Evading the intermediate-temperature embrittlement of L12-strengthened high entropy alloys by alleviating intergranular oxidation

L12-strengthened high entropy alloys (HEAs) usually suffer from severe intermediate-temperature embrittlement. In this study, we revealed that the intermediate-temperature embrittlement of a (Ni2Co2FeCr)92Nb4Al4 L12-strengthened HEA originates from the severe oxidation of intergranular D019 precipitates which weakens the grain-boundary cohesion. With the minor addition of 1.5 at.% Si, we successfully achieved a brittle-to-ductile transition in the alloy via alleviating intergranular oxidation. The alloyed Si preferentially partitioned into the intergranular precipitates, significantly improved their oxidation resistance and pinning effects on the grain boundaries, which effectively mitigated environmentally assisted grain-boundary damage and thus suppressed the crack propagation upon deformation.