MG-GD-Y-ZN-ZR ALLOY AND PROCESS FOR PREPARING THE SAME

Abstract

The present disclosure discloses a Mg—Gd—Y—Zn—Zr alloy with high strength and toughness, corrosion resistance and anti-flammability and a process for preparation thereof. Components and mass percentages in the Mg—Gd—Y—Zn—Zr alloy are: 3.0%≤Gd≤9.0%, 1.0%≤Y≤6.0%, 0.5%≤Zn≤3.0%, 0.2%≤Zr≤1.5%, the balance being Mg and inevitable impurities. The process for preparation thereof comprises: adding pure Mg into a smelting furnace for heating, then introducing mixed gases of CO.sub.2 and SF.sub.6 into the furnace for protection; adding other raw materials in sequence when the pure Mg is completely melted; preparing an ingot; conducting a homogenization treatment on the ingot prior to extrusion; conducting an aging treatment on the extruded alloy. The present invention obtains a wrought magnesium alloy having both superior overall performances and good fracture toughness, corrosion resistance and anti-flammability, with a small amount of rare earth element by adjusting the proportion of the alloy elements and by conventional casting, extrusion and heat treatment processes.

Claims

1. A Mg—Gd—Y—Zn—Zr alloy comprising: 3.0% to 9.0% Gd, 0.8% to 6.0% Y, 0.5% to 3.0% Zn, 0.2% to 1.5% Zr, the balance being Mg and impurities.

2. The Mg—Gd—Y—Zn—Zr alloy according to claim 1, wherein Gd+Y is 11.0% or less.

3. The Mg—Gd—Y—Zn—Zr alloy according to claim 1, wherein the alloy comprises 8.0% Gd, 3.0% Y, 1.0% Zn, 0.5% Zr, the balance being Mg and impurities.

4. The Mg—Gd—Y—Zn—Zr alloy according to claim 1, wherein the alloy comprises Gd: 8.4%, Y: 2.4%, Zn: 0.6%, Zr: 0.4%, the balance being Mg and impurities.

5. The Mg—Gd—Y—Zn—Zr alloy according to claim 1, wherein the alloy comprises Gd: 6.7%, Y: 1.3%, Zn: 0.6%, Zr: 0.5%, the balance being Mg and impurities.

6. The Mg—Gd—Y—Zn—Zr alloy according to claim 1, wherein the alloy comprises Gd: 8.4%, Y: 1%, Zn: 0.7%, Zr: 0.6%, the balance being Mg and impurities.

7. The Mg—Gd—Y—Zn—Zr alloy according to claim 1, wherein the alloy comprises Gd: 7.1%, Y: 2.0%, Zn: 1.1%, Zr: 0.5%, the balance being Mg and impurities.

8. A process for preparing a Mg—Gd—Y—Zn—Zr alloy, the process comprising: (1) increasing a first temperature of a smelting furnace to a second temperature of 760 to 850° C., and adding Mg and Zn into the smelting furnace; (2) reducing the second temperature to a third temperature of the smelting furnace of 730 to 780° C. after the Mg and Zn are melted; (3) adding a Mg—Gd alloy, a Mg—Y alloy, a the Mg—Zr alloy to the smelting furnace to obtain a melt; (4) adjusting the third temperature to a fourth temperature of the smelting furnace of 700 to 750° C., removing slag on a surface of the melt, and introducing preheated argon at a bottom of the smelting furnace; (5) increasing the fourth temperature to a fifth temperature of the smelting furnace of 730 to 760° C., transferring the melt into a holding furnace at a pressure of 0.01 to 0.02 MPa, and holding the fifth temperature and the pressure for 1 to 3 hours; and (6) reducing the fifth temperature to a sixth temperature of the smelting furnace of 700 to 720° C., casting the melt prepared in (5), and cooling a cast ingot with cooling water at room temperature to obtain an ingot of the Mg—Gd—Y—Zn—Zr alloy.

