Symposium SF09—High Entropy Materials II—From Fundamentals to Potential Applications
May 25, 2022
Dmitri Louzguine-Luzgin, Mathematics for Advanced Materials-OIL, National Institute of Advanced Industrial Science and Technology
High Entropy Approach Starting from a Corner of the Phase Diagram in Designing High Strength Fe–Based Alloys
Written by Henry Quansah Afful
Solid solutions can be easily formed by following Hume-Rothery rules and this also applies to high entropy alloys (HEA). In essence, the atomic radii of the solute and solvent must not be different by more than 15% and crystal structures must be similar. The low yield strength of HEAs has been attributed to the disorder in these compositions and introducing some amount of ordering (small or medium range) can enhance the strength. Louzguine-Luzgin tested some HEAs having the Fe–Mn–Al–C base system, and by starting from the corner of the phase diagram, added varying amounts by mass of Co and Ni to replace a portion of Fe and Mn. The compositions tested had both face centered cubic (FCC) and body centered cubic (BCC) phases but the BCC phase was ordered. The Fe–Mn–Co–Al–C alloys formed had high tensile plasticity of 10% and high yield and ultimate strength values of up to 1590 MPa and 1650 MPa, respectively. Louzguine-Luzgin attributed the high strength values to solid solution hardening and deformation strengthening from the thermomechanical treatments.