The anodization of aluminum for nanotechnology applications

In light of the ever-increasing demand for the development of an effective, inexpensive and technologically simple method, a naturally occurring self-organization of oxide nanopores during the anodization of aluminum has recently attracted a vast amount of research attention in the field of nanotechnology. This article gives a brief overview on some of the recent advances in the anodization of aluminum, focusing on the fabrication of highly ordered nanoporous anodic aluminum oxide. Conventional anodization, newly developed hard anodization, pulse anodization process, and generic approaches for the fabrication of three-dimensional pore structures with periodically modulated diameters are discussed.     

Sintered aluminum nitride ceramics for high-power electronic applications

This article provides an overview of some of the critical materials issues involved in the utilization and commercialization of aluminum-nitride ceramics in electronic applications. Critical material defects and microstructural issues that control thermal, electrical, and mechanical properties and the status of metallization technology are reviewed. Finally, a discussion of current and future potential applications of sintered AlN and how these applications tie into key material properties is provided. Jonathan H. Harris earned his Ph.D. in solid state physics at Brown University in 1983. He is currently vice president of technology at Crystalline Materials Corporation.     

Drawn arc aluminum stud welding for automotive applications

Federal regulations have been enacted to significantly reduce atmospheric pollution caused by motor vehicles. This forced the automotive manufacturers to improve fuel efficiency of cars and light trucks by using lightweight materials such as aluminum. The focus of the current study is to develop welding procedures using the drawn arc process for 5754-0 and 6061-T6 aluminum alloys. The mechanical and macrostructural characteristics of the welded joints were evaluated using tensile tests, torque tests, and optical microscopy. Preliminary study indicates that these alloys can be welded with a minimal amount of porosity and good mechanical properties.     

Surface engineering of aluminum alloys for automotive engine applications

The modification and refinement of surface and subsurface microstructure in Al-Si-based cast alloys via laser-induced rapid solidification can create a natural topography suitable for engine applications. The differential wear of the soft aluminum phase, hard silicon, and CuAl in the cell, along with the divorced eutectic nanostructure in the intercellular region, is expected to produce and replenish microfluidic channels and pits for efficient oil retention, spreading, and lubrication. For more information, contact N.B. Dahotre, University of Tennessee, Department of Materials Science and Engineering, Center for Laser Applications, 326 Dougherty Building, Knoxville, TN 37996; (865) 974-3609; fax (865) 974-4115; e-mail ndahotre@utk.edu.     

The development of 5XXX aluminum alloys for RCS applications

The material characteristics necessary for making aluminum ends for beverage cans have changed dramatically as the industry has evolved over the past 30 years. This article traces the evolution of alloys used in end-stock applications from the 1950s to the present. Early experiences with H19 rigid-container sheet alloys that resulted in the development of alloy 5182 are reviewed, with emphasis on work-hardening and partial-annealing behavior. Changes in the industry, particularly coil coating and new end designs, that drove metallurgical changes to the product are discussed.     

船舶用耐蚀铝合金的研究进展

介绍船舶耐蚀铝合金的应用概况,讨论了船舶用耐蚀铝合金的耐蚀性能,对船舶用耐蚀铝合金的发展方向进行了展望。     

Friction stir processing of aluminum cast alloys for high performance applications

Friction stir processing (FSP) is a novel process developed based on the principle of friction stir welding (FSW) that locally manipulates the microstructure by imparting a high level of energy in the solid state resulting in improved mechanical properties. Additionally, FSP has emerged as an advanced tool to produce surface composites by embedding second phase particles into the matrix. Our work to date has shown that FSP can be implemented as a post-casting method to locally eliminate casting defects, such as porosity due to gas evolution during casting. Coarse second phases are broken up into fine nearly equiaxed particles and distributed uniformly in the matrix; grain refinement is also attained by dynamic recrystallization during FSP. This results in improved mechanical properties. Furthermore, our work shows that friction stir processing is a viable means of producing localized composite zones in cast Al components. Such improvements have important implications for manufactured components for diesel engines and for critical and high integrity components. The convenience of FSP as a post-processing step that can easily be carried out during machining operation makes it quite attractive for adoption.     

