SmCo5-χ Cuχ자석합금의 상에 관한 금속학적 연구

송진태 대한금속재료학회(대한금속학회) 1976 대한금속·재료학회지 Vol.14 No.2

600℃와 1000℃ 사이에서 SmCo_(5-x)Cu_x(x=1에서4) 合金系의 構造와 相을 X線回折, electron microprobe analysis, 및 顯微鏡的方法으로 究明하였다. 均質化處理後 800℃에서 소둔시킨 合金試料의 格子常數는 Cu 組成에 따라 變化하고 Cu 含量이 많을수록 커졌으나 Vegard의 法則에는 따르지 않았다. 600℃ 以上의(단 1,100℃아래) 溫度에서 燒鈍試料는 不安定하여 Sm₂Co_(17) 構造를 갖는 새로운 相이 粒界와 粒內에 析出하여 나타났다. microprobe 分析에 依하면 이들 相은 基地에 比하여 Cu 含量이 적고 Co 含量이 많은 析出粒子였다. 實驗結果는 Cu 元素가 SmCo_5 bulk 合金의 共析分解溫度를 600℃ 가까이로 크게 떨어트리고, 소둔시간을 充分히 길게 하여 주면 SmCo_(3·5)Cu_(1·5) 三元合金의 共析分解는 可能할 것이라는 것을 보여주고 있다. 또한 實驗結果에 依하면 600℃ 와 800℃사이에서 일어나는 SmCo_(3·5)Cu_(1·5) 合金의 保磁力의 變化는 磁壁과 Co-rich의 析出粒子사이의 pinning interaction으로 說明할 수 있다는 것을 알 수 있다. The structure and stability of the alloy system SmCo_(5-x)Cu_x with X in the range 1 to 4, have been investigated at temperatures between 600℃ and 1000℃ by X-ray diffraction techniques, electron microprobe analysis, and metallographic methods. It is shown that lattice constants of specimens annealed at 800℃ after homogenization increase with increasing the copper concentration, but do not follow the Vegard's law. In the temperature range higher than 600℃ (but below 1,100℃), annealed specimens are unstable and a new phase having the Sm₂Co_(17) structure primarily precipitate along grain boundaries in the matrix and secondarily in the interior of grains. Electron microprobe analysis has exposed that those phases are enriched in cobalt and poor in copper as compared with the matrix. The result show that the copper element lowers the eutectoid decomposition temperature of SmCo_5 bulk alloy in great extent to near 600℃, and the sufficient heat treatment may cause the eutectoid decomposition of SmCo_(3·5)Cu_(1·5) ternary alloys. They also show that change in coercive force of SmCo_(3·5)Cu_(1·5) alloy between 600℃ and 800℃ can account for pinning interaction between domain wall movement and Co-rich precipitation particle.

고탄소계(高炭素系) Cr-Ti 합금동 레일재의 마모특성(磨耗特性)에 관한 연구

송진태,강계명,고석수 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.12

This study is concerned with the investigation of wear properties of commercial rail steel and high carbon Cr-Ti a1loy steel which is expected to be the new prosperous and energy-saving rail steel. Especially, using rolling contact fatigue test method, the running surface layer of alloy steel and its wear surface were investigated by metallography in detail, in order to clarify the wear behavior of alloy steel. Experimental results showed that the amount of wear of high carbon Cr-Ti alloy steel was half as much as the commercial rail steel. Through the SEM observation of running surface layer, the wear behavior of alloy steel proved to be related to the strain hardening occurring under the wear surface and to voids and microcracks generated in those strain hardened areas as sliding distance increased. The shape of wear debris of this alloy steel showed shallow-rounded sheets. During rolling contact fatigue test, the fatigue cracks of alloy steel were observed as flake type and she11ing damage defects. It has also been thought that those phenomena of alloy steel resulted from pearlite lamella structure of pearlitic steel.

