Work-hardening and recovery of dispersion hardened alloys

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Abstract
Experiments have been carried out in order to test theories of the work-hardening and low temperature recovery in dispersion hardened crystals. Single crystals of copper containing small (∼ 500 Å diameter) particles of SiO2 have been deformed in tension at temperatures between 77 and 450 K, and the primary and secondary dislocation distributions have been determined quantitatively by transmission electron microscopy at 400 kV. It is found that in the temperature range in which the work hardening rate decreases with increasing temperature and at which static recovery occurs (∼300 K), the number of both primary and secondary dislocation loops associated with the particles drops significantly with increasing temperature of deformation. It is shown that this behaviour is consistent with the climb and shrinkage of Orowan loops by pipe diffusion (Gould, Hirsch and Humphreys 1974), but that it is not consistent with the theory of Atkinson, Brown and Stobbs (1974) in which recovery is attributed to processes of dislocation glide.