;

[0054] 8) Aging treatment: The alloy obtained in step 7) was first kept at 200°C for 48 hours, then kept at 225°C for 9 hours, and finally placed in water at a temperature of about 25°C and cooled to room temperature to obtain a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy.

[0055] Example 3

[0056] The preparation method of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided by the present invention comprises the following steps:

[0057] 1) Ingredients: The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy of this embodiment is composed of the following components (raw materials) in percentage by mass: Gd: 8.5%, Y: 2.3%, Sm: 1.3%, Zn: 0.9%, Zr: 0.5%, the total amount of impurity elements Si and Fe is less than 0.02%, and the balance is Mg. The ratio of Gd + Y / Sm / Zn is in the range of 10:1.8:1;

[0058] 2) Raw material impurity removal: First, use a grinding wheel grinder to remove the surface oxide layer of the material; then place the pure magnesium ingot, pure Zn particles, and Mg-Gd master alloy, Mg-Y master alloy, Mg-Sm master alloy, and Mg-Zr master alloy in a drying oven at 250°C and preheat for 30 minutes to remove moisture;

[0059] 3) Preheat the melting furnace at 500°C for 60 minutes; prepare a solution of boron nitride and alcohol in a mass ratio of 1:2, apply it evenly to the inner wall of a low-carbon steel crucible with a brush, and dry it in a drying oven; place the dehydrated pure magnesium ingot in an air-dried iron crucible, and raise the melting furnace temperature to 730°C under the protection of a CO2+SF6 (100:1) mixed gas. After the pure magnesium ingot is melted, add the master alloys Mg-Gd master alloy, Mg-Y master alloy, Mg-Sm master alloy, and pure Zn particles in sequence at 730°C;

[0060] 4) Under the protection of CO2+SF6 (100:1) mixed gas, raise the melting furnace to 780℃, add the master alloy Mg-Zr master alloy, and keep it warm for 10-15 minutes;

[0061] 5) Melt purification: Use a mixed solution of boron nitride and alcohol to evenly coat the inner and outer surfaces of a long-handled low-carbon steel spoon with a slag-removing spoon. After all materials are melted, use the above-mentioned steel spoon to remove the slag on the surface of the melt to obtain a preliminary alloy melt; reduce the temperature of the preliminary alloy melt to 760°C, and use a No. 5 refining agent to refine the preliminary alloy melt; the amount of the No. 5 refining agent is 2% of the total mass of the preliminary alloy melt, and the No. 5 refining agent is placed in a 250°C pit furnace for drying for 30 minutes in advance; the refining operation uses a long-handled low-carbon steel spoon to deliver the No. 5 refining agent to the lower part of the alloy melt, and start stirring up and down for 2 minutes to ensure that the No. 5 refining agent enters the interior of the alloy melt; then rotate and stir for 3 minutes to ensure that the No. 5 refining agent is fully in contact with the preliminary alloy melt. After the refining is completed, an alloy melt is obtained; the alloy melt is fully slag-removed, and then the temperature of the alloy melt is reduced to 740°C, and the alloy melt is kept warm and allowed to stand for 30 minutes before pouring;

[0062] 6) Casting: Evenly coat the inner wall of the permanent metal mold with a mixed solution of boron nitride and alcohol to facilitate cooling and demoulding. Preheat the permanent metal mold in a 250°C pit furnace for 1 hour. After the mold is heated and allowed to stand for 1 hour, pour the mold. Demold the mold after 1 hour and cool it to room temperature in air to obtain the cast magnesium alloy.

[0063] 7) Solution treatment: The alloy obtained in step 6) is subjected to solution treatment at 510° C. for 8 h, and then placed in water at a temperature of about 25° C. and cooled to room temperature to obtain a solid solution magnesium alloy.

[0064] 8) Aging treatment: The alloy obtained in step 7) was first kept at 205°C for 45 hours, then kept at 220°C for 10 hours, and finally placed in water at a temperature of about 25°C and cooled to room temperature to obtain a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy.

[0065] Comparative Example 1:

[0066] The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided in this comparative example has the same components and proportions as those in Example 2, except that it does not contain the Sm element; its preparation method is the same as that in Example 2.

[0067] Comparative Example 2:

[0068] The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided in this comparative example has the following components: Gd: 8.2%, Y: 2.2%, Sm: 3.8%, Zn: 1.0%, and Zr: 0.5%. Its processing technology is the same as that in Example 2, except that the ratio of Gd+Y / Sm / Zn exceeds 9:2.5:1. Its preparation method is the same as that in Example 2.

[0069] Comparative Example 3:

[0070] The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided in this comparative example has the same components and proportions as those in Example 2, except that its aging process is 225°C×16h; its preparation method is the same as that in Example 2.

[0071] Performance testing:

[0072] 1) Morphology test

[0073] This test is for the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloys prepared in Examples 1-3. By performing backscattered electron imaging tests on them, it can be seen that the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloys in Examples 1-3 of the present application all contain lamellar LPSO phase, Mg5(RE,Zn) and Gd-rich, Y-rich square phase, with dense β' phase in the crystal and dense continuous β phase at the grain boundary. The volume fractions of the various phases of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloys prepared in each embodiment and comparative example are shown in Table 1; the backscattered electron imaging images of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloys prepared in Example 1 and Example 2 are shown in Table 1. Figure 1 、 Figure 2 and Figure 3 At the same time, the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared was tested by optical microscope observation. The results are as follows Figure 4 and Figure 5As shown in the figure, it can be seen that after adding the Sm element, the volume fraction of the lamellar LPSO phase in the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy prepared in Comparative Example 1 is greatly reduced, and the β' phase formed in the crystal is sparse and the β phase at the grain boundary is small and discrete, which cannot effectively improve the tensile strength and yield strength of the alloy.

