Abstract
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). 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.
| Original language | English |
|---|---|
| Article number | 100858 |
| Journal | Materials Today Communications |
| Volume | 23 |
| DOIs | |
| State | Published - Jun 2020 |
Funding
The present work was performed under a cooperative agreement between the Army Research Laboratory (ARL) and the University of North Texas (W911NF-18-2-0067). The authors thank the Materials Research Facility for providing access to the microscopy facilities at the University of North Texas. Neutron diffraction work was carried out at the Spallation Neutron Source (SNS), which is the U.S. Department of Energy (DOE) user facility at the Oak Ridge National Laboratory, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences. The authors thank Matthew Frost, Shivakant Shukla and Saket Thapliyal for their assistance in carrying out neutron diffraction experiments. The present work was performed under a cooperative agreement between the Army Research Laboratory (ARL) and the University of North Texas ( W911NF-18-2-0067 ). The authors thank the Materials Research Facility for providing access to the microscopy facilities at the University of North Texas. Neutron diffraction work was carried out at the Spallation Neutron Source (SNS), which is the U.S. Department of Energy (DOE) user facility at the Oak Ridge National Laboratory, sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences . The authors thank Matthew Frost, Shivakant Shukla and Saket Thapliyal for their assistance in carrying out neutron diffraction experiments. Appendix A
| Funders | Funder number |
|---|---|
| Office of Basic Energy Sciences | |
| Scientific User Facilities Division | |
| U.S. Department of Energy | |
| Oak Ridge National Laboratory | |
| Army Research Laboratory | |
| University of North Texas | W911NF-18-2-0067 |
Keywords
- Deformation mechanism
- High entropy alloy
- Martensite
- Metastable
- Neutron
- SFE
- Stacking fault energy
- TRIP
- TWIP
- Transformation
- Twinning
- c-axis
- c/a ratio