Kinetics of Phase Change in Explosively Shock-Treated Alumina

The effect of shock treatment on the kinetics of transformation of transition-phase alumina has been examined. Alumina powder, consisting of spherical particles produced by melting and quenching, was shock-treated at 13- to 26-GPa maximum pressure and subsequently heat-treated at 1000° and 1050°C for various times. At 1050°C, the transformation of unshocked powder was typical of other aluminas with an incubation period of 60 min before significant conversion occurred. In contrast, in the shock-treated material, no incubation period was observed and the α-phase content increased exponentially with time. The growth kinetics of the shocked powder corresponded to a linear growth process with an activation energy of 482 kJ/mol. TEM examination revealed α-phase morphologies consistent with linear growth.