Paper Title:
The Influence of External Mechanical Stresses on Agglomeration and Bending of Solidifying Crystals
  Abstract

The influence of external mechanical stresses on agglomeration and bending of solidifying crystals has been investigated by microstructural characterisation of hypoeutectic Al cast specimens. The samples were produced by near-static cooling, gravity die casting and high pressure die casting (HPDC), where the solidifying crystals experience different levels of mechanical stresses. Electron backscatter diffraction (EBSD) technique was used to acquire grain misorientation data which can be linked to crystal agglomeration and bending behaviour during solidification. The length fraction of low-energy grain boundaries in HPDC samples was substantially higher than in gravity diecast and ‘statically cooled’ samples. This is related to the high amount of shear applied on the solidifying alloy, which promotes crystal collisions and agglomeration. In-grain misorientations were significant only in branched dendritic crystals which were subjected to significant shear stresses. This is attributed to the increased bending moment acting on long, protruding dendrite arms compared to more compact crystal morphologies.

  Info
Periodical
Materials Science Forum (Volumes 654-656)
Main Theme
Edited by
Jian-Feng Nie and Allan Morton
Pages
1367-1372
DOI
10.4028/www.scientific.net/MSF.654-656.1367
Citation
S. Otarawanna, C. M. Gourlay, H. I. Laukli, A. K. Dahle, "The Influence of External Mechanical Stresses on Agglomeration and Bending of Solidifying Crystals", Materials Science Forum, Vols. 654-656, pp. 1367-1372, 2010
Online since
June 2010
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