개량 Al-0.7Mn 합금의 미세조직, 고온 변형 거동 및 성형성

강태훈,황원구,신영철,최호준,노흥렬,이기안 한국소성∙가공학회 2022 소성가공 : 한국소성가공학회지 Vol.31 No.6

The microstructure and high-temperature plastic deformation behavior of the modified Al-0.7Mn alloy were investigated and compared with the conventional Al-0.3Mn (Al3102) alloy. α-Al (matrix) and Al6(Mn, Fe) phases were identified in both alloys. As a result of microstructure observation, both alloys showed equiaxed grains, and Al-0.7Mn alloy showed larger grain size and higher Al6(Mn, Fe) fraction than Al-0.3Mn alloy. High temperature compressive tests, the deformation temperatures of 410℃, 450℃, 490℃, 530℃ and strain rats of 10-2/s, 10-1/s, 1/s, 10/s, were conducted using Gleeble equipment. The flow stress values of Al-0.7Mn alloy were higher than that of Al-0.3Mn alloy at all strain rates and temperature conditions. Constitutive equations were presented using the flow stresses obtained from experimental results and the Zener-Hollomon parameter. In the true stress-true strain curves of the two alloys, the experimental and predicted values were in good agreement with each other. Based on the dynamic material model, eutectic deformation maps of Al-0.7Mn and Al-0.3Mn alloys were suggested, and the plastic instability region was presented. The modified Al-0.7Mn alloy showed a wider plastic instability region than that Al-0.3Mn alloy. Based on the process deformation maps, the MPE tube parts could be manufactured through the actual extrusion process using the suggested conditions.

아랍어 어휘의 의미론적 특징들 -이철동의어, 동철이의어, 동철반의어를 중심으로-

정규영 ( Kyu Young Jung ) 부산외국어대학교 지중해연구소 2015 지중해지역연구 Vol.17 No.1

al-Mutaradif, al-Mushtarak al-Lafzi, and al-Tadadd are important features of Arabic vocabularies. Especially al-Tadadd is not common in many languages of the world. This study aims to elucidate these linguistic terms by way of giving definitions, introducing various opinions of Arab scholars on them, and clarify the reasons and linguistic backgrounds that have led to these vocabularies. al-Mushtarak al-Lafzi is often translated in English as homonym. Every al-Mushtarak al-Lafzi belongs to homonym, but every homonym is not al-Mushtarak al-Lafzi because al-Mushtarak al-Lafzi is defined on the basis of the phonetic views not phonological views. Arabic has more al-Mutaradif than any other languages in the world. According to Arab scholars, in Arabic there are more than one thousand words meaning the sword, more than 500 words meaning the lion, more than 400 words meaning the fox, … etc. This makes Arabic one of the richest languages in the world abundant al-Mushtarak al-Lafzi. This study also tries to elucidate the feature of al-Tadadd, which can be defined as words having the opposite meanings in one word as in /□aqil/ for a wise man and an idiot, and /mawla/ for a master and a slave. These characteristics is very important in teaching the Arabic and help the Arabic learners understand Arabic vocabularies as well.

