3원계 Al-Cu-Sc합금의 시효처리과정에서 석출한 θ′ 및 Al₃Sc 석출물의 성장에 미치는 Sc 및 Cu의 영향

한창석(Chang-Suk Han),심우빈(Woo-Bin Sim) 호서대학교 공업기술연구소 2023 공업기술연구 논문집 Vol.42 No.1

Sc를 소량 첨가한 알루미늄합금은 시효처리를 통하여 뚜렷한 경화현상이 나타난다. Sc가 Al에 용해되는 용해도는 매우 작지만, 이 합금계에서 시효경화는 모상에 정합으로 격자정수가 약간 다른 L12형 규칙상인 평형상 Al₃Sc가 구상으로 미세하게 석출하기 때문이다. 본 연구에서는 Al-2.5 mass%Cu-0.23 mass%Sc인 3원 합금이 시효처리 과정에서 발생하는 2종류의 석출물인 θ′ 및 Al₃Sc에 대하여 각각의 석출물 위에 불균일한 석출과 이와 같은 석출물의 성장에 미치는 Sc 및 Cu의 영향에 대하여 투과형 전자현미경을 이용하여 관찰한 결과를 바탕으로 검토하였다. θ′-Al₂Cu 및 Al₃Sc의 성장은 확산율속으로 진행되며, 오스트왈드 성장법칙에 따른다. θ′-Al₂Cu 위에 Al₃Sc가 불균일하게 석출되는 것은 θ′-Al₂Cu가 성장하여 θ′-Al₂Cu/모상 계면에 형성된 계면전위 부분으로 Sc원자가 이동하기 때문이다. 그리고 Al₃Sc 위에 θ′-Al₂Cu가 불균일하게 석출하는 것은 Al₃Sc/모상계면에 형성된 계면전위 부분으로 Cu원자가 이동하기 때문이다. Aluminum alloys with a small amount of Sc added show a distinct hardening phenomenon through aging. Although the solubility of Sc in Al is very small, age hardening in this alloy system is due to the fine precipitation of the equilibrium phase Al₃Sc into the spheroids, which is the L12-type regular phase with slightly different lattice coefficients in agreement with the parent phase. In this study, two types of precipitates, θ′ and Al₃Sc, formed during the aging process of a ternary alloy with Al-2.5 mass%Cu-0.23 mass%Sc, were examined based on the inhomogeneous precipitation on each precipitate and the effects of Sc and Cu on the growth of these precipitates, which were observed using a transmission electron microscope. The growth of θ′-Al₂Cu and Al₃Sc proceeds at the rate of diffusion and follows the Ostwald growth law. The uneven precipitation of Al₃Sc on θ′-Al₂Cu is due to the growth of θ′-Al₂Cu and the migration of Sc atoms to the interface potential formed at the θ′-Al₂Cu/modified phase interface. And the uneven precipitation of θ′-Al₂Cu on Al₃Sc is due to the migration of Cu atoms to the interface potential formed at the Al₃Sc/matrix interface.

Al-Si-Cu 알루미늄 주조 합금의 열간 균열 민감성에 미치는 Cu 함량의 영향

오승환 ( Seung-hwan Oh ),친밧문크대거 ( Chinbat Munkhdelger ),김헌주 ( Heon-joo Kim ) 한국주조공학회 2021 한국주조공학회지 Vol.41 No.5

