In situ observation of transmission and reflection of dislocations at twin boundary in CoCrNi alloys

Liang, Yanxiang; Yang, Xiaofang; Ming, Kaisheng; Xiang, Shihua; Liu, Qing

doi:10.1007/s11431-019-1517-8

Cited by 11 publications

(1 citation statement)

References 47 publications

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“…Recently, high/medium-entropy alloys (H/MEAs), in which multiple principal elements in equal or near equal molar ratios are occupied randomly on topologically ordered crystallographic lattices, have emerged as an exciting new class of metallic structural materials [19][20][21][22][23]. This unique atom-packing structure with a high chemical disorder imparts HEAs' many extraordinary mechanical properties, such as an excellent combination of strength and ductility [21,[24][25][26][27][28], superior performance at an extremely low temperature [29], high hydrogen and corrosion resistance [30,31], an exceptional "self-sharpening" capability [7] and shock resistance [32,33]. For example, conspicuous element aggregation provides considerable resistance to dislocation glide, which overcomes the strength and ductility trade-off [34,35].…”

Section: Introductionmentioning

confidence: 99%

Atomic-level mechanism of spallation microvoid nucleation in medium entropy alloys under shock loading

Xie

Chen

Wang

et al. 2021

Sci. China Technol. Sci.

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Spallation, rupture under impulsive tensile loading, is a dynamic failure process involving the collective evolution and accumulation of enormous microdamage in solids. In contrast to traditional alloys, the spallation mechanism in medium entropy alloys, the recently emerged multiprinciple and chemically disordered alloys, is poorly understood. Here we conduct molecular dynamics simulations and first principle calculations to investigate the effects of impact velocities and the local chemical order on spallation microvoid nucleation in a CrCoNi medium entropy alloy under shock wave loading. As the impact velocity increases, the microvoid nucleation site exhibits a transition from the grain boundaries to the grains to release redundant imposed energy. During the intragranular nucleation process, microvoids nucleate in the poor-Cr region with a large local nonaffine deformation, which is attributed to the weak metallic bonds in this position with sparse free electrons. For intergranular nucleation, a Franke-like dislocation source forms through the dislocation reaction, leading to enormous dislocations piling up in a narrow twin stripe, which markedly increases the local stored energy and promotes microvoid nucleation. These results shed light on the mechanism of spallation in chemically complexed medium entropy alloys.

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