Unveiling the critical role of crystal orientation in the incipient behavior of FCC FeNiCr multi-principal element alloy

X Zhang and J Fan and H Xiang and J Yan and W Li and W Zhao and Y Lu and K Lu and X Cai, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, 297, 110389 (2025).

DOI: 10.1016/j.ijmecsci.2025.110389

The initial behavior of multi-principal element alloys (MPEAs) is crucial to understanding their deformation mechanism. However, its orientation dependence remains poorly understood. The initial plastic behavior of three typical crystal planes (100), (110) and (111) of FeNiCr MPEA was investigated by nanoindentation experiments, molecular dynamics (MD) simulations and density functional theory (DFT) calculations. Our novel findings reveal that the initial plastic behavior of FeNiCr MPEA is highly orientation-dependent. Specifically, the (111) plane has the highest initial yield load, and (110) plane exhibits the smallest width of displacement burst. This is related to the number of activated slip systems and the evolution behavior of dislocation structure under different crystal orientations. These differences would not lead to different incipient mechanisms and activation volumes. For the first time, MD simulations not only clarify that the dislocation nucleation load is the decisive factor for the initial yield load but also disclose that the incipient behavior of (111) orientation is more sensitive to the lattice distortion (LD). In addition, DFT results unravel that intrinsic LD promotes dislocation nucleation by triggering heterogeneous distribution of charge density. Finally, the orientation dependence of incipient behavior in FCC FeNiCr MPEA shares similarities with conventional metals and other FCC MPEAs, but differs from BCC MPEAs due to their distinct slip systems. The key findings of this paper deepen our understanding of the incipient behavior of MPEAs.

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