Al-Si-Cu 합금은 구리 첨가에 따른 석출경화로 경도와 강도가 현저하게 강한 합금을 생성하는 장점이 있습니다. 그러나 구리를 첨가하면 Al-Si-Cu 합금의 응고 범위가 확장되고 합금은 응고 중에 발생하는 가장 흔하고 심각한 파단 현상 중 하나 열간 균열이 발생하기 쉽습니다. 합금의 열간 균열 특성에 대한 기존의 평가 방법은 이 특성에 대한 정량적 데이터를 제공하지 않는 상대적이고 정성적인 분석 방법입니다. 이 연구에서 Al-Si-Cu 주조 합금의 열간 균열 특성에 대한 더 신뢰할 수있는 정량 데이터를 얻기 위해 Instone et. al 이 개발 한 장치를 부분적으로 수정되었습니다. Cu 원소의 영향을 평가하기 위해 Al-Si-Cu 계 합금에서 4 가지 수준의 Cu 함량을 (0.5, 1.0, 3.0, 5.0) wt. %로 설정하고 각 합금에 대해 열간 균열 특성을 평가했습니다. Cu 함량이 증가함에 따라 열간 균열 강도는 (2.26, 1.53, 1.18, 1.04) MPa)로 감소했습니다. 열간 균열이 발생하는 시점, Cu 함량이 증가함에 따라 고액 공존 범위가 증가하여 동일 온도에서 해당 고상율 및 응고 속도가 감소하였다. 파단면의 형태는 수상 돌기에서 잔류 액상으로 덮인 수상 돌기로 바뀌었고, 열간 균열 발생 인근에서 CuAl₂ 상이 관찰되었다. Al-Si-Cu alloys benefit from the addition of copper for better hardness and strength through precipitation hardening, which results in remarkably strong alloys. However, the addition of copper expands the solidification range of Al-Si-Cu alloys, and due to this, these alloys become more prone to hot tearing, which is one of the most common and serious fracture phenomena encountered during solidification. The conventional evaluation method of the hot tearing properties of an alloy is a relative and qualitative analysis approach that does not provide quantitative data about this phenomenon. In the present study, the mold itself part of a device developed in Instone et al. was partially modified to obtain more reliable quantitative data pertaining to the hot tearing properties of an Al-Si-Cu casting alloy. To assess the influence of Cu element, four levels of Cu contents were tested (0.5, 1.0, 3.0, and 5.0 wt.%) in the Al-Si-Cu system alloy and the hot tearing properties were evaluated in each case. As the Cu content was increased, the hot tearing strength decreased to 2.26, 1.53, 1.18, and 1.04 MPa, respectively. At the moment hot tearing occurred, the corresponding solid fraction and solidification rate decreased at the same temperature due to the increase in the solid-liquid coexistence range as the Cu content increased. The morphology of the fracture surfaces was changed from dendrites to dendrites covered with residual liquid, and CuAl₂ phases were observed in the vicinity of hot tearing.

Al-Si-Cu계 AC2B 합금의 최적 용체화 처리 조건

정재길 ( Jae Gil Jung ),박준수 ( June Soo Park ),하양수 ( Yang Soo Ha ),이영국 ( Young Kook Lee ),전중환 ( Joong Hwan Jun ),강희삼 ( Hee Sam Kang ),임종대 ( Jong Dae Lim ) 대한금속재료학회 ( 구 대한금속학회 ) 2009 대한금속·재료학회지 Vol.47 No.4

The precipitates, hardness, and tensile properties of Al-6.2Si-2.9Cu AC2B alloy were investigated with respect to solution treatment time at 500℃. Al(Cu)-Al2Cu eutectic, Si, θ-(Al2Cu), and Q-(Al5Cu2Mg8Si6) phases were observed in the as-cast specimen. With increasing the solution treatment time at 500℃, the Al(Cu)-Al2Cu eutectic and θ-(Al2Cu) phases were gradually reduced and finally almost disappeared in 5 h. The mechanical properties, such as hardness, tensile strength, and elongation, were improved with solution treatment time until about 5 h due to the dissolution of the Al2Cu particles. With further holding time, the mechanical properties did not change much. The solution treated specimens for over 5 h at 500℃ exhibit almost the same tensile properties even after aging at 250℃ for 3.5 h. Accordingly, the optimal solution treatment condition of the Al-Si-Cu AC2B alloy is considered to be 5 h at 500℃.

Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu 합금의 미세조직 및 경도 변화에 미치는 용체화 처리 조건의 영향

