Effect of nickel additions on the mechanical and sliding wear properties of Al–40Zn–3Cu alloy

In this work, one ternary Al–40Zn–3Cu and six quaternary Al–40Zn–3Cu–(0.5–3)Ni alloys were fabricated by permanent mould casting. Their friction and wear behaviour were investigated using a conforming block-on-disc type tester after determining their microstructure and mechanical properties.The microstructure of the Al–40Zn–3Cu alloy consisted of aluminium-rich α dendrites, eutectoid α + η and θ (CuAl2) phases. In additions to these phases, Al3Ni intermetallic particles were observed in the quaternary alloys containing nickel. Tensile strength and elongation to fracture of the alloys decreased with increasing nickel addition. However, the hardness of the alloys and the microhardness of the α phase showed a marginal decrease and a sharp increase with increasing nickel content. It was observed that the friction coefficient and frictional heating of the alloys decreased with test duration after showing an initial increase and reached a steady-state (constant) value. It was also observed that the wear volume of the alloys exhibited a gradual decrease following an initial increase with increasing percentage of nickel. The wear surfaces of the alloys revealed smearing and scratches. However, smearing was observed to be the dominant wear mechanism for the alloys. As a result of this work, the quaternary Al–40Zn–3Cu–Ni alloys containing more than 1% Ni were found to be superior to the ternary alloy containing no nickel as far as their wear resistance is concerned.