This study explores the use of Fe-Mn-Cr-Si-C master alloy as a sustainable alternative to nickel in press and sinter powder metallurgy, with the goal to improve hardenability and mechanical performance. Two master alloy compositions were optimized for liquid phase sintering using thermodynamic software and then produced through gas atomization. The melting behavior of the master alloys was characterized and compared with thermodynamic predictions. Sintering experiments were performed on compacts from mixes with and without master alloy additions. Continuous cooling transformation (CCT) diagrams were generated to assess hardenability. The results demonstrated that the master alloys improve the hardenability, even at lower cooling rates compared to alloying with Ni. Mechanical testing showed notable improvements in yield strength and apparent hardness comparable to those achieved with Ni additions. These findings support the use of Fe-Mn-Cr-Si-C master alloy as a viable, more sustainable alternative to nickel in powder metallurgy steels.

Powder bed fusion laser beam (PBF-LB) is particularly effective for fabricating compositionally complex alloys such as high-entropy alloys (HEAs) or medium-entropy alloys (MEAs). Fabricating non-equiatomic metastable MEAs using PBF-LB can lead to the formation of unique microstructures that enhance the mechanical performance of these alloys. Nevertheless, plastic anisotropy in materials prepared by additive manufacturing routes including PBF-LB remains to be a technical challenge. This work presents the fabrication of a metastable non-equiatomic Co45Cr25(FeNi)30 MEA using PBF-LB. As-printed samples exhibited the formation of nano-scaled ε-martensite (HCP) phase along with the FCC phase. The HCP phase exhibited Shoji-Nishiyama orientation relationship with the FCC phase. High energy synchrotron X-ray diffraction (HEXRD) and electron backscatter diffraction (EBSD) in-situ tensile testing were employed to investigate the influence of the HCP phase on the alloy's deformation behavior. The presence of the HCP phase initiates stress-induced martensitic transformation well below the macroscopic yield strength. This transformation led to the non-linear stress and strain response for the FCC phase. Further straining resulted in significant load partitioning, with the HCP phase taking the majority of the load as it formed, significantly strain hardening the alloy and reducing the plastic anisotropy induced by texture in the as-printed material.