Fracture mechanical behavior of fine-grained carbon-bonded alumina at room and high temperature

Abstract

The fracture mechanical properties of fine-grained carbon-bonded alumina (Al2O3–C) were investigated in four-point bending tests at single edged V-notched beams (SEVNB) at room and high temperature. Graphite served as a reference material. For measurement of the crack mouth opening displacement (CMOD) an optical system was used. The fracture behavior of Al2O3–C changed from brittle at room temperature to a crack resistance behavior at 1400 °C due to visco-plastic phenomena. The fracture toughness KIc was determined as 0.69 ± 0.07 MPa m1/2 at room temperature and 0.55 ± 0.21 MPa m1/2 at 1400 °C. At room temperature, the work of fracture γwof was determined as 26.3 ± 6.3 J/m2, and Hasselman's thermal shock parameters Rst and R'''' were 8.6 K m1/2 and 0.9 mm, respectively. Although a quantitative analysis of the work of fracture at 1400 °C was hindered by heat shimmer within the chamber, the results indicated significant increases of this parameter as well as Hasselman's thermal shock parameters up to 1400 °C.