Investigating the deformation mechanisms of a highly metastable high entropy alloy using in-situ neutron diffraction

Journal Article · Mon Dec 23 00:00:00 EST 2019 · Materials Today Communications

DOI:https://doi.org/10.1016/j.mtcomm.2019.100858· OSTI ID:1649352

Frank, M. ^[1]; Chen, Y. ^[2]; Nene, S. S. ^[1]; Sinha, S. ^[1]; Liu, K. ^[1]; An, Ke ^[2]; Mishra, R. S. ^[1]

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1. Univ. of North Texas, Denton, TX (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The present study correlates the effect of enhanced metastability on both the well-understood γ-f.c.c. stacking fault energy (SFE) and deformation mechanisms in the ε-h.c.p. phase of a metastable high entropy alloy (HEA). In this work, the SFE of a Fe₄₀Mn₂₀Cr₁₅Co₂₀Si₅ alloy (CS-HEA) was experimentally determined to be ~6.31 mJ m^-2 using in-situ neutron diffraction. The relatively low-measured SFE of the CS-HEA results in a high fraction of the ε-h.c.p. phase (58 %) triggering significant stress partitioning to ε-h.c.p. and a marginal fraction of γ-f.c.c. → ε-h.c.p. transformation (~25 %). The ε-h.c.p. phase accommodated a significant amount of strain marked by the large stress-induced decrease of c/a ratio (from ~1.619 to 1.588), which was accompanied by activation of non-basal deformation modes, such as deformation twinning and pyramidal slip. Using in-situ neutron diffraction, we show by decreasing SFE and stabilization of large fractions of ε-h.c.p., activation of non-basal deformation modes are responsible for high work hardenability in absence of significant γ-f.c.c. → ε-h.c.p. transformation.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1649352
• Journal Information: Materials Today Communications, Journal Name: Materials Today Communications Journal Issue: N/A Vol. 23; ISSN 2352-4928
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Deformation mechanism
High entropy alloy
Martensite
Metastable
Neutron
SFE
Stacking fault energy
TRIP
TWIP
Transformation
Twinning
c-axis
c/a ratio