Dwell sensitive fatigue in titanium alloys at near ambient temperatures was first recognised as a consequence of aerospace component failures. Previous to this, extended periods of loading at peak or high mean stress were assumed to be benign to the accumulation of fatigue damage. Subsequent research has shown that quasi-cleavage facets are synominous with dwell failures. Their formation is due to stress redistribution between 'weak' and 'strong' grains or regions within the bulk material and is therefore encouraged by inhomogeneous microstructures. Slip band models are discussed which account for the redistribution process. Although the dwell effect is mainly an initiation and small crack phenomenon subsequent crack propagation rates under dwell loading can be affected in the presence of selected corrosive species. The influence of oxidising and reducing environments are assessed.
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