In this paper, through a systematic statistical analysis of the characteristics of the serrated yielding, including the stress drop amplitude and the drop duration, etc., the difference between the results of thinner samples (1mm and 2mm) and those of thicker samples (3mm), has been reported. The size effect in Portevin-Le Chrtelier (PLC) effect also manifests itself in the difference of PLC types of jerky flow of 1mm or 2mm thick samples and those of 3mm thick samples under the same experimental conditions. Moreover, the geometrical characteristics of attractor of the former series in phase space are described by using methods of nonlinear time series analysis, and chaotic behavior is proved to exist in these series through the application of principal component analysis. The distribution of stress drops of the latter is found to follow a power-law distribution, which is referred to as the signature of self-organized criticality phenomenon.