Journal articles on the topic 'Plates, Aluminum Cracking'
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1
Jaiganesh, V., D. Srinivasan, and P. Sevvel. "Optimization of process parameters on friction stir welding of 2014 aluminum alloy plates." International Journal of Engineering & Technology 7, no. 1.1 (December 21, 2017): 9. http://dx.doi.org/10.14419/ijet.v7i1.1.8906.
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Aluminum Alloy 2014 is a light weight high strength alloy used widely in the aerospace and also in other industries. 2014 is the second most popular of the 2000-series aluminium alloys, after 2024 aluminium alloy. However, it is difficult to weld, as it is subject to cracking. Joining of 2014 aluminium alloy in friction stir welding which is based on frictional heat generated through contact between a rotating tool and the work piece. Determination of the welding parameters such as spindle speed, transverse feed , tilt angle plays an important role in weld strength. The whole optimization process is carried out using Taguchi technique. The SEM analysis is done to check the micro structure of the material after welding by electron interaction with the atoms in the sample. Tensile test have been conducted and the s-n ratio curve is generated. The test is conducted and analysed on the basis of ASTM standards.
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Zivkovic, Predrag, Slobodan Jovanovic, Konstantin Popov, and Nenad Ilic. "Modification of the aluminum for making offset printing plates." Journal of the Serbian Chemical Society 65, no. 12 (2000): 935–38. http://dx.doi.org/10.2298/jsc0012935z.
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Aluminum as the base of offset printing plates should make good contact with wetting agents and the light sensitive layer and should be resistant to wear and cracking. In order to achieve this, the aluminum is roughened and eventually anodized. A thin, electrochemically deposited chromium layer is used as the non-printing element in bimetallic offset printing forms. Chromium shows excellent wettability and wear resistance. The possibility of chemical deposition of chromium on aluminum from an alkaline solution is examined in this paper. The presence of chromium was confirmed and measured by EDAX. A difference in the spectral reflection characteristic between chromium-treated and non-treated specimens was also detected. An influence of a chromium layer on an aluminum surface was examined by water drop spreading. Chromium-treated samples showed better wettability than non-treated samples, but they are less wettable than anodized samples.
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Zhou, Yu Tong, Zheng Qiang Zhou, Jiong Geng Wang, Hong Jian Luo, Jie Zhang, and Jia Yuan Hu. "Study on Cracking of Aluminum Alloy Strain Clamps for 500kV Transmission Line." Solid State Phenomena 279 (August 2018): 10–15. http://dx.doi.org/10.4028/www.scientific.net/ssp.279.10.
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It was found that a large number of aluminum alloy strain clamps cracked. Cracking mainly occurred in the drainage plate of strain clamps. Nondestructive testing technologies and physicochemical analysis devices such as optical microscope, spectrograph, SEM and EDS were adopted to analyze the reasons of cracking. The results tell that there are numerous shrinkage cavities and cracks inside the drainage plate of strain clamps. The maximum area fraction of shrinkage cavities is 10.7%, and the maximum size is over 1mm2. A lot of shrinkage cavities and cracks gather together to form big flaws, which seriously reduce the mechanical properties of the drainage plates. After a long period of vibration, cracks gradually develop to the surrounding cavities and connect adjacent cavities. Eventually, cracks develop to the surface of drainage plates.
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Chang, Hong, and Wei Zhou. "Stiffness and Crack Behavior of Unbonded Posttensioned Concrete Beam Strengthened with Aluminum Alloy Plate." Advances in Civil Engineering 2020 (September 30, 2020): 1–13. http://dx.doi.org/10.1155/2020/3824543.
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Corrosion resistance of aluminum alloy plates externally bonded by magnesium phosphate cement provides the ability to strengthen inshore infrastructures in harsh environments subject to moisture and humidity. In this study, the aim is to study the stiffness and cracking behavior of concrete beams using this strengthening technique. Six damaged unbonded posttensioned concrete beams were repaired and strengthened and then subjected to monotonic load until failure. This technique improved the stiffness and limited the development of cracks. The formula of elastic-plastic stiffness coefficient related to the comprehensive reinforcement index was established. An influence coefficient δ considering the effect of aluminum alloy plates and unbonded tendons was introduced, and the crack expansion coefficient under short-term load was obtained by statistical analysis. Finally, some simplified methods were proposed to evaluate the stiffness and cracks of unbonded posttensioned concrete beams strengthened with aluminum alloy plates.
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Peter, Ildiko, and Mario Rosso. "Study of 7075 Aluminium Alloy Joints." Scientific Bulletin of Valahia University - Materials and Mechanics 15, no. 13 (October 1, 2017): 7–11. http://dx.doi.org/10.1515/bsmm-2017-0011.
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AbstractHigh-strength EN AW 7075 Al-based alloy (Al-Zn-Mg-Cu) is currently employed in many industrial fields where excellent mechanical performances of structural components are required. In contrast to the many positive features this alloy presents, it is not fusion weldable, because it is subjected to solidification and liquation cracking. In this paper, the possibility to weld low thickness plates, made of 7075 aluminum alloy, by the tungsten inert gas welding technique will be presented. Two types of welding have been performed: for the former one, welding involves only one surface, while for the second one, welding has been carried out on both faces of the plates. After welding, microstructural analysis and mechanical properties investigations have been carried out. The present research highlights that the mechanical properties evolution is affected by the welding procedure. In particular, the mechanical strength reached for the samples welded on both faces, in the proposed setting, is comparable to that of the un-welded alloys.
