Effect of phase composition on the internal friction and magnetostriction in the L12/D03 biphase Fe-27Ga alloys

Abstract

Fe-Ga alloys exhibit unique functional properties such as magnetostriction and high damping that can be adjusted by the phase transitions (D03 to L12) through a proper compositions and heat treatments. In this paper, the effect of phase composition on the internal friction (IF) and magnetostriction in Fe-27Ga alloys were systematically investigated. It was found that proportion of L12 phase in the biphase (L12/D03) Fe-27Ga alloys can be controlled by adjusting the annealing temperature and holding time. Two temperature-dependent IF peaks, i.e., a Snoek-type relaxation peak (P1) associated with the stress-induced jump of interstitial C atoms in the bcc-derived D03 phase and a Zener-type relaxation peak (P2) associated with stress-induced jump of Ga-pairs in the D03 phase were observed. The height of both peaks decreases gradually with the increasing content of L12 phase. The absolute value of magnetostriction at an applied magnetic field higher than 2000 Oe and the amplitude-dependent IF at a strain amplitude up to 10−3 decreases at first and then increases with the increasing content of L12 phase. With the increasing strain amplitude, magneto-mechanical damping of D03 phase increases at first and then decreases, while that of the L12 phase increases monotonously. This indicates that the magnetic domain walls of D03 phase can move easily under a low stress, while those of L12 phase can be driven only when the stress is high enough. Such researches could provide a design concept for high damping Fe-Ga alloys to meet the requirements in different application fields such as micro-vibration field, strong vibration field, magnetic or non-magnetic field.