Al이 도핑된 GaInAsSb/GaSb의 경계면에서의 밴드정렬

심규리,Shim, Kyurhee 한국결정성장학회 2016 韓國結晶成長學會誌 Vol.26 No.6

GaSb 기판위에 Al이 도핑된 GaInAsSb(Al-GaInAsSb)에 대한 최고 가전대 준위(VBM)와 최저 전도대 준위(CBM) 변화를 범용적 밀접결합방법에 근거한 해석적 근사법을 이용하여 계산하였다. GaSb와 Al-GaInAsSb 의 상대적 VBM과 CBM 준위에 따라 경계면에서의 밴드정렬 타입과 가전자대 오프셋(VBO)과 전도대 오프셋(CBO)이 결정된다. 본 논문에서는 Al 도핑이 GaInAsSb의 양이온 자리에 치환된다는 가정하에 이론이 전개 되었으며, Al은 부식등으로 결정의 질을 떨어트릴 수 있는 요인이 되므로 20 %까지 제한하였다. Al 도핑 결과, 전 구간에서 제 II 형의 밴드정렬형태를 갖게 되며, 밴드갭이 증가되는 반면 VBO와 CBO 는 감소됨을 알수 있었다. CBO 에 대한 감소비율 VBO 보다 더 크므로, Al 도핑은 경계면에서의 전자 콘트롤에 더 효율적으로 작용함을 알 수 있었다. Al-GaInAsSb은 전 구간에서 $E({\Gamma})$가 E(L)이나 E(X)보다 낮은 직접 갭을 나타 내고 있지만, Sb 성분이 많아지면(70~80 % 이상) E(L)과 E(X)이 $E({\Gamma})$에 가까워져서 전자 이동도에 영향을 주어 광학적 효율이 다소 떨어질 수 있음을 알 수 있었다. The valence band maximum (VBM) and conduction band minimum (CBM) of Al-doped GaInAsSb alloys substrated on GaSb are calculated by using an analytic approximation based on the tight binding method. The relative positions of the VBM and CBM between Al-GaInASSb and GaSb determine band alignement type, valence band offset (VBO) and conductin band offset (CBO) for the heterojunctions. In this study, aluminium doping is assumed to be substituted in the cation site and limited up to 20 % because it can easily oxidize and degrade materials. It is found that the Al-doped alloys exhibit type-II band alignments over the entire composition range and make the band gaps increase, whereas the VBO and CBO decrease. The decreasing rate of VBO is higher than that of CBO, which implies the Al components play a decisive role in controlling electrons at the interface. The Al-dopled GaInAsSb alloy has a direct band gap induced by $E({\Gamma})$ with a considerable distance from the E(L) and E(X), however, $E({\Gamma})$ approaches to E(L) and E(X) in the high Sb concentration (Sb > 0.7-0.8) which might affect the electron mobility and degrade the optical quality.

열처리가 Al-Mg 코팅 강판의 내식성에 미치는 영향

정재훈(Jae-Hun Jung),양지훈(Ji-Hoon Yang),송민아(Min-A Song),김성환(Sung-Hwan Kim),정재인(Jae-In Jeong),이명훈(Myeong-Hoon Lee) 한국표면공학회 2014 한국표면공학회지 Vol.47 No.4

Double layer films which consisted of aluminum(Al) and magnesium(Mg) have been prepared by e-beam deposition. The structure, alloy phase, and corrosion resistance of the prepared films were investigated before and after heat treatment. The first (bottom) layer fixed with Al, and the thickness ratio between Al and Mg layers has been changed from 1 : 1 to 5 : 1, respectively. Total thickness of Al-Mg film was fixed at 3 μm. The cold-rolled steel sheet was used as a substrate. Heat treatment was fulfilled in an nitrogen atmosphere at the temperature of 400℃ for 2, 3 and 10 min. Surface morphology of as-deposited Al-Mg film having Mg top layer showed plate-like structure. The morphology was not changed even after heat treatment. However, cross-sectional morphology of Al-Mg films was drastically changed after heat treatment, especially for the samples heat treated for 10 min. The morphology of as-deposited films showed columnar structure, while featureless structure of the films appeared after heat treatment. The x-ray diffraction data for as-deposited Al-Mg films showed only pure Al and Mg peaks. However, Al-Mg alloy peaks such as Al3Mg2 and Al12Mg17 appeared after heat treatment of the films. It is believed that the formation of Al-Mg alloy phase affected the structure change of Al-Mg film. It was found that the corrosion resistance of Al-Mg film was increased after heat treatment.

