Heat resistant magnesium alloy and production process thereof

Abstract

Provided are a heat-resistant magnesium alloy which has at the same time both high strength and high ductility even under high temperature environment and is also inexpensive, and a production process of the heat-resistant magnesium alloy. The heat-resistant magnesium alloy includes, in relation to the total amount of the alloy, 1 to 3 at % of Zn, 1 to 3 at % of Y and 0.01 to 0.5 at % of Zr with the balance composed of Mg and inevitable impurities, wherein the composition ratio Zn/Y between Zn and Y falls within a range from 0.6 to 1.3, an a-Mg phase and an intermetallic compound Mg 3 Y 2 Zn 3 phase are finely dispersed, and a long period stacking ordered structure phase is formed in a three-dimensional network shape. The heat-resistant magnesium alloy can be produced by melting a metal material having the above-described composition at temperatures within a range from 650 to 900° C., pouring the molten metal material into a mold and cooling the molten metal material at a rate of 10 to 10 3 K/sec.

1 . A heat-resistant magnesium alloy comprising, in relation to the total amount of the alloy, 1 to 3 at % of Zn, 1 to 3 at % of Y and 0.01 to 0.5 at % of Zr with the balance composed of Mg and inevitable impurities, wherein the composition ratio Zn/Y between Zn and Y falls within a range from 0.6 to 1.3, an α-Mg phase and an intermetallic compound Mg 3 Y 2 Zn 3  phase are finely dispersed, and a long period stacking ordered structure phase is formed in a three-dimensional network shape. 
   
   
       2 . The heat-resistant magnesium alloy according to  claim 1 , wherein the tensile strength thereof in a temperature range from 200 to 250° C. falls within a range from 190 to 240 MPa. 
   
   
       3 . The heat-resistant magnesium alloy according to  claim 1 , wherein the elongation thereof in a temperature range from 200 to 250° C. falls within a range from 8 to 16%. 
   
   
       4 . The heat-resistant magnesium alloy according to  claim 1 , wherein the fatigue strength thereof at 200° C. falls within a range from 70 to 80 MPa. 
   
   
       5 . A production process of a heat-resistant magnesium alloy comprising:
 obtaining a molten alloy by melting at temperatures within a range from 650 to 900° C. a metal material including, in relation to the total amount of the metal material, 1 to 3 at % of Zn, 1 to 3 at % of Y and 0.01 to 0.5 at % of Zr with the balance composed of Mg and inevitable impurities, wherein the composition ratio Zn/Y between Zn and Y falls within a range from 0.6 to 1.3; and   casting the molten alloy by pouring into a mold and thereafter by cooling at a rate of 10 to 10 3  K/sec.   
   
   
       6 . The production process of a heat-resistant magnesium alloy according to  claim 5 , wherein the casting is conducted by means of gravity casting. 
   
   
       7 . The production process of a heat-resistant magnesium alloy according to  claim 5 , wherein the pouring into the mold is conducted while the molten alloy is being maintained at temperatures within a range from 800 to 850° C. 
   
   
       8 . The production process of a heat-resistant magnesium alloy according to  claim 5 , wherein the cooling is conducted at a rate of 20 to 670 K/sec.