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Microstructural Evolution in cryomilled Inconel 625

Published online by Cambridge University Press:  14 March 2011

Jianhong He
Affiliation:
Department of Chemical and Biochemical Engineering and Materials Science, University of California Irvine, Irvine, CA 92697-2575
Enrique J. Lavernia
Affiliation:
Department of Chemical and Biochemical Engineering and Materials Science, University of California Irvine, Irvine, CA 92697-2575
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Abstract

Nanocrystalline Inconel 625 alloy, with a uniform distribution of grains, was synthesized using cryogenic mechanical milling. Microstructures of the powder, cryomilled for different times, were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that both the average powder particle size and average grain size approached constant values as cryomilling time increased to 8 hours. The TEM observations indicated that grains in the cryomilled powder were deformed into elongated grains with a high density of deformation faults, and then fractured via cyclic impact loading in random directions. The fractured fragments from the elongated coarse grains formed nanoscale grains. The occurrence of the elongated grains, from development to disappearance during intermediate stages of milling, suggested that repeated strain fatigue and fracture caused by the cyclic impact loading in random directions, and cold welding were responsible for the formation of a nanocrystalline structure.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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