단일 롤 방법으로 제작한 3원계 Al-Cr-Si 급냉리본의 구조 및 열 특성

한창석,김기웅,김우석 한국재료학회 2021 한국재료학회지 Vol.31 No.5

Al-Cr-Si ternary quench ribbons are fabricated using a single roll method and investigated for their structural and thermal properties. In particular, the sinterability is examined by pulse current sintering to obtain the following results. The Al74Cr20Si6 composition becomes a quasicrystalline single phase; by reducing the amount of Cr, it becomes a twophase mixed structure of Al phase and quasicrystalline phase. As a result of sintering of Al74Cr20Si6, Al77Cr13Si10 and Al90Cr6Si4 compositions, the sintering density is increased with the large amount of Al phase; the sintering density is the highest in Al90Cr6Si4 composition. In addition, as a result of investigating the effects of sintering temperature and pressurization on the sintered density of Al90Cr6Si4, a sintered compact of 99% or more at 513 K and 500 MPa is produced. In particular, since the Al-Cr-Si ternary crystal is more thermally stable than the Al-Cr binary quaternary crystal, it is possible to increase the sintering temperature by about 100 K. Therefore, using an alloy of Al90Cr6Si4 composition, a sintered compact having a sintered density of 99 % or more at 613 K and 250 MPa can be manufactured. It is possible to increase the sintering temperature by using the alloy system as a ternary system. As a result, it is possible to produce a sintered body with higher density than that possible using the binary system, and at half the pressure compared with the conventional Al-Cr binary system.

알 카시의 첨두아치 작도와 티무르조 건축의 곡면구조

최남섭 한국건축역사학회 2023 건축역사연구 Vol.32 No.5

티무르조 말기에 알 카시(Al-Kāshī)는 [수리학의 열쇠(Miftāḥ al-Hisāb)](1427)라는 수학과 기하학 이론서를 저술했다. 여기에 수록된 다섯 논문(Maqālat) 중에 「면적 측정(Misāḥat)」은 ‘군주의 치소와 대형건물(Al-‘Emārāt wa al-Abnīya)에 설치하는 배럴볼트(Azaj)와 돔(Qubba)의 표면적과 부피 측정법을 설명한다. 이를 위해 그가 원호와 직선을 조합해 만든 다섯 개의 첨두아치(Ṭāq)는 이슬람 건축의 곡면구조가 구성되는 원리를 해석할 수 있는 단서이며, 다른 무슬림학자들이 벽면의 기하학적 장식만을 다루었던 성과와 구별되는 기록으로서 건축적으로 면밀하게 탐구할 가치가 있다. 이에 연구자는 수리학의 열쇠 의 ‘군주의 치소와 대형건물’에서 알 카시가 배럴볼트와 돔의 면적측정을 위해 제시한 다섯 첨두아치의 기하학적 특성과 건축적 의미를 살펴보고자 한다. 이러한 연구를 통해 이슬람건축의 기념비 장치로 여겨지는 곡면구조의 계획원리, 활용방법, 유형적 특성을 확인하는 것이 목적이다. 이를 위해 수리학의 열쇠 의 영어 번역본을 중심으로 아랍어와 페르시아어본을 검토해 책의 구성과 저자의 서술 태도를 살폈으며, 이슬람권 학술 전통 안에서 첨두아치 설명의 실용적 측면을 확인했다. 이어서 그가 제시한 첨두아치의 성격을 나누어서 각각의 작도법과 크기, 높이, 곡률 등의 특성을 비교 분석했으며, 첨두아치를 곡면구조로 변환해 기념비 장치로 사용하는 방법도 확인했다. 여기에 더해 알 카시가 규정한 첨두아치가 건물의 단면 계획에서 가지는 의미와 특정 아치 유형의 특성을 공유하게 된 배경을 고찰했다. The study aims to analyze the geometric characteristics of the pointed arches proposed by Al-Kāshī in his book "Miftāḥ al-Ḥisāb" (Key of Arithmetic) and investigate their planning principles, architectural application, and typological characteristics. Al-Kāshī completed this significant work in 1427 and dedicated it to Ulugh Beg, a Timurid Sultan in Samarkand. In the ninth chapter, titled "Al-‘Imārāt wa al-Abnīya" (Amīr’s Mansion and Building), Al-Kāshī sought to measure the surface areas and volumes of barrel vaults (Azaj) and domes (Qubba). To achieve this, he proposed five kinds of pointed arches (Ṭāq) and analyzed their drawing methods and composition principles. The Īwān and Qubba structures, which are curved architectural elements, hold significant importance in Islamic architecture. However, previous research has predominantly focused on comparing the drawings in Al-Kāshī's book with historical buildings, neglecting the inherent characteristics of the drawings themselves. This study intends to contribute to a deeper understanding of Al-Kāshī's remarkable work and shed light on the geometric aspects of monumental structures in the Timurid Period.

