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정태신,전중환,이승훈,이영국,최종술 ( Tae Shin Chung,Joong Hwan Jun,Seung Hoon Lee,Young Kook Lee,Chong Sool Choi ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.2
N/A Degradation and recovery of damping capacity in a Cu-65%Mn alloy have been studied. When the alloy was isothermally aged at 400℃, the highest damping capacity was observed after aging for 4 hours. In case when the alloy aged at 400℃ for 4 hours was maintained at 100℃, the damping capacity gradually decreased with time. The microstructural observations showed that the formation of subdomains and α-Mn precipitates are responsible for the degradation of damping capacity. When the degraded specimen was reheated at 250℃ for 30 minutes, the damping capacity was recovered considerably owing to the redistribution of impurity atoms, the extinction of subdomains and the release of damping sources from α-Mn precipitates during the repeated transformation, fcc↔fct.
Cu-55%Mn 합금의 진동감쇠능에 미치는 각종 열처리의 영향
정태신,전중환,이영국,최종술 ( Tae Shin Chung,Joong Hwan Jun,Young Kook Lee,Chong Sool Choi ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.1
Effects of different heat treatments on microstructure and damping capacity of Cu-55%Mn alloy were investigated to find an optimum heat treatment condition for a maximum damping capacity. The alloy showed the high level of damping capacity in case of the aging at 375 and 400℃. This is ascribed to the FCC→FCT martensitic transformation and microstructural changes from mottled to tweed band type. The damping capacity had a maximum value of 0.33 in logarithmic decrement when the alloy was aged at 375℃ for 14 hours followed by 20 times of thermal cycling between room temperature and 250℃. The refinement of tweed structure by thermal cycling is thought to be responsible for the highest damping capacity.
최종술,이영국,정태신,신중환 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.5
The objective of the present study is to investigate the effects of isochronal and isothermal aging on microstructure and damping capacity of Cu-47%Mn and Cu-55%Mn alloys. In case of the isochronal aging for 8 hours, the maximum damping capacity was shown at 425 for the Cu-47%Mn alloy and 400 for the Cu-55%Mn alloy, respectively. This is due to the lowest value of tetragonality(c/a ratio) which is closely associated with the fcc→fct martensitic transformation. In case of the isothermal aging at 400℃, the aging time far highest damping capacity was 18 hours in the Cu-47%Mn alloy and 8 hours in the Cu-55%Mn alloy, respectively. TEM observation revealed that tweed microstructure of fct martensite is responsible for the high damping capacity.