Effects of Calcium Addition on Mechanical Properties of Mg-6%Zn-0.7%Zr Alloy in As-Cast Condition

The effect of different amounts of calcium (0.5, 1, 1.5, 2, and 3 wt. %) on the mechanicalproperties of ZK60 alloy has been investigated. Micrographs of as-cast alloys were observed byoptical and scanning electron microscopy (SEM). Vickers hardness measurement and tensiletesting were performed on the as-cast specimens before and after Ca additions. Experimental results showed that the addition of calcium results in precipitating a new Ca2Mg6Zn3 phase andstructural refinement. Further Ca addition led to the hardness enhancement of the alloy. It can beattributed to the formation of other intermetallic phases such as Mg4Zn7 and Ca2Mg6Zn3. UTS values of the alloy were increased by adding lower calcium contents (up to 1.5 wt.%), butdecreased by further Ca addition (up to 3.0%). It was also found that the ternary eutectic phase predominantly distributes at the grain boundary and acts as the nucleation sites of micro-cracks during tensile testing

Keywords:

ZK60 alloy , microstructures , as-cast condition , mechanical properties