Thermal stability, crystallization kinetics, and grain growth in an amorphous Al_85Ce_5Ni_8Co_2 alloy

Abstract

Thermal stability and crystallization kinetics of the melt-quenched amorphous Al_85Ce_5Ni_8Co_2 alloy were investigated by x-ray diffraction and differential scanning calorimetry (DSC). The glass transition was followed by a supercooled liquid region (21 °C) and then by a two-step crystallization process. The final microstructure contained Al_3Ce, α–Al, Al_3Ni, and Al_9Co_2 phases. Isothermal annealing of the as-quenched samples in the range of 275–285 °C showed that both crystallization reactions occurred through a nucleation and growth process. Continuous heating DSC measurements following pre-anneals for different times were also carried out to study the crystallization kinetics and the stability of the material. The Avrami analysis of the isothermal DSC-curves revealed that the 3-dimensional nucleation and growth process became more dominant with increasing annealing temperature. The average specific grain boundary energy corresponded to high-angle grain boundaries and indicated independent nucleation events.