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Yang, Yang, Li Xiao, Wenzhong Qu, and Ye Lu. "Passive detection and localization of fatigue cracking in aluminum plates using Green’s function reconstruction from ambient noise." Ultrasonics 81 (November 2017): 187–95. http://dx.doi.org/10.1016/j.ultras.2017.06.021.
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Li, Yanlei, Shanglei Yang, Zeng Peng, Zhentao Wang, and Zihao Gao. "Microstructure, Fatigue Properties and Stress Concentration Analysis of 6005 Aluminum Alloy MIG Welded Lap Joint." Materials 15, no. 21 (November 2, 2022): 7729. http://dx.doi.org/10.3390/ma15217729.
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This paper studies the microstructure and mechanical properties of MIG (Melt Inert Gas) lap welded 6005 aluminum alloy plates. Microstructure analysis (OM) of the joint showed that 15~30 μm small grains were observed at the fusion line. Mechanical analysis shows that the small grains are broken by shielding gas and molten pool flow force. Hardness test shows that there is a softening zone (41~43 HV) in HAZ much lower than BM and WZ. The low cycle fatigue test showed that the performance of lap joint decreased sharply, and the fatigue strength of weld decreased significantly, which was only 27.34% of the base metal. The fatigue fracture (SEM) of the weld observed slip band cracking and a large number of brittle fracture characteristics. Using the stress concentration factor Kt for analysis, it was found that the cause of brittle fracture was mostly stress concentration. Lap joint stress concentration model appears in two ways: firstly, at the weld toe, the weld is subjected to eccentric force, secondly, there is a small gap between the two plates at the weld root, which cracks along the direction of 45° of the maximum shear stress.
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Lee, Ho Sung, Ye Rim Lee, and Kyung Ju Min. "Influence of Tool Rotational Speed on the Mechanical Properties of Friction Stir Welded Al-Cu-Li Alloy." Materials Science Forum 857 (May 2016): 228–31. http://dx.doi.org/10.4028/www.scientific.net/msf.857.228.
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Aluminum-Lithium alloys have been found to exhibit superior mechanical properties as compared to the conventional aerospace aluminum alloys in terms of high strength, high modulus, low density, good corrosion resistance and fracture toughness at cryogenic temperatures. Even though they do not form low-melting eutectics during fusion welding, there are still problems like porosity, solidification cracking, and loss of lithium. This is why solid state friction stir welding is important in this alloy. It is known that using Al-Cu-Li alloy and friction stir welding to super lightweight external tank for space shuttle, significant weight reduction has been achieved. The objective of this paper is to investigate the effect of friction stir tool rotation speed on mechanical and microstructural properties of Al-Cu-Li alloy. The plates were joined with friction stir welding process using different tool rotation speeds (300-800 rpm) and welding speeds (120-420 mm/min), which are the two prime welding parameters in this process.
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Chen, Wenjing, Wei Lu, Guoqing Gou, Liwen Dian, Zhongyin Zhu, and Junjun Jin. "The Effect of Fatigue Damage on the Corrosion Fatigue Crack Growth Mechanism in A7N01P-T4 Aluminum Alloy." Metals 13, no. 1 (January 4, 2023): 104. http://dx.doi.org/10.3390/met13010104.
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A7N01P-T4 aluminum alloy plates for high-speed trains will experience a certain amount of fatigue damage under alternating loads. Three groups of samples, P0 (no fatigue damage), P1 (loading stress 30 MPa), and P2 (loading stress 70 MPa), were created, and corrosion fatigue crack growth (CFCG) tests were conducted in 3.5 wt.% NaC1 solution. The crack growth rate was found to increase after fatigue damage as the damage degree increased. In addition, the A7N01P-T4 aluminum alloy base metal exhibited obvious secondary cracks and crack bifurcations after fatigue damage. It is believed that fatigue damage causes stress concentration in the material, while a certain degree of stress corrosion cracking occurs during the CFCG growth process. This is because hydrogen (H) easily accumulates and diffuses along the grain boundary, which reduces the strength of the grain boundary, thereby becoming the preferred orientation for crack growth. This explains why the CFCG rate of the material is accelerated following fatigue damage to a certain extent.
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Jiang, Lanxin, Shoune Xiao, Jingke Zhang, Ruijuan Lv, Bing Yang, Dawei Dong, Guangwu Yang, and Tao Zhu. "Experimental and Simulation Studies on the Compressive Properties of Brazed Aluminum Honeycomb Plates and a Strength Prediction Method." Metals 10, no. 11 (November 20, 2020): 1544. http://dx.doi.org/10.3390/met10111544.
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To study the compressive mechanical properties of a new type of brazed aluminum honeycomb plate (BAHP), tensile tests on single- and brazed-cell walls as well as compression tests in the out-of-plane, in-plane longitudinal, and transverse directions were conducted. Compared to the material properties of a traditional glued aluminum honeycomb plate (GAHP), those of the single- and brazed-cell walls of the BAHP are entirely different. Therefore, their characteristics should be considered separately when performing theoretical and simulation analysis. Under out-of-plane compression, the core of the BAHP did not debond, owing to its higher strength than that of the GAHP. In comparison, under in-plane compression in the longitudinal and transverse directions, the load–displacement characteristics, ultimate load, and failure modes also differed, and there was no large-scale cracking. Considering the characteristics of the BAHP, a strength prediction method was proposed. The simulation results demonstrated that the model built based on the new method was highly consistent with the experimental results. Defects with uneven height and debonding will cause the overall instability, and the degree of defects will influence the strength and instability displacement, which have little impact on the elastic stage. Moreover, the model considering defects is closer to the test results.
