msepostdoc-list Seminar Reminder for Congying Wang's Preliminary Exam: Seminar, Monday, Dec. 11, at 8:30 a.m., in ARMS 3115; Exam same day at, 10:00, in ARMS 2326. " Slip Systems in Beta-Sn: to Relate Dislocations and Grain Nucleation"

[Son, Rosemary E]

Please consider attending the following:


MATERIALS ENGINEERING
SEMINAR


“Slip Systems in Beta-Sn: to Relate Dislocations and Grain Nucleation”


By
Congying Wang
Purdue MSE Ph.D. Preliminary Exam

Advisors: Professors Carol A. Handwerker and John E. Blendell



ABSTRACT


β-Sn coatings are widely used in the electronic industry to provide better solderability to prevent oxidation.The formation and growth of whiskers are known to be a stress relaxation response of tin films, some of which can grow up to millimeter-long and cause short circuits in electronics. Previous studies indicate that shallow grains are critical for whisker growth, acting as preferred sites for growth compared to columnar grains. Whiskers have been observed to form through recrystallization along grain boundaries (GB) during thermal cycling of as-solidified films of tin-silver-copper alloys (SAC305). In this study, changes in surface morphology were quantified in large-grained tin films during thermal cycling (-35◦C/+85◦C) from the 1st cycle, which suggested a relationship between local dislocation activity and low-angle boundary formation. In order to relate the underlying mechanism of the dislocation motion and the grain nucleation, slip behav-iors in β-Sn has been reviewed. At least 12 nonequivalent families of slip systems have been reported due to the anisotropy of β-Sn. Unlike FCC materials, the crystallography theory and dislocation energy cannot fully explain why specific slip system was activated, or predict which slip system will become active. Other factors influencing the slip behaviors are temperature, grain size, and grain boundary.



Date: Monday, December 11, 2017

Time: 8:30 A.M.
Place: ARMS 3115


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