Dislocations and extended defects in AlN deformed at high temperatures

Polycrystalline AlN could be deformed up to 10% strain in compression at elevated temperatures (1820–1920 K) under constant stress in the range 150–250 MPa or at a fixed strain rate of 5.6 × 10−6 s−1. Stress-strain curves show a marked temperature dependence. TEM investigations point to cavitation at grain boundaries as the main source of damage. Intragranular plasticity is achieved mainly by a-type dislocations. A few dislocations with c + a Burgers vectors could also be observed.