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Li, Zhi Hui, Bai Qing Xiong, Yon Gan Zhang, Xin Yu Lu, Zhen Bo He, Long Bin Jin, Xi Wu Li, and Xiao Lei Han. "Research on Multi-Artificial Aging Applied to Aluminum Alloy 7150 Plate." Materials Science Forum 706-709 (January 2012): 340–45. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.340.
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The AA 7150-T351, in the form of 40 mm thick plates, was subjected to single-stage aging leading to peak aged condition, and two selected multi-artificial aging treatments leading to the over aged conditions. The microstructural differences along the thickness direction of the AA 7150-T351 plate were investigated using OM and electron backscatter diffraction (EBSD) technique, and the microstructural characterization was studied at different stages of multi-artificial ageing process by transmission electron microscopy. Tensile properties and electrical conductivity measurements were used to evaluate the property homogeneity along the thickness direction of the plate under various artificial aging tempers. It was revealed that the microstructural features and tensile property are inhomogeneous in different layers along the thickness direction, and both grain structure and tensile property exhibit appreciable anisotropy at the same thickness layer. The volume fraction of recrystallized grain of T351 plate in the near surface layer is higher than that in the center layer remarkably. It is also shown that two selected multi-artificial aging tempers can provide optimal precipitates in matrix and at grain boundaries, which gives rise to a combination of high strength and stress corrosion cracking (SCC) resistance in such materials.
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Zybin, Igor, Konstantin Trukhanov, Andrey Tsarkov, and Sergey Kheylo. "Backing plate effect on temperature controlled FSW process." MATEC Web of Conferences 224 (2018): 01084. http://dx.doi.org/10.1051/matecconf/201822401084.
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Friction stir welding (FSW) has become an important application in modern industries. Friction stir welding is a widely used solid state joining process for soft materials such as aluminum alloys as it avoids/minimizes common problems of fusion welding processes, i.e. distortion, porosity, solidification and liquation cracking etc. Improper selection of parameters such as welding speed, rotational speed, forge force, back plate material etc. affects the weld quality. Thermal boundary condition at the bottom of the work pieces to be joined is important in determining the result of weld quality and its properties, for a given alloy type, tool geometry and selected process parameters (welding speed, rotational speed etc), These thermal boundary conditions are governed by the back plate material used. By using backing plates made out of materials with widely varying thermal diffusivity this work seeks to elucidate the effects of the root side thermal boundary condition on weld process variables and resulting joint properties. Welds were made in 5-mm-thick AMг5 (AA 5056) using siliceous coating, stainless steel, mild steel, and aluminum as backing plate (BP) material. Effects of backing plate material on the tensile strength and elongation were obtained for a particular case.
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Moreira, Pedro Miguel Guimarães Pires, and Paulo Manuel Salgado Tavares de Castro. "Fatigue Crack Growth on FSW AA2024-T3 Aluminum Joints." Key Engineering Materials 498 (January 2012): 126–38. http://dx.doi.org/10.4028/www.scientific.net/kem.498.126.
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Friction stir welding (FSW) is a solid-state joining process which emerged as an alternative technology to join high strength alloys that were difficult to weld with conventional techniques, [1]. Developments of this technique are being driven by aeronautic, aerospace and railway industries. An advantage of this joining technique is its low heat input when compared with arc welding processes. This feature allows the achievement of high mechanical properties, low distortion and low residual stresses, [2]. Also, since it is a solid-state welding process, hydrogen cracking or heat affected zone (HAZ) softening phenomena are limited. This paper presents a study of fatigue crack growth behaviour of friction stir welded butt joints of AA2024-T3, aluminium commonly used in riveted aeronautic fuselage structures. Crack growth studies are often carried out using uniform thickness joints, ASTM E647 [3]. Nevertheless, for some applications there is a need to join components with different thicknesses, which, under certain limits, can be welded using FSW. Crack growth tests on these joints are not standard. The present study concerns butt joints made using two plates with different thicknesses, 3.8mm and 4.0mm. The joints’ mechanical behaviour was studied performing static (tensile) and fatigue tests. The fatigue crack growth rate of cracks growing in different zones of the welded joint (nugget, heat affected zone - HAZ) and in base material was analysed. The microhardness profile was assessed in order to analyse the influence of the welding process in each weld zone. Further to higher static properties, welded joints present lower crack growth rate when compared with its base material.
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Venkatesan, S., G. P. Rajamani, V. Balasubramanian, and G. Padmanaban. "Fatigue Behaviour of Friction Stir Welded AZ31B Magnesium Alloy Joints." Applied Mechanics and Materials 787 (August 2015): 355–60. http://dx.doi.org/10.4028/www.scientific.net/amm.787.355.
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Friction stir welding (FSW) is a relatively better joining technique particularly for magnesium and aluminum alloys that are difficult to weld by fusion welding techniques. Fusion welding of these alloys is not preferable due to hot cracking, formation of porosity, etc. However solid state welding techniques, such as, friction sitr welding are found to offer solution to the above problems. Many research papers available in open literature focusing tensile properties, microstructural characteristics, and corrosion behaviour of friction stir welded AZ31B magnesium alloys but fatigue behaviour of these welds are not yet investigated. Hence, in this investigation, an attempt has been made to evaluate fatigue behaviour of friction stir welded rolled plates of AZ31B magnesium alloys.Fatigue experiment was conducted using servo hydraulic controlled fatigue testing machine. Fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated. It is found that the fatigue strength of AZ31B welded joints is 46 MPa at 2x106cycles which is approximately 34 % lower than that of the base metal fatigue strength.
