The Role of the γ/ γeutectic and porosity on the tensile behavior of a single-crystal nickel-base superalloy |
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Authors: | W. S. Walston I. M. Bernstein A. W. Thompson |
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Affiliation: | (1) General Electric Aircraft Engines, 45215 Cincinnati, OH;(2) Illinois Institute of Technology, 60616 Chicago, IL;(3) Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University, 15213 Pittsburgh, PA |
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Abstract: | The microstructure of a single-crystal nickel-base superalloy, PWA 1480, has been varied by heat treatment and hot isostatic pressing in order to study the role of the γ/yγ′ eutectic and porosity on subsequent tensile behavior. The level of porosity was found not to affect any of the tensile properties, while the γ/γ′ eutectic strongly influenced ductility. Eliminating the γ/γ′ eutectic increased ductility which was attributed to the cleavage fracture of this constituent. It is proposed that such cleavage of the γ/γ′ eutectic is initiated by the stress created from impinging slip bands, promoting shear localization, and final fracture along {111} slip planes. The precise nature of this fracture process is discussed with emphasis on the role of the γ/′ micro-structure. The deformation structure of PWA 1480 was also studied, and while different in some respects from many other single-crystal superalloys, its fracture process appears to be similar. Formerly Graduate Student, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University. |
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