Residual stresses generated during joining of dissimilar alumina–zirconia composites by plastic deformation and its implications on mechanical properties

Ceramic bars of zirconia toughened–alumina composites were fabricated by pressureless sintering in air at 1450 °C for 4 h. Composite samples were fabricated with two different compositions: zirconia with 60 vol.% alumina (ZT60A) and zirconia with 40 vol.% alumina (ZT40A). Average four-point-bend strengths for the ZT40A and ZT60A were 480 ± 45 MPa and 410 ± 120 MPa, respectively. Three-layered sandwich structures were fabricated by joining two bars of sintered ZT60A with a sintered ZT40A bar. High-temperature plastic joining was accomplished at 1350 °C at a strain rate of 5 × 10−6 s−1 and a compressive stress ranging from 30–40 MPa. Bend tests conducted on the layered structure exhibited average strengths of 707 ± 81 MPa. Strength enhancements for the multilayered structure were higher than those predicted by stress analysis. Stress enhancements were compared with the residual stresses measured in the layered sample using X-ray micro-diffraction at the Advance Photon Source (APS). Scanning electron microscopy (SEM) was also conducted to identify the location of failure causing flaws.