Promoted high-temperature strength and room-temperature plasticity synergy by tuning dendrite segregation in NbMoTaW refractory high-entropy alloy

Abstract

NbMoTaW refractory high-entropy alloy (RHEA) exhibits high strength and excellent softening resistance at elevated temperature, while normal compositional modification cannot overcome the trade-off between high-temperature (HT) strength and room-temperature (RT) plasticity. Here, we proposed a heterostructure strategy by tuning dendrite segregation to reach large RT plasticity without deterioration in HT strength. The optimized Nb45Mo45Ta5W5 RHEA shows large RT plasticity of 6.1% and high yield strength of 440 MPa at 1873 K, which mainly originates from the heterostructure. Nanoscale precipitates form in the interdendrite region after annealing at 1873 K, which further increases the RT plasticity to 9.0% with a comparable yield strength of 415 MPa at 1873 K. The strength retention up to 1873 K arises from the large modulus misfit of Nb45Mo45Ta5W5 alloy and the hetero-deformation in the dendrite and interdendrite regions. The nanoscale precipitates in the interdendrite region is temperature-dependent and stress-promoted, which contributes to work-hardening at RT and softening resistance at 1873 K. The dendritic heterostructure strategy in this work provide a feasible method to toughen brittle RHEAs and paves the way to design RHEAs with excellent HT strength in combination of large RT plasticity.