Influence of Tb on structure and properties of Fe-19%Ga and Fe-27%Ga alloys

Abstract

Abstract Influence of microalloying by Tb on structure and some properties of Fe-19%Ga and Fe-27%Ga type alloys is studied. 0.1%Tb increases magnetostriction of water quenched Fe-19%Ga alloy with A2 structure from 120 to 210 ppm (1.75-fold). Slow cooling decreases magnetostriction in both Tb-free and Tb-doped alloys. Microalloying by Tb increases magnetostriction and influences on phase transitions in the Fe-27Ga type alloys in the range of 20–750 °C as observed by in situ neutron diffraction and vibrating sample magnetometry. The conventional transition sequence of phase transitions at heating D0 3 → L1 2 → D0 19 → B2 → A2 in binary Fe-27Ga is changed for D0 3 → B2 → B2 + L1 2 → B2 + D0 19 → B2 → A2 transitions in the Tb-containing alloy. The increase in Tb content from 0.15% to 0.3% decreases the amount of closed packed phases. At slow cooling (2 K/min), the mixture of D0 3 + L1 2 is recorded in the Tb-containing sample instead of dominating L1 2 (∼90%) and a very limited amount of D0 19 and A2 phases in the binary Fe-27Ga alloy. This influence of Tb on the phase transition kinetics explains temperature dependent magnetization curves with step by step accumulation of the L1 2 phase in subsequent heating and cooling cycles. Thus, we conclude that the additions of Tb stabilize bcc-born phases (A2, B2 and D0 3 ) and prevents the appearance of closed packed (fcc ordered L1 2 and hcp ordered D0 19 ) phases, which contributes to the functional properties of that alloys.