A high-rare earth element content magnesium alloy with consideration of room temperature and high temperature strength and a preparation method thereof

Abstract

The application discloses a Mg-Gd-Y high rare earth element content magnesium alloy with high room temperature and high temperature strength and a preparation method of the alloy plate. The alloy composition comprises the following components in a mass fraction: Gd: 8-12%, Y: 1-3%, Zr: 0.01-0.5%, Ag: 0.01-0.5%, Nd: 0.01-0.5%, and the total mass fraction of rare earth elements is greater than or equal to 10%; impurity elements Al is less than or equal to 0.01%, Fe is less than or equal to 0.04%, Mn is less than or equal to 0.02%, and the total content of impurity elements is less than or equal to 0.1%, and the rest is Mg; the preparation method comprises alloy smelting and deformation heat treatment. The room temperature tensile strength of the alloy plate prepared by the application can be more than 450 MPa, the elongation rate can be more than 5.0%, the tensile strength at 300 DEG C can be more than 200 MPa, and the elongation rate can be more than 20%, and the comprehensive performance is obviously better than that of general magnesium alloy materials.

Description

TECHNICAL FIELD

[0001] The present application relates to a high rare earth content magnesium alloy, in particular to a high rare earth content magnesium alloy with both room temperature and high temperature strength and a preparation method thereof. BACKGROUND

[0002] Magnesium alloy is known as the lightest metal structural material, which has irreplaceable influence on weight reduction of automobiles, 3C and aerospace equipment. In addition, magnesium alloy also has good electromagnetic shielding and good shock absorption, and has wide application prospect in the field of aerospace.

[0003] At present, major equipment and new models of products have higher requirements for the performance of magnesium alloy materials at room temperature and high temperature. While magnesium alloy has good room temperature performance, it is required to have good strength and plasticity at high temperature. The existing rare earth magnesium alloy has a Gd content of 5-9% and a Y content of 1-3%, and after deformation and heat treatment, the room temperature strength can reach about 400 MPa. However, the strength of this kind of rare earth magnesium alloy at a temperature above 250℃ is greatly reduced. It is already difficult to meet the requirements, which greatly limits the application of magnesium alloy. Therefore, it is urgent to develop a kind of magnesium alloy material with both room temperature and high temperature strength.

[0004] Increasing the content of rare earth is an effective way to improve the high-temperature mechanical properties of magnesium alloys. According to the search, the Chinese patent "Heat-resistant rare earth magnesium alloy and heat treatment process of non-uniform wall thickness casting thereof" (Patent No. CN201610074516.X) designs a heat-resistant rare earth magnesium alloy, which comprises the following components, consisting of Y 3.4-3.8, Nd 2.6-3.0, Ag 0.5-0.6, Zr 0.4-0.5, Gd 0.3-0.4, and the rest is Mg and non-removable impurity elements; the process adopted is: the heat-resistant rare earth magnesium alloy non-uniform wall thickness casting is heated to 530-540℃, and then cooled to room temperature at a speed of ≥90℃ / min after solid solution, then heated to 220-230℃, and then aged at room temperature after aging, and then air-cooled. The room temperature tensile strength of the obtained product can be 343MPa, the elongation is 6.2%, the tensile strength at 200℃ can be 257MPa, and the elongation is 11.2%. The Chinese patent "Heat treatment method of heat-resistant cast magnesium alloy material" (CN201811041410.5) designs continuous homogenization and multi-stage aging treatment, and in the embodiment, the Mg-10.5Gd-2.5Y-1.5Nd-0.1Zn-0.5Zr alloy has a room temperature tensile strength of 365MPa, an elongation of 4.5%, a tensile strength of 225MPa at 300℃, and an elongation of 18%. Obviously, the increase of rare earth content improves the high-temperature performance of magnesium alloy. However, when the content of Gd is greater than 10%, the second phase increases, the plasticity of magnesium alloy at room temperature decreases sharply, and it is difficult to process into sheet and strip. Moreover, the room temperature strength of these alloys is still not high, and the potential of such alloys cannot be realized through deformation heat treatment. SUMMARY

[0005] In order to solve the problem of low room temperature and high temperature strength of ordinary magnesium alloy, in order to solve the problem that the room temperature toughness and strength of magnesium alloy are difficult to be improved simultaneously under high rare earth content, the present application adds a large amount of Gd and a small amount of Y, and a proper amount of Zr, Ag and Nd elements, and after optimization, a deformed rare earth magnesium alloy sheet with rare earth content greater than 12%, room temperature tensile strength greater than 420MPa, elongation greater than 5% and excellent high-temperature mechanical properties is obtained for the first time. The alloy can meet the requirements of high-strength heat-resistant magnesium alloy in the fields of aerospace, automobile and other fields for a period of time in the future.

