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

In situ neutron diffraction was carried out during slow strain rate tensile tests in order to monitor the development of lattice strain and hence internal stress in both phases of a 6061 aluminium alloy composite reinforced with 6.8 vol.% of 4 wt.% yttria stabilized zirconia. The results point to a much reduced transfer of load from matrix to reinforcement 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 upon loading. This effect was quantified as a function of plastic strain 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 transverse directions. In addition, the neutron diffraction peak data gave information relating to the extent of the stress-triggered tetragonal to monoclinic transformation in the reinforcement. Given the low level of stress transfer it was, perhaps, not surprising that the zirconia was found to be largely unchanged in terms of its monoclinic-to-tetragonal ratio during the loading experiment.