Hydrogenation kinetics of ZK60 Mg alloy during solid–gas reaction milling in hydrogen

The process of solid–gas reaction milling in hydrogen was applied to achieve the full hydrogenation of ZK60 Mg alloy by forming Mg hydride (MgH2). The hydrogenation kinetics to form MgH2 during reaction milling was experimentally investigated by in situ monitoring of the hydrogen absorbed by the alloy in the vial. The effect of milling parameters and hydrogen pressure on the hydrogenation kinetics was evaluated and the underlying mechanisms were discussed by referring to the mechanical energy input intensity, the vial temperature, and the Gibbs free energy change for the reaction. The kinetic equation, the rate constant, the reaction order exponent, and the activation energy for the hydrogenation reaction to form MgH2 during reaction milling were obtained by fitting the experimental data with the Avrami–Erofeev theory.

► The kinetics can be well described by the equation α = 1 − exp(−ktn).
► The reaction order exponent, n, was found to fall in the range of 3.44–3.95.
► The activation energy was found to be 49.8 kJ/mol.