Al$_2$O$_3$/t-ZrO$_2$ 입자복합체의 미세구조 및 기계적 성질

심동훈,이윤복,김영우,오기동,박홍채 한국세라믹학회 1999 한국세라믹학회지 Vol.36 No.7

Al2O3와 t-ZrO2 분말의 압분체를 공기중 150$0^{\circ}C$ 및 1$600^{\circ}C$에서 2시간 소결하여 제조된 입자복합체의 미세구조와 기계적 성질을 조사하였다. 소수의 미세한 구상의 ZrO2입자는 Al2O3의 입내에 존재하였으나 대분분은 입계에 존재하여 Al2O3의 입계를 고정시키는 것이 가능하였고, 따라서 Al2O3의 입성장을 둔화시켰다. 소결할 동안 입계 ZrO2 입자의 조대회는 응집된 ZrO2 입자내에서의 입계의 소멸과 Al2P3 입계의 이동에 의해서 끌어 당겨진 ZrO2 입자의 합체(coalescence)에 의해서 일어날 수 있었다. ZrO2의 첨가에 의한 Al2O3의 기계적 성질의 변화는 기지상인 Al2O3의 미세구조와 분산된 ZrO2 입자의 크기와 구조에 의존하였다. Al2O3/t-ZrO2 particulate composites were prepared by sintering at 150$0^{\circ}C$ and 1$600^{\circ}C$ for 2h in air and microstructure and mechanical properties of the composites were investigated. Although most ZrO2 particles existed at Al2O3 grain boundaries a few ZrO2 particles within Al2O3 grains. Al2O3 grain growth was depressed due to the pinning effect by ZrO2 particles. During sintering coarsening of intergranular ZrO2 particles occurred as a results of the elimination of ZrO2 intraagglomerate grain boundaries and the coalescence of dragged ZrO2 particles by migrating Al2O3 grain boundries. Changes in mechanical properties of Al2O3 composites were dependant on microstructure of Al2O3 matrix and on size and structure of dispersed ZrO2.

기계적 합금화 및 스파크 플라즈마 소결에 의해 제조된 Al-Fe-X계 합금의 열적 안정성: II. Al-Fe-Cr and Al-Fe-Mo

이현권,이상우,조경식,Lee, Hyun-Kwuon,Lee, Sang-Woo,Cho, Kyeong-Sik 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.1

Mechanical alloying using high-energy ball mill and subsequent spark plasma sintering (SPS) process was applied to Al-Fe-Cr and Al-Fe-Mo powder mixture to investigate effects of Cr and Mo addition on thermal stability of Al-Fe, and thereby to enhance its thermal stability up to $500^{\circC}$. Various analytical techniques including micro-Vickers hardness test, SEM, TEM, X-ray diffractometry and corrosion test were carried out. It was found that addition of Cr and Mo to Al-Fe system played a role of grain growth inhibitor of matrix Al and some precipitates such as $Al_3Fe$ during SPS and subsequent heat treatment. The inhibition of grain growth resulted in increased Vickers hardness and thermal stability up to $500^{\circC}$ comparing to those of Al-Fe alloy system.

