Internal friction phenomena in a wide temperature range up to 800°C in long-term annealed Fe-(0−30) at% Ga alloys

Abstract

The internal friction (IF) phenomena were systematically studied in a temperature range from room temperature (RT) to 800 °C for Fe-(0−30) at% Ga alloys annealed at 480 °C for 14 days, which include the magnetic-related high damping plateau (HDP) and the point of ferro-paramagnetic transition (Tc), grain boundary relaxations, Zener relaxations, and the IF peaks associated with phase transitions. It was found that the rapid decay temperature of the HDP decreases with increasing Ga content, which is consistent with the variation of the Curie point (Tc), and the HDP disappears when the Ga content is greater than 18 at%. In the long-term annealed Fe-30at%Ga alloy, a frequency-independent phase transition IF peak was observed and its mechanism was suggested as the phase transition of L12→A2/B2. The phase transitions in Fe-(0–30 at%)Ga alloys evaluated by the IF technique are in good agreement with the equilibrium phase diagram. In addition, a new relaxation peak was observed before the displacive phase transitions of L12→D019 and L12→A2/B2, and its mechanism could be related to Zener relaxation in the FCC structured L12 phase.