The experiments described in this paper have been designed to understand how particular dopants in alumina (Ca, Mg, Si, and Y) affect microstructural development through the energetics of their associated precipitates. Specifically, the role of the interphase boundary energy and precipitation activation energy are considered to be in competition with grain boundary complexion (disorder) transit...

The effects of boron on the grain boundary and surface energies in iron at 900 and 1000 OC and AISI 316 stainless steel in the temperature range 950-1 250 OC were investigated. It was found that boron reduced these energies in a manner typical of an element with low solubility in the matrix. It has been found that boron improves the grain boundary strength of iron at low temperatures [I] and in...

The beneficial effect of boron on the mechanical properties of austenitic stainless steels is well documented [1, 2]. A number of studies have confirmed that boron segregates to grain boundaries, in a variety of steels and nickel-base alloys (for example, [3, 4, 5]). Segregation of boron is known to occur via two mechanisms (for example, [1]): Equilibrium segregation is caused by the high bindi...

Grain boundaries in polycrystalline magnesia-doped alumina and yttrium aluminum garnet were classified as growing in area or shrinking in area on the basis of topology and curvature considerations. Measurements of dihedral angles at grain boundary thermal grooves were used to determine that the energies of the growing boundaries are, on average, lower than the energies of the shrinking boundari...

Fatigue tests have been conducted on an advanced disc Ni-based superalloy (Low Solvus, High Refractory (LSHR) alloy) at 650 C in air under three-point bend loading to investigate the role of orientation-dependent grain boundary oxidation in crack initiation and early propagation. It is found that crack initiation occurs mainly from bulged grain boundary oxides, and cracks then predominantly pro...

A mesoscopic model of a diblock copolymer is used to study the motion of a grain boundary separating two regions of perfectly ordered lamellar structures under an oscillatory but uniform shear flow. The case considered is a grain boundary separating lamellae along the so called parallel orientation (with wavevector parallel to the velocity gradient direction) and along the transverse orientatio...

in this study, the effect of grain size on nitrogen diffusion into ck45 has been investigated. in order to obtain different grain sizes, samples were annealed and normalized at various temperatures and durations.the grain size was determined with clemex vision software. then, the specimens were exposed to dc plasma nitriding treatment and again analyzed by optical microscope ,scanning electron ...

The half-integer quantum Hall effect (QHE) is often suppressed in graphene grown by chemical vapor deposition on metals. The reason behind the suppression is unclear, and we hypothesize that it might be connected to extended defects in the material. In this paper we present results for the quantum Hall effect in graphene with [0001] tilt grain boundaries connecting opposite sides of Hall bar de...

This brief review describes the major features of grain boundary mobility in metals and current limitations in our theoretical understanding. Although thermally activated exchange of atoms across boundaries provides a basic picture of grain boundary correct to within an order of magnitude, no refinement of this theory is available that accounts for the experimental characteristics of grain mobi...

The segregation of native defects and Bi impurities to a high-angle grain boundary in ZnO is studied by first-principles calculations. It is found that the presence of Bi(Zn) increases the concentration of native defects of acceptor type in the grain boundary. This leads to the formation of a Bi(Zn)+V(Zn)+O(i) interfacial complex under O-rich conditions and exhibits a localized acceptor state. ...