Achieving Exceptional Strength-Ductility Synergy via Nano-precipitation Hardening in a Ni-Fe-Cr-Co-Al Alloy

In the present work, a Ni-Fe-Co-Cr-Al-based medium entropy alloy (MEA) was developed by exploring the vast compositional space provided by the birth of high-entropy alloys (HEAs). The composition was designed via the CALPHAD approach and the designed alloy was melted through the vacuum induction melting (VIM) technique using commercial elements. Post-homogenization treatment, the material was cold deformed up to 73 pct reduction in thickness. This cold-rolled material was annealed with varying duration at a fixed temperature of 900 degrees C for a better understanding of the static recrystallization mechanism. The systematic static recrystallization study was performed to design a heterogeneous grain distribution within the matrix via partial recrystallization. Post-establishment of the annealing schedule, ageing treatment at 600 degrees C for 5 hours was carried out. The room temperature mechanical properties were evaluated for selected ageing conditions. An excellent strength of > 950 MPa accompanied by an appreciable ductility of 60 pct was obtained for the fully recrystallized and aged specimen. The obtained results surpassed the strength-ductility synergy exhibited by various solid solution-strengthened (SS) Ni-based superalloys and heterogeneous HEAs and hold the potential to be explored for elevated temperature applications. A systematic study has also been carried out to estimate the contribution of various strengthening factors in the designed alloy and the predicted results corroborate well with the experimental findings. (C) The Minerals, Metals & Materials Society and ASM International 2024