In situ processing of TiB2, AIN/Al composites by spontaneous infiltration technique and the hardness of the composites.

Aluminum matrix composites have been fabricated with the help of an in situ reaction between titanium, boron nitride and aluminum in nitrogen or argon gas atmosphere. Microstructures of specimens have been observed to identify the size and the shape of the in situ formed particles. The spontaneous infiltration f the powder phase with molten aluminum have completed at 1473K in both nitrogen and argon atmosphere. The temperature of the specimen increases rapidly just after the infiltration due to a reaction between molten aluminum and titanium powder. The formation of TiB2 and AIN particles occured gradually subsequent to the infiltration fmolten aluminum. The differential thermal analysis has revealed that titanium in liquid phase has been required to initiate the in situ reaciton. The molten aluminum infiltrated into the powder compact at a relatively high rate (3.4mm/s). The higher hardness is achieved at the bottom part of the specimen. The microscopic observation has correspondingly revealed that the higher volume fraction of TiB2 and AIN is obtained at the bottom part.