The effect of ageing on the microstructure and hardness of Al10Co25Cr8Fe15Ni36Ti6 high entropy alloys

The effect of ageing time and temperature on the microstructure and hardness of Al10Co25Cr8Fe15Ni36Ti6 high entropy alloys is investigated in this article. The alloy melted in vacuum induction melting furnace and purified using vaccum arc remelting process. Then homogenized at 1220°C for 17 hours. Then sample aged at 850, 900 and 950°C for 1-16 hours and assessed using XRD and SEM. The microstructure is involved ′γand NiAl precipitates and γ matrix. With increasing ageing temperature, the volume fraction and size of ′γ decreased from 60 Vol% and 338 nm at 850°C to 31 Vol% and 123 nm at 950°C, respectively. The ′γprimary morphology is cubic which changed to square and semi-square like. The hardness of alloy is 314, 329 and 327 Hv at 850, 900 and 950 °C, respectively. According to these results, 850°C for 8 hours is the best ageing conditions. The best high temperature tensile properties of 840.9 MPa ultimate tensile strength and 17.9 elongation obtained at 850 °C.