The effects of vacancy depletion and solute atom depletion on the microstructural evolution of the precipitation-free zone (PFZ) near the grain boundary have been examined by Monte Carlo simulations with Kawasaki dynamics. The solute depletion caused by a precipitation of stable phase at grain boundaries lead to a well-defined PFZ, whose width grew by a t power law. The average size of precipit...

he role of additives has long been a theme in sintering science. Recently, it has been discovered that ceramics may contain multiple different rain boundary phases (complexions) that are chemically induced by certain additives. These complexions are useful in explaining a number of nomalous phenomena associated with sintering, such as abnormal grain growth. The current work investigates how tra...

Grain boundaries are observed and characterized in chemical vapor deposition-grown sheets of hexagonal boron nitride (h-BN) via ultra-high-resolution transmission electron microscopy at elevated temperature. Five- and seven-fold defects are readily observed along the grain boundary. Dynamics of strained regions and grain boundary defects are resolved. The defect structures and the resulting out...

Free-standing nanocrystalline copper (Cu) films with grain size around 39 nm are fabricated by thermal evaporation and characterized by the plane-strain bulge test. Young’s modulus and yield stress at a 0.2% offset are about 110 ~ 130 GPa and 400 MPa, respectively. Results show that no grain growth is observed and the predominant plastic deformation mechanism is grain boundary sliding accompani...

The microstructural evolution of heavily deformed polycrystalline Cu is simulated by coupling a constitutive model for polycrystal plasticity with the Monte Carlo Potts model for grain growth. The effects of deformation on boundary topology and grain growth kinetics are presented. Heavy deformation leads to dramatic strain-induced boundary migration and subsequent grain fra,omentation. Grain gr...

The structure and properties of grain boundaries in the intermetallic alloy Ni3A1 have received considerable attention in the past several years due to their interesting mechanical properties. The aim in many of these studies [1-13] was to explain the increase in ductility that occurs when polycrystalline Ni3AI is doped with boron. Experimental observations [1-7] have shown that there is a stro...

We have developed a technique that allows all five macroscopically observable grain boundary degrees of freedom to be characterized for a statistically significant number of interfaces. Using this technique, we have characterized 5 x 10 μm of grain boundary plane area in a 0.15 mm volume of MgO. The observations demonstrate that there is significant texture in the distribution of boundary plane...

Atomistic simulations using the embedded atom method were employed to compute the energies of 408 distinct grain boundaries in bcc Fe and Mo. This set includes grain boundaries that have tilt, twist, and mixed character and coincidence site lattices ranging from R3 to R323. The results show that grain boundary energies in Fe and Mo are influenced more by the grain boundary plane orientation tha...

The aim of this chapter is to shed light on the effects of grain boundary segregation on microstructural evolution in nanostructured metallic materials as well as on their mechanical properties. Several key topics will be covered. First, a brief explanation of mechanical stress-driven grain growth in nanostructured Al, Ni, and Cu thin films will be provided in terms of a deformation mechanism m...