High strength and high toughness magnesium alloy and method of producing the same

Abstract

A high strength and high toughness magnesium alloy, characterized in that it is a plastically worked product produced by a method comprising preparing a magnesium cast product containing a atomic % of Zn, b atomic % in total of at least one element selected from the group consisting of Dy, Ho and Er, a and b satisfying the following formulae (1) to (3), and the balance amount of Mg, subjecting the magnesium alloy cast product to a plastic working to form a plastically worked product, and it has a hcp structure magnesium phase and a long period stacking structure phase at an ordinary temperature; 0.2≦ a ≦5.0  (1) 0.2≦ b ≦5.0  (2) 0.5 a −0.5≦ b   (3)

1 - 38 . (canceled) 
     
     
         39 . A method of producing a high strength and high toughness magnesium alloy comprising;
 a step for preparing a magnesium alloy casting product containing “a” atomic % of Zn, “b” atomic %, in a total amount, of at least one element selected from the group consisting of Dy, Ho and Er and a residue of Mg, wherein “a” and “b” satisfy the following expressions (1) to (3), and   a step for producing a plastically worked product by subjecting said magnesium alloy casting product to a plastic working:
   0.2 ≦a≦ 5.0;  (1)
 
   0.2 ≦b≦ 5.0; and  (2)
 
   0.5 a− 0.5 ≦b.   (3)
 
   
     
     
         40 . (canceled) 
     
     
         41 . The method of producing a high strength and high toughness magnesium alloy according to  claim 39 , wherein said magnesium alloy casting product has a hcp structured magnesium phase and a long period stacking ordered structure phase. 
     
     
         42 - 44 . (canceled) 
     
     
         45 . A method of producing a high strength and high toughness magnesium alloy comprising:
 a step for preparing a magnesium alloy casting product containing “a” atomic % of Zn, “b” atomic %, in a total amount, of at least one element selected from the group consisting of Dy, Ho and Er and a residue of Mg, wherein “a” and “b” satisfy the following expressions (1) to (3);   a step for producing a chip-shaped casting product by cutting said magnesium alloy casting product; and   a step for producing a plastically worked product by solidifying said chip-shaped casting product by a plastic working:
   0.1 ≦a≦ 5.0;  (1)
 
   0.1 ≦b≦ 5.0; and  (2)
 
   0.5 a− 0.5 ≦b.   (3)
 
   
     
     
         46 . (canceled) 
     
     
         47 . The method of producing a high strength and high toughness magnesium alloy according to  claim 45 , wherein said magnesium alloy casting product has a hcp structured magnesium phase and a long period stacking ordered structure phase. 
     
     
         48 - 50 . (canceled) 
     
     
         51 . The method of producing a high strength and high toughness magnesium alloy according to  claim 39 , wherein Mg contains larger than 0 atomic % to 2.5 atomic % or less, in a total amount, of at least one element selected from the group consisting of Al, Th, Ca, Si, Mn, Zr, Ti, Hf, Nb, Ag, Sr, Sc, B, C, Sn, Au, Ba, Ge, Bi, Ga, In, Ir, Li, Pd, Sb and V. 
     
     
         52 . The method of producing a the high strength and high toughness magnesium alloy according to  claim 39 , wherein said plastic working is carried out by at least one process in a rolling, an extrusion, an ECAE working, a drawing, a forging, a press, a form rolling, a bending, a FSW working and a cyclic working of theses workings. 
     
     
         53 . The method of producing a high strength and high toughness magnesium alloy according to  claim 39 , wherein a total strain amount when said plastic working is carried out is 15 or less. 
     
     
         54 . The method of producing a high strength and high toughness magnesium alloy according to  claim 39 , wherein a total strain amount when said plastic working is carried out is 10 or less. 
     
     
         55 . The method of producing a high strength and high toughness magnesium alloy according to  claim 39  comprising a step for heat-treating said plastically worked product after said step for producing said plastically worked product. 
     
     
         56 . The method of producing a high strength and high toughness magnesium alloy according to  claim 55 , wherein said heat treatment is carried out under a condition of a temperature of 200° C. to less than 500° C. and a treating period of 10 minutes to less than 24 hours. 
     
     
         57 . The method of producing a high strength and high toughness magnesium alloy according to  claim 39 , wherein said magnesium alloy after subjecting to said plastic working has said hcp structured magnesium phase having single-digit larger dislocation density than a long period stacking ordered structure phase. 
     
     
         58 . The method of producing a high strength and high toughness magnesium alloy according to  claim 45 , wherein Mg contains larger than 0 atomic % to 2.5 atomic % or less, in a total amount, of at least one element selected from the group consisting of Al, Th, Ca, Si, Mn, Zr, Ti, Hf, Nb, Ag, Sr, Sc, B, C, Sn, Au, Ba, Ge, Bi, Ga, In, Ir, Li, Pd, Sb and V. 
     
     
         59 . The method of producing a the high strength and high toughness magnesium alloy according to  claim 45 , wherein said plastic working is carried out by at least one process in a rolling, an extrusion, an ECAE working, a drawing, a forging, a press, a form rolling, a bending, a FSW working and a cyclic working of theses workings. 
     
     
         60 . The method of producing a high strength and high toughness magnesium alloy according to  claim 45 , wherein a total strain amount when said plastic working is carried out is or less. 
     
     
         61 . The method of producing a high strength and high toughness magnesium alloy according to  claim 45 , wherein a total strain amount when said plastic working is carried out is 10 or less. 
     
     
         62 . The method of producing a high strength and high toughness magnesium alloy according to  claim 45  comprising a step for heat-treating said plastically worked product after said step for producing said plastically worked product. 
     
     
         63 . The method of producing a high strength and high toughness magnesium alloy according to  claim 62 , wherein said heat treatment is carried out under a condition of a temperature of 200° C. to less than 500° C. and a treating period of 10 minutes to less than 24 hours. 
     
     
         64 . The method of producing a high strength and high toughness magnesium alloy according to  claim 45 , wherein said magnesium alloy after subjecting to said plastic working has said hcp structured magnesium phase having single-digit larger dislocation density than a long period stacking ordered structure phase.