Microstructure and Localized Plastic Deformation of Al/Si Alloy Improved with CuAl2 Compound

Abstract

The microstructure of Al-Si-xCu alloys with different percentages (x= 0, 0.1, 0.2, 0.3 wt. %) has been investigated using X-ray diffraction (XRD). Localized permanent plastic deformation (Vickers hardness (HV)) was conducted for all samples before and after the sintering process. From the XRD map, the Al-Si alloy consists of ?-Al and Si phases while the Intermetallic compound (IMC) CuAl₂ has been detected with the addition of Cu. Also, it was found that there was a small shift in the peak position to the high angle as more Cu content was added. This shift is a result of the incoincidence of d_hkl levels in the Al-phase before and after the addition of Cu. This mismatch in d_hkl levels is associated with lattice defects and localized strain deformation. From Vickers hardness results, the formation of CuAl₂ precipitates promotes an increase in hardness from 11.643 Hv in the binary Al-Si to 27.439 Hv in the ternary Al-Si-0.3wt. % Cu whereas the highest value was found 28.755 Hv with 0.2 wt. % of Cu after sintering. This is attributed to the temperature promoting diffusion of copper atoms into Al lattices which improves hardness.