Ti-Ni-Cu 형상기억합금의 상변태 및 초탄성에 미치는 가공열처리의 영향

이오연,박영구,쳔병선 ( O . Y . Lee,Y . K . Park,B . S . Chun ) 한국열처리공학회 1994 熱處理工學會誌 Vol.7 No.4

Transformation behavior and superelastic behavior of Ti-Ni-Cu alloys with various Cu content has been investigated by means of electrical resistivity measurement, X-ray diffraction, tensile test and transmission electron microscopy. Two types of heat treatment are given to the specimens : i) Solutions treatment. ii) thermo-mechanical treatment. The transformation sequence in solution treated Ti-Ni-Cu Alloys substituted by Cu for Ni up to 5at.% occurs to B2◎B19` and it proceeds in two stages by addition of 10at.%Cu, i. e, B2◎B19◎B19`. Also, it has been found that Ti-30Ni-20Cu alloy transformed in one stage : B2◎B19. The thermo-mechanically treated Ti-47Ni-3Cu alloy transformed in two stages : B2◎rhomboheral phase◎B19`, while transformation sequence in Ti-45Ni-5Cu and Ti-40Ni-l0Cu alloy transformed as same as solution treated specimens. The critical stress for inducing slip deformation in solution treated and thermo-mechanically treated Ti-40Ni-l0Cu alloy is about 90㎫ and 320㎫ respectively.

Ti-Ni-B 형상기억합금의 마르텐사이트변태 및 인장변형거동에 미치는 열처리의 영향

이오연,박영구,안행근 ( O . Y . Lee,Y . K . Park,H . K . Ahn ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.1

The purpose of this study is to investigate the effect of heat treatments on the martensitc transformation and tensile deformation behavior in Ti-Ni-B alloys with various boron concentration. Three types of heat treatment are given to the specimens; i) solution treatment ii) aging iii) thereto-mechanical treatment. In solution treated specimens, R-phase transition which is related to abnormal increase of electrical resistance prior to martensitic transformation has been formed at a boron content of 0.2at% and the M, temperature has been decreased with the increasing of boron content. However, It has not been affected by aging, while that of thereto-mechanically treated specimens has been remarkably increased in the vicinity of recrystallization temperature. The thereto-mechanically treated specimen has showed a good thermal fatigue characteristics, shape memory effect and superelasticity in comparison with the solution treated specimen.

7XXX계 단조재의 피로 및 파괴인성에 미치는 제조공정의 영향

이오연,임재규,송기홍,손영일,은일상,신돈수 ( O . H . Lee,J . K . Lim,K . H . Song,Y . I . Son,I . S . Eun,D . S . Shin ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.3

The purpose of this study is to investigate the effect of impurity level and fabrication processes on the strength, fracture toughness and fatigue resistance of 7075, 7050 and 7175 high strength aluminum forgings. It has been verified that plane strain fracture toughness and fatigue characteristics of a specially processed 7175S-T74 alloy is superior to a conventionally processed 7075-T6/T73, 7050-T74 and 7175-T74 alloys. These beneficial effects primarily arise from two view points, i.e., the effect of reducing the impurity level of iron and silicon has significantly diminished the size and volume fraction of second phase particles such as Al_7Cu₂Fe and Mg₂Si. Futher reduction of the amount of nonequilibrium second phase particles has been observed by applying a special fabrication process.

7175Al 대형 단조재의 미세조직과 파괴인성

이오연(O . Y . Lee),장성환(S . H . Jang) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.2

N/A The 7175Al alloy is particularly interesting for its high strength and sufficient ductility, fracture toughness and corrosion resistance. Currently vigorous efforts have been made to develop large rockets usable for various purposes in the space. This has created the demand of big size of 7175Al billet which would be applied to heavy forgings. The aim of this study is to investigate the quality level of big billet and the effect of billet size on the mechanical properties of large 7175Al ring roll forgings. The billets range from 370㎜ to 720㎜ in diameter were homogenized and forged after direct chill casting. The size and volume fraction of second phase particles in Ф720㎜ billet are larger than those of Ф370㎜ billet, and its ductility is lower for the condition of homogenization and T6 treatment. The Cu-rich phases formed in interdendritic sites are considered to provide the preferential crack path during cold upsetting. The fracture toughness of ring roll forgings which are made by Ф370㎜ billet is higher than those of Ф720㎜ billet.

