Effect of heat treatment on the microstructure and mechanical properties of a dual phase Al14Co41Cr15Fe10Ni20 high entropy alloy

The microstructure and mechanical properties of Al14Co41Cr15Fe10Ni20 high entropy alloy is investigated in this work. Both the as-cast and homogenized (1200 °C/20 hours) alloys show a dual phase microstructure consisting from a dendritic solid solution FCC phase and an interdendritic B2 (BCC) phase. Aging treatments in the temperature range of 750 °C-1000 °C were applied on samples for 20 hours. Uniform distribution of precipitates in both dendritic and interdendritic regions were observed after performing the aging treatments. It is observed that with increasing the aging temperature from 750 °C to 1000 °C, the size of precipitates increases and the hardness of alloys decreases due to over-aging. The aged alloy with optimized hardness was selected for further room temperature and high temperature tensile tests. The results of mechanical tests indicate that the room temperature mechanical properties of the investigated alloy are comparable to the mechanical properties of commercial Co-based alloys, although the high temperature ductility of the alloy is very poor in comparison with commercial alloys. The obtained results in this work could be used for the further development of high entropy alloys with dual phase FCC/B2 microstructures.