TESTING 1-2-3
Alternative Modification of A356 for Ductility Studied
The modifying elements calcium and barium through a Ca-Si-Ba addition have been investigated, and it has been found the combination can be a viable
alternative to strontium additions to improve ductility. ALEXANDRE BOIS-BROCHU AND MARIN GHEORGHE, CENTRE DE MÉTALLURGIE DU QUÉBEC, TROIS-RIVIERES, QUEBEC, CANADA FRANCIS BRETON, RIO TINTO, ARVIDA RESEARCH AND DEVELOPMENT CENTRE, ONTARIO, CANADA.
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ypoeutectic aluminum alloys such as A356.0 (Al-7Si-0.3Mg) are usually subjected to strontium additions in order to obtain a
chemically modified eutectic morphol- ogy. The modification of the eutectic silicon from sharp acicular plates to a fibrous structure is normally applied to improve the alloy ductil- ity. However, strontium additions are relatively costly and less expensive
ADDING IT ALL UP Breaking down the latest research is as easy as 1-2-3.
“Alternative Modification of A356 Hypoeutectic Alloy by Ca-Si-Ba Additions” Alexandre Bois-Brochu and Marin Gheorghe, Centre de Métallurgie du Québec, Trois-Rivieres, Quebec, Canada; Francis Breton, Rio Tinto, Arvida Research and Development Centre, Ontario, Canada
Background—Modifiying eutectic silicon from sharp acicular plates to a fibrous structure improves ductility in hypoeutectic aluminum alloys. In order to obtain a chemically modified eutectic morphology, alloy additions are made. Strontium is popular for this but expensive, and alternative additions are sought, such as Ca-Si-Ba addition.
Procedure—The optimal barium and calcium concentration, the effect of phosphorus on such addition, and the fading of the modification through holding the melt at the high temperature and through remelting were evaluated in this study.
Results and Conclusions— The eutectic silicon in A356.2 can be efficiently modified using Ca-Si-Ba additions. The elongation values obtained for Ca-Si-Ba modified A356.0 are equivalent to values from traditional strontium additions.
alternatives are being investigated. One such addition, Ca-Si-Ba, which
is traditionally used as a deoxidizer in the steel industry, is the focus of this study. Te effects of the combination of the modifying elements calcium and barium through a Ca-Si-Ba addition have been investigated, and it has been found that a fully modified microstruc- ture can be obtained. Te elongation values obtained for Ca-Si-Ba modified A356.0 are equivalent to values from traditional strontium additions.
Furthermore, barium and calcium
additions have been observed to be resistant to extensive fading even after holding the melt for 24 hours and also during multiple remelting. Strontium modification of hypoeu-
tectic aluminum alloys is suppressed by a small concentration of phosphorus. In contrast, Ca-Si-Ba modification appears to be insensitive to the pres- ence of phosphorus. If Ca-Si-Ba and strontium are simultaneously found in the alloy, the alloy is still modified.
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