Bidirectional phase transformation facilitated by ε-martensite bands interaction in metastable Fe50Mn30Co10Cr10 dual-phase high entropy alloys

Abstract

The phase transformation-induced plasticity (TRIP) metastable Fe50Mn30Co10Cr10 dual-phase high entropy alloys exhibit an excellent combination of strength and ductility. The interaction between ε-martensite (HCP phase) bands plays a fundamental role in determining the mechanical properties of Fe50Mn30Cr10Co10 alloys. In this work, the phase transition mechanism of Fe50Mn30Co10Cr10 dual-phase high entropy alloy was studied by using electron backscatter diffraction (EBSD), transmission electron microscope (TEM) observation and molecular dynamic (MD) simulations. The results indicated that the orientation relationship and character of the ε-martensite band play a crucial role in the phase transition and growth of ε-martensite bands. As an expanding ε-martensite band is obstructed by another ε-martensite band, the cross slip or dissociation of the Shockley partial dislocations at the ε-martensite junction lead to the growth of the ε-martensite bands. When two ε-martensite bands form a cross structure and the phase transition partial dislocations of the incident ε-martensite band are edge type, a new FCC-structured grain will be formed in the domain where the ε-martensite bands intersect. While the dissociation and gliding of Shockley partial dislocations at the phase boundaries will lead to the growth of the ε-martensite bands when the phase transition dislocations of the incident ε-martensite band are mixed type.