Mechanism of Combustion Synthesis of NiAl-Ni₃Al Composite Materials Within Al-Ni System

The mechanism of combustion synthesisof NiAl-Ni₃Al composite withinAl-Nisystem was studied by means of a combustion front quenching method（CFQM）. Microstructural evolution in the quenched sample was characterized by field-emission scanning electron microscopy（FESEM） equipped with energy dispersive spectrometer（EDS）. The phase compositions of the combustion product were examined by X-ray diffraction（XRD）. The results show that combustion reaction starts with the melting ofAl particles.Al in liquid phase reacts with solid Nito form NiAl₃ through diffusion and melting between NiandAl, and then NiAl₃ reacts with Nito form Ni₂Al₃, and the heat released melts Ni₂Al₃, releasing a large amount of heat. The melted Ni₂Al₃ further reacts with Nito form NiAl with high melting point, and part of NiAl reacts with Nito form Ni₃Al. When the Ni-Al melt is saturated, NiAl and Ni₃Al precipitate from it, and the precipitated grains are continuously spliced and grown under the action of high temperature and liquid phase coating, finallys the matrix with main phases of Ni₃Al and NiAl is formed. Thus, the combustion reaction can be described by the melting-dissolution-precipitation mechanism.