Grain growth suppression of ZTA by multi-step sintering

Abstract Effect of two-step sintering of Zirconia Toughened Alumina (ZTA) on microstructure and mechanical properties were studied in the present work. Al2O3 and 3YSZ nanoparticles were mixed by high speed vibrating mill, and powders were compacted by a uniaxial pressing protocol at 150 MPa, and sintered through both conventional sintering schedule (CSS) and two-step sintering (TSS) schedules. The composition containing 95 wt% Al2O3 and 5 wt% 3YSZ sintered at two-step sintering (TSS-2; 1600 °C/10 min followed by 1500 °C/6 h) exhibits higher Vickers hardness (1835 HV), fracture toughness (4.95 ± 0.1 MPa.√m), compressive strength (900 MPa) and Diametral tensile strength (125 MPa), respectively. The ZTA composite shows relative density 99.2% with grain size 4.5 µm during CSS at 1600 °C for 4 h. However, the TSS-2 facilitates to achieve relative density 98.4% consist of 1.4 µm alumina grain size that eventually experiences ∼21% fracture toughness increment through zirconia phase assisted transformation toughening.