A quantitative measure of internal cavitation in superplastic alloys using photoacoustic analysis
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Y. Ma, X. Zhao, and T. G. Langdon Departments of Materials Science and Mechanical Engineering, University of Southern California, Los Angeles, California 90089-1453 (Received 4 March 1994; accepted 10 May 1994)
Internal cavities often develop during the deformation of superplastic alloys. Experiments were conducted to determine whether a nondestructive photoacoustic method may be used to detect the presence of internal cavities in two different commercial Al-based alloys. An analytical procedure was developed to provide quantitative information on the volume fraction of cavitation. The results confirm that the photoacoustic signal can be used to detect the presence of cavities, and it is demonstrated that the quantitative measurements derived from the photoacoustic data are consistent with observations obtained by sectioning and standard metallographic techniques.
I. INTRODUCTION Superplasticity is defined as the ability of a polycrystalline material to exhibit, in a generally isotropic manner, very high tensile elongations prior to failure.1 In practice, superplastic deformation may be achieved by using metallic alloys with very small grain sizes (typically
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