Mechanical properties and fracture behaviour of TixAly(O)/Al2O3 composites

The TixAly(O)/Al2O3, (alpha-Ti(Al,O)/Al2O3, Ti3Al(O)/Al2O3, TiAl(O)/Al2O3) metal-ceramic composites with different microstructures have been synthesized by using a complex combination of high energy mechanical milling, thermal treatment and powder consolidation process. It has been found that the mechanical properties of the composites were strongly affected by the coarsening of Al2O3 particles. The bending strength of the TixAly(O)/Al2O3 composites with small Al2O3 particles size is much higher than that of the composites with large Al2O3 particles. The bending strength of the composites increased with decreasing the volume fraction of Al2O3 particles. It was found that large particle size and high volume fraction of Al2O3 particles are favourable for achieving high hardness of the materials. The fracture toughness of TixAly(O)/Al2O3 composites is comparable to that of typical ceramic materials, due to the relative high oxygen content in the TixAly metallic matrix. The failure of the composites was dominated by transgranular fracture of TixAly(O) metallic phase and Al2O3 particles.