Magnesium alloy for casting and magnesium-alloy cast product

Abstract

A magnesium alloy for casting according to the present invention is characterized in that, when the entirety is taken as 100% by mass, it includes copper (Cu) in an amount of from 1% by mass or more to 5% by mass or less, calcium (Ca) in an amount of from 0.1% by mass or more to 5% by mass or less, tin (Sn) in an amount of from 0.1 or more to 3 or less by mass ratio with respect to the Ca (Sn/Ca); and the balance comprising magnesium (Mg) and inevitable impurities. By means of including Cu, Ca and Sn, crystallized substances of Mg—Ca—Sn compounds crystallize in crystalline grain boundaries between Mg crystalline grains as network shapes (three-dimensionally mesh shapes), along with Mg—Cu compounds. By means of the three-dimensionally mesh constructions, grain-boundary sliding, which becomes active especially when becoming high temperature, is suppressed, and thereby high-temperature strength and creep resistance at high temperature improve. Moreover, since Sn forms compounds with Ca preferentially, it influence less on the heat conductivity, compared with the other additive elements.

1 . A magnesium alloy for casting, the magnesium alloy being characterized in that, when the entirety is taken as 100% by mass, it includes:
 copper (Cu) in an amount of from 1% by mass or more to 5% by mass or less;   calcium (Ca) in an amount of from 0.1% by mass or more to 5% by mass or less;   tin (Sn) in an amount of from 0.1 or more to 3 or less by mass ratio with respect to the Ca (Sn/Ca); and   the balance comprising magnesium (Mg) and inevitable impurities.   
   
   
       2 . The magnesium alloy for casting as set forth in  claim 1 , wherein the content of said copper (Cu) is from 2% by mass or more to 4% by mass or less. 
   
   
       3 . The magnesium alloy for casting as set forth in  claim 1 , wherein the content of said calcium (Ca) is from 0.5% by mass or more to 3% by mass or less. 
   
   
       4 . The magnesium alloy for casting as set forth in  claim 1 , wherein the content of said tin (Sn) is from 0.1 or more to 2 or less by mass ratio with respect to said Ca (Sn/Ca). 
   
   
       5 . The magnesium alloy for casting as set forth in  claim 1  having a structure in which Mg—Cu compounds and Mg—Ca—Sn compounds are crystallized as network shapes in crystalline grain boundaries between Mg crystalline grains. 
   
   
       6 . A magnesium-alloy cast product being characterized in that it is obtainable by way of the following:
 a molten-metal pouring step of pouring an alloy molten metal into a casting mold, the alloy molten metal including: copper (Cu) in an amount of from 1% by mass or more to 5% by mass or less; calcium (Ca) in an amount of from 0.1% by mass or more to 5% by mass or less; tin (Sn) in an amount of from 0.1 or more to 3 or less by mass ratio with respect to the Ca (Sn/Ca); and the balance comprising magnesium (Mg) and inevitable impurities; when the entirety is taken as 100% by mass; and   a solidifying step of solidifying the alloy molten metal after the molten-metal pouring step by cooling it.   
   
   
       7 . The magnesium-alloy cast product as set forth in  claim 6  having a structure in which Mg—Cu compounds and Mg—Ca—Sn compounds are crystallized as network shapes in crystalline grain boundaries between Mg crystalline grains.