Al-4 % Cu 합금의 석출에 미치는 중성자조사의 효과

송진태,모야수부 대한금속재료학회(대한금속학회) 1974 대한금속·재료학회지 Vol.12 No.1

Al-4%Cu 合金의 析出過程에 미치는 高速性中子의 照射效果를 Vickers 硬度의 測定 및 透過電子顯微鏡으로 관측 고찰하였다. 中性子照射는 日本原子力硏究所材料試驗爐(JMTR)內에서 行하였고 照財中性子量은 各各 2.8×10^(19), 3.4×10^(20), 1.2×10^(21)nvt였다. θ'折出粒子의 成長速度의 觀測은 電子顯微鏡의 hot stage를 사용하였고 測定資料는 析出物의 成長機構에 관한 最近의 ledge 理論式들에 적용 검토하였다. 그 結果 照射한 試料의 擴散係數 및 Arrhenius 振動數項은 未照射試料보다 훨씬 컸고 이것은 照射에 依해서 生成된 過剩空孔(excess vacancies) 또는 interstitials에 기인하는 것이라 믿어진다. 實驗結果는 中性子의 照射가 不均一核生成을 증가시킬 뿐만 아니라 溶質原子의 擴散을 促進시키며 이러한 效果는 照財線量이 많을수록 크며 析出物 成長速度는 보다 커진다는 것을 보여주고 있다. In order to examine the effects of fast neutron irradiation on the precipitation process in Al-4%Cu alloy, hardness measurement and transmission electron microscope were employed. Specimens were irradiated to 2.8×10^(19), 3.4×10^(20) and 1.2×10^(21) nvt neutron doses in the Japan Materials Testing Reactor. Their electron micrographs prior to annealing or at the early stage of annealing at 200℃ showed G. P. 2 and even θ' plates, which it can not normally expect to form. The kinetics of growing of θ'plates in Al-4%Cu alloy were measured by means of hot stage transmission electron microscopy, and the lengthening data of θ'plate measured at each temperature and at each neutron dose have been interpreted in terms of the various equations for recent ledge theories of growth. The calculated diffusivity and frequency factor of Arrhenius' equation of specimen irradiated to 2.3×10^(19) nvt neutron are much larger than the un-irradiated one. This may be attributed to excess vacancies or interstitials produced by irradiation. It is concluded that neutron irradiation does not only bring the enhancement of heterogeneous nucleation, but also give rise to enhanced diffusion of solute atom, and the more the neutron dose increases, the greater the growth rate becomes.

스크린 인쇄법에 의한 YBa2Cu3O7-x/ Ag 고온산화물초전도 후막의 제작

송진태,장호정,도부안광,토신전풍,청수현사,추병량삼 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.9

Superconduction YBa₂Cu₃0_(7-x)./Ag composite thick films on a YSZ substrate were prepared by the screen printing method. Microstructure and supercduction properties such as zero-resistance Tc(Tc^(Zero)), Jc at 77k, and the interface reactions betwean the superconduction thick film and YSZ substrate were investigated. For the YBa₂Cu₃O_(7-x)/Ag composite thick films annealed at 980℃ and 1000℃ in flowing oxygen, Tc^(Zero) and Jc at 77k increased, and the normal state resistivity and the thickness of interface reaction layer decreased strongly with increasing Ag content. The drastic decrease in reaction layer thickness with Ag addition seemed to result from the prevention of interaction between the film and the substrate by liquid Ag which formed during high temperature annealing. SEM analysis showed that the grain size increased as Ag content increased from 7wt% to 24wt%. It seems that the liquid Ag in YBa₂Cu₃O_(7-x)/Ag composite thick films enhances the intergranular coupling of YBa₂Cu_O_(7-x)/Ag grains, which results in the favored sintering process at 980℃.