[0006] The present application is realized by the following technical solutions:

[0007] The high-rare earth element content magnesium alloy with consideration of room temperature and high temperature strength is composed of the following components in percentage by mass: Gd: 8-12%, Y: 1-3%, Zr: 0.01-0.5%, Ag: 0.01-0.5%, Nd: 0.01-0.5%. The total content of rare earth elements (mass fraction) is greater than or equal to 10%; the impurity elements Al is less than or equal to 0.01%, Fe is less than or equal to 0.04%, Mn is less than or equal to 0.02%, and the total content of impurity elements is less than or equal to 0.1%, and the rest is Mg; and the magnesium alloy is a deformed magnesium alloy.

[0008] Preferably, the magnesium alloy is composed of the following components in percentage by mass: Gd: 8.0-11.5%, Y: 1-2.5%, Zr: 0.35-0.5%, Ag: 0.4-0.5%, Nd: 0.35-0.5%. The total content of rare earth elements (mass fraction) is greater than or equal to 10%; the impurity elements Al is less than or equal to 0.01%, Fe is less than or equal to 0.04%, Mn is less than or equal to 0.02%, and the total content of impurity elements is less than or equal to 0.1%, and the rest is Mg.

[0009] Further preferably, the magnesium alloy is composed of the following components in percentage by mass: Gd: 11-11.5%, Y: 2-2.5%, Zr: 0.35-0.4%, Ag: 0.4-0.5%, Nd: 0.35-0.4%, the impurity elements Al is less than or equal to 0.01%, Fe is less than or equal to 0.04%, Mn is less than or equal to 0.02%, and the rest is Mg.

[0010] More preferably, the magnesium alloy is composed of the following components in percentage by mass: Gd: 11.4%, Y: 2.24%, Zr: 0.37%, Ag: 0.5%, Nd: 0.39%, the impurity elements Al is less than or equal to 0.01%, Fe is less than or equal to 0.04%, Mn is less than or equal to 0.02%, and the rest is Mg.

[0011] The preparation method of the high-rare earth element content magnesium alloy with consideration of room temperature and high temperature strength comprises the following steps: step one, alloy melting and casting

[0012] The raw materials are allocated according to the design components; then the melting and casting process is adopted to obtain the casting blank;

[0013] Step two, homogenization treatment

[0014] The obtained casting blank is placed in a heating furnace, heated to 315-325 DEG C, preferably 320 DEG C and kept for 10-12 hours, then heated to 495-505 DEG C, preferably 500 DEG C and kept for 10-12 hours for homogenization annealing and then water quenching; the blank after homogenization treatment is obtained;

[0015] Step three, hot rolling

[0016] The heating furnace is heated to 440-500℃, and after the temperature is stabilized for 20-40min, preferably 25-35min, the homogenized blank is placed in the heating furnace for 20-40min, and then rolling is started, with a 9-10% reduction per pass, and after each pass, the workpiece is returned to the furnace for 5-10min before the next pass, and when the total reduction reaches 30-65%, the workpiece is water quenched to obtain a hot-rolled plate;

[0017] Step four: aging treatment

[0018] The hot-rolled plate is heated to 200-250℃, and after being kept at this temperature, the aging treatment is performed, and a high-rare earth element content magnesium alloy plate with both room temperature and high temperature strength is obtained.

[0019] As a preferred embodiment, the present application provides a method for preparing a high-rare earth element content magnesium alloy with both room temperature and high temperature strength, and the alloy is cast as follows:

[0020] According to the designed components, magnesium is added, and then the temperature is raised to 760-775℃, and then Mg-Gd, Mg-Y and silver are added, and after complete melting, Mg-Zr and Mg-Nd are added, and after being kept at this temperature for 25-35min, refining is performed at 745-755℃. After the refining is completed, the workpiece is kept still for 30-40min, and finally poured into a mold. The whole melting process is performed in an SF6 protective atmosphere, and the casting downward speed is 2-10cm / min.

