Elemental fluctuations in refractory high-entropy alloys for additive manufacturing lead to synergistic enhancement of ultimate strength and plasticity

Advancements in science and technology have led to increasingly stringent performance requirements for materials, and traditional alloys cannot satisfy the demands of modern applications. Refractory high-entropy alloys (RHEAs) composed of W and Mo have the potential to become the next generation of high-performance materials. In this study, a W35Nb25Mo15Ta5Ti10Ni10 alloy was fabricated using laser powder bed fusion (LPBF) and subsequently annealed. Under rapid solidification conditions, the LPBFed alloy exhibited a supersaturated solid solution of Ti elements, while the precipitation of secondary phases effectively suppressed crack defects. The average grain size of the LPBFed alloy was less than 5 μm, and its yield strength exceeded 2050 MPa. The average grain size did not increase after heat treatment. Element diffusion led to the formation of a semi-coherent Ni₄Ti₃ phase with the matrix phase. This caused compositional fluctuations within the matrix phase, increasing the plasticity of the alloy. The annealed alloy exhibited a room-temperature compressive ultimate strength that exceeded 3.1 GPa, with a fracture strain increase of 266.7 %. The heat treatment method, which induced compositional fluctuations through intergranular and intragranular element diffusion, synergistically improved the ultimate strength and plasticity of the alloy. Thus, this study presented a new approach for the synergistic enhancement of ultimate strength and toughness in brittle alloys.