플랜트 엔지니어링을 위한 BCC-Fe 기반 저합금강의 기계적 및 열팽창 특성 합금 효과: Ab Initio 계산

김명재,곽종욱,김지웅,김경남 한국재료학회 2023 한국재료학회지 Vol.33 No.10

High-strength low-alloy steel is one of the widely used materials in onshore and offshore plant engineering. We investigated the alloying effect of solute atoms in α-Fe based alloy using ab initio calculations. Empirical equations were used to establish the effect of alloying on the Vicker’s hardness, screw energy coefficient, and edge dislocation energy coefficient of the steel. Screw and edge energy coefficients were improved by the addition of V and Cr solute atoms. In addition, the addition of trace quantities of V, Cr, and Mn enhanced abrasion resistance. Solute atoms and contents with excellent mechanical properties were selected and their thermal conductivity and thermal expansion behavior were investigated. The addition of Cr atom is expected to form alloys with low thermal conductivity and thermal expansion coefficient. This study provides a better understanding of the state-of-the-art research in low-alloy steel and can be used to guide researchers to explore and develop α-Fe based alloys with improved properties, that can be fabricated in smart and cost-effective manners.

Fe-29%Ni-17%Co 저열팽창 합금의 피로 특성에 미치는 알파상의 영향

김민종,권진한,조규상,이기안,Kim, Min-Jong,Gwon, Jin-Han,Cho, Kyu-Sang,Lee, Kee-Ahn 한국재료학회 2014 한국재료학회지 Vol.24 No.9

The effect of alpha phase on the fatigue properties of Fe-29%Ni-17%Co low thermal expansion alloy was investigated. Two kinds of alloys (Base alloy and Alpha alloy) were prepared by controlling the minimal alloy composition. Microstructure observation, tensile, high-cycle fatigue, and low-cycle fatigue results were measured in this study. The Base alloy microstructure showed typical austenite ${\gamma}$ phase. Alpha alloy represented the dispersed phase in the austenite ${\gamma}$ matrix. As a result of tensile testing, Alpha alloy was found to have higher strengths (Y.S. & T.S.) and lower elongation compared to those of the Base alloy. High cycle fatigue results showed that Alpha alloy had a higher fatigue limit (360MPa) than that (330MPa) of the Base alloy. The Alpha alloy exhibited the superior high cycle fatigue property in all of the fatigue stress conditions. SEM fractography results showed that the alpha phase could act to effectively retard both fatigue crack initiation and crack propagation. In the case of low-cycle fatigue, the Base alloy had longer fatigue life in the high plastic strain amplitude region and the Alpha alloy showed better fatigue property only in the low plastic strain amplitude region. The fatigue deformation behavior of the Fe-29%Ni-17%Co alloy was also discussed as related with its microstructure.

고령토 광물을 활용한 저 열팽창 코디어라이트 세라믹스 합성에 관한 연구

김순호(Soonho Kim) 한국산업기술융합학회(구. 산업기술교육훈련학회) 2023 산업기술연구논문지 (JITR) Vol.28 No.2

MAS(MgO Al2O3 SiO2)계 재료중에 코디어라이트 (2MgO 2Al2O3 5SiO2)의 경우 낮은 열팽창 계수, 내열 충격성, 낮은 유전율, 높은 전기 절연성 등의 특징을 나타낸다. 그러나 코디어라이트는 소결온도 범위가 좁아서 온도가 낮으면 결정이 충분히 형성되지 않고 약간 높으면 cordierite가 다시 postelite, spinel과 mullite로 분해됨에 따라 재료의 열팽창 계수가 크게 증가한다. 이 문제를 해결하기 위해 코디어라이트 조성을 카올린 광물의 혼합범위를 조정하여 소성한 결과 1340℃에서 물리적인 특성인 부피비중, 흡수율 기공율을 만족한 결과를 얻었다. 최적 혼합조건은 MgO/Al2O3 몰 비가 1.006이고 SiO2/Al2O3 몰 비가 2.4277인 것으로 나타났다. 이때 800℃에서 2.20×10-6/℃, 1,000℃에서 2.57×10-6/℃의 저 열팽창 계수와 물리적인 특성 및 수축을 고려하여 코디어라이트 산업을 위해 최적의 조건에서 차세대 이차전지 양극재 소결용 kiln furniture 소재 연구개발을 진행하였다. Cordierite (2MgO·2Al2O3·5SiO2) in the MgO·Al2O3·SiO2 system exhibits a low thermal expansion coefficient, high thermal shock resistance, low dielectric constant, and excellent electrical insulation properties. However, the material has a narrow sintering-temperature range. If the sintering temperature is too low, the crystal structure of cordierite does not form sufficiently; conversely, if it is slightly higher than ideal, the material decomposes into postelite, spinel, and mullite, leading to a significant increase in its thermal expansion coefficient. To overcome this problem, we adjusted the composition of cordierite by mixing it with predetermined amounts of kaolin minerals. After sintering at 1340℃, the resulting ceramic showed satisfactory physical properties, such as bulk density, absorption rate, and porosity. The optimal mixing conditions included a MgO/Al2O3 molar ratio of 1.006 and SiO2/Al2O3 molar ratio of 2.4277. Given its low thermal expansion coefficient(2.20 × 10−6/℃ at 800℃ and 2.57 × 10−6/℃ at 1000℃) and favorable physical and shrinkage properties, the cordierite prepared in this work may have potential applications in the development of kiln furniture materials for sintering next-generation secondary battery cathode materials.

