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Indexed by:Journal Papers

Date of Publication:2019-12-01

Journal:MATERIALS CHARACTERIZATION

Included Journals:EI、SCIE

Volume:158

ISSN No.:1044-5803

Key Words:Synchrotron X-ray radiography; Microstructure; Intermetallic compounds; Solidification; Pulse current

Abstract:In situ synchrotron X-ray radiography is used to study the effect of pulse current on the nucleation and growth of (Cu, Ni)(6)Sn-5 intermetaltic compounds (IMCs) during the solidification of Sn-10Cu-1Ni (wt.%) alloy. The synchrotron tomography analysis reveals that the (Cu, Ni)(6)Sn-5 exhibits a six-fold snowflake-like 3D morphology. As the density of pulse current increases from 0 to 200 A/cm(2), (Cu, Ni)(6)Sn-5 gradually exhibits a direction-dependent morphology and the "self-poisoning" phenomenon caused by gravity segregation is weakened. The competitive growth between the neighboring grains is directly observed. In addition, the Boltzmann function is used as a model for fitting the grain density versus temperature at four different current densities where R-2 >= 0.995 confirms a good correlation of the model with experimental data. The initial nucleation temperature increases with the increasing current density "j" from 0 to 50 A/cm(2), while decreases from 50 A/cm(2) to 200 A/cm(2). Besides, the maximum nucleation rate I-max monotonically increases with the increasing current density; while the final grain density with j = 200 A/cm(2) is less than that with j = 50 A/cm(2) because of the short nucleation duration. The results of this study provide an opportunity to achieve the active control of (Cu, NO6Sn5 morphology by imposing pulse current.