Effect of strontium on liquid structure of Al-Si hypoeutectic alloys using high-energy X-ray diffraction

TitleEffect of strontium on liquid structure of Al-Si hypoeutectic alloys using high-energy X-ray diffraction
Publication TypeJournal Article
Year of Publication2011
AuthorsSrirangam P, Kramer MJ, Shankar S
Journal TitleActa Materialia
Date Published01
ISBN Number1359-6454
Accession NumberISI:000285486300009
Keywordsal-si, aluminum-silicon alloys, coordination number, cu-sn, eutectic solidification, liquid structure, nucleation mechanism, pair distribution function, phases, phosphorus, RANGE ORDER, structure factor, theoretical aspects

High-energy X-ray diffraction experiments were performed using a synchrotron beam source to investigate the effect of strontium on the liquid atomic structure of Al-Si hypoeutectic alloys. The high-temperature liquid diffraction experiments were carried out on Al alloys with 3, 7, 10 and 12.5 (eutectic) wt.% Si, respectively, with 0 and 0.04 wt.% addition of Sr to each of the alloys. Further, the diffraction data for all the alloys were obtained at various melt temperatures (5-220 K) above the respective liquidus temperature. It was observed that the addition of 0.04 wt.% Sr results in significant change in the liquid structure parameters, such as structure factor, pair distribution function, radial distribution function, coordination number and packing density, at any given melt temperature of the alloy. Salient observations were that, for any specific alloy and temperature, addition of Sr significantly decreases coordination number and packing density. Further, with the addition of Sr in the liquid alloy, the atomic coordination number and packing density increases with decreasing temperature and decreasing Si content of the alloy. The results coupled with prior knowledge have enabled an in-depth understanding of the nucleation environment of the solidifying phases, specifically the role of Sr in delaying the clustering tendencies (nucleation) of the eutectic Si phase. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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Alternate JournalActa Mater