Reducing plastic anisotropy through stress induced martensitic transformation in an additively manufactured metastable medium entropy alloy
Journal article, 2025
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.
Load partitioning
Medium entropy alloys
Synchrotron X-ray diffraction
Powder bed fusion-laser beam
Phase transformation
Author
Bala Malladi
Chalmers, Industrial and Materials Science, Materials and manufacture
T. Mishurova
Federal Institute for Materials Research and Testing
Vishnu Anilkumar
Chalmers, Industrial and Materials Science, Materials and manufacture
Bharat Mehta
Chalmers, Industrial and Materials Science, Materials and manufacture
Royal Institute of Technology (KTH)
Alexander Evans
Federal Institute for Materials Research and Testing
Kumar Babu Surreddi
Luleå University of Technology
Malte Blankenburg
Deutsches Elektronen-Synchrotron (DESY)
Ulrich Lienert
Deutsches Elektronen-Synchrotron (DESY)
G. Bruno
Federal Institute for Materials Research and Testing
University of Potsdam
Sheng Guo
Chalmers, Industrial and Materials Science, Materials and manufacture
Lars Nyborg
Chalmers, Industrial and Materials Science, Materials and manufacture
Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
0921-5093 (ISSN)
Vol. 933 148308Subject Categories (SSIF 2025)
Metallurgy and Metallic Materials
Manufacturing, Surface and Joining Technology
Other Materials Engineering
DOI
10.1016/j.msea.2025.148308