9. The process of claim 8, wherein the Mg—Gd—Y—Zn—Zr alloy comprises 3% to 9% Gd, 0.8% to 6% Y, 0.5% to 3% Zn, 0.2% to 1.5% Zr, the balance being Mg and impurities.

10. The process of claim 8, wherein casting the melt prepared in (5) is performed at a casting rate of 42 mm/min, and cooling and crystalizing the cast ingot with water is performed at a pressure of the water of 0.02 MPa.

11. The process of claim 8, wherein the process further comprises: (7) conducting a homogenization treatment on the ingot of the Mg—Gd—Y—Zn—Zr alloy at a temperature of 450 to 550° C. for 8 to 24 hours, and then quenching the ingot in water having a temperature of 50 to 80° C.; (8) conducting an extrusion on the ingot after the homogenization treatment to form an extruded alloy, wherein the extrusion is performed at a temperature of 350 to 450° C., an extrusion ratio of 8 to 20, and a rain speed of 0.05-5 mm/s; and (9) conducting an aging treatment on the extruded alloy at a temperature of 175 to 225° C. for a holding time of 0.5 to 200 hours to form an aged alloy, and quenching the aged alloy with water at a temperature of 50 to 80° C. to obtain the Mg—Gd—Y—Zn—Zr alloy.

12. The process of claim 8, wherein Gd+Y is 11.0% or less of the Mg—Gd—Y—Zn—Zr alloy.

13. The process of claim 8, wherein the process further comprises: (7) conducting a homogenization treatment on the ingot of the Mg—Gd—Y—Zn—Zr alloy at a temperature of 450 to 550° C. for 8 to 24 hours.

14. The process of claim 13, wherein the process further comprises: (8) conducting an extrusion on the ingot after the homogenization treatment, wherein the extrusion temperature is performed at a temperature of 350 to 450° C., an extrusion ratio of 8 to 20, and a rain speed of 0.05-5 mm/s.

15. The process of claim 8, wherein the alloy comprises 8.0% Gd, 3.0% Y, 1.0% Zn, 0.5% Zr, the balance being Mg and impurities.

16. The process of claim 8, wherein the alloy comprises Gd: 8.4%, Y: 2.4%, Zn: 0.6%, Zr: 0.4%, the balance being Mg and impurities.

17. The process of claim 8, wherein the alloy comprises Gd: 6.7%, Y: 1.3%, Zn: 0.6%, Zr: 0.5%, the balance being Mg and impurities.

18. The process of claim 8, wherein the alloy comprises Gd: 8.4%, Y: 1%, Zn: 0.7%, Zr: 0.6%, the balance being Mg and impurities.

19. The process of claim 8, wherein the alloy comprises Gd: 7.1%, Y: 2.0%, Zn: 1.1%, Zr: 0.5%, the balance being Mg and impurities.

20. The process of claim 8, wherein the alloy comprises 8.0% Gd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0027] The technical solution of the alloys and processes herein will be further described below by referring to the Examples. However, the alloys and processes herein are not limited thereto, and any modifications or equivalent alternatives of the technical solution of the present disclosure, without departing from the spirit and scope of the technical solution of the disclosure herein, should be included in the scope of the disclosure herein.

Example 1

[0028] In the Example, the components and the mass percentages thereof contained in the Mg—Gd—Y—Zn—Zr alloy with high strength are: Gd 8.0%, Y 3.0%, Zn 1.0%, Zr 0.5%, and the balance being Mg and inevitable impurity elements. The specific preparation method for the alloy is carried out according to the following steps:

[0029] 1. weighing pure Mg, pure Zn, Mg—Y master alloy, Mg—Gd master alloy and Mg—Zr master alloy according to the ratio of 8% Gd, 3% Y, 1% Zn, 0.5% Zr and the balance of Mg based on mass percentage;

[0030] 2. heating the smelting furnace to 800° C., adding the pure Mg and pure Zn prepared in step 1 into the smelting furnace under the protection of mixed gases of CO.sub.2+10 vol % SF.sub.6;

