The effect of stress on strain ageing

The effect of applying a tensile stress during the strain ageing of iron, niobium and tantalum has been studied. The upper yield stress, the lower yield stress and the yield point elongation are all increased when tensile specimens are aged under stress but the flow stress and damping capacity are unaffected. Tensile test results, damping measurements and electron microscope observations all indicate that the process responsible for the strengthening effect is one involving dislocation rearrangement rather than a stress-enhanced diffusion mechanism.