Atsushi Chino

Mechanical Properties and Microstructures of Tib 2 -ZrO 2 -SiC Fabricated by Hip

Ceramic TiB2 composites with up to 40wt% of ZrO2, 2mol%Y2O3-ZrO2 or 2.5wt%SiC were fabricated by hot isostatic pressing (HIP) both with and without glass encapsulation. The effects of these additions on the mechanical properties and microstructure of TiB2 were investigated. The addition of ZrO2 or 2mol%Y2O3-ZrO2 was very effective in improving the 3-point bend strength of TiB2. The 3-point bend strengths of TiB2 with 10wt% ZrO2 and TiB2 with 10-20wt% (2mol%Y2O3-ZrO2) were 1160-1200MPa, which is three times higher than that of monolithic TiB2 (450MPa). The 3-point bend strength was dependent on the monoclinic Z1O2 content in the HIPed composite. To obtain high strength HIPed materials with strengths greater than 1000 MPa, the content of monoclinic ZrO2 must be less than 10wt%. The fracture toughness was also affected by the addition of Z1O2 or 2mol%Y203- ZrO2. The fracture toughness of TiB2 with 30wt%ZrO2 was 8.2MPam1/2. TiB2 with ZrO2 and TiB2 with (2mol%Y2O3-ZrO2) lacked sinterability. The addition of 2.5wt%SiC was very effective in improving the sinterability of TiB2 with (2mol%Y203-ZrO2). The mechanism of sinterability improvement was thought to be liquid phase sintering.