Heterogeneity generation by thermodiffusional mechanism in rapidly solidified amorphous alloys

Rapid solidification can produce amorphous alloys and materials with homogeneous and microcrystalline structures. However, chemical, structural, topological and other heterogeneities are frequently observed in rapidly solidified materials. Chemical macro-heterogeneity in melt-spun amorphous alloys is considered in this paper. In binary amorphous alloys (i.e. binary glass metals), it is expressed in rising of metalloid content from the contact side to the free surface side of the melt spun ribbon. The thermodiffusional mechanism of this heterogeneity generation is investigated. A mathematical model of the melt-spinning process was developed and numerically calculated for the case of binary alloys. Simulation of the process showed that the concentration wave appears in the liquid alloy film during its quenching. This wave moves from the contact surface to the free surface, and the concentration heterogeneity is developed before the solidification begins. The amplitude of heterogeneity strongly depends on the thermo-physical properties of the material and the process parameters. The simulation results compare favorably with the experimental observation using X-ray spectral microanalysis.