The recycling of standard quality wrought aluminum alloys from low-grade contaminated scrap

In recent decades an increasingly large fraction of the world’s wrought aluminum alloys supply has come from the aluminum scrap recovered from industrial waste and discarded post-consumer items. However, replacing even a minor part of primary aluminum in wrought alloys with recycled counterpart originated from lower grades of scrap (typically scrap contaminated with various non-metallic impurities) without influencing the quality of the allay is very demanding from a metallurgical point of view. This article discusses the two approaches for achieving the requested chemical composition of wrought alloys made from recycled aluminum: (i) before melting, by combining the appropriate qualities and quantities of scrap, primary aluminum, and the alloying elements and (ii) during melting, by diluting impurity content with primary aluminum to the needed level and adding, at the same time, the necessary amount of alloying elements for achieving their standard concentration in diluted melts.     

铝合金轨道车辆结构及合金性能(2)

介绍了轨道车辆用变形铝合金的种类、化学成分、合金元素作用、热处理特点、力学性能,以及高速列车机车车轴齿轮箱和电机齿轮箱箱体所用的ZLAlSi7 Mg铸造铝合金的化学成分和力学性能.     

An Industrial Method for Determining the Amount of Organics in Representative Samples of Aluminum Scrap

In recycling plants, especially those specializing in the recycling of low-grade aluminum scrap for wrought aluminum alloys, timely and accurate information about the amount of organics and other impurities in the incoming scrap is an important parameter in achieving both economic benefits and standard metallurgical quality of the recycled metal. To use aluminum scrap combined with organics as a source of aluminum for producing wrought aluminum alloys of standard quality, its metallurgical composition and the content of organic and other impurities should be quickly and cost-effectively analyzed on representative samples. In this work, an industrial thermogravimetric/differential thermal analysis of representative scrap samples was developed as an efficient analytical methodology for analyzing the humidity and organic impurities in incoming scrap. When performed in continuous mode, under a flowing atmosphere of argon with 1?wt.% of oxygen, this methodology enables a routine measurement of the humidity, the quantity of organics, and the carbon content in representative samples of incoming scrap in less than 15?min within an accuracy of ±0.5%.     

The recycle of wrought aluminum alloys in Europe

Increasing demand for aluminum-based products and globalization of the aluminum industry have contributed significantly to the higher consumption of aluminum scrap for re-production of wrought aluminum alloys. The recycling of wrought auminum alloys not only fills market demand, but does so economically. It is a well-known fact that recycling wrought aluminum alloys from collected scrap consumes 15 times less energy than producing primary aluminum, and the cost of internal scrap is marginal. This paper examines opportunities for recycling scrap to solve the ongoing problem of raw material shortages for European producers of wrought aluminum alloys.     

The development of recycle-friendly automotive aluminum alloys

The continuing growth of aluminum alloy usage in transportation applications, notably passenger automobiles and minivans, and the demonstrated economic benefits of recycling aluminum-rich vehicles increase the need to seriously consider the desirability of designing recycling-friendly alloys. This article focuses on that aspect of the recycling process for passenger vehicles. The goals are to illustrate the opportunities afforded by identifying and taking full advantage of potential metal streams in guiding the development of new alloys that use those streams. In speculating on several possible aluminum recovery practices and systems that might be used in recycling passenger vehicles, likely compositions are identified and preliminary assessments of their usefulness for direct recycling are made. Specific compositions for possible new recycle-friendly alloys are suggested. In addition, recommendations on how the aluminum enterprise, including industry, academia, and government, can work together to achieve the aggressive but important goals described here are discussed.     

The recycling and reclamation of metal-matrix composites

The development of viable techniques for the recycling and reclamation of metal-matrix composites (MMCs) is critical to the commercialization of these advanced materials. The recycling of both MMC wrought alloy (6061) scrap and foundry alloy (high-silicon) returns has been studied. The MMC extrusion alloy scrap has been recycled back into direct-chill cast logs and the resulting billet has been tested to determine whether the composite properties are degraded by repeated recycling. Similarly, fluxing and degassing techniques have been developed so that MMC foundry alloy gates and risers produced in shape-casting may be recycled back into useful castings. These fluxing and degassing processes have been tested commercially. Ultimately, when either type of MMC scrap can no longer be recycled, the alumina particles in the wrought alloys or the silicon carbide particles in the foundry alloys may be removed by common salt or other fluxing techniques. Rotary salt furnace technology has been shown to be effective for this approach, and the results of large-scale trials are reported here.     

