Microstructure and mechanical properties of AlNiCuCoX high-entropy Alloy

Abstract

AlNiCuCoX (X=Cr, CrTi, CrFe, FeTi and CrFeTi) series high-entropy alloys were prepared by vacuum arc furnace. The microstructures and properties of the alloys were analyzed. The results show that the microstructures of AlNiCuCoX alloys are composed of FCC solid solution and BCC solid solution, and the number of phases formed in the alloys is far lower than that predicted by equilibrium phase law. AlNiCuCoCrTi shows chrysanthemum like microstructure, while AlNiCuCoFeTi and AlNiCuCoCrFeTi alloys shows petal-like, chrysanthemum like and reticular (intercrystalline) white microstructure. The principal element is the key factor affecting the solidification mode (hypoeutectic, eutectic and hypereutectic solidification) of AlNiCuCoX series alloys. If the interdendritic phase is not considered, AlNiCuCoCr and AlNiCuCoCrFe high-entropy alloys are solidified in the end-solid solution solidification mode. When Ti is added, the alloy is solidified in the hypoeutectic solidification mode, and the equilibrium microstructure is composed of primary phase and eutectic. The microhardness of the most alloys increased with the increase of the number of principal elements, and the hardness of AlNiCuCoCrFeTi alloys is the highest (548HV). The compressive strength and strain of most AlNiCuCoX alloys are low (especially AlNiCuCoCrFeTi alloy). Both AlNiCuCoCr and AlNiCuCoCrFe alloys have better comprehensive mechanical properties.