Shortening behaviour of drawn and twisted copper wires

Abstract

Previously drawn copper wires were twisted to large strains (γ≍6) at room temperature under free end conditions. Before testing, individual samples were annealed for 1 h at 150, 200, 250, 300, and 550°C. The specimens heated at 150 and 200°C displayed recovered microstructures, whereas those heated at 250°C and above were recrystallised. During twisting, the recovered samples exhibited shortening behaviour (of up to −4%). In contrast, the recrystallised specimens exhibited lengthening (of up to 3%). Before twisting, the textures were determined by mean of pole figure analysis. Three fibres were identified: 〈111〉, 〈100〉, and 〈112〉 – the last appears above the recrystallisation temperature. The changeover in axial behaviour produced by annealing is attributed to the removal of the 〈111〉 component by recrystallisation. Simulations using the rate sensitive Sachs polycrystal model revealed the roles of the different fibre components. The shortening behaviour is caused by the 〈111〉 component. The 〈100〉 fibre together with the random background is responsible for lengthening. The 〈112〉 component does not affect the axial behaviour significantly.

MST/1243