Lightweight Cr_xV_0.5Nb_0.5ZrTi Refractory High-Entropy Alloys: Microstructure and Mechanical Properties

This study investigated two lightweight Cr_xV_0.5Nb_0.5ZrTi (x = 0.1 and 0.3) refractory high-entropy alloys to understand the relationship between phase composition, microstructure, and mechanical properties. The addition of Cr resulted in a transition from a single-phase BCC structure of the base alloy V_0.5Nb_0.5ZrTi to a multiphase structure comprising BCC and Cr-rich Laves phases in the Cr_xV_0.5Nb_0.5ZrTi alloys. The microstructure exhibited a typical dendritic pattern, consisting of BCC dendrites and Cr-rich Laves interdendrites. The area fraction of the Cr-rich Laves phase increased from 5% to 28% with the increase in Cr content. This increase led to elevated yield strength values, rising from 1100 ± 20 MPa to 1330 ± 30 MPa. The primary mechanisms contributing to the mechanical properties were solid-solution strengthening from the BCC phase and the formation of a small amount of hard Laves phase. These mechanisms, combined with the low density of the alloys, resulted in an excellent combination of specific yield strength and plasticity in the Cr_0.1V_0.5Nb_0.5ZrTi alloy. Specifically, it exhibited a specific yield strength of 180 MPa cm³/g and over 40% plastic strain without fracture. Overall, the study provides insights into the design and development of lightweight refractory high-entropy alloys with desirable mechanical properties for various engineering applications.