High strength and ductility in a friction stir processing engineered dual phase high entropy alloy

The potential of high-entropy alloys (HEAs) to exhibit an extraordinary combination of properties by shifting the compositional regime from the corners towards the centers of phase diagrams has ledto worldwide attention by material scientists.

Fig: (a) True stress-true strain curves for the as-homogenized and FSP samples deformed at room
temperature at an initial strain rate of 10−3 s−1, (b–d) EBSD maps showing f.c.c. γ- and h.c.p. ε-phase fractions prior to tensile deformation and, (e–h) EBSD maps and corresponding XRD patterns showing f.c.c. γ- and h.c.p. ε-phase fractions after tensile deformation. AH: as-homogenized; RPM: rotations per minute. — Fig: (a) True stress-true strain curves for the as-homogenized and FSP samples deformed at room temperature at an initial strain rate of 10−3 s−1, (b–d) EBSD maps showing f.c.c. γ- and h.c.p. ε-phase fractions prior to tensile deformation and, (e–h) EBSD maps and corresponding XRD patterns showing f.c.c. γ- and h.c.p. ε-phase fractions after tensile deformation. AH: as-homogenized; RPM: rotations per minute.

© Max-Planck-Institut für Eisenforschung GmbH

Fig: (a) True stress-true strain curves for the as-homogenized and FSP samples deformed at room

temperature at an initial strain rate of 10−3 s−1, (b–d) EBSD maps showing f.c.c. γ- and h.c.p. ε-phase fractions prior to tensile deformation and, (e–h) EBSD maps and corresponding XRD patterns showing f.c.c. γ- and h.c.p. ε-phase fractions after tensile deformation. AH: as-homogenized; RPM: rotations per minute.

© Max-Planck-Institut für Eisenforschung GmbH

In this collaborative project we work on a new class of strong and ductile non-equiatomic HEAs obtained after friction stir processing (FSP). A transformation-induced plasticity (TRIP) assisted reference HEA with composition Fe50Mn30Co10Cr10 (at.%) was severely deformed by FSP and evaluated for its microstructure-mechanical property relationship. The FSP-engineered microstructure of the TRIP HEA exhibited a substantially smaller grain size, and optimized fractions of face-centered cubic (f.c.c., γ) and hexagonal close-packed (h.c.p., ε) phases, as compared to the as-homogenized reference material. This results in synergistic strengthening via TRIP, grain boundary strengthening, and effective strain partitioning between the γ and ε phases during deformation, thus leading to enhanced strength and ductility of the TRIP-assisted dual-phase HEA engineered via FSP.