  Composite materials comprising a porous Ti2AlC matrix and Al 6061 alloy were
fabricated by a current-activated pressure assisted melt infiltration process.
Coarse, medium and fine meso-structures were prepared with Al alloy filled
pores of differing sizes. Materials were subjected to uniaxial compressive
loading up to stresses of 668 MPa, leading to the failure of specimens through
crack propagation in both phases. As-fabricated and post-failure specimens were
analysed by X-ray microscopy and electron microscopy. Quasi-static mechanical
testing results revealed that compressive strength was the highest in the fine
structured composite materials. While the coarse structured specimens exhibited
a compressive strength of 80% relative to this. Reconstructed micro-scale X-ray
tomography data revealed different crack propagation mechanisms. Large planar
shear cracks propagated throughout the fine structured materials while the
coarser specimens exhibited networks of branching cracks propagating
preferentially along Al alloy-Ti2AlC phase interfaces and through shrinkage
pores in the Al alloy phase. Results suggest that control of porosity,
compensation for Al alloy shrinkage and enhancement of the Al alloy-Ti2AlC
phase interfaces are key considerations in the design of high performance
metal/Ti2AlC phase composites.
