Achieving superior mechanical property and large adjustability in a metalloid-free FeCrNi alloy

Advanced structural alloys with high performance and large property adjustability are desired for engineering applications. However, traditional multi-micro-alloying metallurgy depends on the specific manufacturing technique, leading to the narrow processing window, poor welding ability and structural stability. In this proof-of-concept study, a simplified 72.9Fe-18.7Cr-8.4Ni (wt.%) alloy with outstanding mechanical performances and adjustability was designed, via a compositional simplification strategy. The facile adjustment of transformation-induced plasticity (TRIP) and hetero-deformation induced (HDI) hardening effects enables the combination of superior yield strength, uniform elongation, product of strength and elongation (PSE), ranging largely from 270 to 1440 MPa, 1.3% to 21.5%, and 4.9-20.5 GPa·%. The super-high strength, large ductility, and optimal structure-property synergy are readily obtained in the high-density dislocation strengthened cold-rolled sample, recrystallized coarse-grained sample and dual-phase hetero-structured (DPHS) sample with soft FCC (63%) and hard BCC (37%) phases respectively. The optimized HDI hardening effect endows the high-strength over 900 MPa and large PSE beyond 16 GPa·% of the DPHS, over-performing the conventional homogeneous structured counterpart. Prominent strengthening and toughening attribute to the synergistic enhancement of dislocation strengthening, HDI hardening and deformation induced martensite transformation mechanisms. Such composition simplification and multi-principle-component design strategies accord well with the emerging green metallurgy strategy without introducing micro-alloying elements such as carbon, and uncouple common property trade-offs for superior mechanical properties and large adjustability in the next-generation alloy.