The influence of stacking fault energy on high temperature creep behaviour laws: The case of Cu and Cu-4Si

The influence of stacking fault energy during the secondary stage of the creep process is hard to grasp, both experimentally and theoretically. It is, however, well-known that such an effect is very important; indeed, a weak stacking fault energy is likely to produce a noticeable decreasing in creep rate and lead to a better heat resistance.The numerous attempts at grasping this complex phenomenon have in almost all cases been based on empirical laws which express the creep rate evolution as a function of temperature (T) and stacking fault energy (γ).The purpose of our study is to assess the influence of stacking fault energy on Cu () and Cu-4Si () high temperature creep. We try to show that the role of such an energy behaviour law is in accordance with the bibliography results.Several hypotheses have been examined in an attempt to account for the weakness of creep speed values in low stacking fault energies, such as copper and its alloys. On the whole, data analysis proves that copper creep is not controlled by bulk or pipe diffusion but is the result of a thermally actived slip, probably due to the cross - slip.In the case of Cu-4Si, the stacking fault energy represents half of that of Cu, the cross - slip proves to be harder and the creep could be controlled both by diffusion and cross - slip.