| Title |
Effect of Cr addition into Fe-Mn-Al-Ni Superelastic Alloy Fabricated by Laser Direct Energy Deposition on Microstructure and Superelastic Properties |
| Authors |
백하은(Haeun Baik) ; 박지영(Jiyoung Park) ; 임진수랑(Jinsurang Lim) ; 이욱진(Je In Lee) ; 이제인(Wookjin Lee) ; 김도형(Dohyung Kim) |
| DOI |
https://doi.org/10.3365/KJMM.2026.64.5.400 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Additive manufacturing; Fe-Mn-Al-Ni; In-situ alloying; Laser direct energy deposition; Superelasticity |
| Abstract |
In this study, an Fe-Mn-Al-Ni?based superelastic alloy was fabricated by laser direct energy
deposition, and the effect of Cr on its microstructure and superelastic properties was investigated. The Cr
addition up to 7 wt.% changed the dominant solidification phase in the as-built state from a face-centered
cubic phase to a body-centered cubic (BCC) phase. The elemental Cr powders were not fully melted in the
as-built state due to the high melting point of Cr. After solution treatment at 1200 oC for 6 h, all samples,
with and without Cr, consisted of BCC-α and showed no evidence of unmolten Cr powder. Before the cyclic
compression test to evaluate superelastic properties, further heat treatment was performed at 200 oC for 3 h
to ensure high superelasticity through the precipitation of B2?NiAl. In addition to the changes in phase
evolution in the as-built state, the Cr addition also stabilized BCC-α in the heat-treated state, resulting in
an increase in the critical stress in the phase transformation from BCC-α to FCT (face-centered tetragonal)-
γ' from 202.3 MPa for 0Cr to 233.9 MPa for 7Cr. Additionally, the critical stress for slip is also substantially
increased by ~74% (560.6 MPa for 0Cr and 976.9 MPa for 7Cr, respectively). Both are favorable for the
superelastic property. The former could promote reverse phase transformation upon unloading due to higher
BCC-α stability, the latter effectively hinders permanent deformation induced by slip. As a result, the
superelastic displacement increased by ~19%, from 3.567 for 0Cr to 4.257 for 7Cr. |