[0021] The heating furnace of the present application comprises an electric resistance furnace.

[0022] Wherein the Mg-Gd can be Mg-30Gd, and of course other Mg-Gd alloys or Mg-Gd intermediate alloys or Mg-Gd pre-alloys can also be used in the present application.

[0023] Wherein the Mg-Y can be Mg-30Y, and of course other Mg-Y alloys or Mg-Y intermediate alloys or Mg-Y pre-alloys can also be used in the present application.

[0024] Wherein the Mg-Zr can be Mg-20Zr, and of course other Mg-Zr alloys or Mg-Zr intermediate alloys or Mg-Zr pre-alloys can also be used in the present application.

[0025] Wherein the Mg-Nd can be Mg-20Nd, and of course other Mg-Nd alloys or Mg-Nd intermediate alloys or Mg-Nd pre-alloys can also be used in the present application.

[0026] As for the silver element, pure silver and / or corresponding substances containing zero-valent silver can be used.

[0027] The present application carries out stage homogenization, preheats the alloy casting at low temperature of 300-350 DEG C for 10-14h, and when the temperature inside and outside the alloy is the same, the furnace is heated to 500±10 DEG C for 10-14h. The abnormal expansion of the grain size caused by long time high temperature holding can be avoided, and the large temperature difference between inside and outside the casting caused by sudden rising to high temperature can also be avoided, Figure 2 The mechanical properties of the two-stage homogenization treatment and the single-stage homogenization treatment.

[0028] As preferred, the heating furnace is heated to 455-465 DEG C, and after the temperature is stable for 25-35min, the homogenization treated blank is put into the heating furnace for 20-40min, and then the rolling is started, the reduction per pass is 9-10%, after each pass, the blank is returned to the furnace for 5-10min, and then the next pass is continued, and when the total reduction reaches 45-55%, the blank is water quenched; the hot-rolled plate is obtained.

[0029] As preferred, the hot-rolled plate is heated to 200-250 DEG C for 14-18h for aging treatment, and the high rare earth element content magnesium alloy plate with both room temperature and high temperature strength is obtained.

[0030] As further preferred, the hot-rolled plate is heated to 220-230 DEG C for 14-18h for aging treatment.

[0031] The material and process developed by the present application have excellent elongation and mechanical strength at room temperature. Meanwhile, different processes can be selected according to different use temperature ranges and performance requirements. For example, the product of the present application has an elongation of 41% or more at 300 DEG C. For example, the product of the present application has a tensile strength of 220 MPa or more and an elongation of 20% or more at 300 DEG C. For example, the product of the present application has a strength of 330 MPa or more and an elongation of 11% or more at 250 DEG C.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The tensile strength of the alloy of the present application at room temperature can be more than 420 MPa, and after optimization, it can be more than 450 MPa, the elongation can be more than 5.0%, and preferably more than 8%. After optimization, the high temperature tensile strength at 300 DEG C is more than 200 MPa, and the elongation is more than 20%.

[0034] (2) The addition of Zr element in the present application can refine the grain size of the as-cast alloy, and the Nd and Ag elements can improve the room temperature and high temperature strength of the alloy.

[0035] (3) The multi-pass rolling deformation in the present application can reduce the basal plane texture of the alloy, introduce a large number of recrystallized and deformed grains, and significantly improve the mechanical properties of the alloy. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Scanning electron micrograph of as-cast alloy of Example 1 of the present application.

[0037] Figure 2 Scanning electron micrograph of the alloy after two-stage homogenization annealing of Example 1 of the present application.

[0038] Figure 3 Metallographic structure of the alloy after two-stage homogenization and single-stage homogenization of Example 1 of the present application.

[0039] Figure 4 Room temperature stress-strain curves of the as-cast alloy and homogenization annealed alloy of Example 1 of the present application.

[0040] Figure 5 Room temperature and high temperature stress-strain curves of the peak-aged alloy of Example 1 of the present application.

[0041] Figure 6 Photograph of serious transverse cracks of the rare earth magnesium alloy sheet of Comparative Example 1.

