Solving the puzzle of hierarchical martensitic microstructures in NiTi by (111)-oriented epitaxial films

Lünser, K.; Undisz, A.; Wagner, M. F.-X.; Nielsch, K.; Fähler, S.

doi:10.1016/j.mtadv.2023.100441

Solving the puzzle of hierarchical martensitic microstructures in NiTi by (111)-oriented epitaxial films (bibtex)

by K. Lünser, A. Undisz, M. F.-X. Wagner, K. Nielsch, S. Fähler

Abstract:

The martensitic microstructure decides on the functional properties of shape memory alloys. However, for the most commonly used alloy, NiTi, it is still unclear how its microstructure is built up because the analysis is hampered by grain boundaries of polycrystalline samples. Here, we eliminate grain boundaries by using epitaxially grown films in (111)_B2 orientation. By combining scale-bridging microscopy with integral inverse pole figures, we solve the puzzle of the hierarchical martensitic microstructure. We identify two martensite clusters as building blocks and three kinds of twin boundaries. Nesting them at different length scales explains why habit plane variants with <011>_B19' twin boundaries and \ 942 \ habit planes are dominant; but also some incompatible interfaces occur. Though the observed hierarchical microstructure agrees with the phenomenological theory of martensite, the transformation path decides which microstructure forms. The combination of local and global measurements with theory allows solving the scale bridging 3D puzzle of the martensitic microstructure in NiTi exemplarily for epitaxial films.

Reference:

Lünser, K., Undisz, A., Wagner, M. F.-X., Nielsch, K., Fähler, S.: Solving the puzzle of hierarchical martensitic microstructures in NiTi by (111)-oriented epitaxial films, Materials Today Advances 20, 100441, 2023.

Bibtex Entry:

@Article{Luenser2023,
  author    = {Lünser, K. and Undisz, A. and Wagner, M. F.-X. and Nielsch, K. and Fähler, S.},
  journal   = {Materials Today Advances},
  title     = {Solving the puzzle of hierarchical martensitic microstructures in NiTi by (111)-oriented epitaxial films},
  year      = {2023},
  issn      = {2590-0498},
  month     = dec,
  pages     = {100441},
  volume    = {20},
  abstract  = {The martensitic microstructure decides on the functional properties of shape memory alloys. However, for the most commonly used alloy, NiTi, it is still unclear how its microstructure is built up because the analysis is hampered by grain boundaries of polycrystalline samples. Here, we eliminate grain boundaries by using epitaxially grown films in (111)\textsubscript{B2} orientation. By combining scale-bridging microscopy with integral inverse pole figures, we solve the puzzle of the hierarchical martensitic microstructure. We identify two martensite clusters as building blocks and three kinds of twin boundaries. Nesting them at different length scales explains why habit plane variants with <011>\textsubscript{B19'} twin boundaries and \{ 942 \} habit planes are dominant; but also some incompatible interfaces occur. Though the observed hierarchical microstructure agrees with the phenomenological theory of martensite, the transformation path decides which microstructure forms. The combination of local and global measurements with theory allows solving the scale bridging 3D puzzle of the martensitic microstructure in NiTi exemplarily for epitaxial films.},
  doi       = {10.1016/j.mtadv.2023.100441},
  publisher = {Elsevier BV},
}