Microstructural characterization and mechanical properties of in situ cast nanocomposites Al/TiC type

Al matrix nanocomposites reinforced with TiC particles have been successfully fabricated by self-propagating high-temperature reaction during casting from aluminium 1000 alloy and a mixture of powders of Ti, C and Al used as a moderator. The most important issue was to estimate the influence of moderator content on the microstructure. The microstructure of composites containing a lower amount of moderator (1% and 10%) consists of TiC particles, segregated mainly at grain boundaries of aluminium matrix, while a higher moderator content (>50%) allows to obtain materials with nearly homogenous distribution of TiC particles. Moreover, the elimination of brittle, additional phases e.g. TiAl3 and Al4C3, commonly observed in the Al/TiC composites, was evidenced. However, still small amounts of Ti3AlC and TiAl2.4Si0.6 phases that reduce the capacity of TiC were identified. The composites exhibit improved mechanical properties with regard to aluminium base alloy. The highest value of the relative increase of yield strength was found in the composite with 50% of moderator due to relatively small TiC particle size, well separated and uniformly distributed in the matrix.