Spinning phenomena, structure and magnetic properties of Fe-6.5 mass% Si alloy fiber produced by the in-rotating-liquid-spinning process

摘要

Almost zero magnetostrictive Fe-6.5 mass% Sialloy fibers of less than about 90 μm diameter, and showing alarge Barkhausen effect, were obtained by using a laboratory scale,in-rotating-liquid-spinning process (INROLISP). The spinningconditions, jet stability, morphology of dendritic growth andmagnetic properties are discussed for fibers of about 70 μmdiameter with regard to manufacturing. For spinning speeds of lessthan about 10 m/s, the jet bounced on the surface of the rotatingliquid, such as water, water with chemicals lowering the surfacetension, and some oils. For speeds >10 m/s, the jet subsequentlypenetrated under the liquid surface after an interval of around 100ms from the start of ejection. The centrifugal force effect wasconsiderable in this setup. When the jet bounced, in some part ofthe fiber structure primary dendrite arms growing uniformly alongthe fiber direction were observed. In another part, however, thedirection of the primary arm changed gradually far from the fiberaxis and a secondary arm became the primary arm withoutobserving clear grain boundary. It is conceivable that the curvatureof the bouncing jet at the ejection point obstructs the primary armsfrom growing in a straight line. When the jet penetrated, a"bamboo structure" was observed in the fiber. The penetrating jetformed a cavity of coolant downstream from the jet. This indicatesthat the penetrating jet firstly goes through an area of non-contactwith the coolant on the cavity side while making contact with thecoolant on the opposite side. Therefore, primary arms tend to growfrom the contact to the cavity, sides. Using the zone-annealingprocess, it was difficult to make a fairly long single crystal fromany fiber. In order to control the continuous growth of primaryarms along the fiber direction, it is suggested that a process able tocool the jet uniformly around its circumference is required so thatthe primary arms can grow in a straight direction. The necessaryconditions to produce a fiber having a large Barkhausen effect area nearly unidirectional shape and a [100] crystal direction of thealpha-phase parallel to the long axis. Furthermore, to obtain anideal rectangular hysteresis loop, the requirements of a round shapein the cross section, no residual stress and no precipitation are suggested.