[0042] Figure 7 Photograph of abnormal cracking during hot rolling of the rare earth magnesium alloy sheet of Comparative Example 2. DETAILED DESCRIPTION

[0043] The present application is further described below in connection with a specific alloy composition

[0044] Example 1

[0045] (1) Alloy composition

[0046] The alloy composition is (mass fraction): Gd: 11.4%, Y: 2.24%, Zr: 0.37, Ag: 0.5%, Nd: 0.39%, impurity elements Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the rest is Mg.

[0047] (2) Alloy melting and casting

[0048] The weighed alloy is placed in a drying oven, and the temperature of the drying oven is set to 150°C. Then pure magnesium is added, and then the temperature is raised to about 770°C, and Mg-30Gd, Mg-30Y and pure silver are added, and after complete melting, Mg-20Zr and Mg-20Nd are added, and after holding for 30 min, refining is carried out at 750°C, and after completion of the refining, the alloy is left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process is carried out in an SF6protective atmosphere, and the casting downward pulling speed is 2-10 cm / min. The alloy composition meets the above composition requirements.

[0049] (3) Alloy deformation heat treatment

[0050]

[0051] ② Hot rolling. The resistance furnace was heated to 460°C, and after the temperature was stabilized for 30 min, the homogenized alloy was placed in the resistance furnace for 30 min, and then rolling was started, with a 10% reduction per pass. After each pass, the alloy was kept in the resistance furnace for 5 min. When the total reduction reached 50%, the alloy was immediately water quenched.

[0052] ③ Aging treatment. The resistance furnace was heated to 225°C, and then the quenched plate was placed in the resistance furnace for 15 h. A high-strength heat-resistant rare earth magnesium alloy was obtained.

[0053] (4) Mechanical properties

[0054] After T5 + rolling treatment, the alloy of the present example had a tensile strength of 483 MPa at room temperature, an elongation of 8.3%, a tensile strength of 420 MPa at 200°C, an elongation of 6.1%, a tensile strength of 339 MPa at 250°C, an elongation of 12.9%, a tensile strength of 223 MPa at 300°C, and an elongation of 20.7%.

[0055] Example 2

[0056] (1) Alloy composition

[0057] The alloy composition was (by mass fraction): Gd: 11.4%, Y: 2.37%, Zr: 0.37, Ag: 0.5%, Nd: 0.39%, impurities Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the remainder was Mg.

[0058] (2) Alloy melting and casting

[0059] The weighed alloy was placed in a drying oven, and the temperature of the drying oven was set to 150°C. Then pure magnesium was added, and then the temperature was raised to about 770°C. Mg-30Gd, Mg-30Y, and pure silver were added, and after complete melting, Mg-20Zr and Mg-20Nd were added. After holding for 30 min, the alloy was refined at 750°C. After the refining was completed, the alloy was left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process was carried out in an SF6protective atmosphere, and the casting speed was 2-10 cm / min. The alloy composition met the above composition requirements.

[0060] (3) Alloy thermomechanical treatment

[0061] ① Homogenization annealing. The above ingot was placed in a resistance furnace and heated to 320°C and held for 12 h, and then heated to 500°C and held for 12 h before water quenching. ​

[0062] ② Hot rolling. The resistance furnace is heated to 460℃, and after the temperature is stabilized for 30 min, the homogenized alloy is placed in the resistance furnace for 30 min, and then the rolling is started, with a 10% reduction per pass. After each pass, the alloy is kept in the resistance furnace for 5 min. When the total reduction reaches 40%, the alloy is immediately water quenched.

[0063] ③ Aging treatment. The resistance furnace is heated to 225℃, and then the quenched plate is placed in the resistance furnace for 17 h. A high-strength heat-resistant rare earth magnesium alloy is obtained.

[0064] (4) Mechanical properties

[0065] After the T5+rolling treatment of the alloy of the present example, the tensile strength at room temperature is 431 MPa, the elongation after fracture is 3.3%, the tensile strength at 200℃ is 402 MPa, the elongation after fracture is 5.3%, the tensile strength at 250℃ is 330 MPa, the elongation after fracture is 11.2%, the tensile strength at 300℃ is 185 MPa, and the elongation after fracture is 19.7%.

[0066] Comparative Example 1

[0067] (1) Alloy composition

[0068] The alloy composition is (by mass fraction): Gd: 11.4%, Y: 2.37%, Zr: 0.37%, Ag: 0.5%, Nd: 0.39%, impurities Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the rest is Mg.

