Uniaxial and micro-indentation creep tests were conducted on nano-twinned copper at both room temperature and elevated temperatures. Compared with creep behavior in twin-free nanocrystalline copper, nanotwinning can act as an effective approach to slow down the creep deformation as well as increase the thermal stability of nanocrystalline materials. Analysis on the experiment results and microscopic observations show a transition of creep mechanism in nanotwinned materials from diffusion, to partial dislocation nucleation, and finally to interaction of dislocations and twin planes with the increase of stress. The indentation creep in nano-twinned copper was also carried out to serve as supplement to the uniaxial creep tests, which demonstrates sensitivity to load level, loading rate and...[ Read more ]

Uniaxial and micro-indentation creep tests were conducted on nano-twinned copper at both room temperature and elevated temperatures. Compared with creep behavior in twin-free nanocrystalline copper, nanotwinning can act as an effective approach to slow down the creep deformation as well as increase the thermal stability of nanocrystalline materials. Analysis on the experiment results and microscopic observations show a transition of creep mechanism in nanotwinned materials from diffusion, to partial dislocation nucleation, and finally to interaction of dislocations and twin planes with the increase of stress. The indentation creep in nano-twinned copper was also carried out to serve as supplement to the uniaxial creep tests, which demonstrates sensitivity to load level, loading rate and temperature. It also presents some different behavior with uniaxial creep, but they share similar creep mechanism. The activation parameters indicates indentation creep with high load level may be highly related to grain boundary sliding and interaction of dislocations and twin planes, which is consistent with the mechanism in uniaxial creep of high stress level. The indentation can act as an effective method to test the creep behavior and the method itself will not influence the creep behavior.