Thermal Stability of Al-Si-Cu-Mg Cast Alloys Modified with Transition Metals Zr, V and Ti

The hypoeutectic Al-7Si-1Cu-0.5Mg (wt%) alloy was modified with micro-additions of Zr, V and Ti in order to improve its thermal stability. As revealed by a number of experimental techniques, Cu and Mg rich phases along with the eutectic Si dissolved in the temperature range from 300 to 500°C. At the same time, the (AlSi)x(TiVZr) phases containing transition metals were present up to 696–705°C. During isochronal aging, the modified alloy exerted different aging characteristics than the reference A380 grade with a higher peak hardness and a lower temperature of alloy softening. Micro-additions of Ti, V and Zr positively affected the alloy strength during testing both in as-cast state and after T6 heat treatment. Improvements in tensile and compressive strength as compared to the reference alloy were preserved up to temperatures over 200 °C with more positive effect seen for the T6 state.