On the plastic deformation mechanism of Al0.6CoCrFeNi high entropy alloy: In-situ EBSD study and crystal plasticity modeling

Abstract

In this study, in-situ tensile tests with electron back-scattered diffraction (EBSD) were conducted to reveal the microstructural effects on the plastic deformation behavior of dual-phase Al_0.6CoCrFeNi high entropy alloys (HEAs). The in-situ EBSD results demonstrated a uniform distribution of dislocation density in the fine grain (FG) samples, whereas high dislocation density was predominantly localized near body-centered cubic (BCC) phases in the coarse grain (CG) samples. The difference in mechanical properties between face-centered cubic (FCC) and BCC phases caused stress concentration and cracking at the boundaries during tension. The FCC phase within FG samples exhibited excellent plasticity, effectively impeding the propagation and coalescence of microcracks emanating from the BCC phase into longer cracks. For CG samples, brittle cracks formed in BCC phases are easy to merge, thus evolving into long cracks. Crystal plasticity finite element analysis revealed that as the strain increases, stress distribution in FG samples tended to become more homogeneous, whereas for CG samples high stress concentration consistently occurred within BCC phases. The deformation characteristics of FG were attributed to the synergistic effect generated by the FCC phase with heterogeneous grain size and the BCC phase characterized by small grain size.