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

Zr and Sb are simultaneously added to refine and modify primary Mg2Si in Al–20Mg2Si 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 Mg2Si. The unique co-modification effect is mainly derived from the synergistic combination of Sb and Zr. Sb can involve in the formation of Mg3(Sb, Si)2 particles and thereby can act as heterogeneous nuclei of primary Mg2Si, resulting in the uniform distribution and refined particle size of primary Mg2Si crystals. The role of Zr is also indispensable as it can decrease the solidification temperature interval of the primary Mg2Si phase, which could further refine the primary Mg2Si crystals and promote their complete growth. Moreover, the wear resistance of Al–20Mg2Si alloys is also improved owing to the special co-modification effect of Zr and Sb. Since primary Mg2Si 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. © 2018 Elsevier B.V.