Influence of deformation, microstructure, and temperature on the fracture resistance of technically pure tungsten

The fracture resistance of technically pure W with pre-deformed and recrystallized microstructures was tested in a temperature range of ambient to 700 °C. To account for the impact of microstructure anisotropy, samples with different specimen orientations were investigated. Room temperature tests were carried out in a scanning electron microscope and at elevated temperatures in a vacuum furnace. Both, microstructure and testing temperature significantly influence the fracture resistance of W and a strong dependence of the crack propagation resistance on the crack plane orientation was found. Pre-deformation of the testing material increases the fracture resistance in terms of the crack initiation toughness but shortens the measurable crack resistance curve (R-curve). Testing at elevated temperatures results in higher initiation toughness for both states, pre-deformed and recrystallized; however, only the recrystallized structure shows an R-curve behavior for the used sample geometry.