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Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction
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Nanoscale twinning in Fe-Mn-Al-Ni martensite: a backscatter Kikuchi diffraction study
Peter D B Fischer1, Stefan Martin1, Alexander Walnsch1
1Institute of Materials Science, TU Bergakademie Freiberg, Gustav-Zeuner-Strasse 5, Freiberg, 09599, Germany.
Journal of Applied Crystallography
|April 9, 2021
Summary
Low-cost iron-based shape-memory alloys exhibit pseudoelasticity due to a complex martensitic structure. Nanoscale twins and tetragonal distortion were identified, offering new insights into their unique properties.
Area of Science:
- Materials Science
- Metallurgy
- Solid-state Physics
Background:
- Iron-based Fe-Mn-Al-Ni shape-memory alloys offer low cost and significant pseudoelastic properties.
- Understanding the martensitic transformation is key to their functional behavior.
Purpose of the Study:
- To investigate the complex martensitic structure in heat-treated Fe-Mn-Al-Ni alloys.
- To elucidate the crystallographic nature of martensite responsible for pseudoelasticity.
Main Methods:
- Heat treatment of Fe-Mn-Al-Ni alloys at 1473 K followed by quenching.
- Analysis of backscatter Kikuchi diffraction (BKD) patterns.
- Comparison of experimental BKD patterns with dynamically simulated patterns.
Main Results:
- The martensitic structure is more complex than a simple face-centered cubic (f.c.c.) structure.
- Nanoscale twins were observed, diffracting simultaneously.
- A tetragonal distortion was identified in the twinned martensitic structure.
Conclusions:
- The pseudoelastic properties of Fe-Mn-Al-Ni alloys arise from a complex, twinned martensitic structure with tetragonal distortion.
- This detailed structural analysis refines the understanding of martensite in these alloys.
Keywords:
backscatter Kikuchi diffractionelectron backscatter diffractionmartensiteshape-memory alloystwinning
