Directional solidification of Al–Cu–Si–Mg quaternary eutectic alloy

Abstract

The effects of growth rates on the microstructure, microhardness, tensile strength, and electrical resistivity were studied in directionally solidified Al–Cu–Si–Mg (Al–28 wt%Cu–6wt.%Si–2.2 wt%Mg) quaternary eutectic alloy. The directional solidification process was carried out at five different growth rates (V = 9.63–173.5 μm/s) at a constant temperature gradient (G = 6.88 K/mm). The microstructure of the directionally solidified Al–Cu–Si–Mg quaternary eutectic alloy consists of Al solid solution, irregular Si plates, and intermetallic Al2Cu (θ) and Cu2Mg8Si6Al5 (Q) phases with honeycomb morphology. The dependencies of lamellar spacing, microhardness, tensile strength, and electrical resistivity on growth rates were found to be λCuAl2=19.05V−0.41, λCu2Mg8Si6Al5=51.28V−0.43, λSi=8.74V−0.46, HV=170.7+79.08V0.25,HV=237.68(V)0.043, σ=343.45(V)0.15, andρ=3.42×10−8(V)0.10, respectively, for the Al–Cu–Si–Mg quaternary eutectic alloy. The bulk growth rates were also determined as λSi2V=92.24, λCuAl22V=669.2, and λCu2Mg8Si6Al52V=4205.5μm3/s by using the measured values ofλMg2Si, λCuAl2, λCu2Mg8Si6Al52, and V for the Si plates and intermetallic Al2Cu (θ) and Cu2Mg8Si6Al5 (Q) phases in the Al–Cu–Si–Mg eutectic alloy, respectively.