[0031] 3. reducing the temperature of the furnace to 760° C. after the pure Mg and pure Zn are completely melted, adding the Mg—Gd master alloy, the Mg—Y master alloy, and the Mg—Zr master alloy in this order, to obtain a melt;

[0032] 4. reducing the furnace temperature to 740° C., removing the slag on the surface of the melt, refining the melt for 15 minutes by introducing preheated argon at the bottom of the furnace, to improve the purity of the melt;

[0033] 5. increasing the temperature to 750° C., transferring the melt into a holding furnace under a pressure of 0.02 MPa, and holding for 2 hours,

[0034] 6. reducing the temperature to 705° C., casting the melt prepared in step 5 at a rate of 42 mm/min, cooling and crystalizing the cast ingot with cooling water at room temperature and a pressure of 0.02 MPa, to finally obtain a large ingot of the Mg—Gd—Y—Zn—Zr alloy with a diameter of 170 mm and a length of 2.75 m by casting;

[0035] 7. conducting a homogenization treatment on the ingot at 500° C. for 12 hours, then quenching in warm water at 80° C.;

[0036] 8. conducting an indirect extrusion on the ingot after the homogenization treatment, wherein the extrusion temperature is controlled at 390° C., the extrusion ratio is 12:1, and the rain speed is 0.1 mm/s; and

[0037] 9. conducting an isothermal aging treatment on the extruded alloy at 200° C. for 72 hours, and quenching the sample in warm water at 80° C. after the aging treatment, to obtain the target alloy.

[0038] The resultant alloy of the Example has a tensile strength of 465 MPa, a yield strength of 437 MPa, and an elongation of 10.8%. See Table 1 for details.

Example 2

[0039] In the Example, the components and the mass percentages thereof contained in the Mg—Gd—Y—Zn—Zr alloy with high strength are: Gd 8.4%, Y 2.4%, Zn 0.6%, Zr 0.4%, and the balance being Mg and inevitable impurity elements. The preparation method of the Mg—Gd—Y—Zn—Zr alloy with high strength is: firstly, weighing pure Mg, pure Zn, Mg—Y master alloy, Mg—Gd master alloy and Mg—Zr master alloy according to the ratio of 8.4% Gd, 2.4% Y, 0.6% Zn, 0.4% Zr and the balance of Mg based on mass percentage; casting the alloy according to steps 2-6 in Example 1; conducting the homogenization treatment on the ingot at 500° C. for 12 hours, then quenching in the warm water at about 80° C.; conducting the indirect extrusion on the ingot after the homogenization treatment, wherein the extrusion temperature is controlled at 400° C., the extrusion ratio is 12:1, and the rain speed is 0.1 mm/s; conducting the isothermal aging treatment on the extruded alloy at 200° C. for 118 hours, and quenching the sample in the warm water at 80° C. after the aging treatment, to obtain the target alloy. The properties of the alloy are shown in Table 1.

Example 3

[0040] In the Example, the components and the mass percentages thereof contained in the Mg—Gd—Y—Zn—Zr alloy with high strength are: Gd 6.7%, Y 1.3%, Zn 0.6%, Zr: 0.5%, and the balance being Mg and inevitable impurity elements. The preparation method of the Mg—Gd—Y—Zn—Zr alloy with high strength is: firstly, weighing pure Mg, pure Zn, Mg—Y master alloy, Mg—Gd master alloy and Mg—Zr master alloy according to the ratio of 6.7% Gd, 1.3% Y, 0.6% Zn, 0.5% Zr and the balance of Mg based on mass percentage; casting the alloy according to steps 2-6 in Example 1; conducting the homogenization treatment on the ingot at 510° C. for 8 hours, then quenching in the warm water at about 80° C.; conducting the indirect extrusion on the ingot after the homogenization treatment, wherein the extrusion temperature is controlled at 400° C., the extrusion ratio is 12:1, and the rain speed is 0.1 mm/s; conducting the isothermal aging treatment on the extruded alloy at 200° C. for 84 hours, and quenching the sample in the warm water at 80° C. after the aging treatment, to obtain the target alloy. The properties of the alloy are shown in Table 1.

