Abstract
To investigate the creep crack growth properties of aluminum (Al) nano-films deposited by electron-beam evaporation, creep crack growth experiments for freestanding 356 nm- and 139 nm-thick film specimens with a center notch or a single edge notch were conducted. In both Al films, a creep crack stably propagated at first, and then the crack growth rate gradually accelerated, leading to unstable fracture. FESEM observation of fracture surface revealed that fine unevenness presented on the fracture surface of the stable crack growth region while ductile or chisel point fracture occurred in the unstable region. The stable crack growth is presumably due to intergranular fracture. For the 356 nm-thick films, the relationship between the creep crack growth rate and the stress intensity factor depended on the experimental conditions, whereas the creep J-integral at the steady state well characterized the creep crack growth rate regardless of the experimental conditions.
