Characteristics of thermal- and strain-induced ε-martensite in Fe50Mn30Co10Cr10 multi-component alloy: Effect of grain size

Abstract

Electron backscatter diffraction technique is used to systematically investigate the characteristics of thermal- and strain-induced ε-martensite in Fe50Mn30Co10Cr10 multi-component alloy, focusing on the grain size effect. Results show that a clear morphological distinction between thermal- and strain-induced ε-martensite cannot be made, both exhibiting laminate- and blocky-shaped features. The amount of thermal-induced ε-martensite dependence of initial γ-austenite grain sizes is evidenced, revealing the formation of multiple initial ε variants in coarse γ-austenite grains, rather than in fine γ-austenite grains. The external strain effect is advantageous of the formation of secondary ε variants and εtwins, but not the thermal effect. Decreasing γ-austenite grain size hinders the activation of secondary ε variants and εtwin, confirming secondary ε variants and εtwin can be produced in coarse γ-austenite grains under the small strain, rather than in fine γ-austenite grains. Furthermore, under the heavy strain, the saturated ε-martensite is almost dominated by one persisting ε variant in coarse and fine γ-austenite grains.