정성빈,김민수,김대업,홍성길 한국주조공학회 2022 한국주조공학회지 Vol.42 No.6

In order to optimize the solution treatment conditions of Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu alloys, a series of heat treatment exper-iments were conducted under various solution treatment times up to 7 hours at 545oC, followed by a microstructural analysis usingoptical microscopy, FE-SEM, and Brinell hardness measurements. Rapid coarsening of eutectic Si particles was observed in thealloys during the first 3 hours of solution treatment but the size of those Si particles did not change at longer solution treatmentconditions. Meanwhile, the degree of spheroidisation of eutectic Si particles increased until the solution treatment time wasincreased up to 7 hours. Q-Al5Cu2Mg8Si6 andθ-Al2Cu were observed in as-cast Cu-containing Al alloys but the intermetallic com-pounds were dissolved completely after 3 hours of solution treatment at 545oC. Depending on the initial Mg composition of the Alalloys, π-Al8FeMg3Si either disappeared in the alloy with 0.3wt% of Mg content after 5 hours of solution treatment or remained inthe alloy with 0.5wt% of Mg content after 7 hours of solution treatment time. Mg and Cu content in the primary-α phase of the Alalloys increased until the solution treatment time reached 5 hours, which was in accordance with the dissolution behavior of Mg orCu-containing intermetallic compounds with respect to the solution treatment time. From the results of microstructural changes in the Al-7Si-Mg-Cu alloys during solution treatment, it was concluded that at least 5 hours of solution treatment at 545oC is requiredto maximize the age hardening effect of the present Al alloys. The same optimal solution treatment conditions could also be derivedfrom Brinell hardness values of the present Al-7Si-Mg-Cu alloys measured at different solution treatment conditions. 본 연구에서는 Al-7Si-(0.3~0.5)Mg-(0~0.5)Cu 합금의 용체화 처리 조건 최적화를 위해 545oC 온도 조건에서 최대 7시간까지용체화 처리를 수행한 후 광학현미경 및 FE-SEM을 활용한 미세조직 관찰 및 브리넬 경도 측정을 수행하였다 . 합금 내 공정 Si상은 용체화 처리 초반 3시간 동안 급격한 조대화 현상을 나타내었으며 , 이후에는 용체화 처리가 진행되어도 Si 상 크기는 크게변화하지 않았다 . 한편 공정 Si 상의 구상화의 경우 , 용체화 처리 시간이 7시간에 도달할 때 까지 지속적으로 진행되었다 . Cu가첨가된 합금의 주방상태에서는 Q-Al5Cu2Mg8Si6 상과 θ-Al2Cu 상이 확인되었으나 , 545oC에서 3시간 동안 진행된 용체화 처리 이후에는 모두 분해되었다 . 주방상태에서 확인된 π-Al8FeMg3Si 상은 5시간의 용체화 처리 이후에 사라지거나 (0.3wt%Mg) 혹은 7시간의 용체화 처리 이후에도 존재 (0.5wt%Mg)하였다 . 초정 α상 내 Mg 및 Cu 함량은 용체화 처리 시간이 5시간에 도달할 때 까지 증가하였으며 , 이는 Mg 및 Cu를 함유한 금속간 화합물의 용체화 시간에 따른 분해 거동과 일치하였다 . Al-7Si-Mg-Cu 합금의용체화 처리 과정에서 확인한 미세조직 변화를 종합적으로 고려할 때, 본 연구에서 다룬 합금의 석출강화 효과 극대화를 위해서는545oC 조건에서 최소 5시간의 용체화 처리가 필요한 것으로 판단되며 , 용체화 처리 조건 별로 측정된 브리넬 경도 데이터로부터동일한 최적 용체화 처리 조건을 도출할 수 있었다.

초고온용 Zn-Al-Cu계 Pb-free 솔더 합금의 특성

김성준,나혜성,한태교,이봉근,강정윤,Kim Seong-Jun,Na Hye-Seong,Han Tae-Kyo,Lee Bong-Keun,Kang Cung-Yun 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.6

The purpose of this study is to investigate the characteristics of pb-free $Zn-(3\~6)\%Al-(1\~6)\%Cu$ solder alloys for ultra high temperature(>573K) which applied to air craft, space satellite, automotive, oil, gas well exploration and data logging of geo-thermal wells. Melting range, solderability, electric resistivity, microstructure and mechanical properties were examined with solder alloys casted in Ar gas atmosphere. $Zn-4\%Al-(1\~3)\%Cu,\;Zn-5\%Al-(2\~4)\%Cu\;and\;Zn-6\%Al-(3\~5)\%Cu$ alloys satisfied the optimum melting range of 643 to 673k for ultra high temperature solder. A melting temperature increased with increasing Cu content, but decreased with increasing Al content. The spreadability was improved with increasing hi content. But the content of Cu had no effect on the spreadability. The electric resistivity was lowered with increasing Al and decreasing Cu content. In all Zn-Al-Cu solder alloys, primary dendritic $\varepsilon$ phase(Zn-Cu), dendritic $\eta$ phase(Zn-Cu-Al), $\alpha(Al-Zn)-\eta$ eutectic and eutectoid phase were observed. The addition of Al increased the volume fraction of eutectic and eutectoid phase and it decreased f phases. Also, the addition of Cu increased slightly the volume fraction of e, the eutectic and eutectoid phases. With increasing total content of Al and Cu, a hardness and a tensile strength were linearly increased, but anelongation was linearly decreased.

