Enhancing mechanical properties and degradation performance of Mg−0.8wt.%Ca alloy by directional solidification

Abstract

The mechanical properties and degradation performance in Hank's solution of the directionally solidified (DSed) Mg−0.8Ca (wt.%) alloys were investigated and compared with those of the as-cast alloy. The microstructure was studied by OM, SEM, TEM, and EBSD. It is found that the columnar grains in DSed alloys have a consistent growth orientation of <1120>. The mechanical strength and ductility of Mg−0.8Ca alloy are significantly improved after directional solidification. Besides, the corrosion resistance of Mg−0.8Ca alloy in Hank's solution is dramatically enhanced after directional solidification. The Mg−0.8Ca alloys in Hank's solution mainly undergo microgalvanic corrosion, and the corrosion products consist of Mg(OH)2, (Ca, Mg)3(PO4)2, and hydroxyapatite (HA). The superior properties of the DSed Mg−Ca alloy are beneficial from the columnar microstructure and the redistribution of the eutectics. The DSed Mg−0.8Ca alloy with columnar dendritic structure is expected to be used as biodegradable materials.