Structural characterisation of ball-milled Fe70Al 28Cr2 plus Si powder mixtures

High-energy ball-milling of powder mixtures consisting of a Fe 70Al28Cr2 alloy with 5 and 10 wt% Si, respectively, has been studied by Mössbauer spectroscopy and X-ray diffraction. It is observed that milling produces several structural changes, depending on milling time and composition of the powder mixture. The starting metallic phase displays a partially ordered B2 structure with superlattice peaks that vanish upon milling in case of the low silicon mixture, whereas they are retained in the silicon richer material. Prolonged milling leads to a loss of magnetic order in the powder mixture with higher silicon content, with the formation of a disordered Fe-Al-Si solid solution. It remains nearly unchanged upon subsequent annealing at 1000 K. In the powder mixture with a lower silicon content the magnetic order is not destroyed by milling, which leads to the formation of a metastable structure partially ordered by subsequent annealing.