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

Diffusion couples of aluminum nitride (AlN) and Ti were annealed under an argon atmosphere at temperatures ranging from 1300 degrees to 1500 degrees C 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, T2-Ti2AlN, T1-Ti3AlN, T2-Ti3Al, and a two-phase ({alpha}2-Ti3Al+{alpha}-Ti) region in sequence, was observed in between AlN and Ti after annealing at 1300 degrees C. The {alpha}2-Ti3Al region revealed equiaxed and elongated morphologies with {equation} and {equation}. In the two-phase ({alpha}2-Ti3Al+{alpha}-Ti) region, {alpha}2-Ti3Al and {alpha}-Ti were found to satisfy the following orientation relationship: {equation} and {equation}. The {gamma}-TiAl and a lamellar two-phase ({gamma}-TiAl+{alpha}2-Ti3Al) structure, instead of T1-Ti3AlN, were found in between T2-Ti2AlN and {alpha}2-Ti3Al after annealing at 1400 degrees C. The orientation relationship of {gamma}-TiAl and {alpha}2-Ti3Al in the lamellar structure was identified to be as follows: {equation} and {equation}. Compared with the reaction zone after annealing at 1400 degrees C, the {gamma}-TiAl was not found at the interface after annealing at 1500 degrees C. The microstructural development resulting from isothermal diffusion at 1300 degrees C 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. [PUBLICATION ABSTRACT]