Abstract
Mechanical milling of Ti powder in a controlled quantity of nitrogen gas by a high energy ball mill was performed. In the initial stage, the nitrogen pressure was gradually reduced. Nitrogen was dissolved in Ti to form a solid solution. Under suitable conditions, when a critical solubility limit had been reached, the nitrogen pressure drastically dropped to a much lower value and instant formation of TiN took place. Continuation of the milling led to increased content of nitrogen in the nonstoichiometric compound TiN. The particle size also continued to decrease. The phases before and after the rapid reaction to form TiN were carefully studied by X-ray diffraction. The morphological change of the particles during the milling was examined by scanning electron microscopy. The TiN compound was formed by means of self-propagating combustion which was triggered by the large clean surface area and the high strain energy of the Ti powder induced by the milling.