Netsu Sokutei, 35 (4), p. 200, (2008)



Evaluation of the Amorphous-Forming Ability of Some Alloy Systems using the CALPHAD Approach

The amorphous-forming ability of some alloy systems has been evaluated in term of the critical cooling rate for amorphization. In this evaluation, the time-temperature-transformation (TTT) curves, which are a measure of the time necessary for the formation of detectable amounts of a crystalline phase from a supercooled liquid as a function of temperature, were calculated by introducing thermodynamic quantities obtained from the phase diagram calculations into the kinetic formulations. The evaluated amorphous-forming compositional range agreed well with the experimental results. In addition, the calculations showed that, at a given alloy composition, the phase other than the primary crystalline phase controls amorphization. Based on our thermodynamic calculations, this finding was closely related to the smaller entropy of fusion for the phase that controls amorphization versus that of the primary crystalline phase.