Publication detail

Duality of wave modulation and nanotwinning in Ni-Mn-Ga martensite via long-period commensurate states

VERTAT, P. ZELENÝ, M. SOZINOV, A. KLICPERA, M. FABELO, O. CHULIST, R. VINOGRADOVA, M. SEDLAK, P. SEINER, H. HECZKO, O. STRAKA, L.

English title

Duality of wave modulation and nanotwinning in Ni-Mn-Ga martensite via long-period commensurate states

Type

WoS Article

Language

en

Original abstract

Structural modulation is a key ingredient behind the extraordinary (magneto)elastic response of Ni-Mn-Ga martensite, yet its link to fine microstructural features and twin-boundary supermobility remains unresolved. Here we analyse martensitic single crystals of Ni50.0Mn27.7Ga22.3 and Ni50.0Mn28.1Ga21.9. Neutron and X-ray diffraction reveal an anharmonic five-layer structural modulation-evidenced by high-order satellite reflections-that evolves from commensurate (q = 2/5) to incommensurate (2/5 < q < 5/12) upon cooling. Interpreting the refined modulation displacements as a basal-plane stacking sequence links the wave description to the microstructural evolution on cooling. In this view, evolving incommensurability produces periodic nanodomains interpreted as emerging a/b-nanotwins with a characteristic size of approximate to 20 nm at approximate to 290 K. With further cooling, the modulation can lock into long-period commensurate (LP-C) states, such as 34O (q = 7/17), 24O (q = 5/12), and 14O (q = 3/7), whose orthorhombic unit cells can be viewed as a/b-nanotwins. Ab initio calculations show that LP-C structures are energetically competitive with the initial commensurate state, supporting a shallow martensitic energy landscape. We propose a physical picture in which the martensitic transformation selects a commensurate state with q = 2/5 in the Mn-rich compositions studied here, while subsequent cooling drives relaxation within the martensitic landscape toward LP-C states, particularly 24O in the present alloys. The resulting structure is neither purely wave-like nor purely nanotwinned; rather, it reflects coupling between a coherent modulation wave and local accommodation via NM-like tetragonal distortions, nanotwinning, and LP-C lock-ins, providing a structural basis for the wave-nanotwin duality in Ni-Mn-Ga martensite.

Keywords in English

Magnetic shape memory, Structural modulation, Long-period structure, Nanotwinning, Neutron diffraction

Released

2026-09-15

Publisher

Elsevier

Journal

Acta materialia

Volume

317

Number

September

Pages from–to

122510–

Pages count

18

BIBTEX


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  author="{} and Martin {Zelený} and  {} and  {} and  {} and  {} and  {} and  {} and  {} and  {} and  {}",
  title="Duality of wave modulation and nanotwinning in Ni-Mn-Ga martensite via long-period commensurate states",
  journal="Acta materialia",
  year="2026",
  volume="317",
  number="September",
  pages="18",
  doi="10.1016/j.actamat.2026.122510",
  issn="1359-6454",
  url="https://www.sciencedirect.com/science/article/pii/S1359645426006117"
}