チタンを含むAlnico系磁石合金の硫黄添加による磁性の改良

Abstract

Effects of sulphur addition on the structure and magnetic properties of Alnico type alloys containing titanium were studied. Alnico type alloys containing 1 to 5% titanium could be converted into a columnar crystal structure by the addition of sulphur. Consequently, the residual induction amounts to 10100 G, the coercive force 1350 Oe, and the maximum energy product 7.2 M.G.Oe in Alnico 8 magnet alloy.The columnar crystals of Alnico type alloys containing titanium are smaller in diameter than those of Alnico 5. For example, the columnar structure of Alnico 6 (1.2%Ti) contains 150 to 400 crystals per 1 cm2 of the cross section, while in Alnico 5, merely some tens of crystals.The residual induction, 11000 G in the columnar Alnico 7 and 10000 G to 10500 G in the columnar Alnico 8, is not affected by sulphur addition. The coercive forces of columnar Alnico 7 and Alnico 8 containing about 0.2% sulphur are 1100 Oe and 1350 Oe respectively, but they fall down with the increasing sulphur content.The amount of sulphur remaining in the solidified alloys is smaller than that initially added, and the loss of added sulphur through casting and freezing becomes greater as the amount of sulphur addition becomes large.Microstructures of sulphur added Alnicos show needle or rod-shaped precipitations, which increase in amount with the increasing sulphur content and are considered to be some sulphides of metals.