کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5460683 1516172 2017 15 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Effect of Eu on the silicon phase in Al-40Zn-5Si alloys
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد فلزات و آلیاژها
پیش نمایش صفحه اول مقاله
Effect of Eu on the silicon phase in Al-40Zn-5Si alloys
چکیده انگلیسی


- The pre-eutectic Si particles nucleate ahead of the solid/liquid interface.
- The nodular pre-eutectic Si is observed with the addition of 0.3% Eu.
- The eutectic Si leads the irregular eutectic interface in the unmodified alloy.
- The eutectic grains can nucleate on the nodular Si after modification.
- The nodular Si can be attributed to IIT and poisoning of TPRE mechanism.

A series of Al-40Zn-5Si alloys with different additions of Eu were prepared by permanent mold casting. The nucleation phenomenon incorporating the modification of silicon phase was investigated by using the synchrotron radiation imaging technology, scanning electron microscopy, electron probe microanalysis and high resolution high-angle annular dark-field scanning transmission electron microscopy. It was found that the primary phase was α-Al dendrites and the pre-eutectic Si particles were precipitated continuously at the front of the solid/liquid interface in Al-40Zn-5Si alloys. The nodular pre-eutectic Si particles were observed when the Eu addition was 0.3%. Meanwhile, a flake-to-fibrous transition of eutectic Si was also observed. The needle-like eutectic Si crystals were seen to shoot out from the vicinity of primary α-Al dendrites into melt with high velocities leading the irregular eutectic interface in the unmodified Al-40Zn-5Si alloy. However, the eutectic grains with smooth interfaces nucleated mainly near primary or secondary α-Al branches in 0.3% Eu-modified Al-40Zn-5Si alloy. The eutectic grains began to nucleate on the nodular pre-eutectic Si particles when the α-Al surface reached so close to them. The formation of nodular pre-eutectic Si particles was attributed to the adsorption of Eu atoms along the <112> growth direction of Si and at the intersection of Si twins. This is fully consistent with the well-known poisoning of twin plane re-entrant edge (TPRE) and the impurity induced twinning (IIT) modification mechanisms proposed for interpreting the modification of eutectic Si.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Alloys and Compounds - Volume 722, 25 October 2017, Pages 116-130
نویسندگان
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