Abstract
In an attempt to improve the ductility of doped tungsten, effects of Co addition on some properties of powder and sintered bar have been studied.
Simultaneous adding Co together with the common doping agents, Al2O3, SiO2 and K2O affected the average particle size of the reduced powder. Cc reduced the average particle size. Additions of 0.01-0.06 weight % of Co emphasized the restraining effect of Al2O3-doping on grain growth. Fractographs of sintered bars by means of a scanning electron microscope were characteristic and showed many small spherical pores and large tubelar pores. But fra-ctographs of sintered bars containing 0.3% Cc showed straight crystal boundaries and large spherical pores. The high concentration of these pores is attributed primarily to vaporization of doping additives or their products, and it is considered that these pores are closely related to the doping effect on the recrystallization of wires.
