Microstructural Characterization and Phase Development at the Interface Between Aluminum Nitride and Titanium After Annealing at 1300-1500C

Diffusion couples of aluminum nitride (AlN) and Ti were annealed under an argon atmosphere at temperatures ranging from 1300 to 1500C for 0.5-36 h. The morphologies, crystal structures, and chemical compositions of the reaction zones at AlN-Ti interfaces were characterized using analytical scanning electron microscopy and analytical transmission electron microscopy. An interfacial reaction zone, consisting of TiN, t sub(2)-Ti sub(2)AlN, t sub(1)-Ti sub(3)AlN, a sub(2)-Ti sub(3)Al, and a two-phase (a sub(2)-Ti sub(3)Al+a-Ti) region in sequence, was observed in between AlN and Ti after annealing at 1300C. The a sub(2)-Ti sub(3)Al region revealed equiaxed and elongated morphologies with[unconverted image]and[unconverted image]. In the two-phase (a sub(2)-Ti sub(3)Al+a-Ti) region, a sub(2)-Ti sub(3)Al and a-Ti were found to satisfy the following orientation relationship:[unconverted image]and[unconverted image]. The g-TiAl and a lamellar two-phase (g-TiAl+a sub(2)-Ti sub(3)Al) structure, instead of t sub(1)-Ti sub(3)AlN, were found in between t sub(2)-Ti sub(2)AlN and a sub(2)-Ti sub(3)Al after annealing at 1400C. The orientation relationship of g-TiAl and a sub(2)-Ti sub(3)Al in the lamellar structure was identified to be as follows:[unconverted image]and[unconverted image]. Compared with the reaction zone after annealing at 1400C, the g-TiAl was not found at the interface after annealing at 1500C. The microstructural development resulting from isothermal diffusion at 1300C and subsequent cooling at the interface are explained with the aid of the Ti-Al-N ternary phase diagram and a modified Ti-Al binary phase diagram.