HARDENING STAGES OF [112] COPPER SINGLE-CRYSTALS AT INTERMEDIATE AND HIGH-TEMPERATURES .1. MECHANICAL-BEHAVIOR

This study surveys (in two parts) the flow stress, the hardening rate (theta = dtau/dgamma) and the dislocation substructure associated with [112] copper single crystals deformed in tension between 293 and 1145 K. It is shown that beyond stage III, two further stages (called IV and V) are evidenced. It is necessary to distinguish three temperature regimes. This part I reports, for each temperature regime, the characteristics of the different hardening stages together with the transition stresses. In regime 1, theta is stress independent in stage II and IV and decreases when T is raised. In stage III and V, theta is decreasing with stress. In regime 2, stage II is not observed anymore. Theta is still a decreasing function of stress in stage III and V, but increases in stage IV. In regime 3, plastic deformation starts with stage IV where theta is temperature independent and increasing with stress. In stage V, theta is practically stress independent. The transition stresses are found to be temperature and strain-rate dependent. Activation parameters have been determined. For the stress at the onset of stage IV in regime 2 the experimental values are in good agreement with the jog-pair model for non compact slip.