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Unraveling Atomic-Scale Lattice-Distortion Strengthening of Precipitate-Hardened High-Entropy Alloys

High-entropy alloys (HEAs) have outstanding mechanical properties at cryogenic/elevated temperatures. However, intrinsic mechanisms of strengthening in extreme environments are still not well understood. Here we report the synergistic strengthening of atomic-scale lattice distortion and precipitation in HEAs at cryogenic/elevated temperatures, to reveal severe lattice-distortion-dominated hardened behaviour. Severe atomic-scale lattice distortion of HEAs causes the curved dislocation line with kinks located at various local tensile-or-compressive stress fields, to cut more atoms along the slip plane, compared with pure metals. Original cause of high strengths at cryogenic temperature is attributed to the large atomic-scale lattice distortion frozen in the HEA matrix, to difficultly release the lattice-distortion energy by the diffusion. The origin of high strengths at elevated temperatures is due to that the slow diffusion induced by the lattice-distortion-generated deep stress trap along diffusion path results in the relatively-stable structure of precipitate. The critical pinning stress for dislocation slip depends on the stacking-fault width and dislocation-dynamic structure as well as precipitate characteristics, which cause the intense fluctuations of the dislocation-sliding resistance. Hence, atomic simulations provide the mechanistic insight into which severe atomic-scale lattice distortion could enhance the strength at cryogenic/elevated temperatures to further broaden the scope of applications of advanced HEAs.