In-situ investigation of damage mechanisms in duplex AlCoCrFeNi2.1 high entropy alloy

The AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) is a promising casting system with high strength, and numerous studies investigating the effects of various thermomechanical processing routes. However, the ductility of this alloy – especially in its cast state – limits its practical applicability. In this paper, damage evolution and microstrain partitioning behaviour is presented along with bulk mechanical performance of the as-cast and hot rolled AlCoCrFeNi2.1 EHEA to provide experimental reasoning behind observed changes in ductility and strength. Tensile testing coupled with in-situ micro-digital image correlation (μ-DIC) and x-ray computed tomography (XCT) were used to determine the damage and fracture mechanisms. Microstrain analysis documents the effect of phase co-deformation and microstructure morphology on crack formation, and the role of damage evolution is supplemented with XCT. These results suggest methods to improve crack resistance in this alloy system and corroborate macroscopic mechanical property changes.