[0074] Table 1 Phases and volume fractions of the alloys obtained in various embodiments and comparative examples

[0075]

[0076] As can be seen from Table 1, the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy provided in the present application contains lamellar LPSO phase, Mg5(RE,Zn) and Gd- and Y-rich square phases, with dense β' phases in the grains and dense continuous β phases at the grain boundaries. The volume fraction of the lamellar LPSO phase is 20-35%, and the volume fraction of Mg5(RE,Zn) is 0.5-0.65%. By comparing Example 2 with Comparative Example 1, it can be seen that the addition of Sm increases the volume fraction of the LPSO precipitate phase in the magnesium alloy and promotes the high-temperature resistant β' phase in the grains during aging. The precipitation of β phase and grain boundary β phase, thereby having dense β' phase in the grain and dense continuous β phase at the grain boundary, pinning the grain boundary at high temperature, hindering grain boundary sliding, and improving the high strength and heat resistance of the alloy; a comparison between Example 2 and Comparative Example 2 shows that changing the ratio of Gd+Y / Sm / Zn in the composition will result in the amount of LPSO and β, β' phase in the microstructure after heat treatment being almost zero, and no strengthening effect will be achieved; a comparison between Example 2 and Comparative Example 3 shows that adopting an aging treatment process other than that provided by the present invention will result in coarse precipitated phases in the alloy microstructure after aging treatment, resulting in deterioration of alloy performance and poor strengthening effect.

[0077] 2) Mechanical properties test

[0078] The present application conducted performance tests on the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloys prepared in Examples 1-3 and Comparative Examples 1-3. The results are shown in Table 1:

[0079] Table 1 Mechanical properties of alloys in various embodiments and comparative examples at different temperatures

[0080]

[0081]

[0082] As can be seen from Table 2, at 25°C, 300°C, and 350°C, the tensile strength and yield strength of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloys prepared in Examples 1-3 are still at a relatively high level; at 350°C, the tensile strength of the high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy of Example 1 is maintained above 240 MPa, and the yield strength is also maintained above 200 MPa, that is, it has high high-temperature mechanical stability and can strictly meet the high-temperature strength requirements of aerospace, automotive industry, electronic information and other fields.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy, characterized in that: The steps include: 1) uniformly mixing the raw material components, smelting and casting to obtain a cast alloy; 2) subjecting the as-cast alloy to solution treatment and aging treatment in sequence to obtain a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy; In step 2), the aging treatment adopts a step heating step: first, aging treatment is performed at an aging temperature of 195-205° C. for 45-51 hours, and then aging treatment is performed at an aging temperature of 220-230° C. for 8-10 hours to obtain an aged magnesium alloy; The high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy comprises the following components, in mass percentage: Gd: 7.0-8.5%, Y: 1.6-2.3%, Sm: 1.1-2.1%, Zn: 0.9-1.2%, Zr: 0.4-0.5%, and the remainder is Mg and unavoidable impurities, and the content of the impurities is less than / equal to 0.02%; wherein the ratio range of Gd+Y / Sm / Zn is (9-10):(1.5-2.0):

1.

2. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 1, characterized in that: The present invention comprises the following components in percentage by mass: Gd: 8.1%, Y: 2.3%, Sm: 1.1%, Zn: 1.1%, Zr: 0.5%, and the balance being Mg and inevitable impurities.

3. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 1, characterized in that: The present invention comprises the following components in percentage by mass: Gd: 7.7%, Y: 2.1%, Sm: 2.1%, Zn: 1.2%, Zr: 0.4%, and the balance being Mg and inevitable impurities.

4. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 1, characterized in that: The present invention comprises the following components in percentage by mass: Gd: 8.5%, Y: 2.3%, Sm: 1.3%, Zn: 0.9%, Zr: 0.5%, and the balance being Mg and inevitable impurities.

5. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 1, characterized in that: In step 1), the smelting and casting are as follows: under the protection of an inert atmosphere, the temperature is first raised to 720-780°C to melt all the materials, and then mechanically stirred for 2-4 minutes using a low-carbon steel stirring rod, followed by standing for 5-10 minutes to obtain a preliminary alloy melt; then the temperature is lowered to 720-740°C and stood for 15-30 minutes before pouring to obtain a cast magnesium alloy.

6. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 5, characterized in that: In step 1), after obtaining the preliminary alloy melt, the temperature is lowered to 760° C., and a No. 5 refining agent is added to perform a refining treatment on the preliminary alloy melt.

7. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 6, characterized in that: In step 2), the solution treatment is performed at a temperature of 480-510° C. and a solution time of 8-12 h to obtain a solid solution magnesium alloy.

8. The method for preparing a high-strength and heat-resistant Mg-Gd-Y-Sm-Zn-Zr alloy according to claim 7, characterized in that: The raw materials are respectively pure magnesium ingots, pure zinc particles, Mg-Gd master alloy, Mg-Sm master alloy, Mg-Y master alloy, and Mg-Zr master alloy.

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