Semi-solid near-net shape rheocasting of heat treatable wrought aluminum alloys

Flexibility of the CSIR-RCS, induction stirring with simultaneous air cooling process, in combination with high pressure die casting is successfully demonstrated by semi-solid rheocasting of plates performed on commercial 2024, 6082 and 7075 wrought aluminum alloys. Tensile properties were measured for the above mentioned rheocast wrought aluminum alloys in the T6 condition. The results showed that tensile properties were close to or even in some cases exceeded the minimum specifications. The yield strength and elongation of rheocast 2024-T6 exceeded the minimum requirements of the wrought alloy in the T6 condition but the ultimate tensile strength achieved only 90% of the specification because the Mg content of the starting alloy was below the commercial alloy specification. The strengths of rheocast 6082-T6 exceeded all of the wrought alloy T6 strength targets but the elongation only managed 36% of the required minimum due to porosity, caused by incipient melting during solution heat treatment, and the presence of fine intermetallic needles in the eutectic. The yield strength of rheocast 7075 exceeded the required one and the ultimate tensile strength also managed 97% of the specification; while the elongation only reached 46% of the minimum requirement also due to incipient melting porosity caused during the solution heat treatment process.     

变形镁合金材料的研究进展

综述了变形镁合金材料的基本特性和优良性能,讨论了镁合金的合金化原理和主要合金元素在变形镁合金中的作用,介绍了快速凝固方法制备的高性能变形镁合金新工艺以及变形镁合金的主要应用领域。变形镁合金将成为21世纪极有发展前途的轻质商用结构材料。     

6×××系变形铝合金的合金化原理和生产应用

较系统地叙述了6×××系变形铝合金的合金化原理,生产过程中材料成分、组织和性能之间的关系,主要元素Mg、Si及添加元素Cu、Mn、Cr的作用,杂质元素Fe的影响。介绍了有代表性的工业6×××铝合金的特点,以及生产、应用情况。     

Recent advances in micro-alloyed wrought magnesium alloys: Theory and design

Micro-alloying design of wrought magnesium (Mg) alloys is an important strategy to achieve high mechanical properties at a low cost. In the last two decades, significant progress has been made from both theory and experiment. In the present review, we try to summarize recent advances in micro-alloying design of wrought Mg alloys from both theoretical and pragmatic perspectives, and provide fundamental data required for establishing the relationship between chemical composition and mechanical properties of Mg alloys. We start with theoretical attempts for understanding the mechanical properties of Mg alloys at different scales, by involving first principle calculations, molecular dynamics, cellular automata, and crystal plasticity. Then, the role of alloying elements is discussed for a series of promising Mg alloys such as Mg-Al, Mg-Zn, Mg-RE (rare-earth element), Mg-Sn, and Mg-Ca families. Potential challenges in the micro-alloying design of Mg alloys are highlighted at the end. The review is expected to provide helpful guidance for the intelligent design of novel wrought Mg alloys and inspire more innovative ideas in this field.     

Component- and Alloy-Specific Modeling for Evaluating Aluminum Recycling Strategies for Vehicles

Previous studies indicated that the availability of mixed shredded aluminum scrap from end-of-life vehicles (ELV) is likely to surpass the capacity of secondary castings to absorb this type of scrap, which could lead to a scrap surplus unless suitable interventions can be identified and implemented. However, there is a lack of studies analyzing potential solutions to this problem, among others, because of a lack of component- and alloy-specific information in the models. In this study, we developed a dynamic model of aluminum in the global vehicle stock (distinguishing 5 car segments, 14 components, and 7 alloy groups). The forecasts made up to the year 2050 for the demand for vehicle components and alloy groups, for the scrap supply from discarded vehicles, and for the effects of different ELV management options. Furthermore, we used a source-sink diagram to identify alloys that could potentially serve as alternative sinks for the growing scrap supply. Dismantling the relevant components could remove up to two-thirds of the aluminum from the ELV stream. However, the use of these components for alloy-specific recycling is currently limited because of the complex composition of components (mixed material design and applied joining techniques), as well as provisions that practically prevent the production of safety-relevant cast parts from scrap. In addition, dismantling is more difficult for components that are currently penetrating rapidly. Therefore, advanced alloy sorting seems to be a crucial step that needs to be developed over the coming years to avoid a future scrap surplus and prevent negative energy use and emission consequences.     

