Amorphous eutectic composition

A typical crystallisation process in binary alloys can be described, as temperature increases, as follows. In hypoeutectic compositions (where the transition-metal content is greater than the corresponding eutectic composition for a given material), the transition metal crystallises first, until the amorphous phase reaches the eutectic composition, at which both the transition metal and the intermetallic crystallise. In hypereutectic alloys (transition-metal-poor), both phases crystallise simultaneously. Some ternary alloys can also be included in this schematic model, such as Fe-B-Si (Ramanan Fish, 1982) and Ni-B-Si (Baro, Clavaguera and Surinach, 1988). The crystallised phases are a-(Si-Fe) and FejB for the former system, and y-Ni and NijB for the latter. Transmission electron microscopy can be used to study in-situ crystallisation phenomena, identify (Valenzuela et ai, 1982) and evaluate the crystallised fractions (Blanke-Bewersdorff Koster, 1988). 

Harada Y, Uekawa N, Kojima T, Kakegawa K. Fabrication of dense material having homogeneous GdA103Al203 eutectic-like microstructure with off-eutectic composition by consolidation of the amorphous. J Eur Cer Soc 2009 29(ll) 2419-22. 

No potassium phosphate crystals of any kind can be formed in an anhydrous system with a K2O-P2O5 ratio less than 0.5. It was shown above that a 0.5 ratio is the minimum ratio at which [KPOaln crystals can form. The eutectic behavior is the dissolution of [KPOsIm crystals in a melt with a ratio near the eutectic composition when the system contains less than 68% P2O5. When all the amorphous phase with a P2O5 concentration greater than the eutectic composition is depleted, temperatures must be increased to dissolve the remaining [KPOsln crystals in a melt that is richer in K2O than the eutectic composition. This is an explanation of the behavior of this system as determined, but leaves unanswered questions as to... 

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