Orientation Relationships in FeMnNiAl Governed by Martensitic Substructure

• Published in: Shape memory and superelasticity : advances in science and technology Vol. 9; no. 3; pp. 473 - 484
• Main Authors: Mohammed, Ahmed Sameer Khan, Sidharth, R., Abuzaid, Wael, Akamine, Hiroshi, Nishida, Minoru, Sehitoglu, Huseyin
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.09.2023; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Electron back scatter; Martensite; Martensitic transformations; Materials Science; Optimization; Orientation relationships; Original Research Article; Shape memory alloys; Stacking; Stacking fault; Orientation relationship; Twinning; Shape Memory Alloy
• ISSN: 2199-384X; 2199-3858
• DOI: 10.1007/s40830-023-00458-6

This study establishes the Orientation Relationship (OR) between the austenitic and martensitic phases of the new Shape Memory Alloy (SMA) FeMnNiAl from both experiments and analytical modeling. Through Transmission Electron Microscopy (TEM) and Electron Back-Scatter Diffraction, three distinct ORs, namely the Nishiyama-Wassermann (N-W), Pitsch, and Kurdjumov–Sachs (K-S) ORs are established. The observations of non-unique ORs are explained using the energy-minimization theory of martensite revealing dependence of OR on the internal morphology of the martensitic phase, whether twinned or stacking-faulted. It is shown that the twin-variants of an internally twinned martensitic structure individually explain the Pitsch and K-S ORs. The N-W OR was observed in a stacking-faulted substructure of martensite. Through a novel extension to the energy-minimization theory for stacking-faulted substructures, the N-W OR is explained. Thus, the current study challenges the notion of OR as a material-characteristic and reveals a dependence of the OR on the internal substructure of the martensitic phase in SMAs, further establishing the OR for the new SMA FeMnNiAl.