Heat treatment and kinetics of precipitation of β-Mg17Al12 phase in AZ91 alloy
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Université de M'sila
Abstract
This study investigated the effect of aging on the precipitation and kinetics of second phase Mg17Al12 in 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 factor k0 calculated by the isothermal treatment is equal to 1.24
109 s−1. In non-isothermal treatment, the numerical factor m and the Avrami parameter n is 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.
Description
Keywords
AZ91 DSC Mg17Al12 Precipitation Activation energy