Magnesium alloy cast and casting method thereof

Abstract

A magnesium alloy cast, featuring with few casting defects, having precipitation areas dispersed inside magnesium alloy grains is provided by melting magnesium alloy material in an oxygen-free atmosphere and cooling the molten magnesium alloy at a cooling rate in the 1-20K/sec range by the continuous casting for solidification.

What is claimed is:  
     
         1 . A magnesium alloy cast having a plurality of precipitation areas existing inside magnesium alloy grains, the precipitation area containing at least one of aluminum, zinc, and manganese.  
     
     
         2 . The magnesium alloy cast according to  claim 1 , wherein the plurality of precipitation areas is separated from each other from zero to 400 μm measured from an edge to another.  
     
     
         3 . The magnesium alloy cast according to  claim 1 , wherein the area of each precipitation area is from 25×10 −12 πm 2  to 2500×10 −12 πm 2 .  
     
     
         4 . The magnesium alloy cast according to  claim 1 , wherein an amount of aluminum contained is 1.8-9.1 wt. %.  
     
     
         5 . The magnesium alloy cast according to  claim 1 , wherein the cast is formed in a plate-like shape.  
     
     
         6 . A magnesium alloy casting method comprising: 
 a step of putting magnesium alloy material in a melting apparatus, melting the magnesium alloy material in the melting apparatus under an oxygen-free atmosphere, supplying the molten alloy to a cooling mold, and cooling the molten magnesium alloy at a cooling rate in the 1-20K/sec range for solidification; and    a step of drawing the solidified metallic ingot by drawing means for keeping the ingot continuous.    
     
     
         7 . The magnesium alloy casting method according to  claim 6 , wherein the solidified metallic ingot is intermittently drawn by alternatively repeating drawing process and holding process.  
     
     
         8 . The magnesium alloy casting method according to  claim 6 , wherein the molten magnesium alloy is cooled at a cooling rate in the 3-8K/sec range.  
     
     
         9 . The magnesium alloy casting method according to  claim 6 , wherein the magnesium alloy material added in the melting apparatus is a granular solid, and the molten magnesium alloy is molded into the cooling mold with the atmosphere around the melting apparatus being kept inert.  
     
     
         10 . The magnesium alloy casting method according to  claim 6 , wherein a cross-section of an inner wall of the cooling mold is rectangular and at least one part of the inner wall is tapered so that a short side of the rectangle on the melting apparatus side is different from that on the drawing means side.  
     
     
         11 . The magnesium alloy casting method according to  claim 6 , wherein an alloy holding part of the melting apparatus and/or the cooling mold are/is made of graphite.  
     
     
         12 . The magnesium alloy casting method according to  claim 6 , wherein the cooling mold is connected to a side of the melting apparatus and the magnesium alloy is drawn in a horizontal direction.