Enhanced magnetostriction of < 100 >-oriented polycrystalline (Fe₈₁Ga₁₉)_99.8Tb_0.1(NbC)_0.1 alloy by synergy strategy of trace NbC-doping and quenching treatment

The enhancement of the magnetostriction for Fe-Ga alloys can significantly improve the magneto-mechanical conversion efficiency of magnetostrictive devices, which are widely applied in high-end equipment, aerospace and other fields. Recent studies have demonstrated that doping trace rare earth elements into Fe-Ga alloys can significantly enhance their magnetostriction. In this work, the < 100 >-oriented polycrystalline (Fe₈₁Ga₁₉)_99.8Tb_0.1(NbC)_0.1 alloy with excellent magnetostriction was developed by employing a synergistic strategy of trace NbC-doping and quenching treatment. The < 001 >-oriented Fe-Ga alloys along the growth direction were prepared by directional solidification. The addition of NbC increased the solid solubility of Tb in the matrix of Fe-Ga alloy by 9.4 %, and this was further increased by 28.1 % after quenching treatment, inducing more L6₀ heterogeneities and enhancing lattice distortions in the matrix. The saturation magnetostriction of the < 100 > -oriented polycrystalline (Fe₈₁Ga₁₉)_99.8Tb_0.1(NbC)_0.1 alloy before and after quenching reached 200 ppm and 295 ppm, respectively, which was 5.8 % and 5.6 % greater than that of the NbC-undoped (Fe₈₁Ga₁₉)_99.9Tb_0.1 alloy. The saturation magnetostrictions of all selected Fe-Ga alloy compositions after quenching treatment were more than 40 % higher than of the unquenched samples. The initial and average magnetostrictive strain sensitivity (dλ/dH) of all Fe-Ga alloys has been greatly improved after heating at 1200 ℃ for 2 hours. This work reveals that the reasonable alloy design and thermal treatment can effectively increase the solubility of Tb in the matrix and improve the magnetostriction of Fe-Ga alloys, which can provide a crucial guidance for future studies of magnetostrictive Fe-Ga alloys.