On the relationship between grain boundary connectivity, coincident site lattice boundaries, and intergranular stress corrosion cracking

The present work reports on refinements proposed to existing models for predicting the distribution of intergranular stress corrosion cracking based on the frequency of special, crack-resistant, low-Sigma CSL grain boundaries in the microstructure. The accuracy of these models in predicting the extent of intergranular cracking in low-stacking fault FCC materials ranging from Alloy 600 to Admiralty Brass is improved by factors ranging from 2 to more than 6 by discounting isolated, neutral-twins from the measured total special boundary fraction. A stochastic model is presented for easily and accurately determining the proportion of neutral-twins, which do not disrupt connectivity in the network of random boundaries based on the relative frequency of twin-variant boundaries (i.e. Sigma9s and Sigma27s) in the microstructure. Improvements in the predicted susceptibility to intergranular attack achieved from the refinements described herein will enhance current abilities to identify components at high risk of failure by IGSCC based on grain boundary structure. (C) 2004 Elsevier Ltd. All rights reserved.