Crystallization kinetics of amorphous solids under pressure

The pressure effect on crystallization kinetics of amorphous solids was investigated by means of thermodynamic analysis. A model was developed to describe the nucleation process under pressure by considering the crystalline/amorphous (c/a) interface that plays a dominant role in the nucleation process. Applying the model to three types of crystallization process, polymorphous (a-Se), primary (Al₈₉La₆Ni₅), and eutectic (Ni₈₀P₂₀), we found the calculated results can give reasonable explanations for the experimental observations. The calculation suggests that for a-Se and Ni₈₀P₂₀ amorphous alloy, the initial stage of nucleation is a volume expansion process due to the c/a interface formation, resulting in an increase in the nucleation work with an increment of pressure. Hence the crystallization temperature of the amorphous phase rises when a pressure is applied, while for the Al-La-Ni amorphous alloy, the nucleation barrier decreases at higher pressures. The coincidence between the calculation and the experimental results illustrates that the c/a interface formation is the governing factor in the crystallization kinetics of the amorphous solids.