In-situ X-ray tomography investigation of pore damage effects during a tensile test of a Ni-based single crystal superalloy

High-resolution X-ray computed tomography was used to perform in-situ observation of the microporosity evolution during a tensile test of a DD5 nickel-based single crystal superalloy. Every pore with the equivalent diameter over 7.53 μm has been traced. A damage factor that describes the influence of pores on the fracture surface is proposed. The influences of different pore characteristics on crack evolution are investigated. It is shown that clustering pores are the crack initiators rather than the isolated large pores. Pore spacing is the most significant porosity distribution characteristic controlling the crack path and the local stress concentration. Finally, during the rapid fracture stage, the large clustering pores with complex morphology can actually change the crack growth direction, resulting in accelerated cracking propagation. For the first time, the significances of different pore characteristics influencing different crack evolution stages were statistically compared.