THERMOMAGNETIC STUDY OF DEVITRIFICATION IN NANOCRYSTALLINE FE(CR)SIB-CUNB ALLOYS

Structural changes taking place in the course of the amorphous to crystalline transformation in nanocrystalline Fe73.5-xCrxCu1Nb3Si13.5B9 (0 less than or equal to x less than or equal to 5) alloys were investigated by DSC and thermomagnetic measurements. Heating up to temperatures of about 800 K leads to the formation of a nanocrystalline Fe(Si) phase in the amorphous matrix. The grain size is found to be in the range of 15-20 nm, showing no dependence on the chromium content. The composition of the Fe(Si) phase is estimated by the Curie temperature and a significant decrease of the silicon content in that phase, after hearing at higher temperatures, is evidenced. After full crystallization, two main phases are detected, an Fe(Si) phase and another unknown boride bce phase. The effects of the chromium addition are a small increase of the thermal stability of the amorphous alloy and a significant lowering of the Curie temperature of both the amorphous as-cast alloy and the final boride phase, whereas only a slight variation in T-C with composition is observed for the final Fe(Si) phase.