H₂O₂/HCl 처리한 Ti 임플란트의 생체활성 평가

유재선,권오성,이오연,이민호,송기홍,Yue J. S.,Kwon O. S.,Lee O. Y.,Lee M. H.,Song K. H. 한국재료학회 2005 한국재료학회지 Vol.15 No.5

Surface treatment play an important role in nucleating calcium phosphate deposition on surgical Ti implant. Therefore, the purpose of this study is to examine whether the precipitation of apatite on cp-Ti and Ti alloys are affected by surface modification in HCl and $H_2O_2$ solution. Specimens were then chemically treated with a solution containing 0.1 M HCl and 8.8M $H_2O_2$ at $80^{\circ}C$ for 30 mins, and subsequently heat-treated at $400^{\circ}C$ for 1 hour. All specimens were immersed in the HBSS with pH 7.4 at $36.5^{\circ}C$ for 15 days, and the surface was examined with XRD, SEM, EDX ana XPS. Also, pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloy specimens with and without surface treatment were implanted in the abdominal connective tissue of mice for 4 weeks. All specimens chemically treated with HCl and $H_2O_2$ solution have the ability to form a apatite layer in the HBSS which has inorganic ion composition similar to human blood plasma. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was $38.57\;{\mu}m,\;62.27\;{\mu}m\;and\;45.64\;{\mu}m$ in the cp-Ti, Ti-6Al-4V ana Ti-6Al-7Nb alloy specimens with the chemical treatment respectively, and $52.20\;{\mu}m,\;75.62\;{\mu}m\;and\;66.56\;{\mu}m$ in the commercial specimens of cp-Ti, Ti-6Al-4V and Ti-6Al-7Nb without any treatment respectively. The results of this evaluation indicate that the chemically treated cp-Ti, Ti-6Al-4V ana Ti-6Al-7Nb alloys have better bioactivity and biocompatibility compared to the other metals tested.

0.15%C-6%Mn강의 잔류오스테나이트 생성에 미치는 역변태 열처리의 영향

홍호,이오연,이규복 ( H . Hong,O . Y . Lee,K . B . Lee ) 한국열처리공학회 1998 熱處理工學會誌 Vol.11 No.1

The effects of alloying elements and the conditions of reverse transformation studied treatment on the formation of retained sustenite in 0.15C-6%Mn-(Ti, Nb) steels has been studied. The addition of Ti and Nb to 0.15C-6%Mn steel shows no effect on the formation of retained austenite. In case of reverse transformation treatment at various temperatures, the shape of retained austenite was lath type, growing toward the longitudinal and thickness direction with increasing the heat treatment temperatures. The retained austenite formed by the reverse transformation treatment at higher temperature has a lot of stacking faults induced by the internal stress. The retained austenite was stabilized chemically by enrichment of C and Mn in the vicinity of a untransformed sustenite and the chemical stability of retained austenite was decreased with increasing the heat treatment temperature and the holding time. It was effective to heat treat at 650℃ in order to obtain over 30vo1.% of retained austenite, but more desirable to heat treat at 625℃ for a long time, considering the amount and quality of retained austenite.

Ti-Ni-Cu합금의 상변태 및 가역형상기억효과

홍성원,이오연,김동건 ( S . W . Hong,O . Y . Lee,D . K . Kim ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.3

Transformation behavior and reversible shape memory effct of Ti-Ni-Cu alloys with various Cu content has been investigated by means of electrical resistivity measurement, differential scanning calorimetry, X-ray diffraction and strain gage sensor. The transformation sequence in Ti-Ni-Cu alloys substituted by Cu for Ni up to 5at.% occurs to B2↔B19` and it proceeds in two stages by addition of 10 at.%Cu, i.e, B2↔B19↔B19`. But the content of Cu increases up to 20at.%, it has been transformed in one stage ; B2↔B19. The shape change of Ti-40Ni-10Cu alloy which was constrain aged in circular form tended in B2→B19 transformation but it spreaded out in B19→B19` transformation. The amount of reversible shape change(Δε) of Ti-47Ni-3Cu alloy constrain aged at 400℃ after solution treatment has a maximum value of about 5.6×10^(-3), but that of cold rolled and constrain aged specimens exhibits a little value independent of Cu concentrations.

