Fluorescence spectroscopy analysis of Al–Al₂O₃ composites with coarse interpenetrating networks

Fluorescence microprobe spectroscopy was used to characterize the stress fields that develop within an interpenetrating Al–Al₂O₃ composite resulting from both the thermal expansion mismatch during sample processing, and from an external applied load. The 30 vol% Al–70 vol% Al₂O₃ composite that was investigated had an aluminum and alumina phase feature size of 50–100 μm. The residual thermal compressive stress measured in the alumina was ∼40–340 MPa. The effect of varying the metal ligament size on the residual stress distribution is discussed. Additionally, the application of an external load caused a non-uniform stress distribution to develop within the alumina regions around the crack-tip, which was attributed to microstructure inhomogeneities. The crack was further extended and the influence of the stress distribution within the alumina regions on the crack extension direction is briefly discussed.