Boundary micro-cracking in metastable Fe45Mn35Co10Cr10 high-entropy alloys

• Published in: Acta materialia Vol. 168; pp. 76 - 86
• Main Authors: Wei, Shaolou, Kim, Jinwoo, Tasan, Cemal Cem
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-04-2019
• Subjects: Damage; EBSD; In-situ; Martensite; Transformation-induced plasticity (TRIP); Transformation-induced plasticity (TRIP); In-situ; Damage; Martensite; EBSD
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2019.01.036

Mechanically-induced martensitic transformation can be a double-edged sword: depending on composition and processing history it can either lead to various beneficial mechanical effects (e.g. transformation-induced plasticity, transformation-toughening), or induce local brittleness and damage nucleation. While several corresponding guidelines are presented in steels research, controlling microstructure metastability has not drawn sufficient attention in the quick-emerging field of high-entropy alloys. In the present work, we investigated the damage mechanisms of a mechanically metastable Fe45Mn35Co10Cr10 high-entropy alloy under uniaxial tensile loading. Our integrated in-situ scanning electron microscopy/electron backscatter diffraction experiments revealed a two-fold effect of the highly localized strain, induced by asynchronously transformed martensite, leading to boundary damage nucleation and dissimilarly oriented martensitic variant formation. The latter suppresses slip transfer between adjacent grains, further expediting the growth of the nucleated damage incidents. Based on these experimental observations and corresponding theoretical calculations, we discuss the underlying mechanisms and propose a sequence of micro-events that create the observed phenomena.
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