The dislocation structure of slip bands in deformed high entropy alloy nanopillars

Abstract

• Slip bands formed in compressed Al 0.1 CoCrFeNi nanopillars are examined by TEM. • A slip band consists primary and secondary dislocations with the latter mostly behind the slip band. • The role of dislocation pileup in front of the slip band is discussed. • A slip band model is proposed based on browns ellipsoidal slip band with supporting evidence of dislocation dipoles. Remarkable diversity is observed in dislocation interactions that are responsible for intermittent and sudden crystal slips. While large crystal slips can be easily observed on the surface of deformed crystals, unraveling the underlying dislocation interaction mechanisms, however, has been a longstanding challenge in the study of single-crystal plasticity. A recent study demonstrated that the sluggish dislocation dynamics in the high entropy alloy (HEA) of Al 0.1 CoCrFeNi enables the observation of slip bands for a direct link to dislocation avalanches in a nanopillar. Here, we further examined the dislocation structure of slip bands in the HEA nanopillars oriented for single slip. Experimental evidence was provided on the dislocation organization in a slip band based on groups of primary dislocations, secondary dislocations, and dislocation pileups. The results were compared with the previously proposed slip band models. The unique aspects of the HEA that enable such observations were also investigated through an examination of the dislocation microstructure and its response to applied forces in the HEA nanopillars.