NASA Technical Reports Server (NTRS) : Influence pdf

NASA Technical Reports Server (NTRS) : Influence

More Book Details

Description of the Book:

The influence was studied of convection during directional solidification on the resulting microstructure of eutectics, specifically lead/tin and manganese/bismuth. A theory was developed for the influence of convection on the microstructure of lamellar and fibrous eutectics, through the effect of convection on the concentration field in the melt in front of the growing eutectic. While the theory agrees with the experimental spin-up spin-down results, it predicts that the weak convection expected due to buoyancy will not produce a measurable change in eutectic microstructure. Thus, this theory does not explain the two fold decrease in MnBi fiber size and spacing observed when MnBi-Bi is solidified in space or on Earth with a magnetic field applied. Attention was turned to the morphology of the MnBi-Bi interface and to the generation of freezing rate fluctuations by convection. Decanting the melt during solidification of MnBi-Bi eutectic showed that the MnBi phase projects into the melt ahead of the Bi matrix.

Temperature measurements in a Bi melt in the vertical Bridgman-Stockbarger configuration showed temperature variations of up to 25 C. Conclusions are drawn and discussed

• Creator/s: NASA Technical Reports Server (NTRS
• Date: 2/1/1988
• Year: 1988
• Book Topics/Themes: NASA Technical Reports Server (NTRS), CONVECTION, DIRECTIONAL SOLIDIFICATION (CRYSTALS), EUTECTIC COMPOSITES, MICROSTRUCTURE, PHASE TRANSFORMATIONS, BISMUTH ALLOYS, FIBER ORIENTATION, LEAD ALLOYS, MANGANESE ALLOYS, MASS TRANSFER, MORPHOLOGY, SPACE COMMERCIALIZATION, TEMPERATURE EFFECTS, TIN ALLOYS, Wilcox, William R., Eisa, Gaber Faheem, Chandrasekhar, S., Larrousse, Mark, Banan, Mohsen

An excerpt captured from the PDF book