Ti-Jun Chen, Da-Hua Zhang, Wei Wang, Ying Ma, Yuan Hao
November 10, 2015
The effects of Sn and Ca on the microstructure and mechanical properties of Mg–Zn–Y alloys have been investigated. The results showed that Sn had an obvious effect on the microstructure, but its effect was smaller than that of Ca. The grain size first decreased as the Sn/Ca content increased and then slightly increased when the Sn/Ca content exceeded a critical value. These microstructural changes are related to the hindering effect on grain growth and constitutional supercooling resulting from the segregated Sn/Ca atoms at the advancing solid/liquid fronts. The hardness of the alloys continuously increased as the Sn/Ca content increased because of the improved solid solution strengthening and the increased concentration of Sn- or Ca-rich intermetallic compounds. The tensile properties of the alloys increased as the Sn/Ca content increased below the critical value and then decreased when the Sn/Ca content exceeded the critical value. The increased tensile properties were attributed to the improved grain bonding strength in addition to the grain refinement strengthening. The subsequent decrease in these properties was mainly ascribed to the impaired grain bonding strength and grain coarsening. Correspondingly, the fracture regime changed from intergranular to transgranular modes, and then back to the intergranular mode.