Development of constitutive relationship and processing map for Al-6.65Si-0.44Mg alloy and its composite with B4C particulates

High temperature flow behavior of Al-6.65Si-0.44Mg (all in wt%) (A356) alloy and A356+5 wt% B4C composite were investigated by compression test at temperatures 470, 500, 530 and 570 °C and strain rates 10−3, 10−2, 10−1 and 1 s−1. Constitutive relationship was established by the prediction of materials constants α, β, n, Q and lnA. The variations in stable and instable regions of processing map were investigated in A356 alloy and A356+5 wt% B4C composite. It was found that the existence of instability domain for A356 alloy, over the range of temperatures ~510–570 °C and strain rates ~1− 4×10−2 s−1, was extended to regime of temperatures ~470–570 °C over the same strain rates upon 5% B4C reinforcement. The microstructural evolutions by stable and instable regions were studied in scanning electron microscope (SEM) and by the electron backscatter diffraction (EBSD) technique.