Microstructure and mechanical properties of refractory high entropy (Mo0.5NbHf0.5ZrTi)BCC/M5Si3 in-situ compound

Abstract Refractory high-entropy alloy Mo 0.5 NbHf 0.5 ZrTi is selected as the base alloy and element Si is added for preparing the (Mo 0.5 NbHf 0.5 ZrTi) BCC /M 5 Si 3 in-situ compound. The effect of Si on the microstructure and mechanical properties of Mo 0.5 NbHf 0.5 ZrTi alloy is analyzed and discussed. The base alloy has the single body-centered cubic (BCC) phase. After adding Si, the alloy is composed of one BCC phase and the intermetallic M 5 Si 3 phase with hexagonal close-packed (HCP) crystal structure. The microstructure gradually evolves from the hypoeutectic structure to eutectic structure and finally to hypereutectic structure with the increase of Si concentration. The addition of Si reduces the density and increases the hardness and strength of the base alloy due to the formation of M 5 Si 3 phase. The plasticity of Si 0.1 alloy is also improved due to the grain refinement and the weakening of the solution strengthening for the dominant BCC phase and the M 5 Si 3 phase is fine while the plasticity decreases due to the formation of more brittle M 5 Si 3 phase with a larger size as Si content increases.