Effect of Minor Sc Addition on the Microstructure Evolution of Al–Cu–Li–Mg Alloy During Homogenization with Different Cooling Modes

Ya Tang,Daihong Xiao,Lanping Huang,Renxuan You,Xinyue Zhao,Nan Lin,Yunzhu Ma,Wensheng Liu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

The microstructure evolution and mechanical properties of Al–3.92Cu–1.10Li–0.68Mg–0.32Ag–0.23Mn–0.35Zn–0.11Zrand Al–3.92Cu–1.12Li–0.76Mg–0.29Ag–0.24Mn–0.24Zn–0.12Zr–0.083Sc (wt%) alloys during homogenization with differentcooling modes were comprehensively studied. It was clearly revealed that the minor Sc addition refined the grainsof as-cast Al–Cu–Li–Mg alloys through the formation of primary Al3(Sc, Zr) phases during the solidification process, andinduced Sc enrichment in the θ (Al2Cu) eutectic. After the homogenization treatment, the majority of coarse nonequilibriumeutectic phases at the grain boundaries dissolved into the α-Al matrix, leading to the relatively uniform distribution ofeach element. Sc-added alloy after homogenization treatments possessed more superior strength and ductility than Sc-freealloy. Compared to the furnace cooling mode, the air cooling mode could inhibit the precipitation of micron-sized coarse T1(Al2CuLi) phase and improve the mechanical properties of the alloys. After homogenization, the continuous Al2Cuphase inthe as-cast Sc-added alloy dissolved and transformed to an array of W-(Al, Cu, Sc) ternary phase, which was identified asAl6Cu6Scwith the body-centered tetragonal structure. The appearance of spherical Al6Cu6Scparticle could not damage themechanical properties of Al–Cu–Li–Mg alloys after the homogenization treatment. The tensile strength, yield strength andelongation of Sc-added alloy after the homogenization by air cooling were 390 MPa, 265 MPa and 10.8%, respectively. Theinvestigation of Al6Cu6Scphase offered a potential avenue to produce high-quality Sc-added 2xxx series alloys.

Cu 및 Zr 첨가 A356 합금의 열처리 조건에 따른 상 변화와 기계적 특성 분석

송태웅,구자욱,전승병,정창열 대한금속·재료학회 2023 대한금속·재료학회지 Vol.61 No.5

Cast A356(Al-Si-Mg) alloys are widely used in automotive and general applications because of theirmechanical properties and castability. Al-Si-Mg-(Cu) alloys typically lose their strength above 170oC due tocoarsening of precipitates, which limits their application to components. To maintain their strength atelevated temperature, Al-Si-Mg-(Cu) alloys are modified by adding transitional metals. Several studies havebeen carried out to evaluate the effect of Zr addition on the high temperature mechanical properties of castAl-Si alloys because Zr can form thermally stable phases such as Al3Zr. Despite the relative studies on theinfluence of Cu and Zr on the mechanical properties of cast Al-Si-Mg-(Cu) alloys, investigations of the effectof Zr on the phase transformations and the mechanical properties during heat treatment remains limited. Inthis study, the effects of added Cu and Zr on the phase transformations and the mechanical performanceduring heat treatment of A356 cast alloy were investigated. Needle-like and block-like (Al,Si)3(Ti,Zr)dispersoids formed as some Si and Ti replaced Al and Zr in Al3Zr crystal structures were generally observed. Furthermore, with increasing solution treatment time, the size of Zr dispersoids was reduced, and smallerZr particles were precipitated at the same time, which caused a decrease in the area fraction of the Zrdispersoids. In addition, the metastable L12 structures of Zr dispersoids in Al-Si-Mg-Cu-Zr alloys weretransformed into stable D023 during solution heat treatment as the Cu addition accelerated thetransformation. Tensile and low-cycle fatigue (LCF) tests were performed to reveal the effects of (Al,Si)3(Ti,Zr)dispersoids on mechanical properties. As a result, elongation at elevated temperature was highly increased,while maintaining strength, according to the increase in solution heat treatment time, which improved lowcyclefatigue properties.

