by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC, Springfield, Va .
Written in English
|Statement||PI, Surendra N. Tewari.|
|Series||NASA contractor report -- NASA CR-208245|
|Contributions||United States. National Aeronautics and Space Administration.|
|The Physical Object|
Tewari and Shah reported macrosegregation along the lengths of 11 small-diameter (7 mm) rods of Pb–Sn alloys (10–58 wt.% Sn) that were directionally solidified in positive thermal gradients (melt on top, solid below, and gravity pointing downward). The results presented here are numerical simulations of the 11 cases using the compositions (C 0), thermal gradients (G), withdrawal Cited by: An investigation into the influence of a transverse magnetic field ( T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows that the field has no influence on the morphology of dendritic. Cruz et al. investigated the wear performance of Al and 20 wt.%Sn alloys samples directionally solidified under solidification cooling rates in the range 1−20 K/s, and reported microstructures, for any examined sample, formed by an Al-rich dendritic matrix with the Sn-rich eutectic mixture distributed along the interdendritic regions. The Author: Ricardo Oliveira, Thiago A. Costa, Marcelino Dias, Camila Konno, Noé Cheung, Amauri Garcia. An investigation into the influence of a transverse magnetic field ( T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows that the field has no influence on the morphology of dendritic arrays. The field does, however, cause severe distortion in the cellular array morphology.
The numerical simulation of macrosegregation formation during the horizontal solidification of a Sn-3 wt%Pb alloy in a rectangular cavity is presented and compared to experimental results. The benchmark experiment consists in solidifying a rectangular ingot of Sn-3 wt%Pb alloy using a solidification setup with a precise control of the thermal. Effects of traveling magnetic field (TMF) on freckle formation of directionally solidified Pb–Sn alloys were investigated experimentally and numerically. The experimental results demonstrated that freckles could form without any magnetic field and with the upward TMF. In . Macrosegregation has been observed in directionally solidified Pb pct Sn alloys, over a range of freezing rates and temperature gradients. The macrosegregation was shown to result from the upward flow of less dense, tin rich, interdendritic liquid during solidification, using radioactive tracer techniques. For comparison, it was shown that macrosegregation occurred in the opposite direction. Applying RMF in a directionally solidified AlSi7Mg alloy, Zimmermann et al. found that the forced flow resulted in axial macro segregation (rich silicon) in the centre part of sample. Meanwhile, Zaïdat et al. reported that a freckled segregation in the directionally solidifying Al– wt%Ni alloy was induced under the influence of TMF .
Macrosegregation along the length of the directionally solidified samples is produced when Pb-Sn alloys (10 to 58 wt pct Sn) are directionally solidified in a positive thermal gradient (melt on top, solid below, and gravity pointing down) with. Thermosolutal convection in the dendritic mushy zone occurs during directional solidification of hypoeutectic lead tin alloys in a positive thermal gradient, with the melt on the top and the solid below. This results in macrosegregation along the length of the solidified samples. been examining macrosegregation in hypoeutectic Pb-Sn alloys, directionally solidified in a positive thermal gradi- ent, the melt on the top and the solid below. Under such growth conditions, the temperature profile alone is expected to be stabilizing against natural convection. However, the. In this article, gravity-driven flow and its subsequent effect of promoting macrosegregation during unidirectional solidification of dendritic alloys is presented. Examples of macrosegregation that arise during the controlled directional solidification of hypo- and hypereutectic Pb-Sn alloys are shown, and a method of preventing macrosegregation is demonstrated.