Simultaneous synthesis and densification of Ti5Si3 and Ti5Si3–20 vol% ZrO2 composites by field-activated and pressure-assisted combustion

A method to simultaneously synthesize and consolidate the silicide Ti5Si3 and the composite Ti5Si3–20 vol% ZrO2 from powders of Ti, Si, and ZrO2 was investigated. Combustion synthesis was carried out under the combined effect of an electric field and mechanical pressure. The final density of the products increased nearly linearly with the applied pressure. Highly dense Ti5Si3 and Ti5Si3–20 vol% ZrO2 with relative densities of up to 98% were produced under the simultaneous application of a 60 MPa pressure and a 3000 A current on the reactant powders. The percentages of the total shrinkage occurring before and during the synthesis reaction were 22 and 78% for the case of Ti5Si3, and 18 and 82% for the case of Ti5Si3–20 vol% ZrO2, respectively. The respective Vickers microhardness values for these materials were 8.5 and 6.0 GPa. From indentation crack measurements, the fracture toughness values for Ti5Si3 and Ti5Si3–20 vol% ZrO2 were calculated to be 3 and 9 MPa m1/2, respectively.