Bulk ferromagnetic (Fe_(0.87)Co_(0.13))_(71.5-x)Tb_(3.5)Nb_xB_(25) glassy alloys with a high glass-forming ability

摘要

New (Fe_(0.87)Co_(0.13))_(71.5-x)Tb_(3.5)Nb_xB_(25) (x=2.5,3,4,5) glassy alloys were found to exhibit a higher glass-forming ability comparing with the (Fe,Co)-(Nd,Dy)-Nb-B glassy alloys previously reported. With increasing Nb element from x=2.5 at.% to 4 at.%, the supercooled liquid region (ΔTx) increases from 102 K to 110K and the liquidus temperature (Tl) decreases from 1471K to 1452K. The highest Tg/Tl of 0.59 and the largest supercooled liquid region ΔTx of 110K were obtained for the (Fe_(0.87)Co_(0.13))_(67)Tb_(3.5)Nb_4B_(25) glassy alloy. The bulk (Fe_(0.87)Co_(0.13)_(67)Tb_(3.5)Nb_4B_(25) glassy alloy with a diameter up to 3 mm was produced by copper mold casting. The results suggest that smaller atomic ratio of Tb/B would enhance the degree of dense random packing fraction of the (Fe,Co)-Tb-Nb-B glassy alloys. The saturation magnetization decreases with increasing content Nb in (Fe_(0.87)Co_(0.13))_(71.5-x)Tb_(3.5)Nb_xB_(25) glassy alloys. Also the (Fe_(0.87)Co_(0.13))_(71.5-x)Tb_(3.5)Nb_xB_(25) glassy alloys exhibit larger coercive force about 8.76 to 10.9(A/m) . The saturation magnetization and coercive force of the (Fe_(0.87)Co_(0.13))_(67)Tb_(3.5)Nb_4B_(25) glassy alloy with the highest Tg/Tl are 0.73(T) and 9.71(A/m), respectively.