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Ku, Ming-Hsiang, Fei-Yi Hung, and Truan-Sheng Lui. "Embrittlement Due to Excess Heat Input into Friction Stir Processed 7075 Alloy." Materials 12, no. 2 (January 10, 2019): 227. http://dx.doi.org/10.3390/ma12020227.
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The grain size of high strength 7075 hot-rolled aluminum plates was refined by a friction stir process (FSP) to improve their mechanical properties. The results of the tensile ductility tests, which were conducted at various tool rotational speeds, in the friction stir zone indicate significant tensile ductility loss, which even resulted in a ductile-to-brittle transition (DBT). DBT depends on the tool rotational speed. Our 1450 rpm specimens showed large data fluctuation in the tensile ductility and the location of the fracture controlled the formation of friction stir induced bands (FSIB). The crack initiation site located at FSIB was due to the tool rotational speed (1670 rpm). A higher heat-input causes the formation of FSIB, which is accompanied with micro-voids. This contributes significantly to tensile cracking within the stir zone after the application of the aging treatment. This investigation aimed to determine the dominant factor causing tensile ductility loss at the stir zone, which is the major restriction preventing further applications.
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Ford, R. G., R. W. Carpenter, and K. Sieradzki. "Cu Nanoparticle Formation: Copper Redistribution During NaCl Solution Corrosion of Al-Cu-Mg Alloys." Microscopy and Microanalysis 4, S2 (July 1998): 754–55. http://dx.doi.org/10.1017/s1431927600023898.
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Aluminum-copper-magnesium alloys also containing manganese and iron (commercial designation 2024) are susceptible to marine corrosion and stress corrosion cracking. Susceptibility depends on heat treatment, and is thought to involve redistribution of copper from within the microstructure onto the surface of the corroding alloy, but few direct observations of the mechanism have been made. Copper can be distributed in several ways throughout the microstructure, which complicates mechanism studies. The primary age-hardening phase is Al2CuMg (orthorhombic; a=4.01, b=9.25, c=7.15 Å) which appears as more or less large equiaxed S particles at equilibrium, and as metastable S’ plates after aging for shorter times at lower temperature (∼190°C). In addition, ubiquitous so-called “dispersoids” containing copper and manganese (prolate spheroid morphology) or iron (irregular “blocky” morphology) do not go into solution when the alloy is solid state homogenized (-495 °C) and are always present in the microstructure. All of these phases are copper-rich sources for surface redistribution relative to the matrix during corrosion.
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Kecsmar, J., and R. A. Shenoi. "Some Notes on the Influence of Manufacturing on the Fatigue Life of Welded Aluminum Marine Structures." Journal of Ship Production 20, no. 03 (August 1, 2004): 164–75. http://dx.doi.org/10.5957/jsp.2004.20.3.164.
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Designers are constantly looking for ways to reduce the structure weight to lower the overall displacement and hence the cost of fast ferries and other high-speed vessels. The easiest option for the designer is to choose a lightweight material. Aluminum has become the adopted choice of material for high-speed vessels owing to its high strength to weight characteristics. Unlike steel, aluminum is more prone to fatigue cracking and has no fatigue limit. In order to minimize weight, the designer will make use of finite element methods to optimize the scantlings and perform fatigue checks against established codes. This can lead to a structure that has the empirical margins of safety reduced owing to the accuracy of mathematical modeling. However, what is often overlooked is the effect the manufacturing process has on the fatigue life of the fabricated structure. This aspect is excluded from the designer's fatigue calculations, which assist in reducing the scantlings. Currently, there is no guidance for fatigue life reduction for the designer that establishes good and bad workshop practice, other than experience, or the implications of basic shipyard fabrication. It is shown that whereas strain-hardened alloys improve mechanical strength, they reduce ductility. This has consequences when forming the hull plate by potentially introducing crack like flaws into the alloy matrix if the plater overrolls the plate. If there is misalignment or there is too much gap between the plates, the weld will create localized stress concentrations. If the welder has poor joint preparation or gas shielding, porosity can be introduced into the weld. Porosity has a significant effect on the fatigue life of the weldment. This paper brings together a collection of data on such issues that the designer needs to be aware of to prevent an unwanted fatigue failure in the fabrication process.
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Orlando Aguirre Guedes, Lucas Rodrigues de Araújo Estrela, Jordanna Guedes Amorim Mendonça, Mônica Misaé Endo, Helder Fernandes de Oliveira, Cyntia Rodrigues de Araújo Estrela, and Carlos Estrela. "Morphological, chemical and antimicrobial analysis of glass ionomer cements used for ART in posterior primary teethGlass ionomer cements (GICs) have been gaining prominence as material for atraumatic restorative treatment (ART) due to their acceptable ph." RSBO 19, no. 2 (November 7, 2022): 313–21. http://dx.doi.org/10.21726/rsbo.v19i2.1872.