Recrystallization model for hot-rolling of 5182 aluminum alloy

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｒｉｎｇｈｏｔ ｒｏｌｌｉｎｇ ,ａｌｌｏｙｓａｒｅｄｅｆｏｒｍｅｄｆｏｒｖａｒｉ ｏｕｓｐａｓｓｅｓａｔｄｉｆｆｅｒｅｎｔｔｅｍｐｅｒａｔｕｒｅ .Ｒｅｃｒｙｓｔａｌｌｉｚａｔｉｏｎｏｃｕｒｒｅｄａｔｅｖｅｒｙｐａｓｓｃａｎｉｎｆｌｕｅｎｃｅｍａｎｙｐｒｏｐｅｒｔｉｅｓｏｆａｌｌｏｙｓｓｕｃｈａｓｔｈｅｏｃｃｕｒｒｅｎｃｅｏｆｐｒｅｃｉｐｉｔａｔｉｏｎ ,ｐｒｅ ｆｅｒｒｅｄｏｒｉｅｎｔａｔｉｏｎａｎｄｇｒａｉｎｓｉｚｅ[1,2 ] .Ｕｓｕａｌｌｙ ,ｔｈｅｓｔａｔｉｃｒｅｃｒｙ…     

Electrochemical etching model in aluminum foil for capacitor

A novel tunnel growth model is proposed to reveal how hydrogen is transported out of tunnels and explain the phenomena during etching process of aluminum foil for capacitor. Experimental results indicated that tunnel density increased and tunnel width decreased with temperature increasing at the temperature range of 70–80 °C. The pressure in electrolyte had an effect on the tunnel density. The tunnel density after etching at 0.2 atm was larger than that at 1 atm. A pulse electrochemical etching process is described according to the novel tunnel growth model. It considers that hydrogen bubble of nanometer dimension is absorbed on the tunnel’s walls surface during the pulse electrochemical etching process, and the saturated hydrogen at the end of the tunnel is accumulated to be a large bubble before hydrogen is transported out of the tunnel. The large bubble will emanate from the end of tunnel when the pressure in the bubble is equal to that outside. The wall surface passivation phenomena is explained by this model; the naturally corrugated texture with ripples of about 0.1 μm in tunnel’s walls surface is regarded to be produced by the potential periodical changes, which are caused by the large hydrogen bubble at the end of the tunnel. At the same time, the effect of temperature and pressure on the morphology of the tunnel is also investigated by use of the model. The pressure of the large hydrogen bubble in the tunnel is calculated according to the date in other references when the period of the pulse electrochemical etching is inferred to be 3 ms at their experimental conditions. The proposed process of pulse electrochemical etching could explain well the calculation results and the SEM images of etched tunnels under the same experimental conditions.     

The increasing use of aluminum in automotive applications

The average automobile currently produced in North America contains about 90 kg of aluminum. That figure is expected to grow, driven by environmental needs, the Partnership for a New Generation of Vehicles, safety mandates, consumer preferences, and an increasingly global marketplace. This paper examines those issues, along with current automotive applications for aluminum, the technology being developed to meet future demand, and the forces driving changes in technology.     

6082铝合金热变形的本构模型

利用Gleeble-1500热模拟机,研究6082锅合金在变形温度为300～500℃以及应变速率为0.01-10/s下高温单道次压缩过程的热变形流变应力行为.结果表明:6082铝合金高温单道次压缩下的热变形经历了从应变硬化阶段过渡到稳态变形阶段的过程,其软化机制主要为动态回复.该合金流变应力的大小受变形温度、应变速率的强烈影响,它随变形温度升高而降低,随应变速率提高而增大,说明该合金足一个正应变速率敏感的材料.该合金高温流变应力σ可采用Zener-Hollomon参数的函数来描述,函数表达式中参数A,a和n的值分别为3.97×1011s-1、0.011MPa-1、9.16;其热变形激活能Q为143.89kJ/mol.     

