Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and single crystal (SX) hollow turbine blades. In order to investigate the location of freckle occurrence in ...

A 3-D model of freckle (solute channel) formation at a microstructural level was coupled with in situ X-ray radiography to investigate the mechanisms of freckle initiation and growth. The model predictions for solute partitioning, diffusion and convection were validated via in situ X-ray radiographic measurements in Ga–25 wt.% In alloy, showing good agreement. Other key features, such as freckl...

An unexpected difference between online and offline algorithms is observed. The natural greedy algorithms are shown to be worst case online optimal for Online Independent Set and Online Vertex Cover on graphs with “enough” isolated vertices, Freckle Graphs. For Online Dominating Set, the greedy algorithm is shown to be worst case online optimal on graphs with at least one isolated vertex. These...

The formation of macroscopic grain defects during the directional solidification of single crystal Ni-base superalloys can have a significant impact on resulting fatigue and creep properties of critical structural components used in a variety of aerospace applications and gas turbines for power generation. Common casting defects in Ni-base superalloys include freckles, Figure 1, which consist o...

BACKGROUND We sought by use of an adult twin study to investigate the relative contribution of genetic and environmental effects on the expression of nevi and freckles, which are known risk factors for melanoma, and to determine if age and sun exposure influence the heritability of nevi. DESIGN AND METHODS Total nevus and freckle counts were conducted on 127 monozygotic twin pairs and 323 diz...