Studies On Rheologic Mechanical Properties Of Metallic Thin Films

Recently, more and more attentions have been paid to thin films, and research of the mechanical properties of thin films gets to be a hot field. But mechanical properties of thin films are different from those of bulk materials under loading condition. Therefore, it is necessary to study mechanical properties of thin film materials under different load conditions.As a method to evaluate the mechanical properties of thin films, nanoindentation technique is in the popularity for its high displacement resolution, ultra low load and the capability of continuous measurement. The methods of deducing the material con-stitutive equation include the theory of component model, integral equations, yield surface and so on. The method of the component model was used in this paper. Model components include elastic,Plastic and viscous one. In this thesis, the rheologic me-chanical properties of thin films were measured by rheologic theory and research methods combined with the nanoindentation.In this paper, the author take electro deposited nickel thin films for example. Ex-perimental research of the thin films'mechanical properties and theoretical analysis of the material constitutive are the main work of this dissertation. Rheologic mechanical properties were conducted on electro deposited nickel thin films with nanoidetation instrument at room temperature. Based on investigating the commonly mechanical properties of thin films, some correlative researches were done on electro deposited nickel thin films, through analysis of the creep curve results, which received from creep experiment under different load conditions. An appropriate rheological model name improved Burgers model has been found to fit the curve of rheology test. De-rived the integral creep constitutive equation and differential stress-strain constitutive relationship, and presented the testing optimum parameters of the constructed model. The results indicated that experimental curves agree with the typical rheological ones. Figured out the integral kernel of the creep, and the relaxation kernel has also been de-rived by the Laplace transformation. We have tested the relaxation behavior of electro deposited nickel thin films in different displacement conditions, and after comparison, founding that there has the same relaxation rate at the same time. Discussed the equivalence of creep and relaxation experiment, and the creep curve which from ex-periment under different load condition can be converted to relaxation curve.