Effects of Temperature and Frequency on Cyclic Deformation Behaviours of Cu Single Crystals

Temperature and frequency are significant extrinsic factors that influence the cyclic deformation behaviour of face-centred cubic crystal (fcc) single crystals. For Cu single crystals, an increase in temperature causes the disappearance of the plateau region in the cyclic stress-strain (CSS) curves and a significant decrease in the saturation resolved shear stress at low strain amplitudes. This is attributed to the enlargement of the space between Persistent Slip Band (PSB) ladders, resulting in a lower volume fraction of the rungs in PSBs, leading to a lower saturation shear stress. Conversely, an increase in frequency does not affect the appearance of the plateau behaviour in CSS curves, but it slightly increases the corresponding plateau stress. This is because a higher frequency increases the probability of interaction between edge dislocations, leading to an increase in the local flow stress in the rungs, ultimately resulting in an increment of the saturation stress.