Temperature dependence of mechanical properties of alumina up to the onset of creep

Mechanical properties of a commercial polycrystalline alumina are evaluated as a function of temperature up to the onset of creep. Hertzian indentation tests in combination with finite element modelling (FEM) are used to determine its elastic and plastic properties from the corresponding indentation stress–strain curves at prescribed temperatures up to 1200 °C. The results reveal a strong decline in the Young's modulus and the yield stress of the material at about 600 °C that is attributed to grain boundary degradation occurring around that temperature. The results are compared with dynamic Young's modulus and Vickers hardness measurements from the literature. The practical interest of measuring the mechanical properties of ceramics at intermediate temperatures is discussed and a general guideline to retain optimum elastic and plastic properties at intermediate temperatures is outlined.