Time-Resolved X-ray Diffraction Study of SHS-produced NiAl and NiAl-ZrO2 Composites

NiAl and NiAl-ZrO2 intermetallic composites were prepared from pressed elemental powders by SHS in a dynamic vacuum. The effect of diluent properties (such as conductivity and grain size) on the parameters of the SHS reaction has been investigated by time-resolved X-ray diffraction (TRXRD). By decreasing the reactivity of the green mixture, these nonreactive additives not only slow down the velocity of combustion front propagation but can also give rise to local melting of the product. Synchrotron radiation was also used to elucidate the reaction mechanism. It has been found that the combustion synthesis of NiAl is triggered by aluminum melting and proceeds via the formation of two transient intermetallic phases, NiAl3 and Ni-2 Al-3. In the final product, only the NiAl phase has been detected.