Dense WSi2 and WSi2-20 vol.% ZrO2 composite synthesized by pressure-assisted field-activated combustion

The simultaneous synthesis and consolidation of WSi2 and WSi2-20 vol.% ZrO2 from elemental powders of W, Si, and ZrO2 additive was investigated. The synthesis was carried out under the combined effect of an electric field and uniaxial pressure. The final density of the products increased nearly linearly with the applied pressure in the range 10 to 60 MPa. Highly dense WSi2 and WSi2-20 vol.% ZrO2 with relative densities of up to 98.0% were produced with the application of a 60 MPa pressure and a 3000 A DC current. The percentages of the total shrinkage occurring before and during the synthesis reaction were 17.5 and 82.5% for the case of WSi2, and 25.8 and 74.2% for the case of WSi2-20 vol.% ZrO2, respectively. The respective Vickers microhardness values for these materials were 8.2 and 10.6 GPa. From indentation crack measurements, the fracture toughness values for WSi2 and WSi2-20 vol.% ZrO2 were calculated to be 3.2 and 9.4 MPa m(1/2), respectively. (C) 2001 Elsevier Science B.V. All rights reserved.