Abstract:In this work, U720Li castings with different W contents (1.02 wt.%, 0.52 wt.% and 0 wt.%) were prepared by vacuum induction melting and subsequently homogenized. The effect of W on hot deformation behavior and fracture characteristics of as-homogenized U720Li alloy was studied emphatically. The 1000 ℃ tensile test results of homogenized and furnace cooled alloys revealed that with the reduction of W content the deformation resistance decreased gradually, and when the W content was reduced to zero the tensile plasticity was greatly improved and the fracture mode was shifted from intergranular fracture to a mixed-mode of intergranular and transgranular fracture. For both furnace-cooled and air-cooled alloys, with the reduction of W addition the grain-interior microhardness decreased gradually, the size of precipitation strengthening phase γ′ increased and the volume fraction of γ′ decreased markedly. The main reason for the influence of W on deformation resistance and thermal plasticity is that the decrease of W not only reduced the solid solution strengthening, but also modified the characteristic of γ′ which promoting the occurrence of dynamic recrystallization. In addition, the distribution of W in U720Li alloy has been revealed in this paper, i.e., W is mainly enriched in the γ matrix, and the mechanism by which W influencing the precipitation of γ′ was discussed accordingly in the text.