Residual Stresses in Al/SiC Nanolayered CompositesDanny R.P. Singh & Nikhilesh Chawla, Arizona State University, MET DMR-0504781 Al=100nm, SiC=33nm Al=50nm, SiC=70nm Al=50nm, SiC=50nm Al=50nm, SiC=15nm Al=50nm, SiC=33nm Nanolayered metal-ceramic composites are a novel class of materials exhibiting new and enhanced properties over conventional materials. Residual stresses are developed in the Al-SiC nanolayered system (Fig. 1) during processing (by DC/RF sputtering) which can severely affect mechanical properties. We are studying the development of residual stresses in these materials by x-ray diffraction using a synchrotron source at Brookhaven National Lab. A synchrotron source produces highly intense and collimated x-ray beam compared to a conventional x-ray source. This makes it possible to analyze residual stresses in thin film materials, ordinarily not possible using laboratory x-ray source. The x-ray energy used in this study was 8keV with a wavelength of 1.5498 Å and stresses were calculated using (331) peak shifts using a standard sin2ψtechnique (Fig. 2). Compressive residual stresses develop in the Al/SiC multilayers. Peak compressive stresses develop at a SiC volume fraction of about 33%. (Fig. 3). The trend in residual stress with volume fraction of SiC is not well understood and requires further investigation. when sin2ψ=0, ε = ε33 sin2ψ=1, ε = ε11 Fig. 1: Al-SiC multilayer structure on Si substrate. Fig. 2: Variation of lattice spacing with sin 2 . Fig. 3: Variation of residual stresses in nanolayered Al/SiC composite with varying volume fraction and layer thickness
Residual Stresses in Al/SiC Nanolayered CompositesDanny R.P. Singh & Nikhilesh Chawla, Arizona State University, MET DMR-0504781 To encourage undergraduate students in research, particularly women and minorities, Materials Science and Engineering undergraduate students participated in the NSF-Research Experience for Undergraduates (REU) and Fulton Undergraduate Research Initiative (FURI) . Students presented their work at the FURI Symposium. They were coached by the PI and graduate students in our group. The students learned to conduct research in the laboratory and write formal abstracts and reports. They also prepared and practiced their poster presentations for the event. The photograph on the right shows undergraduate student Casey McClimon characterizing microstructures using optical microscopy.