Dynamics of phase transformation during thermal explosion in the Al–Ni system: Influence of mechanical activation

Time-resolved X-ray diffraction (TRXRD) techniques, which allowed for in-situ investigation of the dynamics of phase transformation during rapid, gasless heterogeneous reactions, were used to study the thermal explosion (TE) process in the stoichiometric Ni–Al system. Comparison of the phase transformation sequences for initial mixtures of the precursors and those after short-term high-energy ball milling shows that while for the former case the necessary condition for TE is melting of the reactive media, in the latter case TE occurs solely through solid-state reactions. It is also concluded that the rates of solid-state reaction are significantly enhanced due to an increase of oxygen-free contact surface area and a decrease of the scale of heterogeneity in the composite particles formed during mechanical treatment.