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Fe-Mn 합금의 γ↔ε마르텐사이트변태에 필요한 구동력
이영국,최종술 ( Young Kook Lee,Chong Sool Choi ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.4
Dilatometric experiment and thermodynamic calculation have been performed to determine M_s, A_s and driving forces for γ→ε martensitic transformation of Fe-Mn alloys. The transformation temperatures(M_s, A_s, T_o) were decreased with increasing manganese content and were newly formulated as a function of manganese content. Driving force for γ→ε martensitic transformation was increased from -75J/mole to -105J/mole with increasing manganese content from 15wt.% to 25wt.%. Transformation temperature hysteresis(A_s-M_s) was also increased from 50K to 80K with increasing mangenese content from 15wt.% to 25wt.%. The small driving force(-75J/mole-105J/mole) and small ΔT(50K∼80K) for γ→ε martensitic transformation indicated that Fe-Mn alloys behave like thermoelastic martensitic alloys : We would like to call them semi-thermoelastic martensitic alloys.
논문 : 상변태 ; Fe-Mn 이원계합금의 γ→ε 마르텐사이트변태에 대한 열역학
이영국 ( Young Kook Lee ),전중환 ( Joong Hwan Jun ),최종술 ( Chong Sool Choi ) 대한금속재료학회 ( 구 대한금속학회 ) 1996 대한금속·재료학회지 Vol.34 No.11
In order to avoid the confusion due to inconsistency between thermodynamic calculations(free energy difference between γ and ε, △G γ→ε of γ→ε martensitic transformation for Fe-Mn binary alloys reported by previous workers, the thermodynamic data of Fe-Mn alloys, △G(γ→ε)Fe and △G(γ→ε)Mn, were newly formulated, and the thermodynamic calculations of γ→ε martensitic transformation for the Fe-Mn binary alloys were performed with a regular solution model. The calculation results were well consistent with experimental results in wide range of 15 to 28wt%Mn, and were closely approached to Takaki`s calculation results rather than Murakami`s calculation results.
Fe-Ni-C 마르텐사이트 합금에서 마르텐사이트의 형상이 진동감쇠능과 기계적 성질에 미치는 영향
이영국,신한철,최종술 ( Young Kook Lee,Han Chul Shin,Chong Sool Choi ) 한국열처리공학회 1997 熱處理工學會誌 Vol.10 No.3
Effect of martensite morphology on damping capacity and hardness of Fe-Ni-C martensitic alloys were studied. The morphologies of martensite such as lath, butterfly, lenticular and thin plate were prepared by adjusting nickel content and austenite grain size. The hardness increased in order of lath, lenticular, thin plate, butterfly. The damping capacities of the lath and butterfly martensites were higher than those of the other two morphologies, indicating that the dislocation substructure is more effective in the damping capacity than the twin substructure. Especially, the butterfly martensite showed the highest damping capacity among these morphologies because of presence of not tangled but free dislocations in there.
Fe-7%Ni-0.4%C 마르텐사이트합금의 미세조직과 진동감쇠능에 미치는 용체화처리온도의 영향
이영국,지광구,최종술 ( Young Kook Lee,Kwang Koo Jee,Chong Sool Choi ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.1
The objective of this study is to investigate the effect of solution-treatment temperature on the microstructure and damping capacity of a martensitic Fe-7%Ni-0.4%C alloy. The size of lath increased from 0.3㎛ to 0.55㎛ with increasing the solution-treatment temperature from 700 to 1100℃. In addition, the size of block, packet, and austenite grain had tendency to increase with increasing solution-treatment temperature. The damping capacity of the Fe-7%Ni-0.4%C martensitic alloy decreased with increasing the solution treatment temperature. The reason is not attributed to the increase in the size of lath, block, packet, and austenite grain, but to the increase in vacancy concentration which hinders dislocation motion.
Fe-17%Mn 합금의 진동감쇠능에 미치는 ε 마르텐사이트 함량과 진폭변형율의 영향
전중환,이영국,최종술 ( Joong Hwan Jun,Young Kook Lee,Chong Sool Choi ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.2
The effects of ε martensite content and strain amplitude on damping capacity of an Fe-17%Mn alloy have been studied to establish damping mechanism of Fe-Mn system corresponding to the magnitude of strain amplitude. In a range of 1×10^(-4)∼3×10^(-4) strain amplitude, the damping capacity is linearly proportional to the ε martensite content, which suggests that stacking faults and ε martensite variant boundaries are the principal damping sources. In the range of 4×10^(-4)∼6×10^(-4) strain amplitude, however, a maximum damping capacity is observed around 68 vol% ε. This behavior is very similar to dependence of relative area of γ/ε interface on ε martensite content. This means that in this strain range, γ/ε interface acts as damping source in addition to the stacking faults and variant boundaries in Fe-17%Mn alloy.
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.
논문 : 상변태 ; Fe-(17~23)%Mn 마르텐사이트 합금의 진동감쇠능에 관한 연구
전중환 ( Joong Hwan Jun ),이영국 ( Young Kook Lee ),최종술 ( Chong Sool Choi ) 대한금속재료학회 ( 구 대한금속학회 ) 1996 대한금속·재료학회지 Vol.34 No.11
The effects of ε martensite content and strain amplitude on damping capacity of Fe-(17~23)%Mn martensitic alloys have been investigated to Clarify reson that Fe-17%Mn alloy shows the maximum damping capacity among Fe-Mn binary system. It was observed that the damping capacity of Fe-(17~23)%Mn alloys were decreased with increasing manganese content when the specimens had similar amount of ε martensite. The deterioration of the damping capacity with increasing manganess content is attributted to the following two factors: (l)The decrease in density of stacking faults in ε martensite and γ/ε interface areas. (2) The decrease in mobility of γ/ε interface. Below 3×10-4 strain amplitude, the damping capacity of Fe-17%Mn alloy was linearly Proportional to the ε martensite content, which suggests that stacking faults and variant boundaries in ε martensite plates are the principal damping sources. Above 4×10-4 strain amplitude, however, a maximum damping capacity was observed around 60~70vol.% ε. This means that γ/ε interface acts as the damping source in addition to the stacking faults and variant boundaries in Fe-17%Mn alloy.