Microstructure and mechanical properties of bulk TiN–AlN composites processed by FAST/SPS

Abstract TiN–AlN powder mixtures of commercial TiN and AlN powders with variable AlN contents (15 vol% and 25 vol%) were ball-milled for 3 and 6 h before subsequent consolidation by spark plasma sintering (SPS). The high-energy ball milling process induced mechanical alloying of the TiN with AlN, which was associated with the incorporation of AlN into the crystal structure of the TiN. In addition to the primary phases, which were the face centered cubic TiN and hexagonal wurtzitic AlN, the sintered samples contained crystalline γ-AlON after sintering. This study investigated the effect of the powder milling time, the sintering temperature and the AlN volume fraction on the hardness, fracture toughness and compressive strength of the TiN–AlN composites. It was found that the sintering temperature (1600 °C or 1700 °C) had only a marginal influence on the mechanical properties. An increase in hardness and a slightly enhanced average fracture toughness were caused by the increase of the AlN content from 15 vol% to 25 vol%. An influence of the AlN volume fraction on the compressive strength could not be determined.