High strength TiC matrix Fe28Al toughened composites prepared by spontaneous melt infiltration

Fe28Al bound TiC matrix composites with TiC content of 75-90% in volume (vol.%) were successfully fabricated by spontaneous melt infiltration. Amounts of Fe28Al in excess and below the pore volume of the TiC preform were used for optimization of fabrication techniques. Young's modulus, hardness, flexural strength and fracture toughness of the composites were measured. Four-point bending strength of Fe28Al/90-75 vol.% TiC ranges to 990-1260 MPa. The high strength is attributed to the good infiltration ability of molten Fe28Al in the porous TiC preform and to processing refinements. TiC preform pre-sintering and indirect infiltration all lead to fully dense and defect-free composites. The relationship between Vickers hardness and indentation fracture toughness and the dependence of mechanical properties on microstructure of the composites were also studied. Results of SEM and XRD analysis show TiC and Fe28Al as the only crystalline phases of the composite. Fe28Al ligaments have ductile behaviour and greatly toughen the composites. Crack front deviation during fracture also increased the fracture resistance of the composites.