An investigation of zinc addition on the structural, mechanical and friction-wear properties in unlubricated conditions of Al-17Si-4Cu-0,6Mg-0,2Ti alloy

In this study, one for each Al-17Si, Al-17Si-4Cu, Al-17Si-4Cu-0.6Mg, Al-17Si-4Cu-0.6Mg-0.2Ti and five Al-17Si-4Cu-0.6Mg-0.2Ti-Zn with different content of zinc were produced by permanent mould casting. Chemical composition of the produced alloys was confirmed by spark optical emission spectrometry (Spark OES) method. Structural examinations of the alloys were carried out with optical and scanning electron microscopy (SEM). The hardness values of the alloys were determined by the Brinell hardness measurement method and Vickers hardness measurement method was used to measure the microhardness of the alloys. The mechanical properties of the alloys were determined by tensile tests performed with a universal testing machine. The microstructure of the Al-Si alloys consisted of aluminum rich α, eutectic Al-Si, primary silicon and β phases. Al-17Si-4Cu alloy showed a microstructure consisting of the θ (CuAl2) phase in addition to phases observed in the Al-17Si alloy. Al-17Si-4Cu-0.6Mg alloy showed a microstructure consisting of Mg2Si in the addition to the phases observed in the Al-17Si-4Cu alloy. In addition to this the β phase turned into π phase in the quaternary alloy. In the microstructure of Al-17Si-4Cu-0.6Mg-Ti and Al-17Si-4Cu-0.6Mg-0.2Ti-Zn alloys, no new phase was formed, with the increase in zinc ratio, but primary silicon particles were become coarsen. Copper, magnesium and titanium additions resulted in an increase in the hardness, yield strength, tensile strength and wear resistance of the alloys, while they caused a decrease in the elongation to fracture. The hardness of the alloys increased with increasing zinc additions, but the yield, tensile strength and wear resistance increased up to %3 zinc content. The results obtained from mechanical and tribological tests were discussed on the basis of structural changes observed in the alloys tested.