Macrokinetics of thermal explosion in a niobium-aluminum system. II. Phase-formation dynamics

The thermal explosion in a gas-free mixture of metal powders has been studi ed for the first time using the method of dynamic x-ray structural analysis . The dynamics of formation of new crystalline phases at all stages of the process is determined. It is shown that melting of aluminum is followed by dissolution of niobium in the melt and crystallization of the intermediate product NbAl3, and the melt does not wet niobium particles, A dramatic impr ovement in wetting is observed at a temperature of approximate to 1040 K (a pparently, due to the destruction of oxide films). This: results in a therm al explosion, and the Nb2Al phase is formed. The reaction during the therma l explosion also follows the dissolution-crystallization mechanism.