Microstructure and Nano-hardness of Reduced Activation FeCrV-Based High Entropy Alloys with Abundant Ti Addition

In this study, we designed and prepared a series of reduced activation FeCrV-based high-entropy alloys (HEAs) with varying titanium (Ti) content to investigate the relationship between thermodynamic parameters and phase structures, and nano-hardness. Our investigation revealed that the addition of Ti promotes the formation of the Laves phase in FeCrV-based alloys. Even in equiatomic FeCrVTi alloy, the presence of the Laves phase highlights the significant role of enthalpy in multi-principal element alloy design. Specifically, the FeCrV alloy free of Ti (x = 0) forms a single BCC phase; while FeCrVTi_x alloys with x = 25, 30, 35, 40, and 45 atomic percentage (at.%) consist of a BCC matrix phase and a secondary Laves phase. The utilization of the valence electron concentration (VEC), atomic size difference (δ), and electronegativity difference (Δχ_Allen) criteria accurately predicted the phase composition of these alloys, aligning with experimental findings. Interestingly, we observed that the nano-hardness of these alloys did not show a significant increasing with higher Ti content. Instead, the equiatomic FeCrVTi alloy demonstrated the highest nano-hardness value, attributed to the balance of solid solution strengthening and second phase strengthening mechanisms. These discoveries provide valuable insights into the design of reduced activation FeCrV-based high-entropy structural materials for advanced nuclear energy systems.