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Lookup NU author(s): Emeritus Professor Terry Evans
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The tensile properties of a commercial copper-1% cadmium alloy have been investigated at 77, 300 and 420 K. The presence of cadmium produces a sharp yield point similar to that observed in mild steel and in aluminium-magnesium alloys. The yield and flow stresses of the material were found to obey the Hall-Petch relation and it is concluded that cadmium strengthens copper mainly by increasing the grain-size-dependent component of the strength. The alloy exhibits strain ageing. The interaction between a cadmium atom and dislocations in the alloy is considered and it is shown that the atomic size misfit interaction is dominant. It is concluded that cadmium atoms can strongly pin both dissociated edge and screw dislocations in copper. The value of the grain-size-dependent component of the yield strength at low temperatures and its temperature dependence suggest that the critical event at yield is the unpinning of dislocation sources within the grain boundaries. It also appears that this process is still important in the region of homogeneous deformation at higher strains, in contrast to what occurs in copper, where the grain-size dependent component of the flow stress diminishes markedly with increasing plastic strain. A possible mechanism for the persistence of a strong grain-size effect in the alloy is suggested.
Author(s): Behnood N, Douthwaite RM, Evans JT
Publication type: Article
Publication status: Published
Journal: Acta Metallurgica
Print publication date: 01/08/1980
ISSN (print): 0001-6160
ISSN (electronic): 1878-0768
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