High purity aluminium powder was sintered in a dilatometer in flowing high purity nitrogen. The distinct shrinkage segments observed on the dilatometry curves were the basis of experiments consisting of interrupted sintering. In this way compacts with microstructure frozen at different steps of sintering cycle were produced. Optical microstructure examinations and LECO analysis of nitrogen content showed the development of aluminium nitriding. Additionally, X-ray diffraction was used to examine phases appearing in the system investigated. Microstructure analysis of structural components revealed evidence that isothermal sintering proceeds in the presence of a liquid phase, despite taking place below the melting point of aluminium. It seems that aluminium nitrogen interactions are responsible for the appearance of this phase, which is accompanied by extensive shrinkage.
