An investigation of effects of zinc, manganese and magnesium additions on microstructure, mechanical and tribological properties of Al-12Si-3Cu based alloy

In this study, the effects of Zn, Mn and Mg on microstructure, mechanical and tribological properties of Al-12Si-3Cu based alloy were investigated. T6 heat treatment was applied some of produced alloys and results were compared to their as-cast states. Microstructure of the alloys were observed to consist of α-Al, Si, θ (CuAl2), α-Al15Mn3Si2, Mg2Si, π (Al8Mg3FeSi6) ve Q (Al5Mg8Cu2Si6) phases depending on addition elements. T6 heat treatment caused to breaking up needle-like silicon particles and transformation them to nearly spherical shape. It was observed that these particles showed a homogenous distribution in matrix after T6 heat treatment. It was determined that mechanical and ductility properties of Al-12Si-3Cu based alloy increased as the Zn addition increased. On the other hand, the hardness of this alloy increased in case of increasing Mn addition but its tensile strength and ductility decreased. Hardness and strength properties of Al-12Si-3Cu based alloy reached to the maximum values at %0,5 Mg addition, above which they decreased with increasing Mg addition. However, it was found that quaternary alloys containing Zn, Mn and Mg exhibited higher hardness than the ternary Al-12Si-3Cu alloy. Tensile fracture of the alloys took place the propagation of cracks formed as result of breaking up brittle phases or their detachment of matrix. It was seen that Zn, Mn and %0,5 Mg additions increased the wear resistance of base alloy. Al-12Si-3Cu-2Zn, Al-12Si-3Cu-1Mn, Al-12Si-3Cu-0,5Mg, Al-12Si-3Cu-2Zn-0,5Mn and Al-12Si-3Cu-2Zn-1Mn-0,5Mg alloys showed a suitable mechanical and tribological properties amongst the others. T6 heat treatment resulted in a significant improve in mechanical and tribological properties of the alloys.