Study On The Role Of Cu In Amorphous FINEMET Alloy

nanocrystal alloy, commercially called "FINFEMET", has some exellent soft magnetic properties. Although the atom percentages of Cu and Nb are small, Cu and Nb play an important role in the nanocrystallization process of amorphous FINEMET alloy. Besides, Cu is considered as the key element of promoting the formation of the nanocrystal. To explore the role Cu played in the nanocrystallization process, we did a reasearch on the structural analysis functions and the Chemical short-range order of amorphous Cu5Fe95and Fe73.5Si13.sB9CuiNb3by ab-initio molecular dynamics simulation. Furthermore, the resistance variations in the nanocrystallization process of amorphous Fe78Si9B13and Fe73.5Si9B13.5Cu1Nb3are measured.Structural analysis on the amorphous Fe73.5Si9B13.sCu1Nb3shows that strong interaction exists in Cu-Si pair, but there is almost no interaction in Cu-Cu pair and Cu-Nb pair. Around Cu atom, the nearest Cu atoms are located in its second neighbor. Analysis on the gFeSi(r), gFeB(r) and gsiB(r) shows that there are two kinds of atom cluster,(FeSiCu) and (FeBCu), around Cu atom. Analysis on the chemical short-range order around Cu atom shows that compared with a random distribution, Cu trends to attract more Si atoms and reject B atoms, while the analysis on the Chemcal short-range order around Nb atom shows that the distribution of Nb atom is uniform. Comparing the result with that of amorphous Fe78Si9B13alloy, we can find that the addition of Cu promotes the separation tendency in Si-B pair, which promotes the separation between FeSi and FeB clusters.Comparative analysis on the resistance measurement results of the commercial1K101amorphous ribbons (nominal proportion Fe78Si9B13) with different widths shows that in the heating process, the resistance variation of the1K101amorphous ribbons can be divided into three stages:from the beginning of the treatment to the beginning of first crystallization process, the resistance increases as the temperature increase; then resistance decreases as the temperature increase, and two crystallization stages are included in this temperature rang; after the crystallization stage, resistance increases as the temperature increase. The crystallization process (crystallization temperature and crystallization temperature range) indicated by the Electrical Resistance Measurements are matched well with that indicated by DSC method in a reasonable error range.Comparative analysis on the resistance measurement results of the commercial1K107amorphous ribbons (nominal proportion Fe73.5Si9B13.5Cu1Nb3) with different widths shows that the resistance increases as the temperature increase. The resistance variation doesn’t indicate the crystallization process in the heating process. We can not explain this result clearly so far. Besides, the Electrical Resistance Measurement of amorphous FINEMET alloy is not in accordance with the information of Cu cluster as we expect.To figure out the relationship between the resistance variation and the heat effect in the alloy system, a simple quantitative model is built. Analysis on this model shows that both the rate of resistance and heat effect change are controlled by the rate of phase change in the alloy system.