고 Mn 내열강에서 Ti 및 B 에 의한 석출상과 기계적 성질과의 관계에 대하여

천병선 대한금속재료학회(대한금속학회) 1975 대한금속·재료학회지 Vol.13 No.1

1. 서론 18%Cr-8%Ni austenitic stainless steel에 있어 高價인 Ni의 含量을 감소 시키고자 하는 硏究가 제2차 세계대전 이후 활발히 진행되어 왔다. 大部分은 Ni의 함량을 감소시키고 Mn 및 N으로 대체시킨 Fe-Cr-Mn-Ni-N steel이다. 本 硏究에서는 Ni을 완전히 Mn과 Co로 대체시킨 Fe-17% Mn-14% Cr-2% Co austenitic steel에 있어 Ti 및 B을 첨가시키어 800℃ 및 600℃의 일정한 온도에서 장시간 시효 처리함으로 생성되는 析出物을 X-ray diffraction pattern에 의하여 조사하였고 고온 현미경 조직을 관찰하여 相의 변화를 조사하여 기계적 성질에 미치는 영향을 硏究하였다. 2. 실험방법 고주파 유도 전기로에서 주조된 강괴는 공냉 하였으며 약 880℃에서 3시간 annealing처리를 행한 후에 시료를 채취하여 약 1150℃에서 1시간 45분 동안 용체화 처리를 한 후 수냉 시켰다. 600℃ 및 800℃에서 각각 일정하게 유지된 전기로에서 時效 處理를 行하여 록크웰 경도기로 경도 변화를 측정하여 과시효 현상을 X-ray diffraction pattern에 의해 析出相을 구별하였다. 또한 고온 현미경으로 시효 처리 온도에서 입계 반응에 의해서 析出物의 생성을 관찰하여 과시효 단계에서 析出物의 변화를 연구하였다. 3. 실험 결과 및 고찰 그림 1.2에서 잘 알 수 있듯이 장시간 비교적 높은 온도인 600℃ 및 800℃에서 시효 처리한 시료의 硬度 변화는 Ti 첨가강이 과시효 현상을 빠르게 나타내고 있다. 이는 Co 합금강과 달리 析出 硬化型이므로 고온에서 Austenite 입계에 반응이 활발히 진행함에 따라서 Carbide 相 및 σ相으로 분해한다고 생각된다. B첨가 합금강은 B이 주로 입계에 편석함으로서 입계 반응을 억제시키어 析出物의 생성 및 성장 속도가 매우 느리기 때문에 과시효 현상이 나타나지 않고 계속 硬化함을 알 수 있다. 시효 처리 과정에서 최대 경도에 달했을 때 600℃ 및 800℃에서의 고온 현미경 조직은 사진 1과 같다. 4. 결론 1) Ti첨가 합금강에서의 硬化에 기인하는 가장 큰 析出物은 M_(23)C_6라 생각된다. 2) Co는 solution hardening metal로서 C의 확산을 저지시키어 Carbide 析出物의 생성 속도가 느리므로 硬化속도가 비교적 느리다. 3) B첨가 합금강은 B이 입계에 편석하여 입계 반응을 억제시키어 과시효 단계를 나타내지 않고 계속 硬化가 되고 있었다.

Al-Li-Cu-Zr 합금의 기계적 성질에 미치는 저온 시효 열처리의 영향

천병선,김종희,이용연 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.2

The effects of low temperature aging on the impact toughness and mechanical properties of Al-1.9%Li-3.0%Cu-0.15%Zr alloy have been investigated. It shows that the impact absorption energy and elongation are increased in the order of over-aged, peak-aged and under-aged specimen at the various aging temperature, and these values in the specimen peak-aged at lower aging temperature are increased. In the specimens aged at 120℃ and 140℃, dimples are observed in the matrix and around the grain boundary. Intergranular fracture has been observed noticeably in the 160℃ peak aged specimen. These results are attributed to the microstructural changes by the low temperature aging treatment that forms more dense and homogeneous distribution of T₁ phases on the dislocations within the matrix and more narrow precipitate free zone in the grain boundary at 120℃ and 140℃ than at 160℃.

Ti-Ni-Cu 형상기억 합금의 상변태 및 열 싸이클에 의한 피로특성

천병선,이오연,남궁정,조광희 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.2

Martensitic transformation and effects of thermal fatigue cycles on the transfer mation temperature and shape recovery of Ti-Ni-Cu alloys were investigated by means of electrical resistance measurement, thermal fatigue tests and transmission electron micros copy. Thermo-mechanical treatment at 600℃ for one hour after cold rolling showed the best shape recovery effect irrespective of Cu concentration. Substitution of a small amount of Cu for Ni in the equiatomic composition of Ti-Ni showed folling results ; Ms-temperature of the Ti-Ni-Cu alloy increased slightly with the increase of Cu content, The range of transformation temperature for Ti_(50)Ni_(40)Cu_(10) alloy(i.e., T_(Mf-Af)) was reduced to 7℃. After stress relief treatment at 750 ℃ for one hour, the Ti_(50)Ni_(45)Cu_5 alloy showed good two-way memory effect. Change of the M_s temperature was observed to a certain number of thermal cycles, and it became nearly constant after a critical number of thermal fatigue cycles.

