INTERNAL-STRESS INDUCED DEBONDING IN A ZIRCONIA-REINFORCED 6061 ALUMINUM-ALLOY COMPOSITE

In situ neutron diffraction was carried out during slow strain rate te nsile tests in order to monitor the development of lattice strain and hence internal stress in both phases of a 6061 aluminium alloy composi te reinforced with 6.8 vol.% of 4 wt.% yttria stabilized zirconia. The results point to a much reduced transfer of load from matrix to reinf orcement compared with previous experiments on the Al-SiC particulate system. Microstructural examination of failed specimens indicated that significant debonding of the particle-matrix interface had occurred u pon loading. This effect was quantified as a function of plastic strai n by modulus measurements. Using an Eshelby-based model, the debonding measurements were shown to be consistent with the observed reduction in the efficacy of load transfer. provided the debonded particles were taken to offer no constraint on the matrix either in the axial or tra nsverse directions. In addition, the neutron diffraction peak data gav e information relating to the extent of the stress-triggered tetragona l to monoclinic transformation in the reinforcement. Given the low lev el of stress transfer it was, perhaps, not surprising that the zirconi a was found to be largely unchanged in terms of its monoclinic-to-tetr agonal ratio during the loading experiment.