Method for reducing macrosegregation in alloys

Macrosegregation in metal alloy castings and other alloys having similar solidification behavior is reduced by slowly rotating a mold or the like containing the liquid alloy about an axis at an acute angle to the vertical from the time the liquid alloy is poured into the mold until substantially all of the alloy has solidified. The mold is rotated at a speed below that which produces a centrifuging effect or causes stirring or agitation of the interdendritic liquid.https://digitalcommons.mtu.edu/patents/1116/thumbnail.jp

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

Experiments with constrained chimney-plume flows in the system ammonium chloride-water: Comparison with the unconstrained case

Thermo-solutal chimney-plume flows from a solidifying dendritic mushy region have been promoted in thin-walled glass tubes of internal radii from 0.3 mm-2.0 mm. Flow rates, liquid compositions and temperatures were measured as functions of the depth of immersion of capillary tubes in the advancing mushy region. The results demonstrate competition between buoyancy pressures and the restrictions of liquid recirculation within the dendritic array and have been analysed to provide permeability data for the mushy region at high liquid fractions. These data have been used to take some assessments of channel/plume dimensions for naturally occurring, unconstrained flows in the same system

Using fractal analysis to describe irregular microstructures

Some complex microstructures defy description in terms of Euclidean principles. Fractal geometry, however, can make numerical statements about any shape or collection of shapes, however irregular and chaotic they may seem. To better understand the potential of this method, the following presents examples of fractal analysis as applied to the characterization of metallographic images. © 1995 TMS

Growth mechanisms of silicon in Al-Si alloys

Eutectic silicon in Al-Si alloy has been examined by optical, SEM and TEM methods. Normal flake silicon grows anisotropically and has a low twin density; quench modified fibrous silicon is essentially twin free and grows isotropically (non-faceted); sodium modified silicon contains a very high twin density and the fibers are somewhat faceted. It is concluded that in the absence of sodium, molecular attachment by the TPRE mechanism is incidental but in the presence of sodium this is the dominant growth mechanism. Various aspects of the modification mechanism are discussed. © 1985

Dendritic array growth in the systems NH \u3c inf\u3e 4 Cl-H \u3c inf\u3e 2 O and [CH \u3c inf\u3e 2 CN] \u3c inf\u3e 2 -H \u3c inf\u3e 2 O: Dendrite tip behavior and the origin of side arm evolution

Dendrite side arms evolve from perturbations behind primary dendrite tips and develop with exponentially increasing amplitudes before coalescence and ripening begin. Measurements of the spacings and amplitudes of these initial perturbations extrapolate to small finite displacements at the primary tips, compatible with small oscillatory fluctuations in the mean growth velocity. The frequency of these oscillations correspond to the initial side arm spacings and this oscillatory mode is an intrinsic characteristic of dendritic growth. © 2002 Elsevier Science B.V. All rights reserved

Directional solidification and microstructural evolution between diopside and anorthite in the system CaO-MgO-Al \u3c inf\u3e 2 O \u3c inf\u3e 3 -SiO \u3c inf\u3e 2

Silicate mixtures close to the diopside-anorthite tie line have been unidirectionally solidified by float-zone melting in an arc image furnace and the microstructures examined by optical microscopy, scanning electron microscopy, electron microprobe analysis and from electron backscatter patterns. The structures which evolved have been interpreted by reference to available phase diagram data for the anorthite-diopside eutectic surface within the four-component oxide system, CaO-MgO-AOa-SiC. It is demonstrated how the microstructures and segregation paths can be described in a visually explicit way within the quaternary system. The morphologies of primary diopside, anorthite and the eutectic mixture are described and discussed. In this silicate system the low liquid diffusion rates lead to glass formation at rapid cooling rates and at temperatures close to the freezing point, so that local equilibrium is only partially realized. The consequences are interpreted with reference to the quaternary phase diagram. © 2000 The Royal Society

Dendritic array growth in the systems NH \u3c inf\u3e 4 Cl-H \u3c inf\u3e 2 O and [CH \u3c inf\u3e 2 CN] \u3c inf\u3e 2 -H \u3c inf\u3e 2 O: The detachment of dendrite side arms induced by deceleration

Dendrite array adjustments have been measured in transparent material during the transient conditions attending deceleration. There is considerable hysteresis between the responses of dendrite tip radii and primary spacings to velocity changes and this promotes the dissolution of the necked regions, where side arms attach themselves to primary stems. Simple analyses of the transient dendritic dimensions are offered to illustrate a detachment mechanism. This phenomenon is relevant to the development of an equiaxed zone in metal castings. © 2002 Elsevier Science B.V. All rights reserved

Dendritic array growth in the systems NH \u3c inf\u3e 4 Cl-H \u3c inf\u3e 2 O and [CH \u3c inf\u3e 2 CN] \u3c inf\u3e 2 -H \u3c inf\u3e 2 O: Steady state measurements and analysis

Dendrite array dimensions have been measured under steady state growth conditions in the transparent material systems, ammonium chloride-water and succinonitrile-water. The measurements were made as functions of growth rate, V, and temperature gradient, G, and the results compared with the current analysis of Hunt and Lu. Close agreement with the analysis was found for the system [CH2CN]2-H2O, but less so for the system NH4Cl-H2O in which the volume fraction of solid is very small. The data are presented as a reference base for subsequent examination of array behavior under transient conditions following deceleration. © 2002 Elsevier Science B.V. All rights reserved