Influence of Si Addition on the Microstructure and Mechanical Behaviour of Mg-5Sn-3Zn-1Mn Alloy

A new alloy Mg-5Sn-3Zn-1Mn-xSi (x = 0.5, 1, 1.5, 2wt %) with varied composition is investigated. Morphological behavior of as-cast Mg-5Sn is studied with the addition of Zn and Mn. Mg2Sn phases are mostly present in the grain boundaries. Grain refinement is observed on the micrographs with the addition of Zn and Mn. With the different addition of Si in Mg-5Sn-3Zn-1Mn alloy, Mg2Si phase is formed along with the Mg2Sn phase. With lower addition of Si forms eutectic Mg2Si phase with Chinese script shape morphology. When Si addition exceeds 1 %, primary Mg2Si polygonal particles also formed along with eutectic Mg2Si phase. Addition of Si up to 1 % by weight sufficiently improves the mechanical property. Above 1 wt% Si, a slight reduction in tensile strength is observed, accompanied by the formation of hard and brittle primary and coarse Chinese script Mg2Si phases.