High strength and high toughness metal and method of producing the same

Abstract

This invention provides a high-strength and high-toughness metal which has strength and toughness each high enough to be put to practical use in expanded applications of magnesium alloys, and a process for producing the same. The high-strength and high-toughness metal is a magnesium alloy comprising a crystal structure containing an hcp-structure magnesium phase and a long-period layered structure phase. At least a part of the long-period layered structure phase is in a curved or flexed state. The magnesium alloy comprises a atomic % of Zn and b atomic % of Gd with the balance consisting of Mg.

1 - 28 . (canceled) 
     
     
         29 . A high strength and high toughness metal comprising a magnesium alloy having a crystal structure having an hcp-Mg phase and a long-period stacking ordered structure phase,
 wherein at least a part of said long-period stacking ordered structure phase exists in a lamellar form with a 2H structure Mg phase,   wherein said magnesium alloy contains Zn in an amount of “a” atomic % and of at least one element selected from the group consisting of Gd, Tb, Tm and Lu in a total amount of “b” atomic %, wherein “a” and “b” satisfy the following expressions (1) to (3):
   0.2 ≦a≦ 5.0;  (1)
 
   0.5 ≦b≦ 5.0; and  (2)
 
   0.5 a− 0.5≦ b.   (3)
 
   
     
     
         30 - 32 . (canceled) 
     
     
         33 . The high strength and high toughness metal according to  claim 29 ,
 wherein said magnesium alloy contains at least one element selected from the group consisting of Yb, Sm and Nd in a total amount of “c” atomic % and at least one element selected from the group consisting of La, Ce, Pr, Eu and Mm in a total amount of “d” atomic %, wherein “c” and “d” satisfy the following expressions (4) to (6):
   0 ≦c≦ 3.0;  (4)
 
   0 ≦d≦ 2.0; and  (5)
 
   0.5 ≦b+c+d≦ 6.0.  (6)
 
   
     
     
         34 - 42 . (canceled) 
     
     
         43 . The high strength and high toughness metal according to  claim 29 ,
 wherein said magnesium alloy contains at least one element selected from the group consisting of Gd, Tb, Tm and Lu in a total amount of less than 3 atomic %.   
     
     
         44 - 48 . (canceled) 
     
     
         49 . The high strength and high toughness metal according to  claim 29 ,
 wherein said magnesium alloy is produced by the following manner:   a mineral ore containing rare-earth elements is refined to prepare a rare-earth alloy containing plural rare-earth elements; and   the rare-earth alloy is used as a part of starting material for casting to produce said magnesium alloy which contains the rare-earth elements in a total amount of 6.0 atomic % or less.   
     
     
         50 - 135 . (canceled)