Formation of stray grain defects particularly around re-entrant features of the turbine blade airfoils is one of the major problems in directional and single crystal solidification processes. In this work, directional solidification tests of the GTD-111 Ni-based superalloy were conducted at different withdrawal velocities of 3, 6 and 9 mm.min-1 using various stepped cylindrical and cubic design...

An ultrafine grain surface layer with average crystallite size of 28 nm was produced on annealed mild steel through a wire brushing process. The effects of grain size reduction on the inhibition performance of sodium phosphate were investigated using polarization and electrochemical impedance spectroscopy (EIS) measurements. The crystal grain size of wire brushed surface was analyzed by X-ray d...

A theoretical model for describing effective thermal conductivity (ETC) of nanocrystalline materials has been proposed, so that the ETC can be easily obtained from its grain size, single crystal thermal conductivity, single crystal phonon mean free path (PMFP), and the Kaptiza thermal resistance. In addition, the relative importance between grain boundaries (GBs) and size effects on the ETC of ...

Thin fi lms with microcrystalline and nanocrystalline grains are used in MEMS and thin fi lms for electronics. These systems have mechanical properties that depend on the microstructure. Grain size is frequently reported only as mean values or bounds. It has been demonstrated, however, that a mean grain size value is insuffi cient to describe the microstructure of these materials and the result...

Gallium nitride light emitting diodes were deposited on a sapphire substrate that was pre-patterned with an ordered two-dimensional structure. The size and arrangement of the substrate surface pattern was designed to increase the diffraction and extraction of light from the device as well as define the grain size and thus dislocation density of the GaN crystal. A close-packing of self-assembled...

Acoustic emission experiments were performed on polycrystalline and single crystal 99.990/0 aluminium while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single di...

A systematic approach has been followed in the production and characterization of Pd foils to be used in excess heat production experiments [1][ 2] . Starting with a metal foil as supplied, palladium samples have been fabricated and characterized in a step by step process, and then subjected to electrolysis deuterium loading. The characterized metallurgical properties include the main grain siz...

We perform atomistic Monte Carlo simulations of bending a Lennard-Jones single crystal in two dimensions. Dislocations nucleate only at the free surface as there are no sources in the interior of the sample. When dislocations reach sufficient density, they spontaneously coalesce to nucleate grain boundaries, and the resulting microstructure depends strongly on the initial crystal orientation of...

manufactured single crystal components using ni-base super alloys are routinely used in the hotsections of aero engines and industrial gas turbines due to their outstanding high temperaturestrength, toughness and resistance to degradation in corrosive and oxidative environments. tocontrol the quality of the single crystal turbine blades, particular attention has been paid to grainselection, whi...