Effect of Zr, V and Ti on hot compression behavior of the Al–Si cast alloy for powertrain applications

Abstract

The uniaxial compression test was used to assess the influence of micro-additions of V and Zr on the hot deformation behavior of the Al–7Si–1Cu–0.5Mg–0.1Ti (wt.%) base cast alloy. The temperature in the range of 200–400°C and, to a lesser extent, strain rate in the range of 10−3–1s−1 affected the flow stress of both alloys with the peak stress of the V and Zr modified alloy being consistently higher. Constitutive equations were employed to evaluate the material constants and to correlate them with the hot deformation behavior. The presence of V and Zr increased the activation energy of the plastic deformation from 282.6kJ/mol to 315.2kJ/mol, supporting improved resistance to hot deformation. As revealed through metallographic examinations, fracturing and re-orientation of the second phase particles occurred during compression. For both alloys, the intermetallic particles experienced substantially more frequent cracking than the eutectic silicon. At the same time, in the modified alloy, both the eutectic silicon and intermetallics experienced less frequent fracturing. The precipitates in the modified alloy were also more resistant to rotation within the alloy matrix as a result of hot deformation. The beneficial role of the transition metals V, Zr and Ti in improving the high temperature performance of cast Al alloys was discussed.