Fabrication of dense TiB2/[ZrO2-Al2O3] composites with both high hardness (≥20 GPa) and fracture toughness (≥12 MPa·m1/2) simultaneously by pulsed electric-current pressure sintering

In order to produce ceramic composites having both high Vickers hardness Hv ≥20 GPa and high fracture toughness KIC ≥10 MPa·m1/2, dense TiB2/[ZrO2-Al2O3] composites have been fabricated using pulsed electriccurrent pressure sintering (PECPS) at 1873 K under 50 MPa for 6.0 × 102 s in Ar. As the former starting materials, two kinds of TiB2 powders were adopted; i) mono-modal particle size (Ps) distribution with an average particle size <Ps> of 3.24 μm and ii) bi-modal Ps distribution with <Ps> of 3.06 μm, composed of the small Ps of 0.58 and the large Ps of 3.27 μm. On the hand, the latter was the mixed powders composed of ZrO2(2.5 mol%Y2O3) solid solution (ss) and α-Al2O3 powders: each primary Ps was 0.1~0.2 μm. Thus fabricated composites consisting of TiB2, tetragonal/monoclinic ZrO2 and α-Al2O3 with relative densities more than 99.0% showed improved mechanical properties, especially bi-modal TiB2/[ZrO2-Al2O3] composites revealed high Hv of 22.3 GPa and KIC of 12.8 MPa·m1/2. These high-mechanical behaviors might be explained in terms of i) better powder particle configuration, ii) high chemical stability of TiB2, iii) the most proper composition, with adoption of iv) bi-modal TiB2 powder and v) the most suitable sintering condition. ©2019 Japan Society of Powder and Powder Metallurgy.