Nitride-reinforced HfNbTaTiV high-entropy alloy with excellent room and elevated-temperature mechanical properties

Abstract

Nitride-reinforced (HfNbTaTiV)90N10 high-entropy alloy aiming at high-temperature applications is designed in this paper. Abundant FCC nitride phases are formed in situ in theBCC matrix by arc melting technique, without complex deformation or heat treatment. The (HfNbTaTiV)90N10 alloy exhibits a remarkable yield strength of 2716 MPa and ultimate compressive strength of 2833 MPa with a plastic strain of 10% at room temperature. Besides, the alloy remains a high yield strength of 279 MPa at 1400 °C. The nitride phases play an essential role in maintaining the excellent strength-ductility combination at room temperature and enhancing the high-temperature softening resistance. Alternating BCC and FCC phases possess the semi-coherent interface, which not only strengthens the BCC matrix but also promotes the compatible deformation of the duplex microstructure. The lattice coherency structure of the semi-coherent interface is conducive to the slip transfer of partial dislocations through the interface, which facilitates the accommodation of plastic deformation. The cross-slip of the screw dislocations effectively eliminates stress concentration and leads to good ductility of the dual-phase alloy. The results demonstrate that the nitride phases achieve coordinate deformation with the matrix without deteriorating the ductility of the (HfNbTaTiV)90N10 alloy.