Stabilization of bcc-born phases in Fe-27Ga by adding Tb: Comparative in situ neutron diffraction study

• Phase transitions in two Fe-27Ga-(Tb) alloys are studied.
• In situ neutron diffraction is used to find out influence of Tb.
• 0.3%Tb suppresses phase transitions in Fe-27Ga both at heating and cooling.

Significant influence of 0.3 at%Tb on phase transitions in the Fe-27.4Ga alloy in the range of 20–850 °C is observed by in situ neutron diffraction. The conventional transition sequence at heating D03→L12→D019→B2→A2 in binary Fe-27.4Ga is changed for D03→(B2(~75%)+L12(~25%))→(B2(~85%)+D019(~15%))→B2→A2 transitions in the Tb-containing alloy. At slow cooling (2 K/min) the mixture of D03(90%)+L12(10%) is recorded in the Tb-containing sample instead of dominating L12(~90%) and very limited amount of D019 and A2 phases in the binary Fe-27.4Ga alloy. We conclude that the addition of a small amount of Tb stabilizes bcc-born phases (A2, B2 and D03) and prevents appearance of closed packed (fcc ordered L12 and hcp ordered D019) phases.

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