Synchrotron radiation micro-beam analysis of the effect of strontium on primary silicon in Zn-27Al-3Si alloy

The influence of Sr on two- and three-dimensional morphology of primary Si in Zn-27Al-3Si alloy was investigated. Distribution and crystalline structure of Sr were analyzed by using synchrotron radiation micro-beam. The results show that Sr could modify polygonal primary Si to nearly standard spherical shape. Modified primary Si enriched with Sr, which partially evolves as Al2Si2Sr, while partially presents as independent atoms. Sr promotes high-density paralleled and intersected {111}Si twins during the growth of primary Si. These observations thus provide experiment evidence to support the modification mechanisms based on impurity-induced twinning and poisoning of twin plane reentrant edge.