Dresden 2017 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 49: Microstructure and Phase Transformations - shape memory alloys
MM 49.1: Vortrag
Mittwoch, 22. März 2017, 15:45–16:00, IFW B
Role of nano-precipitates in thermoelastic martensitic transformation in Fe-Mn-Al-Ni shape memory alloys — •Toshihiro Omori1, Makoto Nagasako2, and Ryosuke Kainuma1 — 1Department of Materials Science, Tohoku University, Sendai 980-8579, Japan — 2Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Fe-Mn-Al-Ni alloy shows superelasticity associated with the α(bcc)/γ(fcc) martensitic transformation. Although Fe-Mn-Al ternary alloys show non-thermoelastic martensitic transformation, the addition of Ni results in the precipitation of fine β-NiAl (B2) particles and changes the transformation manner to thermoelastic. Therefore, it is considered that Ni plays a key role in the thermoelastic transformation. In this study, the effect of Ni on the martensitic transformation was investigated. The microstructures of Fe-36Mn-15Al-Ni (at%) alloys with different Ni contents were observed using TEM and HAADF-STEM. It was found that the β particle with about 10 nm is coherent with the martensite phase in 7.5Ni alloy, and the B2 lattice was distorted. In the martensite phase, the nano-twins were frequently introduced and the shear angle became smaller. These facts suggest that there is interaction between the β precipitate and martensite matrix due to the coherency, and it is deduced that the compatibility between the parent and martensite phases becomes high. The thermoelasticity comes from this microstructural feature.