[0069] (2) Alloy melting

[0070] The weighed alloy is placed in a drying oven, and the temperature of the drying oven is set to 150℃. Then pure magnesium is added, and then the temperature is raised to about 770℃. Mg-30Gd, Mg-30Y and pure silver are added, and after complete melting, Mg-20Zr and Mg-20Nd are added. After 30 min of holding at 750℃, the alloy is refined, and after the refining is completed, the alloy is left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process is carried out in an SF6protective atmosphere, and the casting downward speed is 2-10 cm / min. The alloy composition meets the above composition requirements.

[0071] (3) Alloy thermo-mechanical treatment

[0072] ① Homogenization annealing. The above ingot is placed in a resistance furnace and heated to 320℃ and held for 12 h, and then heated to 500℃ and held for 12 h, and then water quenched.

[0073] ② Hot rolling. The resistance furnace was heated to 460℃, and after the temperature was stabilized for 30 min, the homogenized alloy was placed in the resistance furnace for 30 min, and then the rolling was started, with a 10% reduction per pass. After each pass, the alloy was kept in the resistance furnace for 5 min. When the total reduction reached 65%, the alloy was immediately water quenched.

[0074] ③ Aging treatment. The resistance furnace was heated to 225℃, and then the quenched alloy plate was placed in the resistance furnace for 11 h. A high-strength heat-resistant rare earth magnesium alloy was obtained.

[0075] (4) Mechanical properties

[0076] Due to excessive deformation, obvious transverse cracks were visible on the surface of the alloy, and the mechanical properties of the alloy could not be tested. Figure 5 ).

[0077] Comparative Example 2

[0078] (1) Alloy composition

[0079] The alloy composition was (by mass fraction): Gd: 11.4%, Y: 2.37%, Zr: 0.37%, Ag: 0.5%, Nd: 0.39%, impurities Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the remainder was Mg.

[0080] (2) Alloy melting

[0081] The weighed alloy was placed in a drying oven, and the temperature of the drying oven was set to 150℃. Then pure magnesium was added, and then the temperature was raised to about 770℃. Mg-30Gd, Mg-30Y and pure silver were added, and after complete melting, Mg-20Zr and Mg-20Nd were added. After 30 min of holding at 750℃, the alloy was refined, and after the refining was completed, the alloy was left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process was carried out in an SF6 protective atmosphere, and the casting speed was 2-10 cm / min. The alloy composition met the above composition requirements.

[0082] (3) Alloy hot deformation treatment

[0083] ① Homogenization annealing. The above ingot was placed in a resistance furnace and heated to 320℃ and held for 12 h, and then heated to 500℃ and held for 12 h before water quenching.

[0084] ② Hot rolling. The resistance furnace was heated to 400℃, and after the temperature was stabilized for 30 min, the homogenized alloy was placed in the resistance furnace for 30 min, and then the rolling was started, with a 10% reduction per pass. The alloy cracked in the first pass and could not be processed further.

[0085] (4) Mechanical properties

[0086] The alloy sheet cracked and the mechanical properties could not be tested. Figure 6

[0087] Example 3

[0088] (1) Alloy composition

[0089] The alloy composition is (mass fraction): Gd: 8.1%, Y: 2.07%, Zr: 0.41%, Ag: 0.5%, Nd: 0.5%, impurity elements Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the rest is Mg.

[0090] (2) Alloy melting

[0091] The weighed alloy is placed in a drying oven, and the temperature of the drying oven is set to 150°C. Then pure magnesium is added, and then the temperature is raised to about 770°C. Mg-30Gd, Mg-30Y and pure silver are added, and after complete melting, Mg-20Zr and Mg-20Nd are added. After holding for 30 min, refining is carried out at 750°C. After the refining is completed, the alloy is left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process is carried out in an SF6protective atmosphere, and the casting down-draw speed is 2-10 cm / min. The alloy composition meets the above composition requirements.

[0092] (3) Alloy hot deformation treatment

[0093] ① Homogenization annealing treatment. The above ingot is placed in an electric resistance furnace and heated to 320°C and held for 12 h, and then heated to 500°C and held for 12 h, and then water quenched.

[0094] ② Hot rolling. The electric resistance furnace is heated to 450°C, and after the temperature is stabilized for 30 min, the homogenized alloy is placed in the electric resistance furnace and held for 40 min, and then rolling is started, with a 10% reduction per pass. After each pass, the alloy is held in the electric resistance furnace for 10 min. When the total reduction reaches 50%, the alloy is immediately water quenched.

