High temperature deformation behavior of activated sintered W powder compacts was investigated. The compression tests were carried out in the temperature range between 900 and 110 at the strain rate of . The sintered specimens of Ni-doped submicron W powder compacts showed decrease in W grain size with increasing the Ni content. As the result, the flow stress was significantly increased with increasing the Ni content. We obtained Ni-activated sintered W compacts with the relative density of 94 l％and the average grain size of less than 5. A moderate true strain up to 0.60 was obtained without fracture even at 110 with the strain rate of for the activated W compact despite adding the 1.0 wt％Ni to submicron W powder.

The high temperature deformation behavior of the activated sintered W powder compacts was investigated. The W compact showed the relative density of 94% with the average W grain size of by activated sintering at for 1 hour. Compression tests were carried out in the temperature range of at the strain rate range of /sec - /sec. True stress-strain curve and microstructure exhibited the grain boundary brittleness which was dependent on the compression test temperature. The activated sintered W compact showed that the maximum stress as well as the strain at the maximum stress was abruptly decreased as the test temperature increase from to 1000 and regardless of the strain rate. The discrepancy of the microstructure in the specimen center was obviously observed with the increase of the test temperature. After compression test at the W grain was severely deformed normally against the compression axis. However, after compression test at and the W grain was not deformed, but the microcrack was formed in the W grain boundary. The Ni-rich second phase segregated along the W grain boundary could be partly unstable over and affect the poor mechanical property of the activated sintered W compact.