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Stress redistribution and cavity nucleation near a diusively growing grain boundary cavity
 

Summary: Stress redistribution and cavity nucleation near a diusively
growing grain boundary cavity
Peter M. Anderson *, Paul G. Shewmon
Department of Materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210-1179, USA
Received 16 March 1999; received in revised form 13 August 1999
Abstract
This article considers the growth of an isolated grain boundary cavity by diusive Żow of matter along the cavity
surface and onto the grain boundary, while surrounding grains deform elastically. The analysis addresses the early life
of the cavity, in which surface diusion is rapid enough to maintain a near-equilibrium cavity shape with a uniform
curvature. Although the stress normal to the grain boundary is largest at the cavity edge in the purely elastic case,
diusive Żow shifts the stress peak to many radii away from the cavity. The magnitude of the stress peak is typically 5±
25% greater than the remote stress normal to the grain boundary. The probability of a new cavity nucleating in the
stress peak of an existing cavity is predicted to increase as the cube of the site distance from the cavity. Secondly, the
stress concentration provided by the existing cavity, despite the small value, is predicted to increase the nucleation rate
by several orders of magnitude. Ó 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Cavity; Diusion; Stress concentration; Nucleation rate; Creep failure; Grain boundary; Void
1. Introduction
Grain-boundary fracture by the formation of a closely packed array of cavities is common in strong
alloys stressed to fracture at 0.4±0.75 of the absolute melting temperature. It is found in creep failures
(Ashby et al., 1975), hydrogen attack of pressure vessel steels (Hakkarainen et al., 1980; Chen and

  

Source: Anderson, Peter M. - Department of Materials Science and Engineering, Ohio State University

 

Collections: Materials Science