Heat treatment and kinetics of precipitation of β-Mg 17Al 12 phase in AZ91 alloy

摘要

This study investigated the effect of aging on the precipitation and kinetics of second phase Mg17Al12in AZ91 magnesium alloy (Mg-9?wt% Al-1?wt% Zn), using X-ray diffraction, microhardness measurements and differential scanning calorimetric analysis (DSC). With the last instrument, the all samples were heated from room temperature to 400?°C, at heating rates of 10–30?°C/min. The results were supplemented by measuring the average of activation energies, using isothermal treatments by Johnson–Mehl–Avrami (JMA) methods and by non-isothermal treatments using Ozawa, Boswell, Kissinger, Mahadevan, Augis and Bennett methods, were around 67.18 and 62.02?kJ/mol. The frequency factork0calculated by the isothermal treatment is equal to 1.24 109?s?1. In non-isothermal treatment, the numerical factormand the Avrami parameternis estimated to be approximately equal to 3 and 2.79 respectively. This value corresponding that the bulk nucleation with a constant number of nuclei was dominant in three-dimensional (polyhedron) controlled by interface reaction.