For a better understanding of both recrystallization and ductile to brittle transition temperature, tensile tests are performed on potassium doped tungsten (WVWM), up to 2000 掳C at different loading rates (0.2 and 42 mm/min). The mechanical properties are highly dependent on the microstructure. The fracture surfaces after tensile testing are microstructurally assessed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) is used to investigate the original specimen as the beginning point.