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Glass ionomer cements (GICs) have been gaining prominence as material for atraumatic restorative treatment (ART) due to their acceptable physicochemical and biological properties. Objective: To analyze the surface morphology, chemical constitution, and antimicrobial action of GICs used for ART in posterior primary teeth. Material and methods: The tested materials were Vitro Molar®, Ketac Cem Easymix® and Riva Self Cure®. For the structural and chemical analysis, polyethylene tubes with an internal diameter of 3 mm and 3 mm in length were prepared, filled, and then transferred to a chamber with 95% relative humidity and a temperature of 37oC. The surface morphology of the tested materials was examined by scanning electron microscopy (SEM) and main components were investigated by energy-dispersive X-ray microanalysis. For the antimicrobial efficacy analyses, strains of Streptococcus mutans (ATCC 27853) were used. Petri dishes with brain heart infusion agar (BHIA) were inoculated with the microbial suspensions and three cavities were made in each agar plate and filled with one of the GICs. The plates were pre-incubated for 1 hour at room temperature and then incubated at 37oC for 24 to 48 hours. The inhibition zone around each well was recorded in mm. Results: SEM revealed irregular and rough external surface. Cracking was not observed. The main constituents were found to be aluminum, silicon, sodium, and fluoride. Barium was only observed in Vitro Molar®, while lanthanum was only observed in Ketac Cem Easymix®. Elemental mapping of the outer surface revealed high concentration of aluminum and silicon. Inhibition halos were only observed in Riva Self Cure®. Conclusion: The GICs presented irregular outer surfaces and similar chemical elements. Only Riva Self Cure® showed antibacterial action against the S. mutans.
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Pardoen, T., Y. Marchal, and F. Delannay. "Thickness dependence of cracking resistance in thin aluminium plates." Journal of the Mechanics and Physics of Solids 47, no. 10 (October 1999): 2093–123. http://dx.doi.org/10.1016/s0022-5096(99)00011-3.
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Ilyushenko, R., and V. Nesterenkov. "Novel Technique for Joining of Thick Section Difficult-to-Weld Aluminium Alloys." Materials Science Forum 519-521 (July 2006): 1125–30. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.1125.
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One of the “show stoppers” in fusion welding of highly alloyed aerospace aluminium alloys is their susceptibility for liquation cracking in the weld heat-affected zone. Liquation cracking is a microscopic intergranular discontinuity, which occurs under the effect of welding thermal cycle and in the presence of stresses involved with the welding process. These intergranular discontinuities are often observed in welding of thick plates and extrusions, which usually have relatively coarse elongated grains, that are generally oriented parallel to each other. Friction Stir Welding (FSW) is a low temperature non- fusion process, which produces very fine equiaxed grain structure in the weld nugget for majority of Al-alloys. It was found that bead-onplate FS welds performed on alloy, which in fusion welding is susceptible to liquation cracking, were crack free. It was therefore proposed to use FSW for grain refining of the parent material by putting a number of overlapping FS welds onto the edges of both parent plates prior to joining by fusion welding. Experimentation has shown that there was no liquation cracking after the final weld was performed. This novel welding method has been successfully proven for Electron Beam Welding (EBW) of various Al-alloys including joining of dissimilar materials. The details of experiments as well as welded coupons test results are presented.
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Gerosa, R., B. Rivolta, and U. Derudi. "Influence of ageing on tensile and stress corrosion cracking behaviour of 7075 aluminium alloy plates." International Journal of Microstructure and Materials Properties 5, no. 1 (2010): 15. http://dx.doi.org/10.1504/ijmmp.2010.032498.
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Demianenko, E. M., M. I. Terets, L. M. Ushakova, S. V. Zhuravskyi, Yu I. Sementsov, V. V. Lobanov, O. V. Filonenko, V. S. Kuts, A. G. Grebenyuk, and M. T. Kartel. "A theoretical study on the effect of heteroatoms (N, B, Si) on the interaction of aluminum clusters with a carbon graphene-like plane." Himia, Fizika ta Tehnologia Poverhni 13, no. 4 (December 30, 2022): 391–404. http://dx.doi.org/10.15407/hftp13.04.391.
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It is known that the addition of a small amount of carbon nanomaterials significantly improves the mechanical properties of composites with a metal matrix. One of the most important, promising and available metals as a matrix for such modification is aluminum. However, at the interface between the carbon material and Al, aluminum carbides of different composition are formed, which are brittle and have the main disadvantage - solubility in water. Therefore, the appearance of aluminum carbide is a serious problem, since it contributes to the formation of defects, which, when the composite is deformed, leads to cracking of the composite due to the presence of microneedles. In this regard, in order to predict the features of the interaction of aluminum itself with the surface of carbon nanomaterials, it is advisable to model such processes using quantum chemistry methods. The aim of the work was to reveal the effect of temperature on the chemical interaction of aluminum clusters with native, boron-, silicon-, and nitrogen-containing graphene-like planes (GLP). All the calculated by three methods (B3LYP/6-31G(d,p), MP2/6-31G(d,p) and PВЕ0/6-31G(d,p)) values of the dependence of the Gibbs free energy on temperature for different cluster sizes of aluminum and graphene-like clusters are the highest for native graphene-like planes. In all cases, the values of the Gibbs free energy increase with temperature. The lowest values of the temperature dependence of the Gibbs free energy vary as dependent on the size of the reactant models and research methods, this is especially characteristic of the presence of boron and silicon atoms in the graphene-like clusters. Therefore, the absence of heteroatoms in the composition of the nanocarbon matrix contributes to the fact that aluminum carbide islands should not be formed in the carbon-containing nanocomposite with aluminum, which negatively affects the physical and chemical characteristics of the resulting nanocomposite.
