High strength magnesium alloy and method of production of the same

Abstract

A high strength magnesium alloy improving the high temperature strength while not using any expensive rare earth elements and thereby reducing the cost and its method of production are provided, that is, a high strength magnesium alloy of a composition of the formula Mg 100−(a,b) Zn a X b wherein X is one or more elements selected from Zr, Ti, and Hf, a and b are the contents of Zn and X expressed by at %, and the following relationships (1), (2), and (3): (1) a/28≦b≦a/9, (2) 2<a<10, (3) 0.05<b<1.0 are satisfied and comprising an Mg matrix phase in which Mg—Zn—X-based quasi-crystals and their approximant crystals are dispersed in the form of fine particles and a method of production of a high strength magnesium alloy comprising melting Mg in an inert atmosphere to form an Mg melt, adding Mg—Zn—X-based quasi-crystals (X being at least one of Zr, Ti, and Hf) into the Mg melt to form an alloy melt, casting the alloy melt, and heat treating the obtained casting to make the quasi-crystal and their approximant crystals precipitate in an Mg matrix phase.

1 . A high strength magnesium alloy of a composition of the formula Mg 100−(a+b) Zn a X b  wherein X is one or more elements selected from Zr, Ti, and Hf, a and b are the contents of Zn and X expressed by at %, and the following relationships (1), (2), and (3):
     a/ 28 ≦b≦a/ 9   (1)     2<a<10   (2)     0.05<b<1.0   (3)   
       are satisfied and
 comprising an Mg matrix phase in which Mg—Zn—X-based quasi-crystals and their approximant crystals are dispersed in the form of fine particles. 
 
     
     
         2 . A high strength magnesium alloy as set forth in  claim 1 , wherein said quasi-crystals are at least one type selected from Mg 11 Zn 83 Zr 6 , Mg 11 Zn 83 Ti 6 , and Mg 11 Zn 83 Hf 6 . 
     
     
         3 . A method of production of a high strength magnesium alloy as set forth in  claim 1 , including:
 a step for melting Mg in an inert atmosphere to form an Mg melt,   a step of adding Mg—Zn—X-based quasi-crystals (X being at least one of Zr, Ti, and Hf) into said Mg melt to form an alloy melt,   a step of casting said alloy melt, and   a step of heat treating the obtained casting to make said quasi-crystals and their approximant crystals precipitate in an Mg matrix phase.   
     
     
         4 . A method of production of a high strength magnesium alloy as set forth in  claim 3 , further comprising preparing said Mg—Zn—X-based quasi-crystals by:
 a step of weighing the Mg, Zn, and X materials to give a quasi-crystal composition,   a step of charging said weighed materials in a crucible and melting them in an inert atmosphere to form a melt,   a step of lowering a temperature of said melt and holding it at a single phase region where only said quasi-crystals are present, and   a step of cooling from the temperature of said single phase region to room temperature.