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Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/29512

Title: Experimental Study of the Microstructural Evolution of Chemical Vapor Deposited (CVD) Nickel upon Annealing
Authors: Chichi, Chen
Advisor: Wang, Zhirui
Department: Materials Science and Engineering
Keywords: CVD nickel
detwinning
five-fold twinned particles
bi-modal grain size distribution
Chemical vapor deposition
Issue Date: 23-Aug-2011
Abstract: The effect of annealing conditions on the microstructure evolution of CVD nickel was investigated systematically in the present study by differential scanning calorimetry, optical microscopy and transmission electron microscopy (TEM), upon both ex-situ and in-situ annealing. TEM observation revealed the as-deposited CVD nickel possessed a bi-modal grain structure, with large columnar grains embedded in nanocrystalline matrix. Ultrafine and nano growth twins were present as well as multiply twinned grains with five-fold symmetry. Microstructure observation upon annealing showed that grain growth did not occur until annealing at 400ºC. Detwinning was observed at 400ºC and higher temperatures. The ultrafine and nano twins tended to transform into dislocation cell structures and this phenomenon was driven by the excess free energy associated with the high density of grown-in twin boundaries. The five-fold twinned grains were found to be thermally stable up to 600ºC. The hardness was observed to decrease with increasing annealing temperature.
URI: http://hdl.handle.net/1807/29512
Appears in Collections:Master

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