Strain behaviors of solder bump with underfill for flip chip package under thermal loading condition

곽재 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12

Since the introduction of Cu/low-k as the interconnect material, the chip-package interaction (CPI) has become a critical reliabilitychallenge for flip chip packages. Revision of underfill material must be considered, which compromises the life of flip chip interconnectby releasing the stresses transferred to the silicon devices from the solder bumps, and thereby maintain the overall package reliability. Thus, it is important to understand the thermo-mechanical behavior of solder bumps. In this study, the solder bump reliability in flip chippackage was investigated through an experimental technique and numerical analysis. For the experimental assessment, thermomechanicalbehavior of solder joints, especially the solder bumps located at the chip corners where most failures usually occur was investigated. Digital image correlation (DIC) technique with optical microscope was utilized to quantify the deformation behavior and strainsof cross-sectioned solder bump of flip-chip package subjected to thermal loading from 25°C to 100°C. The results clearly show captureddeformations of solder bump under thermal loading. Finally, finite element analysis (FEA) was conducted by simulating the thermalloading applied in the experiments, and validated with experimental results. Then, consistently using the FEA analysis, parametric studyfor underfill material properties were performed on the reliability of flip chip package, by varying the glass transition temperature (Tg),Young’s modulus (E), and coefficient of thermal expansion (CTE). Averaged plastic work of the corner solder bump and stress at the dieside were obtained and used as damage indicators for solder bumps and low-k dielectrics layer, respectively. The results show that highTg, and E of underfill are generally desirable to improve the reliability of solder interconnects in the flip chip package.

MgO와 ZrO₂가 첨가된 Al₂TiO₅ 세라믹의 열·기계적 물성

김다미,김형태,김형준,김익진,최성철,김용찬,남궁정,류성수,Kim, Da-Mi,Kim, Hyung-Tae,Kim, Hyeong-Jun,Kim, Ik-Jin,Choi, Seong-Cheol,Kim, Yong-Chan,NamKung, Jung,Ryu, Sung-Soo 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.4

The characteristics of $Al_2TiO_5$ ceramics were influenced by the additives and the heat treatment that controls the microcrack behavior at grain boundaries. The effect of additives on $Al_2TiO_5$ ceramics were investigated in terms of mechanical properties and thermal expansion at high temperature. The $Al_2TiO_5$ were synthesized at $1500^{\circ}C$, $1550^{\circ}C$ and $1600^{\circ}C$ for 2h by reaction sintering. The formation of $Al_2TiO_5$ phase was increased by additives that enhanced the volume of the microcrack that can lead to low thermal expansion. The mechanical properties of the stabilized $Al_2TiO_5$ ceramics were increased remarkably at $1100^{\circ}C$, $1200^{\circ}C$ and $1300^{\circ}C$ due to the oneset of mechanical healing of grain-bondary microcracks at a high temperature. The amount of microcrack was decreased at lower sintering temperature that causes the increase of mechanical properties at high temperature.

SiO2 및 ZrO2가 함유된 티탄산 알루미늄 내화물의 용강 내 미세구조 변화

김다미 ( Da Mi Kim ),김형태 ( Hyung Tae Kim ),류성수 ( Sung Soo Ryu ),김형준 ( Hyeong Jun Kim ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.2

Aluminum titanate (AT) ceramics has high potential as alloy casting refractory materials due to their good thermal shock resistance which results from their low coefficient of thermal expansion. In a previous study, AT doped SiO2 and ZrO2 were developed to achieve stability and mechanical strength at high temperature. In this work, the changes of microstructure of AT doped SiO2 and ZrO2 were investigated in molten steel. A finger rotating test of sintered AT was carried out at 1300 ℃ for 30 min, 1 h, 2 h, and 3 h. Even if there was no reaction between AT and molten steel, a new surface was formed, followed by the decomposition of AT by the heat from molten steel, which was dominantly constituted of Al and Si due to decomposition of AT and Mullite phases. Some of the new surface layer was found to have been eroded by fluctuations of the molten steel.

