Effects of boron addition on phase structure and magnetostriction of Fe-Ga alloys

The studies of phase structure and magnetostriction for B element doped (Fe_0.81Ga_0.19)_100-xB_x (x = 0-20) alloys showed that the as-cast alloy with x = 1 consists of A2 (bcc Fe (Ga)) and Fe₂B phases, while the alloys with x = 5, 10, 15 and 20 consist of Fe₂B, A2 and L1₂ (α-Fe₃Ga) phases; the alloys with x = 1 and 5 oil-quenched at 800°C for 3 h contain modified-D0₃ (Fe₃Ga) and Fe₂B phases, while the quenched alloys with x = 10, 15 and 20 consist of Fe₂B, modified-D0₃ and L1₂ phases. The saturation magnetostriction λ_s of the as-cast alloys with x = 1 and 10 exhibited two peaks; the λ_s values of the oil-quenched alloys increased first and then decreased with increasing B content. The λ_s of the alloy with x = 10 reached the maximum, 80% larger than that of the oil-quenched Fe₈₁Ga₁₉. With the increase of B content, Fe₂B phase precipitated in the oil-quenched alloy, leading to the increase of Ga content in the matrix of modified D0₃, resulting in the increase of the magnetostriction. Further increasing B content, much more amount of Fe₂B and L1₂ phases appeared, resulting in the decrease of magnetostriction.