0.4 wt Ni 을 첨가한 W 활성소결체의 고온압축 특성 연구

Abstract

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 23 ㎛ by activated sintering at 1400℃ for 1 hour. Compression tests were carried out in the temperature range of 900 - 1100℃ at the strain rate range of 100/sec - 10-3/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 900℃ to 1000 and 1100℃ 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 900℃ the W grain was severely deformed normally against the compression axis. However, after compression test at 1000℃ and 1100℃ 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 900℃ and affect the poor mechanical property of the activated sintered W compact.