Effect of CuAl2 on the Microstructure and Hardness of Al-Si-xCu Alloys Produced by Powder Metallurgy

Abstract

Aluminum alloys are important in many industrial applications because of their light weight and good mechanical properties. In this study, the effect of copper addition with different percentages ( 0, 0.1, 0.2, 0.3wt. %) on  the  microstructure  and  mechanical  strength  of Al-Si alloy were studied using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and Vickers hardness (Hv) tests. XRD and SEM analyses showed that the Al-Si alloy consisted of α-Al and Si phases. The intermetallic compound (IMC) CuAl₂ was detected with the addition of Cu. This IMC causes a change in the lattice constant and inter-atomic spacing (d_hkl). The distortion and dense of the microstructure are considered indications of the enhancement in the hardness of alloys. The Vickers hardness (Hv) was measured for the samples before and after sintering. The highest value was 28.755 Hv with 0.2wt. % Cu after sintering, whereas the smallest value was 11.643 Hv without Cu content before sintering. This improvement in hardness is attributed to the temperature that promotes the diffusion of Cu atoms into theAl lattices.