Structure and Mechanical Behavior of Bulk Nanocrystalline Materials

摘要: The reduction of grain size to the nanometer range (˜2-100 nm) has led many interesting materials properties, including those involving mechanical behavior. In case metals, Hall-Petch equation, which relates yield stress inverse square root size, predicts great increases in strength with refinement. On other hand, theory indicates that high volume fraction interfacial regions leads increased deformation by grain-boundary sliding metals low end nanocrystalline range. Nanocrystalline ceramics also have desirable properties. Chief among these are lower sintering temperatures and enhanced strain failure. These two properties acting combination allow for some unique applications, such as low-temperature diffusion bonding (the direct joining each using moderate pressures). Mechanical sometimes affected fact a fine-grained form stable different (usually higher pressure) phase than is considered “normal” ceramic. To extent ceramic dependent on its crystal-lographic structure, differences will become evident at smaller scales.It uncertain how takes place very materials. It been recognized time relationship, usually explained basis dislocation pileups boundaries, must break down sizes cannot support pileup. Even basic assumptions may no longer be appropriate this regime. Recently considerable progress made simulating behavior extremely under molecular-dynamics techniques. Molecular-dynamics (MD) simulations nanophase Ni Cu were carried out temperature 300–500 K, constant applied uniaxial tensile stresses between 0.05 GPa 1.5 GPa, samples average ranging from 3.4 nm 12 nm.