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Indexed by:期刊论文

Date of Publication:2011-04-01

Journal:MATERIALS RESEARCH INNOVATIONS

Included Journals:Scopus、SCIE、EI

Volume:15

Issue:2

Page Number:156-159

ISSN No.:1432-8917

Key Words:Dendritic growth; Coarsening mechanism; Synchrotron radiation; Metals and alloys

Abstract:Synchrotron microradiography technique was applied in situ to observe the evolution of dendrite morphology of Sn-Bi alloy during solidification at controlled cooling rates. It is shown by in situ observations that different coarsening mechanisms of secondary dendrite arm might operate under different cooling conditions or solidification stages. Coarsening mainly occurred in the early solidification stage due to the competition of secondary dendrite arms, and therefore, secondary dendrite arm spacing is mainly determined in this stage. Coalescence was the dominant coarsening mechanism in the late solidification stage. In particular, at lower cooling rate, e. g. 1.5 K min(-1), dendrite fragmentation frequently occurred, and played an important role in dendrite coarsening. The real time observations in real alloy provide verification of the dendrite arm coarsening models.