Crystallization kinetics in an amorphous Al-Ni-Mm-Fe alloy

Differential scanning calorimeter (DSC) has been used to study the crystallization kinetics of Al(87.5)Ni(7)Mm(5)Fe(0.5) alloy. Both isochronal and isothermal DSC plots showed that the Al(87.5)Ni(7)Mm(5)Fe(0.5) alloy undergoes three stages crystallization process. The first peak corresponds to the precipitation of fcc-Al from the amorphous matrix at around 160degreesC. Isothermal DSC traces showed that there is a short incubation stage for the formation of nanoscale Al particles. The value of Avrami exponent suggests that the crystallization of Al crystals starts with a nucleation process for a short time and finally controlled by a growth mechanism. The second peak corresponds to the crystallization of Al-11(La,Ce)(3) from the matrix at around 320degreesC with a nucleation rate, which decreases with time, and a constant growth rate. The activation energy calculated for the crystallization of Al-11(La,Ce)(3) phase is 288 +/- 5.9 kJ/mol, 324.6 +/- 18 kJ/mol, 292 +/- 6 kJ/mol by Kissinger, Johnson-Mehl-Avrami and Arrhenius type equations. The difference in the values of kinetic energy is mainly due to different annealing conditions. The third peak at around 340degreesC corresponds to the precipitation of intermetallic compounds from the remaining matrix