Heat-resistant magnesium alloy

Abstract

A heat-resistant magnesium alloy according to the present invention has Mg as the major component, includes Al, Ca and Mg, and has a metallic structure that comprises Mg crystalline grains and grain-boundary crystallized substances being crystallized out in a grain boundary between the Mg crystalline particles. The grain-boundary crystallized substances comprise a mixed crystal phase of a Laves-phase compound with a type-“C14” crystalline structure, and another Laves-phase compound with a type-“C36” crystalline structure. Moreover, a relative angle between a normal vector to the hexagonal-system basal plane of the Mg crystalline grains and another normal vector to the hexagonal-system basal plane of the grain-boundary crystallized substances is from 88 deg. to 92 deg. at an interface between the Mg crystalline grains and the grain-boundary crystallized substances at least. The present magnesium alloy exhibits high mechanical characteristics in high-temperature atmospheres, because it has the metallic structure in which a basal-plane slip is much less likely to occur than ever before, and because the basal-plane slip is less likely to occur even at high temperatures.

1 . A heat-resistant magnesium alloy being characterized in that:
 it is a heat-resistant magnesium alloy that includes:
 magnesium (Mg) making the major component; 
 aluminum (Al); 
 calcium (Ca); and 
 manganese (Mn); and 
   it has a metallic structure that comprises:
 Mg crystalline grains; and 
 grain-boundary crystallized substances being crystallized out in a grain boundary between the Mg crystalline particles; 
   said grain-boundary crystallized substances comprise a mixed crystal phase of a Laves-phase compound with a type-“C14” crystalline structure and another Laves-phase compound with a type-“C36” crystalline structure; and   a relative angle between a normal vector to the hexagonal-system basal plane of said Mg crystalline grains and another normal vector to the hexagonal-system basal plane of said grain-boundary crystallized substances is from 88 deg. to 92 deg. at an interface between the Mg crystalline grains and the grain-boundary crystallized substances at least.   
     
     
         2 . The heat-resistant magnesium alloy as set forth in  claim 1 , wherein said grain-boundary crystallized substances comprise an Mg—Al—Ca-system compound. 
     
     
         3 . The heat-resistant magnesium alloy as set forth in  claim 1 , wherein said mixed crystal phase includes the type-“C14” crystalline structure more than the type-“C36” crystalline structure. 
     
     
         4 . The heat-resistance magnesium alloy as set forth in  claim 1 , the heat-resistance magnesium alloy including:
 Ca in an amount of from 1.235 atomic % or more to 2.470 atomic % or less;   Al in an amount of from 1.34 or more to 1.63 or less by an atomic ratio of Al with respect to Ca (i.e., Al/Ca);   Mn in an amount of from 0.13 atomic % or more to 0.27 atomic % or less; and   the balance comprising Mg and inevitable impurities;   when the entirety is taken as 100 atomic %.   
     
     
         5 . The heat-resistance magnesium alloy as set forth in  claim 4 , the heat-resistance magnesium alloy including Mn in an amount of from 0.15 atomic % or more to 0.25 atomic % or less. 
     
     
         6 . The heat-resistance magnesium alloy as set forth in  claim 2 , the heat-resistance magnesium alloy including:
 Ca in an amount of from 1.235 atomic % or more to 2.470 atomic % or less;   Al in an amount of from 1.34 or more to 1.63 or less by an atomic ratio of Al with respect to Ca (i.e., Al/Ca);   Mn in an amount of from 0.13 atomic % or more to 0.27 atomic % or less; and   the balance comprising Mg and inevitable impurities;
 when the entirety is taken as 100 atomic %. 
   
     
     
         7 . The heat-resistance magnesium alloy as set forth in  claim 3 , the heat-resistance magnesium alloy including:
 Ca in an amount of from 1.235 atomic % or more to 2.470 atomic % or less;   Al in an amount of from 1.34 or more to 1.63 or less by an atomic ratio of Al with respect to Ca (i.e., Al/Ca);   Mn in an amount of from 0.13 atomic % or more to 0.27 atomic % or less; and   the balance comprising Mg and inevitable impurities;
 when the entirety is taken as 100 atomic %.