Microstructure and microhardness of as-cast and 800 °C annealed AlxCr0.2Fe0.2Ni0.6-x and Al0.2Cr0.2FeyNi0.6-y alloys

The microstructure and phase analysis of the arc-melted AlxCr0.2Fe0.2Ni0.6-x (x = 0.07-0.53) and Al0.2Cr0.2FeyNi0.6-y (y = 0.06-0.53) alloys, in both the as-cast state and after annealing at 800 °C for 30 days, were experimentally investigated by scanning electron microscopy and X-ray diffraction. With the exception of alloys with a high Al content, the Al-Cr-Fe-Ni alloys are composed of BCC-type and/or FCC-type phases. In the as-cast state, with Cr content fixed at 20%, the amount of the B2 phase increases with the Al content. The BCC and/or FCC solid solution separates from the B2 phase when annealed at 800 °C. Once annealed, these alloys are all composed of two or more phases. The uniform nanoparticle B2+BCC structure was observed in the 800 °C annealed Al0.2Cr0.2FeyNi0.6-y (y = 0.36-0.53) alloys. The phase size decreased with the increase of the Fe content. Moreover, the microhardness of the alloys linearly increased with the Al content in the AlxCr0.2Fe0.2Ni0.6-x alloys, while the effect of Fe and Ni content on the microhardness is limited. After annealing at 800 °C, the hardness of the AlxCr0.2Fe0.2Ni0.6-x (x = 0.24-0.44) alloys decreased by around 100 HV, while that of Al0.2Cr0.2FeyNi0.6-y (y = 0.16-0.54) alloys decreased by 120-180 HV. This information will help to design Al-Cr-Fe-Ni based multi-component alloys.