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Staley, J. T. "Corrosion of Aluminium Aerospace Alloys." Materials Science Forum 877 (November 2016): 485–91. http://dx.doi.org/10.4028/www.scientific.net/msf.877.485.
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The Junkers F13 airplane, which began production in 1919, was the first plane to be built using aluminum aerospace alloys. Nearly 100 years later, approximately 1,800 new planes are being built each year with aluminum aerospace alloys. For the five trillion or so dollars worth of existing aging airplanes, cost of aerospace corrosion in United States alone is an estimated 23 billion dollars per year. In addition, hidden corrosion costs have contributed to a bigger impact in the commercial aircraft industry. In 1988, in the corrosion sensitive environment of the Hawaiian islands, an Aloha Airlines 737 aircraft suffered an in-flight failure due to crevice corrosion in the lap joint of the fuselage. After this event, the aviation technical community launched a new era of advanced technology, improved procedures and higher standards for maintaining the world’s aging and corroding aircraft. This paper discusses types of corrosion that affect aluminum aerospace alloys including crevice corrosion, pitting, exfoliation, intergranular, stress corrosion cracking (SCC) and corrosion fatigue. Standardized testing to determine if the alloy is susceptible to these types of corrosion is explained and examples of how to mitigate certain types of corrosion is discussed.
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Teyeb, Ahmed, João Silva, Jamil Kanfoud, Phil Carr, Tat-Hean Gan, and Wamadeva Balachandran. "Improvements in the Microstructure and Mechanical Properties of Aluminium Alloys Using Ultrasonic-Assisted Laser Welding." Metals 12, no. 6 (June 17, 2022): 1041. http://dx.doi.org/10.3390/met12061041.
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Welding high-strength aluminium alloys is generally a delicate operation due to the degradation of mechanical properties in the thermally affected zone (TAZ) and the presence of porosities in the molten metal. Furthermore, aluminium alloys contain compounds that solidify before the rest of the base alloy, therefore acting as stress concentration points that lead to the phenomenon of hot cracking. This paper investigates the process of applying ultrasonic vibrations to the molten pool aluminium alloy AA6082 to improve both its microstructure and mechanical properties. We analysed conventional and ultrasonic-assisted laser welding processes to assess the sonication effect in the ultrasonic band 20–40 kHz. Destructive and nondestructive tests were used to compare ultrasonically processed samples to baseline samples. We achieved a 26% increase in the tensile and weld yield strengths of laser welds in the aluminium plates via the power ultrasonic irradiation of the welds under optimum ultrasonic variable values during welding. It is estimated that the ultrasound intensity in the weld melt, using a maximum power of 160 W from a pair of 28 kHz transducers, was 35.5 W/cm2 as a spatial average and 142 W/cm2 at the antinodes. Cavitation activity was significant and sometimes a main contributor to the achieved improvements in weld quality.
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Tran, Tu Anh, Varughese Mathew, Wen Shi Koh, K. Y. Yow, and Y. K. Au. "Dicing Development for low-k Copper Wafers using Nickel-Palladium-Gold Bond Pads for Automotive Application." International Symposium on Microelectronics 2012, no. 1 (January 1, 2012): 001085–96. http://dx.doi.org/10.4071/isom-2012-thp31.
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New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on the development of dicing process for low-K-copper wafers having aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold Over Pad Metallization (OPM). Development wafers were pizza mask wafers on which multiple die designs and scribe grid production control (SGPC) modules were designed. SGPC modules are designed with aluminum probe pads that are used to monitor wafer-level process control. All aluminum features on the wafer were plated with nickel/palladium/gold OPM. With nickel about four times as hard as aluminum, OPM plated SGPC's were much more difficult to dice than conventional SGPC's with aluminum pads. Cracking on silicon sidewall with crack propagating towards the die was found to cause back-end-of-line (BEOL) delamination and device failure. Surface roughness and hardness measurements were taken on OPM variations. Extensive mechanical dicing studies were conducted to modulate the failures and resolve the dicing challenge. Laser grooving followed by mechanical dicing of OPM wafers was also performed. Packages underwent extensive reliability stress conditions. The associated process improvements described in this paper supported a successful integration of a 55nm die technology in Low Profile Quad Flat Package with Exposed Pad (LQFP-EP) meeting and exceeding AEC grade 0 requirements.
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Tran, Tu Anh, Varughese Mathew, Wen Shi Koh, K. Y. Yow, and Y. K. Au. "Dicing Development for low-k Copper Wafers using Nickel-Palladium-Gold Bond Pads for Automotive Application." International Symposium on Microelectronics 2013, no. 1 (January 1, 2013): 000657–62. http://dx.doi.org/10.4071/isom-2013-wp24.
