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 CO2 and SF6 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.

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.