Strengthening in multi-principal element alloys with local-chemical-order roughened dislocation pathways

By Qing-Jie Li, H. Sheng, E. Ma. Nature Communications, 2019

755 citations recorded by the source corpus.

High-entropy and medium-entropy alloys are presumed to have a configurational entropy as high as that of an ideally mixed solid solution (SS) of multiple elements in near-equal proportions. However, enthalpic interactions inevitably render such chemically disordered SSs rare and metastable, except at very high temperatures. Here we highlight the wide variety of local chemical ordering (LCO) that sets these concentrated SSs apart from traditional solvent-solute ones. Using atomistic simulations, we reveal that the LCO of the multi-principal-element NiCoCr SS changes with alloy processing conditions, producing a wide range of generalized planar fault energies. We show that the LCO heightens the ruggedness of the energy landscape and raises activation barriers governing dislocation activities. This influences the selection of dislocation pathways in slip, faulting, and twinning, and increases the lattice friction to dislocation motion via a nanoscale segment detrapping mechanism. In contrast, severe plastic deformation reduces the LCO towards random SS. Multi-principal-element alloys have been assumed to have the configurational entropy of an ideal solution. Here, the authors use atomistic simulations to show that instead NiCoCr exhibits local chemical order, raising the activation barriers of dislocation activities to elevate mechanical strength.

Subfields: Aerospace Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/f4800e49e0c402db73117386cf3dc0dff8f8d0dc

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In Aerospace Engineering

1. F. Cao
2. Yun-Jiang Wang
3. L. Dai

In Mechanical Engineering

1. F. Cao
2. Yun-Jiang Wang
3. L. Dai

Citations in the corpus

• Novel atomic-scale mechanism of incipient plasticity in a chemically complex CrCoNi medium-entropy alloy associated with inhomogeneity in local chemical environment (2020, methodology): “This potential provides a relatively accurate description of both the unstable and stable SFEs compared with DFT calculations, which is important for atomic simulations of dislocation nucleation [44].”