Phase transformation induced by severe gradient shear deformation in an Al_0.1CoCrFeNi alloy

High-entropy alloys (HEAs) are emerging as promising wear-resistant materials for engineering applications, owing to their exceptional mechanical properties and wear resistance. Nevertheless, the atomic friction and wear mechanisms of HEAs remains poorly understood, limiting the establishment of a comprehensive microstructure evolution framework that spans multiple length scales. Here, in-situ TEM was employed to investigate atomic scale friction and wear mechanisms of an Al_0.1CoCrFeNi alloy. The results reveal that the phase transformation from [011]_FCC to [001]_FCC, induced by the frictional gradient shear deformation, is correlated with significant strain relaxation at the intersections of stacking faults near the scratch surface. Additionally, numerous intermediate phases, resulting from lattice contraction and expansion due to atomic slip within the {111} planes, are observed in the friction subsurface. These findings enhance fundamental understanding of atomic-scale friction mechanisms in HEAs and provide valuable insights into the underlying damage mechanisms of wear-resistant materials subjected to friction-induced shear deformation. © 2025 Elsevier Inc.