Assessment of hardness in as-cast and homogenized Zn-Al-Cu alloys

A study of the effect of chemical composition on microstructure and hardness of the as-cast and homogenized Zn-Al-Cu alloys was carried out. Five different composition alloys were prepared and they were homogenized at 623K for 648 ks in order to eliminate the dendritic structure. Rockwell "B" hardness was determined in the as-cast and homogenized alloys. XRD diffraction analysis of the as-cast and homogenized alloys indicated the presence of the α, η, ε, θ, τ' and β phases and α, η, ε, θ, and τ' phases, respectively. The hardness of both the as-cast and homogenized alloys increased with the increase in volume fraction of the Cu-containing ε, θ, and τ' phases. A multiple-linear regression analysis permitted to obtain the two equations, HRB_As-cast = 97.5 + 6.8 ln(at%Cu)-4.7 ln (at%Zn) and HRB_Homogenized = 52.1 + 3.6 ln(at%Cu)- 27:5 ln(at%Zn), to assess the hardness in the as-cast and homogenized Zn-Al-Cu alloys.