Structural modifications in a Mn54Al43C3 melt-spun alloy induced by mechanical milling and subsequent annealing investigated by atom probe tomography

The structural changes upon milling and subsequent annealing of a Mn54Al43C3 alloy containing the intermetallic tetragonal L10 MnAl phase (τ phase) as the major phase were investigated by X-ray diffraction and atom probe tomography. The analyses show that milling the starting powder for 10 h leads to the nanostructuration of the sample. The milled sample is partly oxidised and contains both non oxidised Mn60±5Al40±5 regions and oxidised regions. Annealing the powder for 1 h at 500 °C leads to enrichment in Al of the oxidised regions, and to the phase transformation of the non-oxidised regions into a nanostructured β-Mn-like phase with a composition close to Mn3Al2.