Impression creep study of a Cu–0.3Cr–0.1Ag alloy

The creep behavior of Cu–0.3Cr–0.1Ag alloy was investigated by the impression creep testing technique in the as-processed (AP) and aging-treated (AT) conditions. The tests were carried out under constant punching stress in the range 175–550 MPa, at temperatures in the range 725–855 K. The creep resistance of the AT material was much higher than that of the AP alloy at all applied stresses and temperatures, as indicated by their corresponding minimum creep rates. This was attributed to the dispersive distribution of Cr-rich phase in the aged condition. Assuming a power-law relationship between the impression stress and velocity, average stress exponents of 5.7–6.6 and 6.4–8.0 were obtained for the AP and AT conditions, respectively. Analysis of the data showed that the activation energy for both materials decreased with increasing stress. The stress-dependent average energy values of 144.3 kJ mol−1 and 142.6 kJ mol−1, found respectively for the AP and AT conditions, are close to 138 kJ mol−1 for dislocation climb, assisted by vacancy diffusion through dislocation cores in the Cu. This, together with the stress exponents of about 7 suggests that creep is controlled by a stress assisted dislocation climb mechanism.