Kinetics study on non-isothermal crystallization of amorphous alloy Mg_(65)Cu_(15)Ag_(10)Y_(10)

摘要

The crystallization kinetics of amorphous alloy Mg_(65)Cu_(15)Ag_(10)Y_(10) has been studied by differential scanning calorimetry in the mode of continuous heating annealing. It is found that both DSC curves and activation energy show a strong dependence on the heating rate. The activation energy for crystallization are determined as 186.1 and 184.4 KJ mol~(-1) for the heating rates β=5–20 K min~(-1), and 107.5 and 110.0 KJ mol~(-1) for the heating rates β=20–80Kmin~(-1), when using the Kissinger equation and the Ozawa equation, respectively. Local activation energy at any volume fraction crystallized was obtained by the general Ozawa's isoconversional method. The average value of local activation energy for heating rates ranging from 5 to 20Kmin~(-1) is 180.9 KJ mol~(-1) and for heating rates ranging between 20 and 80Kmin~(-1) is 110.2 KJ mol~(-1). Using the Surinach curve fitting procedure, the kinetics mode was specified. The JMA kinetics is manifested as a rule in the early stages of the crystallization. The JMA exponent, n, initially being larger than 4 and continuously decreases to about 2 along with the development of crystallization. The NGG-like mode dominates in the advanced stages of the transformation. These two modes are mutually independent. The proportion between the JMA-like and the NGG-like modes is related to the heating rate.