Magneto-mechanical and damping properties in Fe79.9Al20-xGaxTb0.1 alloys

Abstract

Large magneto-mechanical properties are attained for Fe79.9Al20−xTb0.1Gax alloys prepared by directional solidification (DS). We obtain high delta E (ΔE) effect of 9.1–13.4 % and magneto-mechanical coefficient (K) of 29.7–49.5 % with good controllability of E by H and high sensitivity of E at low H, beneficial for the practical applications. The enhanced ΔE effect and K is sensitive to Ga content mainly due to the increased magnetostriction susceptibility (dλ///dH). The improved dλ///dH is contributed from the increased Δλ mainly due to lattice softening with Ga substitution for Al in A2 phase and also magnetic softening, possibly associated with higher (110) texture. The almost linear relationship between ΔEs/E0 and K2 suggests the experimental ΔEs/E0 obtained from IEV-RFDA (f ∼ 2 kHz) well agrees the theoretical estimated K2 according to the sound propagation theory. Besides, Ga substitution decreases damping capacity of the alloys Ψ(=ΔW/W), the change of the damping capacity (ΔΨ) with H, from 3.73 % for x = 0–0.73–1.04 % for x = 5–20. The almost linear relation between the experimental ΔΨ and theoretically estimated Ψeth reveals the micro eddy-current mechanism dominates the ΔΨ at 2 kHz. The decreased in ΔΨ, measured by RFDA with Ga substitution is mainly related to the reduction of the magnetic domain width and the decrease of E0 due to lattice softening. Several anelastic effects are reported for sub-resonance forced vibrations (DMA: 0.1–30 Hz): thermally activated Snoek (P1) and Zener (P2) effects and high damping plateau (background Qb−1) below 200 °C even for low strain (5 ×10−3 %). Dependence of the background damping level (Qb−1) on ratio Al/Ga is also non-linear with the maximum in ternary compositions Fe-20(Al+Ga).