Example 4

[0041] In the Example, the components and the mass percentages thereof contained in the Mg—Gd—Y—Zn—Zr alloy with high strength are: Gd 8.4%, Y 0.8%, Zn 0.7%, Zr 0.6%, and the balance being Mg and inevitable impurity elements. The preparation method of the Mg—Gd—Y—Zn—Zr alloy with high strength is: firstly, weighing pure Mg, pure Zn, Mg—Y master alloy, Mg—Gd master alloy and Mg—Zr master alloy according to the ratio of 8.4% Gd, 0.8% Y, 0.7% Zn, 0.6% Zr and the balance of Mg based on mass percentage; casting the alloy according to steps 2-6 in Example 1; conducting the homogenization treatment on the ingot at 510° C. for 8 hours, then quenching in the warm water at about 80° C.; conducting the indirect extrusion on the ingot after the homogenization treatment, wherein the extrusion temperature is controlled at 400° C., the extrusion ratio is 12:1, and the rain speed is 0.1 mm/s; conducting the isothermal aging treatment on the extruded alloy at 200° C. for 84 hours, and quenching the sample in the warm water at 80° C. after the aging treatment, to obtain the target alloy. The properties of the alloy are shown in Table 1.

Example 5

[0042] In the Example, the components and the mass percentages thereof contained in the Mg—Gd—Y—Zn—Zr alloy with high strength are: Gd 7.1%, Y 2.0%, Zn 1.1%, Zr is 0.5%, and the balance being Mg and inevitable impurity elements. The preparation method of the Mg—Gd—Y—Zn—Zr alloy with high strength is: firstly, weighing pure Mg, pure Zn, Mg—Y master alloy, Mg—Gd master alloy and Mg—Zr master alloy according to the ratio of 7.1% Gd, 2.0% Y, 1.1% Zn, 0.5% Zr and the balance of Mg based on mass percentage; casting the alloy according to steps 2-6 in Example 1; conducting the homogenization treatment on the ingot at 510° C. for 8 hours, then quenching in the warm water at about 80° C.; conducting the indirect extrusion on the ingot after the homogenization treatment, wherein the extrusion temperature is controlled at 400° C., the extrusion ratio is 12:1, and the rain speed is 0.1 mm/s; conducting the isothermal aging treatment on the extruded alloy at 200° C. for 84 hours, and quenching the sample in the warm water at 80° C. after the aging treatment, to obtain the target alloy. The properties of the alloy are shown in Table 1.

TABLE-US-00001 TABLE 1 The properties of the alloys in the Examples and WE43 (comparative sample) Weight loss in salt spray test Ignition UTS YS ε Kq (mg .Math. point (MPa) (MPa) (%) (MPa .Math. m.sup.1/2) cm.sup.−2 .Math. d.sup.−1) (° C.) Example 1 465 437 10.8 31.2 0.32 748 Example 2 455 425 10.2 25.1 0.37 722 Example 3 428 409 10.1 21.6 0.50 728 Example 4 436 422 11.3 21.3 0.56 746 Example 5 451 423 10.7 22.4 0.37 708 WE43 352 243 11.5 15.0 0.61 765

[0043] The present invention obtains a wrought magnesium alloy having superior overall performances with a small amount of rare earth element by adjusting the proportion of the alloy elements and by conventional casting, extrusion and heat treatment processes. At room-temperature, the tensile strength thereof is 428-465 MPa, the yield strength is 409-437 MPa, and the elongation is 10.1%44.4%; meanwhile, it also has excellent fracture toughness, corrosion resistance and flame retardant property. The cost of the alloy is reduced while the strength of the alloy is maintained.