Investigation Of Indentation Size Effect And Creep Properties

In recent years, with the rapid development of the preparation method for materials, more and more low-dimensional samples such as thin films, nanowires, nanoparticles, are prepared. These small-scale materials are getting more and more attentions for their distinguished properties from the corresponding bulk materials. And just because of the small scale and special properties, the low-dimensional materials are gradually applied in the engineering.The mechanical properties are the foundation for materials'reasonable design and safely effective application. Along with the fast development of small-scale materials, to characterize their special mechanical features is becoming a hotspot. For their small scale, traditional methods are no longer valid to measure the mechanical properties. The newly developmental technique nanoindentation is now widely used to characterize the small-scale materials'mechanical properties because this new method is of many advantages like the simple operation and sample preparation, high resolution, real-time monitoring and vastly data gathering ability.The major task of this paper is to study the method that characterizing the electrodeposited nickel films'mechanical properties by nanoindentation. The whole work is made up by the following two parts:1. The low-load and high-load indentation tests are carried out and the indentation data at different depth from about 0.5% to 3 times of the flim thickness are gathered. According to the change of hardness with the indentation displacement, we divide the whole thickness of the flim/substrate material into three parts: the indentation size-effect range, the transitional range and the substrate-guiding range. On the basis of the Nix-Gao model, the real hardness of the flim is calculated out to be about 6.2 GPa during the indentation size-effect range.2. The creep behavior is studied by changing the loading rate, holding time or unloading rate. According to the indentation results, we find that the hardness and Young's modulus vary largely due to the change of loading rate or holding time , but the influence of unloading rate to those two material parameters is not sensitive.