[0095] ③ Aging treatment. The electric resistance furnace is heated to 225°C, and then the quenched sheet is placed in the electric resistance furnace and held for 15 h. A high-strength heat-resistant rare earth magnesium alloy is obtained.

[0096] (4) Mechanical properties

[0097] After T5+rolling treatment, the alloy of the present example has a room temperature tensile strength of 425 MPa, an elongation after fracture of 9.3%, a tensile strength at 200°C of 350 MPa, an elongation after fracture of 8.3%, a tensile strength at 250°C of 212 MPa, an elongation after fracture of 21.7%, a tensile strength at 300°C of 132 MPa, and an elongation after fracture of 57.9%.

[0098] Example 4​

[0099] (1) Alloy composition

[0100] The alloy composition is (mass fraction) Gd: 10.1%, Y: 1.98%, Zr: 0.5%, Ag: 0.42%, Nd: 0.49%, impurity elements Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the rest is Mg.

[0101] (2) Alloy melting

[0102] The weighed alloy is placed in a drying oven, and the temperature of the drying oven is set to 150°C. Then pure magnesium is added, and then the temperature is raised to about 770°C. Mg-30Gd, Mg-30Y and pure silver are added, and after complete melting, Mg-20Zr and Mg-20Nd are added. After holding for 30 min, refining is carried out at 750°C. After the refining is completed, the alloy is left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process is carried out in an SF6protective atmosphere, and the casting downward pulling speed is 2-10 cm / min. The alloy composition meets the above composition requirements.

[0103] (3) Alloy hot deformation heat treatment

[0104] ① Homogenization annealing treatment. The above ingot is placed in an electric resistance furnace and heated to 320°C and held for 12 h, and then heated to 500°C and held for 12 h, and then water quenched.

[0105] ② Hot rolling. The electric resistance furnace is heated to 460°C, and after the temperature is stabilized for 30 min, the homogenized alloy is placed in the electric resistance furnace and held for 40 min, and then rolling is started, with a 10% reduction per pass. After each pass, the alloy is held in the electric resistance furnace for 10 min. When the total reduction reaches 50%, the alloy is immediately water quenched.

[0106] ③ Aging treatment. The electric resistance furnace is heated to 225°C, and then the quenched plate is placed in the electric resistance furnace and held for 17 h. A high-strength heat-resistant rare earth magnesium alloy is obtained.

[0107] (4) Mechanical properties

[0108] After T5+rolling treatment, the alloy of the present example has a room temperature tensile strength of 456 MPa, an elongation after fracture of 9.0%, a tensile strength at 200°C of 389 MPa, an elongation after fracture of 7.9%, a tensile strength at 250°C of 253 MPa, an elongation after fracture of 14.5%, a tensile strength at 300°C of 176 MPa, and an elongation after fracture of 41.2%.

[0109] Example 5

[0110] (1) Alloy composition

[0111] The alloy composition is (mass fraction) Gd: 11.4%, Y: 2.37%, Zr: 0.37%, Ag: 0.5%, Nd: 0.39%, impurity elements Al≤0.01%, Fe≤0.04%, Mn≤0.02%, and the rest is Mg.

[0112] (2) Alloy melting

[0113] The weighed alloy is placed in a drying oven, and the temperature of the drying oven is set to 150°C. Then pure magnesium is added, and then the temperature is raised to about 770°C, and Mg-30Gd, Mg-30Y and pure silver are added. After complete melting, Mg-20Zr and Mg-20Nd are added, and after holding for 30 min, refining is carried out at 750°C. After the refining is completed, the alloy is left to stand for 30-40 min, and finally poured into a steel mold. The entire melting process is carried out in an SF6protective atmosphere, and the casting downward pulling speed is 2-10 cm / min. The alloy composition meets the above composition requirements.

[0114] (3) Alloy deformation heat treatment

[0115] ① Homogenization annealing treatment. The above ingot is placed in an electric resistance furnace and heated to 320°C and held for 12 h, and then heated to 500°C and held for 12 h, and then water quenched.

[0116] ② Hot rolling. The electric resistance furnace is heated to 500°C, and after the temperature is stabilized for 30 min, the homogenized alloy is placed in the electric resistance furnace and held for 20 min, and then rolling is started, with a 10% reduction per pass. After each pass, the alloy is held in the electric resistance furnace for 10 min, and when the total reduction reaches 50%, the alloy is immediately water quenched.

