Damage evolution in nickel-base alloy torsion specimens and its influence on subsequent tensile deformability

The massive forming process can consist of consecutive deformation steps. Voids, initiated in preceding forming steps or present from the material production process, can reduce the deformability in the subsequent forming processes.Therefore, this work evaluates the influence of initiated voids on the deformability in a two step forming process. In the first step voids were initiated in a nickel-base alloy by torsion deformation of a rod. Tension specimens were machined from this predamaged rod and deformed until failure at a test temperature of 1000 °C. The tensile elongation leads to failure as a result of the growth and coalescence of the inherent voids. A constant void volume fraction at fracture was obtained for the specific material and test conditions, whereas the reduction in area – or fracture strain – varies significantly.