Torsional stress relaxation behavior of microscale copper wire

Torsional stress relaxation behavior of copper wire with a diameter of 50 µm and grain size of 3.7 µm is experimentally investigated at room temperature. It is revealed that the stress relaxation occurs in both elastic and plastic regions. An elevated stress drop and a reduced apparent activation volume with increasing initial stress levels are also found in both elastic and plastic regions. Extremums of stress drop and activation volume are observed around the elastic limit. Meanwhile, high strain rate and rapidly exhaustive mobile dislocation density are observed. Finally, the cross-slip is considered to be the operating mechanism.