Behavior of cordierite materials under mechanical and thermal biaxial stresses

TOMBA, A.G.; CAMERUCCI, M.A; URRETAVIZCAYA, G.; CAVALIERI, A.L.

British Ceramics Transactions

Maney

Año: 2002 vol. 101 p. 94 - 99

0967-9782

commercial cordierite powder (impurities level < 0.17 wt-%) was selected to study the material behaviour under mechanical and thermal stresses. Disks were slip casted, sintered for 2 h 1450 °C and indented (Vickers; 44.1 N) at the centre of the surface to be subjected to mechanical and thermal shock tests. The sintered bodies (84 wt-% cordierite, 10 wt-% mullite, and 6 wt-% glass) reached 95% of the theoretical density. The microstructure consisted of homogeneous, mainly equiaxed, grains (mean size » 0.5 µm) and a few elongated grains (aspect ratio » 1.9). A glass phase was identified at triple points and intergranular pores (< 10 µm) and a few isolated larger pores (up to 40 mm) were observed. The fracture strength (sF) was measured by biaxial flexure, employing a ball on discontinuous ring configuration with displacement control (0.05 mm.min-1). In each thermal shock test, the indented specimen was heated up to a selected temperature and suddenly cooled on the disk centre using a high-velocity air jet at room temperature. The initial temperature was increased by increments of 10 °C until crack propagation was detected and the value of the thermal shock resistance (DTC) was evaluated. The values obtained were compared with cordierite disks without indents and with alumina materials. The fracture features of the specimens broken in both mechanical and thermal shock tests (crack patterns and fracture surfaces) were characterised taking into account the developed microstructures (grains, phases, pores) and the controlled size defect introduced by indentation which was the fracture origin.