Composition optimization and deformation behavior of FeNiCrCoCu based high entropy alloys at elevated temperatures

This work proposed a materials design strategy combining deep learning (DL), experimental investigations and molecular dynamics (MD) simulations to search for high entropy alloys (HEAs) with high strength at elevated temperature in a model Fe-Ni-Cr-Co-Cu alloy system. The developed DL model evaluated the critical role of element selection in optimizing the performance of FeNiCrCoCu HEAs and contribute to the broader understanding of how multi-element alloys can be tailored for high temperature field. Fe1.1NiCr1.2CoCu0.9 HEAs was designed and fabricated for experimental microstructure characterization and mechanical testing. The microstructure studies showed a dendritic structure containing Fe, Cr, Ni and Co, Cu segregation was detected at the interdendritic regions. Mechanical tests showed the strength of 790 MPa and 446 MPa at 400 and 600 °C. Microcracks initiated at Cu-rich phases and propagated along GBs, resulting in quasi-cleavage fracture. Dynamic recovery occurred at 400 °C and CDRX grains nucleated at 600 °C. Deformation at 400 °C was dominated by dislocation storage, SF accumulation, and strong Cu-rich barrier effects. At 600 °C, the alloy exhibited reduced defect density, weaker phase barrier effects, and more pronounced recovery, shifting the balance toward softening rather than strain hardening. Then MD simulations explored the mechanical behavior at atomic scale, providing detailed insights into dislocation nucleation, grain boundary sliding, and phase transformations. This study contributed to the multi-scale understanding of deformation mechanisms at elevated temperatures.