The work presents results of investigations on reliability of sintered particulate composites  with alumina or zirconia matrix. These oxides are basic structural materials widely applied in engineering.  

The reliability analysis were made in two aspects – the resistance on subcritical crack growth

and dispersion of bending strength in meaning of the Weibull statistic.

Generally, the investigations result showed that manufacturing of composites on the base of mentioned oxides could profitably influence mechanical properties. However, potential reliability improvement wasn’t obvious, and its scale could change in very wide range.

The potential property improvement could be particularly significant in composite systems with alumina matrix. The scale of property improvement in zirconia matrix composites was limited (when compared with results for alumina matrix).

The scale of property improvement mainly depended on kind, amount and dispersion of strengthening phase. The change of these parameters was effective in differentiation such composite parameters as: the matrix grain size (the Zener effect), the inclusion agglomeration ratio or the interphase boundary state. The mentioned factors influenced potential size and size distribution of critical flaws what determined the Weibull statistic of composites.

One couldn’t omit important role of residual stresses in composites. These stresses are generating by the mismatch of thermal expansion coefficients of constituent phases in composites. Locally, the value of these stresses could be significant, comparable with the bending strength of investigated materials. Such stresses, their value and character (tension or compression) were also very important for resistance on subcritical crack growth.

But, this feature was mainly influenced by the presence of a new category of grain boundaries – the interphase boundaries. They substantially changed the way of degradation of grain boundaries under subcritical loading.

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