Effect of Si addition on microstructure, hardness and wear resistance of as cast Mg-5Sn and Mg-10Sn alloys were investigated. For this purpose alloys with wt.-% 0, 0.5, 1, 1.5 Si were cast using an induction furnace. Addition of Si to both alloys caused an increasement in the amount of intermetallic phases at the grain boundaries. Also refined grain structure was reported with increasing Si content in the cast alloys. Both increased amount of intermetallics and decreased grain size caused an increase in the hardness of the alloys. Wear resistance of the binary alloys first increased with Si addition and then decreased. Increased amounts of Si in the alloys caused crack formation during wear tests and decreased wear resistance. Sliding speed also has a dramatical effect on the wear resistance of the alloys. Increased sliding speed resulted with higher wear resistance. Worn surfaces of the alloys also investigated under scanning electron microscope to understand the wear mechanisms operated during wear tests. (c) 2018 Published by Elsevier B. V. on behalf of Chongqing University.