In situ studies of atomic ordering in Fe-19Ga type alloys

Structure of binary Fe-19Ga and ternary Fe-19Ga-Tb alloys at room temperature are investigated by TEM and high-resolution neutron diffraction (ND). In contrast with as cast or water quenched samples with A2 structure, the D03 ordering was detected in slowly cooled or annealed samples by ND. According to TEM, the D03 ordering takes place in the form of ordered clusters with the size of about 5 nm embedded into an A2 matrix. Disordering of the D03 clusters at heating and ordering at cooling were investigated by three in situ techniques: ND, vibrating sample magnetometry (VSM), and internal friction (IF). Temperatures of ordering-disordering were estimated by VSM and IF to be close to 500 °C. The effect of Fe-Ga alloys doping with Tb is also analyzed.