Anelasticity of Fe–Ga based alloys

Abstract

Frequency, amplitude, and temperature dependent effects of anelasticity in Fe–Ga and Fe–Ga–Al alloys are studied by mechanical spectroscopy techniques using forced bending and torsion subresonance vibrations (f from 0.001 to 200Hz, ε from 10−6 to 10−2, T from 0 to 600°C). The structure and the properties of the studied alloys are characterized by scanning electron microscopy and magnetic force microscopy. Main regularities of amplitude dependent damping are attributed to magnetomechanical damping, which is very sensitive to the structural state of alloys, their composition, magnetostriction, and testing method. Two maximal damping peaks at about 18% and 27%Ga correspond to similar maxima of magnetostriction against %Ga. Both temperature dependent thermally activated relaxation effects and anelastic effects due to phase transitions are discussed in terms of alloys structures. Thermally activated internal friction peaks are ascribed to different atomic mechanisms. A phase transition from bcc originated structures (A2 and D03) to an fcc ordered structure (L12) is accompanied by a transient anelastic effect typical for a shear diffusionless transition.