Effect of order-disorder transition on magnetic properties of rapidly soldified high silicon-iron ribbons
The effect of ordering on the soft magnetic properties of 6.5% silicon-iron ribbons obtained by rapid solidification is studied. The atomic order cannot be prevented by the fast cooling. It is shown that isothermal aging at 700 degrees C induces a small decrease in coercive force and hysteresis losses, while aging at 500 degrees C induces an increase in these parameters. The magnetic evolutions are corroborated by Lorentz microscopy observations. The values obtained and the observations suggest a weak individual interaction, which may be due to local variation of exchange and anisotropy energy. >
The nature of ordered structures in melt spun iron-silicon alloys
Increasing the silicon content is known to improve the magnetic properties of iron-silicon alloys (I). However, the associated loss of ductility has prevented the use of high silicon alloys in practical applications. The melt spinning of high silicon alloys can,produce wide tapes with reasonable ductility that are now regarded as one of the promising materials for magnetic applications (2-8). Investigations of the magnetic and mechanical properties consistently indicate a variation with silicon content (2- , 8-II). The best property combinations seem to exist for 6.5 wt % silicon alloy. Narita and Enokizono (10) have shown that in bulk Fe-Si alloys with high silicon contents, the B2 and $DO_3$ ordering lead to different property changes and that cooling rate has major influence on magnetic properties. The magnetic and mechanical properties of rapidly solidified melt spun alloys are shown to be significantly different (3-5,7- 10-12). For example, the permeability of melt spun tapes is different for different alloys. It has a maximum value for a 6.5 wt % Si alloy which is different behavior from that observed in a well annealed sample (12). In order to understand the reasons for such behavior, a clear understanding of the structure is necessary. There exists considerable confusion in the literature regarding the structure of the melt spun alloys (3-5,7-8,13). For example, $DO_3$ ordering is assumed to be predominant in melt spun 6.5 wt %'SJ alloy by many investigators (4-7). Chang et al. (5) have presented TEM evidence of it Jn the shape of a 010 superlattice spot observable Jn a [100] zone selected area diffraction pattern. However, this is not adequate to differentiate between the B2 and $DO_3$ ordering. A different conclusion that the structure is a predominantly disordered phase (A2) with a very small amount of B2, was reported by Enokizono et al. (3). They have also reported the absence of domain structure. Guntherodt (7) and Warlimont (8) highlighted the suppression of the ordering reaction by melt spinning as the main reason for the improved ductility of the melt spun tapes.
Kinetics of antiphase domain growth
Abstract The antiphase boundary, APB, energy was recalculated, indicating that, in the B2 superlattice, it is even more isotropic than previously believed. High vacancy concentrations at APB were also analyzed with respect to their positional energy at the boundaries as compared to that in the perfectly ordered crystal. Finally, the motion of APB in β brass has been analyzed with particular emphasis placed upon the geometrical constraints imposed on atom movement by the superlattice. Two cases were considered, the shrinking of an isolated spherical domain, and the flattening of wavy APB. The former is associated with a parabolic rate law similar to that of grain growth in pure metals. The latter is extremely sensitive to the amplitude and period of the boundary.