Magnesium alloy and heat treatment method thereof

Abstract

A magnesium alloy having excellent castability and creep properties has compositions of 1.0-6.0 wt % Zn, 0.5-3.0 wt % Ca, 1.0 wt % or less Zr, 1.0-5.0 wt % at least one lanthanoid, the remainder being Mg and unavoidable impurities. This magnesium alloy undergoes heat treatment of heating the magnesium alloy to 430-470 ° C., quenching, and then heating to 150-250 ° C. for aging. Hot tearing and temperature strength are improved by the addition of an element which is effective for causing eutectic reaction and peritectic reaction with Mg and making Mg particles divied finely.

What is claimed is:  
     
         1 . A magnesium alloy having excellent high pressure die casting properties and creep characteristics, comprising: 
 calcium(Ca) in the content range of 0.5 to 3.0 wt %;    zinc(Zn) in the content range of 1.0 to 6.0 wt %;    zirconium(Zr) in the content range of 1.0 wt % or less (exclusive of 0 wt %);    at least one rare earth element in the content range of 1.5 to 2.7 wt %;    the remainder being magnesium; and    unavoidable impurities.    
     
     
         2 . A magnesium alloy according to  claim 1 , wherein the content range of Zn is 2.0 to 4.0 wt %.  
     
     
         3 . A magnesium alloy according to  claim 1 , wherein the content range of Ca is 0.7 to 1.5 wt %.  
     
     
         4 . A magnesium alloy according to  claim 1 , wherein the content range of Zr is 0.4 to 1.0 wt %.  
     
     
         5 . A magnesium alloy according to  claim 4 , wherein the content range of Zr is 0.5 to 1.0 wt %.  
     
     
         6 . A magnesium alloy according to  claim 1 , wherein the content range of the rare earth element is 2.0 to 2.7 wt %.  
     
     
         7 . A magnesium alloy according to  claim 1 , wherein the rare earth element is a lanthanoid.  
     
     
         8 . A magnesium alloy having excellent high pressure die casting properties and creep characteristics, comprising: 
 calcium(Ca) in the content range of 0.5 to 3.0 wt %;    zinc(Zn) in the content range of 1.0 to 6.0 wt %;    zirconium(Zr) in the content range of 1.0 wt % or less;    at least one rare earth element in the content range of 1.5 to 2.7 wt %;    alminum (Al) in the content of 2.0% or less (exclusive of 0 wt %);    manganese (Mn) in the content of 1.0 wt % or less;    the remainder being magnesium; and    unavoidable impurities.    
     
     
         9 . A magnesium alloy according to  claim 8 , wherein the content range of Zn is 2.0 to 4.0 wt %.  
     
     
         10 . A magnesium alloy according to  claim 8 , wherein the content range of Ca is 0.7 to 1.5 wt %.  
     
     
         11 . A magnesium alloy according to  claim 8 , wherein the content range of Zr is 0.4 to 1.0 wt %.  
     
     
         12 . A magnesium alloy according to  claim 11 , wherein the content range of Zr is 0.5 to 1.0 wt %.  
     
     
         13 . A magnesium alloy according to  claim 8 , wherein the content range of rare earth element is 2.0 to 2.7 wt %.  
     
     
         14 . A magnesium alloy according to  claim 8 , wherein the rare earth element is a lanthanoid.  
     
     
         15 . A heat treatment method of a magnesium alloy, comprising: 
 calcium(Ca) in the content range of 0.5 to 3.0 wt %;    zinc(Zn) in the content range of 1.0 to 6.0 wt %;    zirconium(Zr) in the content range of 1.0 wt % or less;    (exclusive of 0 wt %) at least one rare earth element in the content range of 1.5 to 5.0 wt %;    the remainder being magnesium; and    unavoidable impurities, comprising the steps of: 
 a) heating the magnesium alloy in the temperature range of 430 to 470° C.:  
 b) quenching the heated aloloy; and  
 c) heating the alloy to in the temperature range of 150 to 250° C. to age the same.  
   
     
     
         16 . A heat treatment method of a magnesium alloy according to  claim 15 , wherein the heating step a) at 430° C. is carried out 5 to 24 hours.  
     
     
         17 . A heat treatment method of a magnesium alloy according to  claim 15 , wherein the heating step c) carried out for 0.5 to 24 hours.  
     
     
         18 . A heat treatment method of a magnesium alloy according to  claim 15 , wherein the temperature range of the step c) is 150 to 200° C.  
     
     
         19 . A heat treatment method of a magnesium alloy according to claim 15, wherein the temperature range of the step c) is 180 to 200° C. within 0.5 to 2 hours.  
     
     
         20 . A heat treatment method of a magnesium alloy according to claim 15, wherein the rare earth element is a lonthanoid.