ORDERED STRUCTURE AND MECHANICAL PROPERTIES OF Fe-6.5%Si ALLOY FABRICATED BY RAPID QUENCHING

Fe-6.5%Si alloy is one excellent soft magnetic material. However, due to the appearance of ordered phases, this alloy is very brittle at room temperature and is very hard to be fabricated into thin sheet by conventional rolling process. In this work, continuous Fe-6.5%Si ribbons of 20 mm in width, and 35-50 mu m in thickness were fabricated by rapid quenching technique. The ribbons exhibited good ductility compared with ordinary cast ingots. TEM and XRD were employed to analyze the ordering and microstructure of the ordinary cast ingots and the ribbons. The long range order parameters of B2 ordered phase in these two alloys were calculated. The results showed that the cast ingot contained amounts of B2 and D0(3) ordered phases, and had high degree of order. While in rapid quenched ribbons, the grains were extremely fine, the formation of D0(3) ordering was suppressed effectively and the growth of B2 was largely decreased. The decreased ordering content and degree of order in rapid quenched ribbons lowered the anti-phase boundary energy, leading to the reduction in slip resistance, which improved the mobility of superlattice dislocations, and then obviously enhanced the ductility of the alloy.