Full textAbstract:
New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on the development of dicing process for low-K-copper wafers having aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold Over Pad Metallization (OPM). Development wafers were pizza mask wafers on which multiple die designs and scribe grid production control (SGPC) modules were designed. SGPC modules are designed with aluminum probe pads that are used to monitor wafer-level process control. All aluminum features on the wafer were plated with nickel/palladium/gold OPM. With the hardness of nickel and palladium being more than 10 to 15 times the hardness of aluminum, OPM-plated SGPC's were much more difficult to dice than conventional SGPC's with aluminum pads. Cracking on silicon sidewall with crack propagating towards the die was found to cause back-end-of-line (BEOL) delamination and device failure. Extensive mechanical dicing studies were conducted to modulate the failures and resolve the dicing challenge. Specifically, dicing was observed to be not centered on SPGC pads on the pizza mask. Off-centered dicing produced drastic change in Ni loading at the center of the blade and on the edges of the blade. Packages underwent extensive reliability stress conditions. The associated process improvements described in this paper supported a successful integration of a 55nm die technology in Low Profile Quad Flat Package with Exposed Pad (LQFP-EP) meeting and exceeding AEC grade 0 requirements.
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Choe, Chanyang, Chuantong Chen, Seungjun Noh, and Katsuaki Suganuma. "Thermal Shock Performance of DBA/AMB Substrates Plated by Ni and Ni–P Layers for High-Temperature Applications of Power Device Modules." Materials 11, no. 12 (November 28, 2018): 2394. http://dx.doi.org/10.3390/ma11122394.
Full textAbstract:
The thermal cycling life of direct bonded aluminum (DBA) and active metal brazing (AMB) substrates with two types of plating—Ni electroplating and Ni–P electroless plating—was evaluated by thermal shock tests between −50 and 250 °C. AMB substrates with Al2O3 and AlN fractured only after 10 cycles, but with Si3N4 ceramic, they retained good thermal stability even beyond 1000 cycles, regardless of the metallization type. The Ni layer on the surviving AMB substrates with Si3N4 was not damaged, while a crack occurred in the Ni–P layer. For DBA substrates, fracture did not occur up to 1000 cycles for all kind of ceramics. On the other hand, the Ni–P layer was roughened and cracked according to the severe deformation of the aluminum layer, while the Ni layer was not damaged after thermal shock tests. In addition, the deformation mechanism of an Al plate on a ceramic substrate was investigated both by microstructural observation and finite element method (FEM) simulation, which confirmed that grain boundary sliding was a key factor in the severe deformation of the Al layer that resulted in the cracking of the Ni–P layer. The fracture suppression in the Ni layer on DBA/AMB substrates can be attributed to its ductility and higher strength compared with those of Ni–P plating.
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Deng, Yun, Tarlan Hajilou, and Afrooz Barnoush. "Hydrogen-enhanced cracking revealed by in situ micro-cantilever bending test inside environmental scanning electron microscope." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2098 (June 12, 2017): 20170106. http://dx.doi.org/10.1098/rsta.2017.0106.
Full textAbstract:
To evaluate the hydrogen (H)-induced embrittlement in iron aluminium intermetallics, especially the one with stoichiometric composition of 50 at.% Al, a novel in situ micro-cantilever bending test was applied within an environmental scanning electron microscope (ESEM), which provides both a full process monitoring and a clean, in situ H-charging condition. Two sets of cantilevers were analysed in this work: one set of un-notched cantilevers, and the other set with focused ion beam-milled notch laying on two crystallographic planes: (010) and (110). The cantilevers were tested under two environmental conditions: vacuum (approximately 5 × 10 −4 Pa) and ESEM (450 Pa water vapour). Crack initiation at stress-concentrated locations and propagation to cause catastrophic failure were observed when cantilevers were tested in the presence of H; while no cracking occurred when tested in vacuum. Both the bending strength for un-notched beams and the fracture toughness for notched beams were reduced under H exposure. The hydrogen embrittlement (HE) susceptibility was found to be orientation dependent: the (010) crystallographic plane was more fragile to HE than the (110) plane. This article is part of the themed issue ‘The challenges of hydrogen and metals’.
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Kurzawa, Adam, Dariusz Pyka, Krzysztof Jamroziak, Marcin Bajkowski, Miroslaw Bocian, Mariusz Magier, and Jan Koch. "Assessment of the Impact Resistance of a Composite Material with EN AW-7075 Matrix Reinforced with α-Al2O3 Particles Using a 7.62 × 39 mm Projectile." Materials 13, no. 3 (February 7, 2020): 769. http://dx.doi.org/10.3390/ma13030769.
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The paper presents the results of studies on the effects of shooting composite materials produced by pressure infiltration with the EN AW-7075 alloy as a matrix and reinforcement in the form of preforms made of α-Al2O3 particles. Composite materials were made with two reinforcement contents (i.e., 30% and 40% vol. of α-Al2O3 particles). The composites produced in the form of 12 mm thick plates were subjected to impact loads from a 7.62 × 39 FMJ M43 projectile fired from a Kalashnikov. The samples of composites with different contents of strengthening particles were subjected to detailed microscopic examination to determine the mechanism of destruction. The effect of a projectile impact on the microstructure of the material within the perforation holes was identified. There were radial cracks found around the puncture holes and brittle fragmentation of the front surfaces of the specimens. The change in the volume of the reinforcement significantly affected the inlet, puncture and outlet diameters. The observations confirmed that brittle cracking dominated the destruction mechanism and the crack propagation front ran mainly in the matrix material and along the boundaries of the α-Al2O3 particles. In turn, numerical tests were conducted to describe the physical phenomena occurring due to the erosion of a projectile hitting a composite casing. They were performed with the use of the ABAQUS program. Based on constitutive models, the material constants developed from the identification of material properties were modelled and the finite element was generated from homogenization in the form of a representative volume element (RVE). The results of microscopic investigations of the destruction mechanism and numerical investigations were combined. The conducted tests and analyses shed light on the application possibilities of aluminium composites reinforced with Al2O3 particles in the construction of add-on-armour protective structures.