Mo-Al 복합 산화물의 질화반응 처리된 촉매상에서 암모니아 촉매 분해반응

백서현 ( Seo-hyeon Baek ),윤경희 ( Kyunghee Youn ),신채호 ( Chae-ho Shin ) 한국화학공학회 2022 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.60 No.1

MoO₃ 비율을 10-50 중량비로 변화하여 제조한 Mo-Al 복합 산화물 상에서 소성 후 승온 질화반응을 통하여 얻은 Mo-Al 질화물 상에서 암모니아 분해반응에서의 촉매 활성을 검토하였다. 제조된 촉매의 물리·화학적 특성을 알아보기 위하여 N₂ 흡착분석, X-선 회절분석(XRD), X-선 광전자분석법(XPS), 수소 승온환원(H₂-TPR), 투과전자현미경(TEM)분석을 수행하였다. 600 ℃에서 소성 후 Mo-Al 복합산화물은 γ-Al₂O₃와 Al₂(MoO₄)₃ 결정상을 나타냈으며 질화반응후의 질화물은 비정형 형태를 보여주었다. 질화반응 후의 비표면적은 MoO₃의 위상전환반응에 의해 Mo 질화물 형성으로 인해 증가하였으며, Mo 질화물이 γ-Al₂O₃에 담지된 형태를 보여주었다. 암모니아 분해반응에서의 촉매 활성은 40 wt% MoO₃가 가장 좋은 활성을 보여주었고, 질화반응 시간이 증가함에 따라 활성이 증가하였으며 이에 따라 활성화에너지 감소 효과를 나타냈다. Catalytic activity in ammonia decomposition reaction was studied on Mo-Al nitride obtained through temperature programmed nitridation of calcined Mo-Al mixed oxide prepared by varying the MoO₃ quantity in the range of 10-50 wt%. N₂ sorption analysis, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and H₂- temperature programmed reduction (H₂-TPR), and transmission electron microscopy (TEM) to investigate the physicochemical properties of the prepared catalyst were performed. After calcination at 600 ℃, the XRD of Mo-Al oxide showed γ-Al₂O₃ and Al₂(MoO₄)₃ phases, and the nitride after nitridation showed an amorphous form. The specific surface area after nitridation by topotactic transformation of MoO₃ to nitride was increased due to the formation of Mo nitride, and the Mo nitride was observed to be supported on γ-Al₂O₃. As for the catalytic activity in the ammonia decomposition reaction, 40 wt% MoO₃ showed the best activity, and as the nitridation time increases, the activity increased, and thus the activation energy decreased.

$Al/SiC/Al_{2}O_{3}$복합재료의 기계적 성질 및 마멸특성

임흥준,김영한,한경섭 대한기계학회 1993 대한기계학회논문집 Vol.17 No.10

$Al/SiC/Al_{2}O_{3}$ hybrid composites are fabricated by squeeze infiltration method. From the misconstructive of $Al/SiC/Al_{2}O_{3}$ hybrid composites fabricated by squeeze infiltration method, uniform distribution of reinforcements and good bondings are found. Hardness value of $Al/SiC/Al_{2}O_{3}$ hybrid composites increases linearly with the volume fraction of reinforcement because SiC whisker and $Al_{2}$O$_{3}$ fiber have an outstanding hardness. Optimal aging conditions are obtained by examining the hardness of $Al/SiC/Al_{2}O_{3}$ hybrid composites with different aging time. Tensile properties such as Young's modulus and ultimate tensile strength are improved up to 30% and 40% by the addition of reinforcements, respectively. Failure mode of $Al/SiC/Al_{2}O_{3}$ hybrid composites is ductile on microstructural level. Through the abrasive wear test and wear surface analysis, wear behaviour and mechanism of 6061 aluminum and $Al/SiC/Al_{2}O_{3}$ hybrid composites are characterized under various testing conditions. The addition of SiC whisker to $Al/SiC/Al_{2}O_{3}$ composites gives rise to improvement of the wear resistance. The wear resistance of $Al/SiC/Al_{2}O_{3}$ hybrid composites is superior to that of Al/SiC composites. The wear mechanism of aluminum alloy is mainly abrasive wear at low speed range and adhesive and melt wear at high speed range. In contrast, that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is abrasive wear at all speed range, but severe wear when counter material is stainless steel. As the testing temperature increases, wear loss of aluminum alloy decreases because the matrix is getting more ductile, but that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is hardly varied. Oil lubricant is more effective to reduce the wear loss of aluminum alloy and $Al/SiC/Al_{2}O_{3}$ hybrid composites at high speed range.