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Deformation, Recovery and Stress Corrosion Cracking of Nickel-Base Alloy 600 by X-ray Rocking-Curve Measurements

Published online by Cambridge University Press:  06 March 2019

Chi Fung Lo ,
Gajiang Feng ,
William E. Mayo  and
Sigmund Weissmann
Chi Fung Lo
Affiliation:
Department of Mechanics and Materials Science, Rutgers University, P.O. Box 909, Piscataway, NJ 08855-0909
Gajiang Feng
Affiliation:
Department of Mechanics and Materials Science, Rutgers University, P.O. Box 909, Piscataway, NJ 08855-0909
William E. Mayo
Affiliation:
Department of Mechanics and Materials Science, Rutgers University, P.O. Box 909, Piscataway, NJ 08855-0909
Sigmund Weissmann
Affiliation:
Department of Mechanics and Materials Science, Rutgers University, P.O. Box 909, Piscataway, NJ 08855-0909
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Abstract

The aim of this investigation was the establishment of a quantitative link between micro and macrodeformation and kinetic recovery of nickel-base Alloy 600 as well as the early detection of microcracks in this alloy when exposed to stress corrosion. To reach these objectives, X-ray rocking-curve measurements were carried out using the method known by its acronym CARCA (computer-aided rocking-curve analysis). Supported by transmission electron microscopy, a calibration curve was established relating dislocation density, X-ray rocking-curve halfwidth and strain. Applying CARCA, deformation levels and work-hardening characteristics of the alloys were measured by quantitative characterization of the induced defect structure. By correlating the analysis of the defect structure to the kinetic recovery of the alloys, including determination of the activation energies, it was possible to infer from the thermal stability of the alloys the dislocation obstacles responsible for hardening at different strain levels. It was shown that the recovery of the alloys was conditioned by their low stackingfault energy and that it depended on the strain level. Rapid recovery associated with grain boundary diffusion occurred at very small plastic strains up to about 0.7% with measured activation energies of recovery of about 25.6 Kcal/mol. At higher strains bulk diffusion was necessary to overcome the obstacles by dislocation climb with Q — 67 kcal/mol, The CARCA method proved itself to be a valuable research tool for assessing quantitatively the defect density and the mechanically and thermally induced changes. Relaxation effects, recorded by CARCA in the apex region of stressed C-rings exposed to a caustic medium, may open a path for early nondestructive detection of microcracks in stress-corrosion cracking.

Type
Research Article
Information
Advances in X-Ray Analysis , Volume 33: Thirty-Eighth Annual Conference on Applications of X-ray Analysis, July 31 - August 4, 1989 , 1989 , pp. 33 - 53
Copyright
Copyright © International Centre for Diffraction Data 1989

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