Effect of annealing process on atomic-scale structure,dislocation and mechanical behaviour of nano-grained Al–Cr–N thin films

Although Al–Cr–N films have excellent oxidation resistance, they also need to have matched mechanical properties. Both the oxidation resistance and mechanical property are essentially determined by microstructure. At present, atomic-scale microstructures of Al–Cr–N films are scarce due to the difficulty of tracing the evolution of nanocrystalline grains, dislocation annihilation and mechanical properties. In this work, atomic-scale structure, phase transformation and dislocation behaviour in Al–Cr–N films were studied by high-resolution transmission electron microscope. The grain size showed no obvious variation when the annealing temperature is lower than 1000°C, but it increased from ∼5 to ∼50 nm when the temperature approached up to 1100°C. Edge dislocations in the deposited films disappeared after the obtained samples were heated. Mechanical properties showed no obvious fluctuations as the temperature was lower than 800°C.