焊前预热对康复器械用铝合金焊接残余应力的影响

运用Abaqus有限元软件对康复器械用6061-T6薄板的MIG对接焊进行模拟,通过盲孔法测量实际焊接试样残余应力。研究了不同预热焊接工艺对铝合金焊接残余应力的影响。室温下的实验结果与模拟结果吻合良好,验证了计算模型的正确性。模拟结果表明,焊前预热能够明显减小焊缝附近的纵向残余应力,对横向残余应力影响较小;预热温度越高,残余应力消除效果越好;预热后采用降低热输入的焊接工艺的消除残余应力效果要好于预热后增加焊接速度的焊接工艺。     

2A97铝锂合金蠕变本构模型的建立

对2A97新型铝锂合金在温度180℃不同应力水平条件下进行多组蠕变试验,通过数值拟合,建立了经典蠕变本构模型与基于双曲正弦函数的等温蠕变本构模型。结果表明,采用基于双曲正弦函数的等温蠕变本构模型得到的拟合曲线与试验值吻合较好,能准确描述蠕变时效成形过程。     

铝合金薄板搅拌摩擦焊温度场模型

根据能量检测系统得出的搅拌摩擦焊接实时功率,结合M.Song等人提出的热输入模型,在此提出了简化的热输入模型.在深入考虑焊接过程的具体条件后,利用ANSYS有限元分析程序建立随热源一起移动的坐标系,模拟出瞬态温度场以及焊缝及母材区任何位置上的热循环曲线.通过模拟结果与热电偶测得的特征点温度曲线的比较,验证了热模型和模拟方法的正确性.     

An improved finite-element model for electromagnetic analysis in aluminum cells

This article presents the use of an improved finite-element model to calculate the static electromagnetic field for an aluminum reduction cell. Consisting of three solid cells and their surrounding bus bars, the model can evaluate the non-uniformity of the current distribution in the inside conductors and bus bar system and couple the current into the sequential magnetic analysis through a conversion routine. Voltage potential distribution in the molten aluminum was investigated based on one industrial 320 kA aluminum cell with two designed bus bar arrangements. Characteristics of magnetic components’ distributions were also given.     

A dislocation-density-based 3D crystal plasticity model for pure aluminum

A dislocation-density-based crystal plasticity finite-element model (CPFEM) is developed in which different dislocation densities evolve. Based upon the kinematics of crystal deformation and dislocation interaction laws, dislocation generation and annihilation are modeled. The CPFEM model is calibrated for pure aluminum using experimental stress–strain curves of pure aluminum single crystal from the literature. Crystallographic texture predictions in plane-strain compression of aluminum are validated against experimental observations in the literature. The framework is implemented in ABAQUS with user interface UMAT subroutine.     

Effect of pass deformation on microstructure, corrosion and electrochemical properties of aluminum alloy anodes for alkaline aluminum fuel cell applications

The effect of pass deformation in rolling processes on the microstructure, corrosion resistance and electrochemical activity of Al-Mg-Bi-Sn-Ga-In alloy anodes operated in an alkaline solution (85 °C, 5 mol·L^?1 NaOH with addition of NaSnO₃) with current density of 800 mA·cm^?2 was investigated. To analyze the microstructure of aluminum alloy anodes, we used scanning electron microscope, transmission electron microscope and electron backscatter diffraction techniques. We also used the hydrogen evolution method and electrochemical testing techniques to investigate the corrosion and electrochemical behavior of aluminum alloy anodes. The results showed that uniform microstructures with homogeneous distribution of fine active segregated phases as well as an excellent electrochemical performance of the aluminum alloy anodes were achieved by the dynamic recrystallization under pass deformation of 40%. We found that the aluminum alloy anodes (under pass deformation of 40%) had the lowest hydrogen evolution rate (0.092 mL·min^?1·cm^?2) and the most negative electrode potential (?1.585 V).