Speaker
Description
The magnetostrictive performance of Fe-Ga alloys is strongly governed by atomic ordering and metastable phase stability, yet the role of rare-earth microalloying under non-equilibrium processing remains poorly understood. This study investigates the effect of a minor Tb addition (0.1 at.%) and rapid water quenching on the phase stability and microstructure of Fe-26Ga and Fe-27Ga alloys using X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Rapid quenching from 900°C suppresses long-range B2 and D0₃ ordering, retaining a predominantly disordered A2 matrix. However, XRD reveals a persistent tetragonal distortion (c/a ≈ 1.0041-1.0043), indicating stabilisation of a non-cubic lattice domains under non-equilibrium conditions. TEM analysis shows that this distortion originates from nanoscale ordered regions with local symmetry breaking as determined from non-colinear superlattice reflections observed from electron diffraction. In Fe-26Ga-0.1Tb, Tb remains in solid solution and enhances these nanoscale distortions, producing a chemically homogeneous matrix with sustained tetragonality. In contrast, Fe-27Ga-0.1Tb exhibits Tb-rich precipitation, leading to microstructural heterogeneity and a slight relaxation of lattice distortion. These results demonstrate that Tb modifies atomic ordering locally rather than suppressing it, with the resulting phase stability and tetragonality strongly dependent on Ga concentration and solubility. This provides a structural basis for tailoring magnetostrictive performance in rare-earth-doped Fe-Ga alloys.
| Apply for student award at which level: | MSc |
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| Consent on use of personal information: Abstract Submission | Yes, I ACCEPT |