Hardening Mechanism for Nano-multilayer Films

The study of the hardening mechanism for the nano-multilayer films is the foundation for the preparation of those films. Several different models were proposed to interpret the super-hard effect in the nano-multilayer films, though they cannot interpret all the phenomena in those films. The progress of the research on the superhardness effect in the nano-multilayer films was reviewed. It shows that all the mechanisms are related to the movement of the dislocation. The difference of the elastic modulus between the two materials plays the important role for the superhadness effect in the nano-multilayer films, while the alternated strain field plays the less important role. The developmental directions and the problems for the nano-multilayer films were also discussed.