SOME FACTORS ON SURFACE CRYSTALLIZATION OF FE-BASED AMORPHOUS-ALLOYS WITH AL AND TI IMPURITIES

The effects of quench rate during casting and alloy composition on sur face crystallization and the magnetic properties are investigated for amorphous Fe-Si-B alloys containing Al and Ti as impurities. In the pr esence of these impurities, the amorphous alloys tend to be surface-cr ystallized. Furthermore, the surface crystallization is more prominent at low quench rates. Also, the alloys of high Fe content (low glass f orming ability) are found to have the same tendency. TEM observation o f the free side of the ribbons reveals that there is a big difference between Al and Ti in crystallization behavior. These phenomena are sup posed to originate from the difference in lattice coherency between al pha-Fe and the precipitates in which two impurities act as nuclei of c rystallization.