Molecular dynamics-based analysis of the effect of voids and HCP-Phase inclusion on deformation of single-crystal CoCrFeMnNi high-entropy alloy
YM Qi and XH Chen and ML Feng, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 791, 139444 (2020).
In this study, molecular dynamics is used to examine a typical single- crystal CoCrFeMnNi high-entropy alloy, and the effect of spherical voids and hexagonal close-packed (HCP)-phase inclusion on the microstructural development of the material. First, considering different void sizes of 5 A, 10 A and 15 A, we record snapshots of microstructural changes to investigate the interaction of the alloy with these intrinsic stacking faults, and reveal the reason for the increasing material strength. Meanwhile, by analyzing the evolution of the voids, we elucidate their effects on the deformation mechanism of the single-crystal CoCrFeMnNi high-entropy alloy under tension. The results reveal the relationship between the peak/flow stress and the void size during tensile loading, and the mechanistic details of the dislocation reaction that results in Lomer-Cottrell dislocation junctions and Orowan processes. Second, the effects of HCP-phase inclusion in the center of the single-crystal CoCrFeMnNi on the deformation mechanism are simulated under tensile loading. Unlike in the case of void defects, in this scenario there exists a critical value for peak/flow stress as the inclusion size is increased. Parallel twin and Lomer-Cottrell dislocation junctions emerge, akin to those observed in the simulations of different void sizes. Due to the discrepancy between the HCP and face-centered cubic (FCC) lattice parameters, an interface between these two phases exists pre-stress, so we explore the spatial distribution of average stress under different strains. The simulation results suggest that with increasing strain, the phenomenon of stress concentration at the interface between the HCP and FCC phases gradually disappears.
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