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.

Automated summary

The mechanical behaviors of metallic materials at small scales were studied using experimental measurements and computational simulation. The effect of in-solution carbon or silicon on plasticity initiation in iron was analyzed and characterized through nanoindentation pop-in phenomenon. The coherency at a ferrite-cementite interface significantly influenced plasticity initiation and macroscopic yielding behavior. The stability of austenite phase in TRIP steel was evaluated by analyzing indentation-induced deformation, revealing a constraint effect by an adjacent harder phase. Heterogeneous microstructures with bimodal grain size in fcc metals exhibited inhomogeneous mechanical behavior depending on the location of the fine microstructure. The plasticity of pure iron was analyzed using a statistical model, showing a Gaussian function in the early stage and a power-law function in the subsequent stage. Molecular Dynamics simulation characterized the elemental steps in plastic deformation of metallic glass, indicating that plasticity inhomogeneity depends on the initially inhomogeneous atomistic structure.