Fracture toughness of cast and extruded Al6061/15%Al2O3p metal matrix composites

This paper reports fracture toughness data on aluminium alloy 6061 reinforced with 15 vol% of Al2O3 particulate of average size 13 mu m. Composites were cast/extruded and heat-treated to give under-aged, peak-aged and over-aged samples, with both longitudinal (L-S) and transverse (T-S) properties being measured to determine the effects on toughness of the banded structure produced via extrusion. This anisotropy was reflected in the toughness results, primarily in the tearing modulus. Comparisons were made to the behaviour of layered/laminated composites where the effects are more dramatic and designed into the structure. This suggests that greater improvements to the fracture critical properties (at least in one orientation) could be obtained by purposely segregating the reinforcement during casting, then extruding/rolling to create a more segregated composite than that tested presently. The current results are compared with those from other similar composites reported in the literature. [GRAPHICS]