Microcrack identification on particulate-reinforced metal matrix composite

This is a study of particle damage based on image analysis of light optical micrographs obtained by serial sectioning of an Al-Si-Mg alloy reinforced with Si particles. To quantify damage in the material, it is necessary to determine the cracked surface area, Unfortunately, there is a deviation in the gray level distribution on the images, so that a simple thresholding does not work. In this study, four methods for allowing the identification of crack pixels on an image are investigated. Three of the methods do not identify the crack pixels to within an acceptable error. The fourth method, which is based on the isolation of each particle and the definition of crack pixels through a gray level step over the particle pixels, is found acceptable and is, hence, chosen. An application is done on three images, and the damage areas in the three sections are compared. (C) 2001 Elsevier Science Inc. All rights reserved.