Ultrasound-assisted brazing of Cu/Al dissimilar metals using a Zn-3Al filler metal

Xiao, Y.,Ji, H.,Li, M.,Kim, J. Scientific and Technical Press ; Elsevier Science 2013 Materials & design Vol.52 No.-

Ultrasound-assisted brazing of Cu/Al dissimilar metals was performed using a Zn-3Al filler metal. The effects of brazing temperature on the microstructure and mechanical properties of Cu/Al joints were investigated. Results showed that excellent metallurgic bonding could be obtained in the fluxless brazed Cu/Al joints with the assistance of ultrasonic vibration. In the joint brazed at 400<SUP>o</SUP>C, the filler metal layer showed a non-uniform microstructure and a thick CuZn<SUB>5</SUB> IMC layer was found on the Cu interface. Increasing the brazing temperature to 440<SUP>o</SUP>C, however, leaded to a refined and dispersed microstructure of the filler metal layer and to a thin Al<SUB>4.2</SUB>Cu<SUB>3.2</SUB>Zn<SUB>0.7</SUB> serrate structure in the Cu interfacial IMC layer. Further increasing the brazing temperature to 480<SUP>o</SUP>C resulted in the coarsening of the filler metal and the significantly growth of the Al<SUB>4.2</SUB>Cu<SUB>3.2</SUB>Zn<SUB>0.7</SUB> IMC layer into a dendrite structure. Nanoindentation tests showed that the hardness of the Al<SUB>4.2</SUB>Cu<SUB>3.2</SUB>Zn<SUB>0.7</SUB> and CuZn<SUB>5</SUB> phase was 11.4 and 4.65GPa, respectively. Tensile strength tests showed that all the Cu/Al joints were failed in the Cu interfacial regions. The joint brazed at 440<SUP>o</SUP>C exhibited the highest tensile strength of 78.93MPa.

Effects of Interactions Among Alloying Elements on the Microstructure, Phase Transitions, and Electrical Resistivity of the Cu81Al19 Alloy

R. D. A. Pinto,L. D. R. Ferreira,R. A. G. Silva 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

Cu–Al alloys have been used for marine applications due to their corrosion resistance and smart materials based on the shapememory effect. A technological tendency for Cu–Al alloys is the development of increasingly complex formulations, althoughthe role of alloying elements still unclear in comparison to other metallurgical systems, such as steels. In the present study,2 at% Cu were substituted by equal quantities of Ni and Ga in the Cu81Al19alloy, which are elements from the same periodand similar in size to the Cu atom. The obtained alloys were analyzed by several characterization techniques. The resultsshowed that the Ni addition increases the critical temperatures and decreases the microhardness values. The Ga additionhas the opposite effect. Both alloying elements produce new phases in the microstructures, hamper the α phase ordering,accelerate the β phase decomposition, and increase the conductivity of the Cu81Al19alloy. From this study, it is possible torealize that small changes in atomic features (electronic structure, atomic radius, valence, electronegativity) from a portionof atoms are enough to obtain distinctive materials, which turns the design of new Cu–Al alloys and the prediction of theirproperties a challenging task.

Texture Evolution of Hot Rolled Al–Cu–Mg–Zr Alloy During Annealing

Qi Zhao,Zhiyi Liu 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12

Texture growth and relative mechanism of Al–Cu–Mg–(Zr) alloy during annealing have been investigated by three dimensionalOrientation Distribution Functions (ODFs), Electron Back Scattered Diffraction (EBSD) and Transmission ElectronMicroscopy (TEM). The results show that Zr addition in Al–Cu–Mg alloy restricts the preferable growth of recrystallizedGoss grain, and fails to improve the total intensity of Goss texture. Recrystallized Goss is difficult to nucleate within Brassorientation even after full recrystallization, and Copper and S grains cannot preferably transform into Cube grains in Al–Cu–Mg–Zr alloy. Instead, the growth of random textures is favorable at the expense of deformed Brass, Copper and S textures. These phenomena can be well explained by relating to the disappearance of Σ5, Σ7 and Σ9 boundaries caused by Al3Zrpinningdislocation. In addition, it is found that the Brass texture of Al–Cu–Mg–Zr alloy can be enhanced at specific annealingtemperature, which is attributed to the formation of recrystallized Brass grains. Lastly, the deformed Goss of Al–Cu–Mg–Zralloy is energy-unstable as compared with Brass during annealing, and these deformed Goss grains will subsequently evolveinto recrystallized Brass or random orientations.