Effect of stacking fault energy on deformation behavior of cryo-rolled copper and copper alloys

Pure copper and Cu–12.1 at.%Al–4.1 at.%Zn alloy were subjected to rolling in liquid nitrogen. TEM studies showed that dynamic recovery during the deformation process was effectively suppressed and hence microstructures with dislocation substructure and deformation twins were formed. Mechanical properties were assessed via microtensile testing that shows improved yield strength, 520 ± 20 MPa, and ductility, 22%, in the case of pure copper. Alloying with Al and Zn results in reduction in stacking fault energy (SFE) which can contribute to enhanced strength and good ductility. Physical activation volume obtained via stress relaxation tests is 26 b3, and 8 b3 for pure copper, and Cu–12.1 at.%Al–4.1 at.%Zn, respectively. The effect of SFE on work hardening rate of samples is discussed. Although twinning is observed in the alloy, it is concluded that network dislocation strengthening plays the major role in determining the mechanical properties.