[0117] ③ Aging treatment. The electric resistance furnace is heated to 225°C, and then the quenched plate is placed in the electric resistance furnace and held for 15 h. A high-strength heat-resistant rare earth magnesium alloy is obtained.

[0118] (4) Mechanical properties

[0119] After T5+rolling treatment, the alloy of the present example has a room temperature tensile strength of 432 MPa, an elongation after fracture of 5.1%, a tensile strength at 200°C of 395 MPa, an elongation after fracture of 4.5%, a tensile strength at 250°C of 281 MPa, an elongation after fracture of 9.8%, a tensile strength at 300°C of 174 MPa, and an elongation after fracture of 16.3%.

[0120] Table 1 Properties of products obtained in examples and comparative examples

[0121]

Claims

1. A magnesium alloy with high rare earth element content that balances room temperature and high temperature strength, characterized in that: It is composed of the following components by mass percentage: Gd: 11~11.5%, Y: 2~2.5%, Zr: 0.35~0.4%, Ag: 0.4~0.5%, Nd: 0.35~0.4%, impurity elements Al≤0.01%, Fe≤0.04%, Mn≤0.02%, the total content of impurity elements does not exceed 0.1%, and the remainder is Mg; the magnesium alloy is a deformed magnesium alloy. The magnesium alloy with high rare earth element content that balances room temperature and high temperature strength is prepared by the following steps: Step 1 Alloy Melting and Casting The raw materials are allocated according to the design group; then the casting process is used to obtain the cast billet. Step 2 Homogenization The billet is placed in a heating furnace, heated to 315~325℃ and held for 10~12h, then heated to 495~505℃ and held for 10~12h for homogenization annealing, followed by water quenching; the homogenized billet is obtained. Step 3 Hot rolling The heating furnace is heated to 455-465℃. After the temperature stabilizes for 25-35 minutes, the homogenized billet is placed in the heating furnace and held for 20-40 minutes. Then, rolling begins, with a reduction of 9-10% per pass. After each pass, the billet is returned to the furnace and held for 5-10 minutes before the next pass. When the total reduction reaches 45-55%, the billet is water-quenched to obtain hot-rolled sheet. Step Four: Time-Limited Processing Hot-rolled sheets are heated to 200-250℃, kept at that temperature, and then aged to obtain magnesium alloy sheets with high rare earth element content that balance room temperature and high temperature strength.

2. The high rare earth element content magnesium alloy according to claim 1, which combines room temperature and high temperature strength, is characterized in that: The magnesium alloy comprises the following components by mass percentage: Composition: Gd: 11.4%, Y: 2.24%, Zr: 0.37%, Ag: 0.5%, Nd: 0.39%, impurity elements Al≤0.01%, Fe≤0.04%, Mn≤0.02%, the remainder is Mg.

3. A high rare earth element content magnesium alloy according to claim 1, which combines room temperature and high temperature strength, characterized in that: The alloy is cast as follows: Magnesium is added according to the design composition, and then the temperature is raised to 760~775℃. Then Mg-Gd, Mg-Y and silver are added. After they are completely melted, Mg-Zr and Mg-Nd are added. The mixture is kept at 745~755℃ for 25~35 minutes and then refined. After refining, it is allowed to stand for 30~40 minutes and then poured into the mold. The entire melting process is carried out under an SF6 protective atmosphere, and the casting pull-down speed is 2~10cm / min.

4. A high rare earth element content magnesium alloy according to claim 1, which combines room temperature and high temperature strength, characterized in that: In step two, the billet is placed in a resistance furnace, heated to 320℃ and held for 10-12 hours, then heated to 500℃ and held for 10-12 hours for homogenization annealing, followed by water quenching; the homogenized billet is obtained.

5. A high rare earth element content magnesium alloy according to claim 1, characterized in that: Hot-rolled sheets are heated to 200-250℃ and held for 14-18 hours for aging treatment to obtain magnesium alloy sheets with high rare earth element content that balance room temperature and high temperature strength.

6. A high rare earth element content magnesium alloy according to claim 5, which combines room temperature and high temperature strength, characterized in that: The hot-rolled sheet is heated to 220-230℃ and held for 14-18 hours for aging treatment.

Images