Microstructure evolution and mechanical properties of NbHfTiVCx novel refractory high entropy alloys with variable carbon content

A refractory high entropy alloy (RHEA) NbHfTiV was selected as the master alloy and carbon element was introduced to synthesize the novel NbHfTiVCx RHEAs (x = 0, 0.1, 0.2, 0.3), which perform outstanding strength and excellent ductility simultaneously. Phase identification, microstructure evolution, and me-chanical properties were systematically analyzed. The results show that the primary MC-type carbides and nano-precipitate carbides are generated in the BCC matrix phase with the addition of carbon. The primary carbides evolve from solid spheroid (x = 0.1) to sandwich-like pattern (x = 0.2, 0.3), and grain size is sig-nificantly refined from 537 mu m (x = 0) to 25 mu m (x = 0.3). Compressive tests show that the yield strength increases from 958 MPa to 1115 MPa, and the fracture mechanism is changed from ductile fracture to ductile and brittle mixed fracture with carbon content increasing. Meanwhile, the atomic size mismatch and elastic mismatch of the matrix phase reduce with carbon content increasing, which could decrease the lattice distortion degree and soften the matrix phase.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the synthesis of a novel alloy by introducing carbon element to a refractory high entropy alloy. The results demonstrate that the addition of carbon changes the phase identification, microstructure evolution, and mechanical properties of the alloy. With increasing carbon content, the alloy exhibits higher strength and a change in fracture mechanism.