Three-Dimensional Microstructure Visualization of Porosity and Fe-Rich Inclusions in SiC Particle-Reinforced Al Alloy Ma
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THE design and development of high-performance materials requires a thorough understanding and careful control of microstructure and its effect on mechanical properties. In order to understand the fatigue performance of metal matrix composites (MMCs), it is important to investigate the size, morphological characteristics, and distribution of inclusions and porosity in the material. Previous work by the authors has shown that fatigue cracks often nucleate at these ‘‘rogue’’ inclusions, as well as SiC particle clusters.[1] Figure 1 shows the fracture surface of a SiC particle-reinforced aluminum alloy composite where the primary fatigue crack initiated close to the specimen surface at an Fe-rich inclusion. Thus, it is necessary to visualize and quantify the distribution of such defects in three dimensions. In addition to visualization, such microstructural data sets can be incorporated into finite element models to predict the onset of local damage mechanisms and the macroscopic deformation behavior.[2–5] FLA´VIO DE ANDRADE SILVA, formerly Visiting Scientist, Materials Science and Engineering, Arizona State University, Tempe, AZ 85287-6106, and Graduate Research Assistant, Department of Civil Engineering, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, is Postdoctoral Fellow, Institute of Construction Materials, Technical University of Dresden, 01062 Dresden, Germany. JASON J. WILLIAMS, Research Scientist, is with Materials Science and Engineering, Arizona State University. NIKHILESH CHAWLA, Professor, is with Materials Science and Engineering, Arizona State University. Contact e-mail: [email protected] BERND R. MU¨LLER, Head of Working Group, General X-ray Topography, MANFRED P. HENTSCHEL, Scientist Emeritus, and PEDRO D. PORTELLA, Director and Professor, are with the Federal Institute for Materials Research and Testing (BAM), D-12200 Berlin, Germany. Manuscript submitted October 2, 2009. Article published online May 29, 2010 METALLURGICAL AND MATERIALS TRANSACTIONS A
Several techniques have been used for visualization of microstructures in three dimensions. Serial sectioning techniques such as serial mechanical polishing coupled with optical microscopy[2,3,5–7] or focused ion beam milling[8] and image reconstruction have been used. While serial sectioning is a powerful technique for generating virtual 3-D microstructures, it presents some drawbacks. In particular, the sample preparation process is time consuming and destructive. X-ray tomography is a promising technique that[3,9] eliminates cross sectioning and allows for superior resolution and image quality with minimal sample preparation. 3-D visualization of heterogeneous microstructures by X-ray tomography has been successfully performed in Pb-free solder joints,[9] powder metallurgy steels,[3] and metal matrix composites.[10–12] Synchrotron radiation has been extensively used for X-ray tomography[10] and holotomography[11,12] in MMCs in order to visualize their microstructure. Babout et al.[10] used this technique to visualize the micros
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