Machined alumina containing 20 vol% SiC whiskers have been subjected to various heat-treatments. The effect on local fracture stress has been investigated as a function of crack-healing temperature and time. By heating at 1673 K for 10 h, the machined specimen was fractured not from the cracks introduced by the hard machining but from the other region. Thus, it was concluded that the machining cracks were completely healed by this heat treatment. Moreover, the strength at elevated temperatures of the healed samples exhibited similar properties to the healed polished samples. It can be demonstrated that the crack-healing was useful for an increase in the strength of machined ceramics economically.
