HIGH-TEMPERATURE MOSSBAUER-SPECTROSCOPY ON THE PHASE DYNAMICS IN FERROSILICON SYSTEMS

High temperature Mossbauer spectroscopy has been used for studying ''i n situ'' the phase dynamics of the silicon rich part of the binary Fe- Si system. In particular the rate and mechanism of the transformation of the so-called zeta-alpha phase of iron disilicide to the zeta-beta phase is of special interest, since there still remains uncertainty ab out the stability and the structure of the phase in this system which influence material properties such as compressive strength and disinte gration. In the present work the phase transition from the zeta-alpha phase to the zeta-beta phase is followed by a time sequence of Mossbau er spectra recorded every three hours at a fixed temperature around 80 0 K. The exponential precipitation rate is analysed and the exponent c alculated. Samples with differing degree of impurities have been studi ed and the effect of aluminium impurities on the rate of the transitio n will be discussed. The Debye temperature of the two phases was deter mined from series of Mossbauer spectra recorded at temperatures betwee n 300 and 800 K.