On the compositional partitioning during phase transformation in a binary ferromagnetic MnAl alloy
Abstract
We introduce a new perspective on the classical massive mode of solid-state phase transformation enabled by the correlative use of atomic-scale electron microscopy and atom probe tomography. This is demonstrated in a binary MnAl alloy which has Heusler-like characteristics. In this system, the τ phase formed by a massive transformation from the high-temperature ε phase is metastable and ferromagnetic. The transformation results in a high density of micro-twins inside the newly grown τ phase. Atomic-scale compositional analysis across the interface boundaries and atomic structure of the micro-twins reveals the involvement of both structural modification and also the compositional partitioning during the growth of the τ phase. This is assisted by the migrating τ/ε interface boundary during transformation. Finally, the role of micro-twins on nucleating the equilibrium phases and the influence of the defects and phase formation on the magnetic properties are discussed.
- Publication:
-
Acta Materialia
- Pub Date:
- August 2019
- DOI:
- 10.1016/j.actamat.2019.05.037
- Bibcode:
- 2019AcMat.174..227P
- Keywords:
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- MnAl ferromagnetic alloy;
- Massive transformation;
- Twin boundary segregation;
- Atom probe tomography (APT);
- Transmission electron microscopy (TEM)