Microstructure and wear behaviour of Al-20Mg2Si alloy with combined Zr and Sb additions

Abstract Zr and Sb are simultaneously added to refine and modify primary Mg 2 Si in Al–20Mg 2 Si alloys. Compared with single addition of Zr or Sb, the combined addition of Zr and Sb can result in an enhanced refinement and modification effect on primary Mg 2 Si. The unique co-modification effect is mainly derived from the synergistic combination of Sb and Zr. Sb can involve in the formation of Mg 3 (Sb, Si) 2 particles and thereby can act as heterogeneous nuclei of primary Mg 2 Si, resulting in the uniform distribution and refined particle size of primary Mg 2 Si crystals. The role of Zr is also indispensable as it can decrease the solidification temperature interval of the primary Mg 2 Si phase, which could further refine the primary Mg 2 Si crystals and promote their complete growth. Moreover, the wear resistance of Al–20Mg 2 Si alloys is also improved owing to the special co-modification effect of Zr and Sb. Since primary Mg 2 Si can be optimized by enhancing heterogeneous nucleation and decreasing solidification temperature interval, such idea can be extended to guide the microstructure control in other alloy systems.