A comprehensive study on the damage tolerance of ultrafine-grained copper

In this study the fracture behavior of ultrafine-grained copper was assessed by means of elasto-plastic fracture mechanics. For the synthesis of the material high pressure torsion was used. The fracture toughness was quantitatively measured by J(IC) as a global measure by recording the crack growth resistance curve. Additionally, the initiation toughness in terms of the crack opening displacement (COD(i)) was evaluated as a local fracture parameter. The results presented here exhibit a low fracture initiation toughness but simultaneously a remarkably high fracture toughness in terms of J(IC). The origin of the large difference between these two parameters, peculiarities of the fracture surface and the fracture mechanical performance compared to coarse grained copper will be discussed.