Eutectic modification of Al-Si alloys with rare earth metals

Nogita, K, McDonald, SD and Dahle, AK (2004) Eutectic modification of Al-Si alloys with rare earth metals. Materials Transactions, 45 2: 323-326. doi:10.2320/matertrans.45.323


Author Nogita, K
McDonald, SD
Dahle, AK
Title Eutectic modification of Al-Si alloys with rare earth metals
Journal name Materials Transactions   Check publisher's open access policy
ISSN 1345-9678
Publication date 2004-01-01
Sub-type Article (original research)
DOI 10.2320/matertrans.45.323
Volume 45
Issue 2
Start page 323
End page 326
Total pages 4
Editor A Kamio
Y Ohmori
T Sakamoto
Place of publication Japan
Publisher Japan Institute of Metals
Language eng
Subject C1
291302 Physical Metallurgy
671004 Castings
Abstract The effects of different concentrations of individual additions of rare earth metals (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) on eutectic modification in Al-10mass%Si has been studied by thermal analysis and optical microscopy. According to the twin-plane re-entrant edge (TPRE) and impurity induced twinning mechanism, rare earth metals with atomic radii of about 1.65 times larger than that of silicon, are possible candidates for eutectic modification. All of the rare earth elements caused a depression of the eutectic growth temperature, but only Eu modified the eutectic silicon to a fibrous morphology. At best, the remaining elements resulted in only a small degree of refinement of the plate-like silicon. The samples were also quenched during the eutectic arrest to examine the eutectic solidification modes. Many of the rare-earth additions significantly altered the eutectic solidification mode from that of the unmodified alloy. It is concluded that the impurity induced twinning model of modification, based on atomic radius alone, is inadequate and other mechanisms are essential for the modification process. Furthermore, modification and the eutectic nucleation and growth modes are controlled independently of each other.
Keyword Metallurgy & Metallurgical Engineering
Eutectic
Aluminium-silicon Alloy
Solidification
Modification
Rare Earth
Modified Al-7wt-percent-si Alloy
Solidification Mode
Growth
Materials Science, Multidisciplinary
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 13:32:36 EST