Residual stresses in particulate composites with alumina and zirconia matrices
Zbigniew Pędzich, Grzegorz Grabowski Akademia Górniczo-Hutnicza, Wydział Inżynierii Materiałowej i Ceramiki, Katedra Ceramiki Specjalnej, al.Mickiewicza 30, 30-059 Kraków
Quarterly No. 2, 2006 pages 76-80
DOI:
keywords: composites, residual stresses
abstract The paper summarized calculation of typical stresses caused by the coefficients of thermal expansion (CTE) mismatch in particulate composites with alumina and zirconia matrices containing tungsten carbide and metallic tungsten. Differences in local stress distribution due to matrix and inclusion kind were established (Figs. 3-6). The FEM simulations were compared with results of mechanical tests on mentioned composites (Table 1). Conclusions were assisted by SEM analyze of true composite microstructures, especially focused on a crack path near the interphase boundaries (Figs. 7-10). It was established that the effective improvement of fracture toughness in alumina-based composites is larger than in zirconia-based ones. This fact could be connected with stress state in the materials which influenced the way of cracking. In zirconia-based materials crack is deflected directly on inclusion grains, probably due to extremely high tensile stress value in the interphase boundary area). In materials with alumina matrix crack is deflected before it reaches the interphase boundary. Such way of cracking assures more effective fracture toughness improvement. Observations presented in the paper are only qualitative, but they could help to understand the effect of relatively high level of toughening in alumina based composites.