납기와 작업준비비용을 고려한 병렬기계에서 딥러닝 기반의 일정계획 생성 모델

유우식,서주혁,이동훈,김다희,김관호 한국전자거래학회 2019 한국전자거래학회지 Vol.24 No.3

As the 4th industrial revolution progressing, manufacturers are trying to apply intelligent information technologies such as IoT(internet of things) and machine learning. In the semiconductor/LCD/tire manufacturing process, schedule plan that minimizes setup change and due date violation is very important in order to ensure efficient production. Therefore,in this paper, we suggest the deep learning based scheduling generation model minimizes setup change and due date violation in parallel machines. The proposed model learns patternsof minimizing setup change and due date violation depending on considered order using the amount of historical data. Therefore, the experiment results using three dataset dependingon levels of the order list, the proposed model outperforms compared to priority rules. 4차 산업혁명이 진행되면서 제조업에서 사물인터넷(IoT), 머신러닝과 같은 지능정보기술을 적용하는 사례가 증가하고 있다. 반도체/LCD/타이어 제조공정에서는 납기일(due date)을 준수하면서 작업물 종류 변경(Job change)으로 인한 작업 준비 비용(Setup Cost)을 최소화 하는 일정계획을 수립하는 것이 효과적인 제품 생산을 위해 매우 중요하다. 따라서 본 연구에서는 병렬기계에서 딥러닝 기반의 납기 지연과 작업 준비 비용 최소화를 달성하는 일정계획 생성 모델을 제안한다. 제안한 모델은 과거의 많은 데이터를 이용하여 고려되어지는 주문에 대해 작업 준비와 납기 지연을 최소화하는 패턴을 학습한다. 따라서 세 가지 주문 리스트의 난이도에 따른 실험 결과, 본 연구에서 제안한 기법이 기존의 우선순위 규칙보다 성능이 우수하다는 것을 확인하였다.

Co2레이저를 이용한 Ti-6Al-4V합금의 Tin 및 TiC 가스 합금화

송기홍,이오연 ( K . H . Song,O . Y . Lee ) 한국열처리공학회 1996 熱處理工學會誌 Vol.9 No.3

Surface alloying of Ti alloy by CO₂laser is able to produce few hundred micrometers thick TiN or TiC surface-alloyed layer with high hardness on the substrate by injecting reaction gas(N₂or CH₄). Laser surface alloying by means of process control is in many applications essential in order to obtain predictable hardening layer. This research has been investigated the effect of such parameters on TiN and TiC gas alloying of Ti-6Al-4V alloy by CO₂laser. The maximum surface hardness of TiN layer was obtained 1750Hv on the conditions of 0.8㎾ laser power, 0.8m/min scanning speed and 100% N₂atmosphere. However, the maximum hardness of TiC formation layer after laser treatment was about 630Hv. As scanning speed was increased, the hardness and depth of these layers were decreased at constant laser power.

0.15C-6Mn TRIP강의 미세조직과 기계적 성질에 미치는 역변태 열처리의 영향

홍호,이오연,송기홍,Hong, H.,Lee, O.Y.,Song, K.H. 한국재료학회 2003 한국재료학회지 Vol.13 No.7

In this paper the effect of interstitial heat treatment on the microstructure and mechanical properties was examined both in the 0.15C-6Mn steels and 0.15C-6Mn steels added with Nb or Ti. This result will be applied into the development of a steel which has the properties of high strength and high ductility resulted from the transformation induced plasticity. The strength-elongation combination was increased as the holding time was increased when the temperature is at $625^{\circ}C$. However, the strength-elongation combination was decreased sharply as the holding time was increased when the temperature is at $675^{\circ}C$. The tensile strength and elongation of a reverse transformed steels added with Ti or Nb was 93 kg/$\textrm{mm}^2$ and 40%, respectively. This steel shows higher strength more than 10% of the 0.15C-6Mn steel without loss of ductility. The autenite formed from the reverse transformed treatment has a fine lath type, which has the width size of 0.1-0.3 $\mu\textrm{m}$. The TRIP sequence normally transforms the austenite to martensite, however, some of the sequence will produce retained austenite \longrightarrow deformation twin \longrightarrow martensite