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

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 degrees 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)(similar to 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. (C) 2016 Elsevier B.V. All rights reserved.