한국주조공학회

Microstructural characteristics and strengthening behavior in Mg-5wt%Zn-0.6wtZr alloys have been investigated by a combination of optical, secondary electron and transmission electron microscopy, differential thermal analysis, and hardness and tensile, creep property measurements. The result have been compared with those of Mg-5wt%Zn alloys. The as-squeeze cast rnicrostructure consisted of dendrite on-Mg, interdendrite or intergranular Mg-,.Zn3 and fine dispersoids of ZIIZI2. The size of secondary solidification phases in Mg-5wt%Zn-0.6wtZr alloys was significantly smaller than that of the Mg-5wt%Zn alloys due to the existence of fine dispersoid of ZnZr2 which also effected the refinement of grain size. TEM study showed that the main cause of age hardening is formation of fine rodlike B,‘ precipitates as well as fine ZnZr2 dispersoids. Due to the observed microstructural characteristics mechanical propeties of Mg-5wt%Zn-0.6wtZr alloys was found to be superior to those of Mg-5wt%Zn alloys.