Enhanced strength-ductility synergy of a partially recrystallized Al$_6$Cr$_{25}$Fe$_{34}$Ni$_{35}$ multi-principal element alloy

Co-free and Al-alloyed FCC multi-principal element alloys (MPEAs) have attracted increasing interest due to their low-cost, high potential to show excellent corrosion/oxidation resistance and mechanical properties. Here we report the mechanical deformation behavior of a single face-centered cubic (FCC) and partially recrystallized Al6Cr25Fe34Ni35 (at.%, AlCrFeNi) MPEA at room temperature and 550 °C with comparisons to other model MPEAs (including CoCrFeMnNi, CoCrNi and CrFeNi). The AlCrFeNi alloy exhibits higher strength-ductility synergy than the CoCrFeMnNi MPEA tested at the same conditions, especially at elevated temperature. Besides, it also shows higher yield strength than the CoCrNi and CrFeNi MPEAs. Microstructural investigations unveiled that, the deformed microstructures manifest a high density of dislocations (in the form of tangles and walls/cells). These tangles and walls/cells contributed to the AlCrFeNi's stage I and II strain hardening behaviors, respectively, as well as to the enhanced strength-ductility synergy. Further analyses also pinpointed the origins of higher yield strength in AlCrFeNi than in other MPEAs.