The microcrack inhibition and mechanical properties of an in-situ synthesized refractory high-entropy alloy fabricated by additive manufacturing

Abstract

A crack-free refractory high-entropy alloy (RHEA), composed of (Cr25Mo25Nb25V25)99C1 was synthesized in-situ from blended elemental powders using laser directed energy deposition (DED). This study revealed that a minor addition of carbon effectively enhances the grain-boundary cohesion of the DEDed RHEA, thereby mitigating microcrack propagation along the grain boundaries during the additive manufacturing process. Notably, the DEDed RHEA exhibited exceptional high-temperature mechanical properties, highlighted by a yield strength of 787 MPa at 1000 °C along with sustained strain-hardening capacity, surpassing other additively manufactured high-entropy alloys reported to date. The remarkable high-temperature strength of the DEDed RHEA can be attributed to the potent pinning effect exerted on dislocations within both dendritic and interdendritic regions at elevated temperature. This effect stems from severe lattice distortion, local chemical fluctuations (LCFs), solute atom pinning, and dislocation interactions. The method employed to inhibit microcrack formation, along with the elucidation of the high-temperature strengthening mechanism, opens avenues for the fabrication of RHEAs tailored for high-temperature structural applications.