Paper Title:
Role of Bi and Ca Additions in Controlling the Microstructure of Sr-Modified 319 Alloys
  Abstract

The role of bismuth (50 to 9000 ppm) and calcium (50 to 200 ppm) additions on the microstructural characteristics in Sr-modified 319 alloys (with/without 0.4 wt% Mg addition) were investigated using optical and electron microscopy, and image analysis. It was found that the modification effect of Sr continuously diminished with Bi addition up to ~3000 ppm Bi; further Bi addition led to the modification of the Si particles due to the presence of Bi. In the Ca-containing alloys, a coarse eutectic Si structure resulted with Ca additions of 50 ppm, due to the formation of Alx(Ca,Sr)Siy compounds. Increased Ca additions (up to 200 ppm) did not alter the Si particle size. The Alx(Ca,Sr)Siy phase particles appeared in rod-like form in the Sr-modified alloys and in plate-like form in the 319+0.4 wt% Mg alloys. MgO, Al2O3, and AlP particles appear to act as nucleants for the precipitation of the plate-like Alx(Ca,Sr)Siy phase.

  Info
Periodical
Materials Science Forum (Volumes 519-521)
Edited by
W.J. Poole, M.A. Wells and D.J. Lloyd
Pages
1257-1264
DOI
10.4028/www.scientific.net/MSF.519-521.1257
Citation
S. El Hadad, A.M. Samuel, F.H. Samuel, H.W. Doty, S. Valtierra, "Role of Bi and Ca Additions in Controlling the Microstructure of Sr-Modified 319 Alloys", Materials Science Forum, Vols. 519-521, pp. 1257-1264, 2006
Online since
July 2006
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$32.00
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