Availableonlineatwww.sciencedirect.com SCIENCE Acta materialia ELSEVIER Acta Materialia 53(2005)1511-1520 www.actamat-journals.com Measurement of residual stress distributions in Al2O3/3Y-TZP multilayered composites by fluorescence and aman microprobe plezo-spectroscopy Goffredo de portu Lorenzo Micele a, b, Yutaka Sekiguchi, Giuseppe Pezzotti b National Research Council, CNR-ISTEC, Faenza, Italy b Department of Materials, Ceramic Physics Laboratory Research Institute for Nanoscience, RIN, Kyoto Institute of Technology Sakyo-ku, Matsugasaki, 606-8.5 NGK Spark Plug Co, Ltd, R&D Center, Kommaki-shi, Aichi 485-8510, Japan Received 16 September 2003: received in revised form 14 July 2004: accepted 1 December 2004 Available online 8 January 2005 Abstract Microscopic distributions of residual stresses were evaluated in multilayered composite specimens consisting of AlO3/3 mol% Y2O3-stabilized zrO2 (3Y-TZP) layers with different compositions and thicknesses. Residual stress measurements were performed both by raman and fluorescence piezo-spectroscopy, and they revealed the existence of tensile and compressive hydrostatic stresses in the zirconia and alumina phases, respectively. Residual stresses mainly arose from thermal expansion and elastic mismatch between the constituent ceramic phases. However, the overall residual stress field consisted of two separate components: ()a micro- scopic stress field originating on the microstructural scale from grain-to-grain thermal and elastic mismatches between Al2O3 and From a comparison between stress data collected according to different piezo-spectroscopic techniques (i.e, based on fluorescence and Raman band shift for Cr-doped Al2O3 and 3Y-TZP, respectively), a reliability assessment of the stress measurement could be also obtained. The macroscopic stress field piled up among different layers could be separated from the microscopic grain-to-grain stress field and quantitatively evaluated to a degree of precision by employing a calibration procedure using chromophoric Al2O3 phase as a"stress sensor". Some fine details of the internal stress distribution were also revealed, as for example the existence of a anabolic stress profile within 3Y-TZP layers with substantial stress intensification nearby the junctions between neighbouring lay- ers. The total stress field was found to remarkably depend on layer thickness for given constant dimensions of the multilay ructure c 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved Keywords: Multilayered composite structures; Residual stress distribution; Raman and fluorescence piezospectroscopy 1. Introduction tively thick layers made of different phases. Residual tresses arise from mismatches in coefficients of thermal Ceramic multilayered composites may undergo resid- expansion(CTE)and elastic constants between the con ual stresses of remarkable magnitude upon cooling from stituent phases and among neighbouring layers [1]. In sintering temperature, especially if they consist of rela he phase(or layers)with lower CTE, compressive resid ual stresses are produced, while tensile residual stresses Corresponding author. Tel:+81 75 7247568; fax: +81 75 724 usually appear in the phase(or layers)with higher CTE In addition, it is known that the magnitude of these resid ual stresses is proportional to the CTE mismatch between 1359-6454$30.00 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved doi: 10. 1016/.actamat. 2004.12.003Measurement of residual stress distributions in Al2O3/3Y-TZP multilayered composites by fluorescence and Raman microprobe piezo-spectroscopy Goffredo de Portu a , Lorenzo Micele a,b, Yutaka Sekiguchi c , Giuseppe Pezzotti b,* a National Research Council, CNR-ISTEC, Faenza, Italy b Department of Materials, Ceramic Physics Laboratory & Research Institute for Nanoscience, RIN, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan c NGK Spark Plug Co., Ltd., R&D Center, Komaki-shi, Aichi 485-8510, Japan Received 16 September 2003; received in revised form 14 July 2004; accepted 1 December 2004 Available online 8 January 2005 Abstract Microscopic distributions of residual stresses were evaluated in multilayered composite specimens consisting of Al2O3/3 mol% Y2O3-stabilized ZrO2 (3Y-TZP) layers with different compositions and thicknesses. Residual stress measurements were performed both by Raman and fluorescence piezo-spectroscopy, and they revealed the existence of tensile and compressive hydrostatic stresses in the zirconia and alumina phases, respectively. Residual stresses mainly arose from thermal expansion and elastic mismatch between the constituent ceramic phases. However, the overall residual stress field consisted of two separate components: (i) a micro￾scopic stress field originating on the microstructural scale from grain-to-grain thermal and elastic mismatches between Al2O3 and 3Y-TZP phases; and, (ii) a macroscopic stress field, which is established to obey equilibrium conditions between adjacent layers. From a comparison between stress data collected according to different piezo-spectroscopic techniques (i.e., based on fluorescence and Raman band shift for Cr3+-doped Al2O3 and 3Y-TZP, respectively), a reliability assessment of the stress measurement could be also obtained. The macroscopic stress field piled up among different layers could be separated from the microscopic grain-to-grain stress field and quantitatively evaluated to a degree of precision by employing a calibration procedure using chromophoric Al2O3 phase as a ‘‘stress sensor’’. Some fine details of the internal stress distribution were also revealed, as for example the existence of a parabolic stress profile within 3Y-TZP layers with substantial stress intensification nearby the junctions between neighbouring lay￾ers. The total stress field was found to remarkably depend on layer thickness for given constant dimensions of the multilayered structure.
2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Multilayered composite structures; Residual stress distribution; Raman and fluorescence piezo-spectroscopy 1. Introduction Ceramic multilayered composites may undergo resid￾ual stresses of remarkable magnitude upon cooling from sintering temperature, especially if they consist of rela￾tively thick layers made of different phases. Residual stresses arise from mismatches in coefficients of thermal expansion (CTE) and elastic constants between the con￾stituent phases and among neighbouring layers [1]. In the phase (or layers) with lower CTE, compressive resid￾ual stresses are produced, while tensile residual stresses usually appear in the phase (or layers) with higher CTE. In addition, it is known that the magnitude of these resid￾ual stresses is proportional to the CTE mismatch between 1359-6454/$30.00
2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actamat.2004.12.003 * Corresponding author. Tel.: +81 75 724 7568; fax: +81 75 724 7580. E-mail address: pezzotti@ipc.kit.ac.jp (G. Pezzotti). Acta Materialia 53 (2005) 1511–1520 www.actamat-journals.com