To investigate the effect of grain size and temperature on the fracture energy (γ
eff) of polycrystalline alumina ceramics γ
eff 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, γ
eff 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 γ
eff 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 γ
eff values, shifted from 16 to 42μm at 1200°C. γ
eff of alumina bodies having grain size of 2μm showed no significant variations up to 1200°C, but increased extremely over 1400°C. γ
eff of alumina bodies having grain sizes of 16, 22 and 42μm passed through maxima at 1000° and 1200°C, and remarkable increases in γ
eff were observed at 1500° and 1600°C. On the other hand, γ
eff 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.
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