Abstract
To investigate the effect of grain size and temperature on the fracture energy (γeff) of polycrystalline alumina ceramics γeff of sintered pure alumina bodies having various grain sizes was measured by work of fracture test from room temberature to 1600°C. At room temperature, γeff of polycrystalline alumina increased and then decreased with increase in grain size of alumina, passing through a maximum at the grain size around 16μm. The values of γeff and its grain size dependence for polycrystalline alumina agreed well with the literature data obtained from work of fracture test. The grain size, which gives a maximum in the γeff values, shifted from 16 to 42μm at 1200°C. γeff of alumina bodies having grain size of 2μm showed no significant variations up to 1200°C, but increased extremely over 1400°C. γeff of alumina bodies having grain sizes of 16, 22 and 42μm passed through maxima at 1000° and 1200°C, and remarkable increases in γeff were observed at 1500° and 1600°C. On the other hand, γeff of an alumina body having grain size of 70μm was smaller than that of other bodies and decreased gradually up to 1500°C and increased at 1600°C.
