Nano Mechanical Characterization and Physical Modeling of Plastic Deformation Chapter 2: Strengthening Mechanisms by Various Lattice Defects

Mechanical behaviors of metallic materials in a small scale are characterized and physically modeled based on experimental measurements and computational simulation. An effect of in-solution carbon or silicon in Fe on a plasticity initiation was characterizes by nanoindentation pop- in phenomenon. A coherency at a ferrite-cementite interface significantly affects to a plasticity initiation leading to a different macroscopic yielding behavior. A stability of an austenite phase in TRIP steel was evaluated though the analysis of indentation-induced deformation behavior, demonstrating a significant constraint effect on stabilization by an adjacent harder phase. Heterogeneous microstructures with a bimodal grain size in fcc metals show an inhomogeneous mechanical behavior depending on a location of the fine microstructure. An intermittent plasticity in pure iron was analyzed through a statistical model showing a Gaussian function by thermally activated process in the early stage and a power-law one by an avalanche type phenomenon in the subsequent stage. An elementally step in a plastic deformation in a metallic glass was characterized through Molecular Dynamics simulation indicating that the plasticity inhomogeneity depends remarkably on the initially inhomogeneous atomistic structure.