TiNi 계 형상기억합금의 상변태 및 기계적 거동

천병선 대한금속재료학회 1991 대한금속재료학회 학술대회 개요집 Vol.1991 No.1

고분해능 전자현미경에 의한 SiAiON-SiC 복합재료의 미세구조와 파괴 특성

천병선,최경식,이병택,평가찬이 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.12

Microstructure and fracture behavior of pressurelessly-sintered SiAlON-SiC composite containing different SiC contents was investigated using high-resolution electron microscopy(HREM) and micro-indentation fracture(MIF) technique. The SiAlON-6%SiC composite showed the highest Vickers hardness and fracture toughness. The composite contained nanometer-size SiC particles dispersed homogeneously both in SiAlON grains and at grain boundaries. The grain boundary were formed with a 1-2㎚ thick amorphous layer regardness of the SiC content. The interface between SiAlON and SiC embedded in the grain, however, were formed without any amorphous layer. The typical fracture mode of the monolithic SiAlON was intergranular. That is, cracks propagate along The SiAlON grain boundaries with amorphous layers. In SiAlON-6wt%SiC, mixed mode of intergranular and transgranular fracture was observed, which seems to be caused by the nanometer-size SiC distributed in the SiAlON grains. In SiAlON-12wt%SiC, cracks propagated more straight through the SiAlON grains with submicron-size SiC particles, and the typical fracture mode was transgranular.

정응력하에서 Ti50NI35Pd15 형상기억합금의 변형거동에 관한 연구

천병선,이갑호,오현숙,홍석균 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.9

The B₂⇔ B_(19) transformation behaviours in a ternary Ti_(50)Ni_(35)Pd_(15)(at.%) alloy were investigated by means of electrical resistivity measurements, differential scanning calorimetry and constant load thermal cycling tests and they were compared with the B₂⇔ R and B₂⇔ B_(19) transformations in a thermo-mechanically treated binary Ti-50.2Ni alloy. The transformation start temperature of B₂→ B_(19) transformation and transformation finish temperature of B_(19) → B₂ transformation increased lineary with increasing applied stress. The stress dependence of the transformation start temperature, transformation elongation and hysteresis of the B₂⇔ B_(19) tranformations in the ternary alloy were 10.0MPa/K in the reciprocal form(dσ/dT) where σ in the critical stress for inducing the transformation, 2.1% and 25K, respectively. The B₂→ B_(19) transformation in the ternary Ti-Ni-Pd alloy lies between the B₂→ R and B₂B_(19)' transformation in the binary Ti-Ni alloy. And the transformation elongation associated with the B₂⇔ B_(19) transformation increased rapidly for stresses less than 80MPa and slowly above 80MPa with increasing applied stress.

高 망간 耐熱鋼의 熱處理에 의한 析出物에 관한 硏究

千炳善 충남대학교 공업기술개발연구소 1976 工業技術開發硏究所論文集 Vol.3 No.1

High Manganese steel with Mn, Cr, Co and Ti were studied mainly by micorography on the isothermal carbide precipitation after solution treatment. High Manganese austenite stainless steel has been developed for the high temperature application especially in boiler tubes. It was found that the hardness of the steels increased with increasing of the Titanium content and the solution temperatures. This hardness is due to dispersion hardening caused by undissolved Titanium-carbide particles. The major hardening phase was TiC and M_23C_6.

용사법에 의한 세라믹 코팅재의 고온마모 특성

천병선,한규석 대한금속재료학회 1991 대한금속재료학회 학술대회 개요집 Vol.1991 No.1

탄소강/Cu Bimetal 접합부의 강도에 관한 연구

천병선,이철로,류광현,임승택 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.9

A bimetal was produced by a welding method. Its base metal was carbon steel containing 0.53 wt% C and the weld metal was pure copper containing 1 wt% Sn which was added as a deoxidizer. The yield strength and the ultimate tensile strength of the bimetal bonding were 6.8 ㎏/㎟ and 21.5 ㎏/㎟, respectively. The Charry V-notch impact absorption energy of the bimetal was 41.8 J/㎠ and the fracture was found to take place in copper near the interface indicating relatively high interface strength. The elastic-plastic fracture toughness value under static load, Jic, was 1.1 ㎏/㎜ and the mode of fracture was similar to that in the Charpy impact test, The wear resistance of the base metal was superior to that of SUS 304 stainless steel.

열분석법에 의한 2090 Al-Li 합금의 시효거동에 미치는 In 첨가의 영향

천병선,이용연 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.2

The effects of indium on the phase transformation of 2090 Al-Li alloys has been studied with a differential scanning calorimeter (DSC), a transmission electron microscope(TEM), and a micro-hardness tester at the temperature ranges of 130℃∼220℃. The results show that indium addition to the 2090 Al-Li alloy retards the formation of prior precipitate(precursor) and δ´phase, whereas it accelerates the formation of T₁ and θ´(especially θ´phase). Above 190℃, the formation of δ´phases is retarted than those at 130℃ and at 160℃. The addition of 0.15wt% indium increases the hardness at the early stage of aging. The cause of this effect is attributed to the formation of GP zone. The main phases, in peak aged condition of indium free 2090 alloys are δ´and T₁; indium bearing 2090 alloys are θ´and T₁ (especially θ´Phases).