Non-isothermal kinetic analysis of the oxidation of Al–50Mg powder mixture

In this research, non-isothermal kinetic analysis of the oxidation process of Al–50Mg (wt%) powder mixture was performed by employing differential scanning calorimetry and thermogravimetry analysis techniques. The research findings revealed that oxidation of this powder mixture was completed at lower temperatures compared to that of pure aluminum powder; and furthermore, it enjoyed a higher thermal efficiency than that of pure magnesium powder. Oxidation of this mixture powder led to the formation of magnesium oxide (MgO) and spinel phase (MgAl2O4) during the first and second oxidation steps, respectively. Moreover, to calculate the activation energy (E) over a wide range of degree of conversion (α), two isoconversional methods, including Starink and Friedman methods were used. Activation energies decreased as the reaction progressed at both stages, indicating that these stages were multi-step reactions. Furthermore, the invariant kinetic parameter method and fitting model were used to determine the empirical kinetic triplets (i.e. E, pre-exponential factor (A) and reaction model (g(α))). The obtained results showed that the first stage was controlled by the second order Avrami-Erofeev mechanism (A2), two-dimensional phase boundary reaction (R2), and two-dimensional diffusion (D2) models at heating rates of 5, 10, and 30 °C/min. The second stage was controlled by the third order Avrami-Erofeev mechanism (A3) and A2 at heating rates of 5 and 10 °C/min, while for a heating rate of 30 °C/min, the mechanism of reaction changes from A3 to A2.