| Abstrakt: |
The influence of the magnetic pulse treatment (MPT) on the crystallization kinetics, phase composition and morphology of the structural components of the Al-7Si-4Fe melt is studied by X-ray diffractometry, direct thermographic and DSC analysis. As shown, the elevated iron content in the Al-7Si- 4Fe melt shifts the crystallization temperature of the primary aluminium dendrites to the crystallization temperature of pure aluminium. MPT of the melt does not affect the temperature ranges of the components crystallization; however, it increases the eutectic crystallization rate by three times. The effect is explained by the enhancement of the melt microliquation, which intensifies with an increase in the pulse repetition rate of the magnetic field, while the areas of microheterogeneity of the liquid alloy are significantly dispersed. In the framework of the cluster model, the ideas about a probable structure of the Al-7Si-4Fe melt near the liquidus temperature and the effect of the MPT modes on its formation are set forth. For the first time, it is hypothesized that under conditions of rapid cooling of the melt, the realization of separate or abnormal mechanisms of eutectic crystallization is related to the ratio in the melt of the fractions of Al1-xSix clusters with metallic and covalent bonds. MPT leads to the formation and significant increase in the fraction of clusters with metallic bonds and to the enhancement of the abnormal mechanism of eutectic crystallization. As shown, an increase in the pulse repetition rate twofold and, as a consequence, doubling the energy effect on the melt not only enhance the dispersion of the microliquation areas of the melt, but leads to the formation of a stable configuration of AlnFemSil clusters characterized by short-range order, similar to the ordering of atoms in the Al9Fe2Si2 phase. [ABSTRACT FROM AUTHOR] |