Sol-Gel 법에 의한 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 다공성 결정화 유리의 제조 : (II) Sol-Gel 법에 의해 제조된 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 괴상겔의 결정화

조훈성,양중식 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.4

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

Thermal stability of Al2TiO5 ceramics for new diesel particulate filter applications-a literature review

김익진 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4

The use of Al2TiO5 ceramics in diesel engine exhaust systems has been limited by the problem of thermal stress and thermal instability caused by the anisotropic thermal expansion between different materials. In order to avoid this problem, one of the choices is to develop low or zero-level thermal expansion materials that can be used, for example in diesel particulate filters (DPF), in which the original dimensions of the material are maintained, without being affected by thermal shock at high temperatures. For such applications, Al2TiO5 ceramic particulate filters must also have chemical inertness, thermal durability,high filtration efficiency, low pressure drop-, and adequate strength. In particular, DPF ideally combine low thermal expansion, low pressure drop for engine efficiency, high filtration efficiency, high strength, and low production cost. This study examined the publications and patents for thermal stability of Al2TiO5 ceramics with different inorganic materials having a low thermal expansion and high thermal shock resistance, suitable porosity and a narrow pore size distribution suitable for diesel exhaust filtration applications.V

Fe-Ni-Co 저열팽창성 합금의 고온 변형 특성 및 열간가공에 따른 열팽창 거동 연구

이기안,박종혁,조봉현,남궁정,김문철 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.9

The high temperature deformation behavior and the effect of hot compression on the thermal expansion behavior of Fe-29Ni-17Co low thermal expansion Kovar alloy were investigated in the compressive temperature range of 900~1300℃ at the strain rate range of 25~0.01 sec.^(-1). The temperature (T) and strain rate (ε˙) dependence of the flow stress (σ_(0.7)) could be well described by hyperbolic sine law as ε˙= A [sinh(0.0084 σ)^(5.2018)] exp(-330.41/RT). Surface hot cracking and significant voids around grain boundary could be found at low temperature below 1000℃ and low strain rate (0.01 sec.^(-1)). Thermal expansion coefficient α_(30~400) generally increased with increasing compressive temperature. Moreover, α_(30~400) remarkably increased as strain rate decreased at high temperature above 1100℃. However the thermal expansion coefficient α_(30~400) of low compressive temperatures (900℃ and 1000℃) anomalously increased especially at high strain rates. Experimental results indicated that not only α phase appearance but also grain size had definite influence on the thermal expansion behavior with hot deformation. The correlation between microstructure and thermal expansion behavior of Kovar alloy were also discussed.

Fe-29%Ni-17%Co 저열팽창 합금의 열팽창 특성에 미치는 냉간 가공 및 열처리의 영향

이기안 ( Kee Ahn Lee ),권진한 ( Jin Han Gwon ),박종혁 ( Jong Hyuk Park ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.1

The changes to thermal expansion and mechanical properties by cold working were investigated in the Fe-29%Ni-17%Co (wt%) low thermal expansion alloy. The Fe-29%Ni-17%Co alloy was cold rolled gradually and prepared for plating with reduction ratios of 0%, 20%, 40%, 60%, and 80%. The effect of annealing on the property was also studied. Thermal expansion was measured from 25 ℃ to 600 ℃ using a vacuum differential dilatometer. We found that the thermal expansion coefficient (α30~400) slightly decreased (at a reduction ratio of 20%) and then remarkably increased (above reduction ratios of 40%) with increasing reduction ratios of cold rolling. The thermal expansion coefficient (α30~400) sharply decreased after heat treatment. Yield and tensile strengths continuously increased and elongation decreased by cold rolling. Microstructural observation and XRD analysis results showed that the α phase significantly increased as the reduction ratio increased. The slight decrease of the thermal expansion coefficient below a reduction ratio of 20% could be explained by the destruction of short-range ordering and decrease in grain size. The significant increase in the thermal expansion coefficient with cold rolling attributed to the appearance of the α phase. The correlation between the microstructural cause and invar effect of the low thermal expansion behavior is also discussed. (Received April 7, 2014)