稀土類金属코발트 鑄造磁石의 磁氣特性

宋振泰 대한전기학회 1976 대한전기학회 워크샵 Vol.1976 No.8

초전도자석의 선재와 응용기술

송진태,Song, Jin-Tae 한국전기산업진흥회 1990 電氣産業 Vol.1 No.3

Martensite 와 Bainite 의 혼합조직을 갖는 Ni-Cr-Mo 강의 소려취성 (燒戾脆性) 에 관한 연구

송진태,오영근 대한금속재료학회(대한금속학회) 1983 대한금속·재료학회지 Vol.21 No.4

A stdy has been made on tempered embrittlement of AISI 4340 steel having martensite-bainite duplex structure, as compared with that in tempered martensite, metallographically. For making martensite-bainite duplex structure, lower bainite formation was achieved in a salt bath held at 315℃, upper bainite at 400℃, and subsequently quenched into iced brine. After the isothermal transformation, they were tempered for lhr in the range between 200℃ and 500℃, and then the mechanical properties were examined. Impact toughness was measured by Charpy Impact Tester, microstructure was examined by means of optical and transmission electron microscope, and fracture surface scanning electron microscope. The lower bainite was precipitated acicularly so as to partition prior austenite grain and the upper bainite was precipitated massively so as to fill prior austenite grain. These shapes of bainite had an effect on the impact toughness, temper embrittlement, and brittle fracture resistance of martensite-bainite duplex structure. The 300℃-tempered martensite embrittlement was greatly improved by martensite-bainte duplex structure and the ductile-brittle transition temperature of martensite-bainite duplex structure was lower than that of martensite. The former, the improvement of tempered martensite embrittlement by martensite-bainite duplex structure, may have been attributed to the shape and distribution of carbide which precipitated differently compared with those of martensite structure during tempering. They also affected on the fracture behavior. And, it seemed that the latter, the increment of brittle fracture resistance, have been due to the partitioning of prior austenite grain, with the result of fining cleavage crack path by lower bainite.

Fe-Cr-Co-R (R:稀有金屬) 자석재료의 개발에 관한 연구

송진태 대한금속재료학회(대한금속학회) 1975 대한금속·재료학회지 Vol.13 No.3

Fe-Cr-Co-R(R: 稀有金屬 Y와 Sm) 磁石合金의 磁氣特性과 機械的性質을 조사하여 그들 特性의 機構를 熱處理와 관계시켜 硏究考察하였다. 많은 Fe-30%Cr-25%Co-(1∼2%)R 四元合金의 試料는 알곤(Ar) 분위기의 아크爐를 사용하여 熔解 제작하였으며 均質化處理後 試料는 다시 100℃와 800℃사이의 各溫度에서 여러 時間동안 소둔되었다. 實驗結果는 Fe-Cr-Co-R 四元合金의 磁氣特性과 기계적성질은 500℃와 600℃ 사이에서 소둔시켰을 때 가장 우수하였고 Fe-Cr-Co 三元合金에 比하여 월등하였다. 特히 Fe-30%Cr-25%Co-2%Sm 合金의 保磁力은 Fe-Cr-Co 磁石合金에 비교하여 현저히 컸으며 最大磁氣에너지積은 580℃에서 16時間 소둔시킨 상태에서 3.3MGOe였다. 合金의 保磁力과 硬度가 peak를 이루는 소둔온도는 거의 같았으며 이것은 많은 析出型磁性材料에서 볼 수 있는 것과는 다소 달랐다. 本磁石合金들의 保磁力과 引張强度가 500℃와 600℃의 時效溫度사이에서 뛰어난 特性을 보인 것은 높은 飽和磁東密度를 갖는 (Fe-Co-R)相과 非强磁性相인 Cr rich相이 spinodal 分解로 微細한 變調組織을 이루기 때문이라 믿어진다. Magnetic and mechanical properties of Fe-Cr-Co-R (R: rare earth metals Y and Sm) magnet alloys were studied and the mechanism bringing about their characteristics is closely examined through the heat treatment. A number of Fe-30%Cr-25%Co-(1∼2)%R quaternary alloys for specimens were prepared by arc melting under a protective atmosphere and specimens were annealed for various times at the aging temperatures between 100℃ and 800℃. It was found that the magnetic and mechanical properties of Fe-Cr-Co-R quaternary alloys annealed between 500℃ and 600℃ were the best and superior to Fe-Cr-Co ternary alloys. Especially, the coercive force of Fe-30%Cr-25%Cr-2% Sm was remarkable compared to Fe-Cr-Co magnet alloys and the maximum energy product 3.3 MGOe was obtained at the state annealed at 580℃ and for 16hrs. Temperature difference between the peak of coercive force and hardness of alloys was almost nothing, which was less than the temperature difference in many precipitated magnetic materials. It may be concluded that the significant increment of coercive force and tensile strength between aging temperatures 500℃ and 600℃ of these alloys is due to the modulated structure of fine (Fe-Co-R) phases with a high saturation magnetization and non-ferromagnetic Cr rich phase produced by the spinodal decomposition.

Al-3 . 4 % Cu 합금의 석출경화와 소성변형의 전자현미경고찰

송진태 대한금속재료학회(대한금속학회) 1973 대한금속·재료학회지 Vol.11 No.1

銅 3.4%를 含有하는 Al系 合金을 時效熱處理시켜 時效에 따라 일어나는 合金의 機械的性質의 變化와 時效硬化 및 塑性變形의 slip 特性을 replica 및 透過電子顯微境으로 관찰하였다. 時效溫度는 220℃ 및 250℃ 이고 試料變形은 破壞에 이르기까지 引張시켰다. 合金硬度의 時效曲線은 모두 single stage 曲線을 나타내고 220℃와 250℃에서 관측된 金屬組織은 明確한 板狀의 G. P. 2와 θ' 析出相으로 {100} 基地面에 Widmansta¨tten 조직을 이루었다. 析出硬化型合金의 强度에 관한 여러가지 硬化理論을 θ' 析出相의 조직을 갖는 Al-3.4%Cu 合金에 適用시켜 合金의 降伏强度를 計算하여 實驗値와 比較檢討하였고 試料의 塑性變形에서 관측된 여러 형태의 slip 線을 그들의 形成機構에 관한 諸理論으로 고찰하여 보았다. 結論的으로 slip 線은 析出粒子를 通過하여 그들을 變形, 굽어지게하고 Al 3.4% Cu 合金의 時效硬化는 化學的析出硬化機構로서 說明할 수 있음이 分明하다. In order to study the agehardening and metallography of slip characteristics of the heat-treated aluminium-3.4% copper alloy, replica and transmission electron microscopy have been used. After the alloys have been aged at 220℃ and 250℃ they were stretched up to fracture. Their hardness showed single stage aging curve. The θ' phase and G. P. 2 zone were definite platelets and formed on the {100} matrix planes in a Widmansta¨tten pattern. Rough estimates were made on the yield strength of alloys containing intermediate θ' precipitates in the matrix, using a few models for the strength of precipitation-hardened alloys. Slip lines which were found in this experiment are the interpreted in terms of various theories appropriate to each one. It is clearly concluded that slip lines pass through the precipitate particles causing platelets in their path to deform and the age hardening of aluminium 3.4% copper alloy can be explained by considering the internal stress and the precipitate-matrix interfacial energy produced when a dislocation penetrates precipitates in the matrix.

TMT (가공열처리) 가 국산 레일강의 피로특성에 미치는 효과

송진태,강계명 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.8

The effect of thermomechanical treatment(TMT) on the fatigue and wear properties of a rail steel was examined. The sample was austenitized at 1090℃ and then transformed to pearlitic structure by holding at 700℃ for 17 hr. Samples were then cold rolled to the thickness of 25 ㎜. These samples were heated at 760℃ for 5 to 50 sec. The reduction of pearlitic interlamellar spacing and refinement of the austenite gram size were achieved by the TMT. The sample heated at 760℃ for 10 sec after cold rolling showed better fatigue strength and wear resistance than both the sample without cold rolling and the one with only cold rolling treatment. The fatigue cracks tend to orient them selves parallel to pearlite lamellars. This could be explained by Miller-Smith model. The higher fatigue srtrngth the sample has, the higher wear resistance it has.