Piezo-spectroscopy at low temperatures:: residual stresses in Al2O3-ZrO2(Y2O3) eutectics measured from 77 to 350 K

High-resolution, piezo-spectroscopic studies were performed in alumina/zirconia eutectic composites with different Y2O3 contents and microstructures at different temperatures using the ruby R-line luminescence. Measurements at 77 K allowed the precise determination of the average stress and its distribution in the alumina phase. A normal distribution function was obtained in most of the cases. In some composites the highest stresses are relaxed by micro cracking, giving an asymmetrical distribution function. In the composites with stabilized zirconia the residual stresses originate from the differences in the thermal expansion coefficients of the component phases. A linear dependence of the thermostresses with temperature was obtained in the 77-350 K temperature range. The effective elastic modulus for thermostresses was 118 +/- 2.7 GPa. Using the coefficients of thermal expansion of the component phases and making an extrapolation of the low temperature values the stress-free temperature of 1270 +/- 35 K was determined. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.