Intra-variant substructure in Ni–Mn–Ga martensite: Conjugation boundaries

Journal Article · Sun Jun 01 04:00:00 EDT 2014 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2014.03.018· OSTI ID:1132214

Muntifering, B.; Pond, R. C.; Kovarik, L.; Browning, N. D.; Müllner, P.

The microstructure of a Ni–Mn–Ga alloy in the martensitic phase was investigated using transmission electron microscopy. Inter-variant twin boundaries were observed separating non-modulated tetragonal martensite variants. In addition, intra-variant boundary structures, referred to here as “conjugation boundaries”, were also observed. We propose that conjugation boundaries originate at the transformation interface between austenite and a nascent martensite variant. In the alloy studied, deformation twinning was observed, consistent with being the mode of lattice-invariant deformation, and this can occur on either of two crystallographically equivalent conjugate View the MathML source{101}(101⁻) twinning systems: conjugation boundaries separate regions within a single variant in which the active modes were distinct. The defect structure of conjugation boundaries and the low-angle of misorientation across them are revealed in detail using high-resolution microscopy. Finally, we anticipate that the mobility of such boundaries is lower than that of inter-variant boundaries, and is therefore likely to significantly affect the kinetics of deformation in the martensitic phase.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1132214
• Report Number(s): PNNL-SA-99492; 47296; KP1704020
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: C Vol. 71; ISSN 1359-6454
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory