Studies on microstructural changes and phase transition during preparation of FeGeNi ternary alloy by mechanical alloying

FeGeNi ternary alloy has been prepared by mechanical alloying followed by thermal treatment. Microstructure of the as-milled and annealed samples as well as thermally induced phase transition and variations in degree of order were investigated through a combination of X-ray diffraction and Mössbauer spectroscopy. The results show that alloying in the (Fe0.81Ni0.19)3.94Ge2 ternary system initiates during ball milling, with the appearance of partially D03-ordered A2 solid solution phase and paramagnetic B82 FeGeNi ternary phase. A subsequent thermal treatment of 2 h at 800 K produces a remarkable increase in the degree of the D03 order, whilst ferromagnetic phase with amorphous character in the as-milled sample is transformed into paramagnetic B82 FeGeNi ternary phase where almost all Ni atoms occupy the vacant 2d site. Therefore in the annealed system coexist two phases, namely the D03 phase and paramagnetic B82 FeGeNi ternary phase.