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Warner, Timothy, Diana Koschel, Ricky Whelchel, Paul Smith, Geoffrey Scamans, and Randall Merrill. "Effect of testing conditions, gauge and temper on stress corrosion cracking of AA7xxx aluminum aerospace plate alloys." Corrosion, October 24, 2022. http://dx.doi.org/10.5006/4142.
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The European Aviation Safety Agency’s recent safety information bulletin (SIB 2018-04R2) describes a brittle intergranular cracking phenomenon in 7xxx aluminum alloys and recommends testing conditions. These testing conditions are severe compared with expectations regarding, temperature, humidity, and stress in aerostructures. In this study, strong increases in time to failure of smooth specimens tested in humid air were observed when reducing either temperature or stress to levels closer to representative in service conditions. The cracking morphologies after testing in hot humid air were identical to those described in the literature for in service occurrences of stress corrosion cracking (SCC), including the observation of crack arrest markings consistent with a mechanism of alternate local corrosion and crack propagation by hydrogen embrittlement. The differences between such fracture surfaces and those observed in the industry standard SCC screening test, which uses a chloride containing solution to accelerate initiation and propagation, can be attributed to pitting of the crack surface in a chloride containing solution in the wake of the propagating crack. The performances of 7xxx-T7 aluminum plates SCC testing in either hot humid air or a chloride containing aqueous solution have been compared as a function of thickness, over-aging treatment, and composition. There is a strong effect of plate thickness in both tests, with substantial decreases in initiation time and lifetime for thinner plates. The effect of plate gauge is such that “legacy” materials (such as 7010-T7651, 7050-T7651 and 7050-T7451) passing the SIB 2018-04R2 test at high thicknesses, fail at lower gauges, yet have been flying for nearly 50 years. An increase in SCC performance with increased over-aging is observed in both tests. In consequence comparisons of SCC performance of alloy compositions should be made wherever possible at identical plate thickness and for aging treatments that result in comparable strengths. When this is done, high Zn concentration 7449-T76++ (7449-T7651 with additional aging) shows a slightly worse strength-SCC balance than 7010-T7651 and 7050-T7651. The observed trends in SCC performance in the two tests are consistent, suggesting that similar repeated initiation and propagation mechanisms are responsible for cracking in humid air and in aqueous NaCl environments.
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Ovchinnikov, V. V., R. N. Rastopchin, and L. P. Andreeva. "Effect of scandium alloying of filling wire on properties of welded joints of high-strength aluminum alloys." Blanking productions in mechanical engineering (press forging, foundry and other productions), 2021, 248–57. http://dx.doi.org/10.36652/1684-1107-2021-19-6-248-257.
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The results of the effect of scandium alloying of additive wires such as SvАМg4 and SvАМg63 on the structure and mechanical properties of welded joints of sheets and plates of 1420 alloy in mechanized single-passing and manual multi-pass welding are presented. It is shown that the introduction of 0.17...0.25 % scandium in the SvАМg4 and SvАМg63 filling wires contributes to decrease in the cracking rate and significant increase in the critical rate of deformation of the sample during welding on the МVТU sample. The level of microporosities and their location in multi-pass welding of plates of 1420 alloy depend on the magnesium content in the filling wire. The alloying of the SvАМg4 and SvАМg63 filling wires by scandium increases the ultimate strength of both the welding joint as whole and the weld metal.
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Palanisamy, Saravanakumar, Saravanan Murugesan, Jijo Prasad Jayaprasad Remani, Suresh Babu Gopalkrishna, Ashok Kumar Nallathambi, Daniel Juhre, and Eckehard Specht. "Experimental Investigation of Heat Transfer During Quenching of Semi-Solid Aluminum Plates Under Hot Cracking Condition." SSRN Electronic Journal, 2022. http://dx.doi.org/10.2139/ssrn.4034393.
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Gencalp Irizalp, Simge, and Burcak Kardelen Koroglu. "Stress Corrosion Cracking Behavior of Tungsten Inert Gas Welded Age-Hardenable AA6061 Alloy." Journal of Engineering Materials and Technology 141, no. 4 (March 20, 2019). http://dx.doi.org/10.1115/1.4042662.
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The effects of two temper conditions (T4 and T6 heat treatments) upon the stress corrosion cracking (SCC) of AA6061 plates have been investigated in this work. AA6061 alloys were double-side-welded by the tungsten inert gas (TIG) welding method. SCC behavior of both the as-welded and as-received alloys was reported. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to determine the precipitate structure of the thermal-altered zones and the base metal (BM), and also the hardness variations were examined using microhardness testing (Vickers hardness). The small-size precipitate structures in the T6 tempered alloy and the coarser precipitate structures in the T4 tempered alloy were found by microstructural investigations. As a result, T4 temper heat treatment of this alloy considerably reduced its susceptibility to stress corrosion cracks due to relatively coarse and more separate precipitate morphology. In welded specimens, SCC failure occurred in the area between the heat-affected zone (HAZ) and the base metal. Stress corrosion resistance in the fusion zone was strong in both temper conditions. The aim of this work was to obtain the effects of heat treatment and welding on SCC behavior of the age-hardenable aluminum alloy. The authors conclude that a deep insight into the SCC resistance of AA6061 alloy indicates the precipitate particle distributions and they are the key point for AA6061 alloy joints in chloride solution.