PROPERTY-MICROSTRUCTURE CORRELATION IN IN-SITU FORMED AL2O3, TIB2 ANDAL3TI MIXTURE-REINFORCED ALUMINUM COMPOSITES

The in situ formed Al2O3, TiB2 and Al3Ti mixture-reinforced aluminium composites were successfully fabricated by the reaction sintering of t he TiO2-B-Al system in a vacuum. With increasing boron content in the TiO2-B-Al system, the amount of generated TiB2 in the composites incre ased and Al3Ti content decreased. At the same time the distribution un iformity of the in situ formed Al2O3 and TiB2 particulates was obvious ly improved, and the size of the Al3Ti particles was reduced. The in s itu Al2O3 and TiB2 particulates had sizes from 0.096-1.88 mu m The int erface between the in situ formed particulates and the aluminium matri x was clean, and no consistent crystallographic orientation relationsh ip was found. The strength and elastic modulus of the composites was s ignificantly improved by lowering the AI,Ti content. When the boron co ntent in the TiO2-B-Al system rose, the morphology of the tensile frac ture surface of the composites was changed from large fractured Al3Ti blocks and fine dimples, to fine dimples and pulled-out particulates. The strengthening and fracture of the composites have been modelled.