汽车铝合金锻件及冲挤件

为了建设低碳汽车产业,全世界汽车的轻量化正在加速进行,尽量多地以铝代钢、铸铁、铜等制造零部件,是目前及今后一段时间内实现汽车轻量化最可取与最现实的措施。较为详细地介绍了铝合金锻件及冲挤件的生产工艺与性能,标准锻件铝合金及一些公司研发的非标定锻件铝合金的成分与性能,介绍了一些世界级铝合金锻件及冲挤件生产企业概况,铝合金锻件在汽车中的用量虽不大(仅占总铝用量的1.3%左右),却很重要。提出中国应尽快建设二三个汽车铝合金锻件厂及冲挤件厂的建议。     

基于人工神经网络与遗传算法的Al-Mg-Si系合金抗拉强度预测模型

为了研究Al-Mg-Si系合金热处理制度和合金成分对力学性能的影响规律,采用人工神经网络（artificial neural network, ANN）和遗传算法（genetic algorithm, GA）相结合的方法,构建了Al-Mg-Si系合金强度预测模型（ANN-GA模型）。通过单因素和双因素分析,研究了合金元素含量和热处理工艺参数对铝合金抗拉强度的影响规律。结果表明,随着Si含量的增加,铝合金的抗拉强度呈现先降低后升高的趋势;随着Mg含量的增加、Cu含量的增加或者Fe含量的减少,铝合金的抗拉强度整体上呈现升高的趋势。双因素分析更能反映输入参数对铝合金抗拉强度的影响。Mg/Si比、Mg+Si总量和时效时间对Al-Mg-Si系合金力学性能的影响显著。铝合金的硬度随时间的变化趋势与ANN-GA模型的计算结果一致,峰值时效时间为29 h,相对误差为11.86%。     

Magnesium secondary alloys: Alloy design for magnesium alloys with improved tolerance limits against impurities

The development of secondary magnesium alloys requires a completely different concept compared with standard alloys which obtain their corrosion resistance by reducing the levels of impurities below certain alloy and process depending limits. The present approach suitable for Mg-Al based cast and wrought alloys uses a new concept replacing the β-phase by τ-phase, which is able to incorporate more impurities while being electro-chemically less detrimental to the matrix. The overall experimental effort correlating composition, microstructure and corrosion resistance was reduced by using thermodynamic calculations to optimise the alloy composition. The outcome is a new, more impurity tolerant alloy class with a composition between the standard AZ and ZC systems having sufficient ductility and corrosion properties comparable to the high purity standard alloys.     

Recent Progress and Development in Extrusion of Rare Earth Free Mg Alloys: A Review

Mg and its alloys are the lightest structural metals available and are extremely attractive for applications as lightweight components, particularly in the automobile, electronic, and aerospace industries. The global market for wrought Mg alloys has steadily expanded over the past decade. And numerous studies have been carried out to meet this increasing demand of high-performance Mg alloys. However, Mg extrusion alloys have had a very limited usage so far. To overcome existing industrial challenges, one desirable approach is the development of low-cost rare earth(RE) free Mg extrusion alloys with superior mechanical properties. This review will introduce the recent research highlights in the extrusion of Mg alloys, specifi cally focusing on low-cost RE-free Mg alloy. The results from both the literature and our previous study are summarized and critically reviewed. Several aspects of RE-free Mg extrusion alloys are described in detail:(1) novel alloying designs including Mg–Al-, Mg–Zn-, Mg–Ca-, Mg–Sn-, and Mg–Bi-based alloys,(2) advanced extrusion techniques, and(3) extrusion-related severe plastic deformation(SPD) processing. Accordingly, considering the large gap in mechanical properties between the current RE-free Mg alloys and high-performance aluminum alloys, new alloy design, processing route control, and recommendations for future research on RE-free Mg extrusion alloys are also proposed. We hope this review will not only off er insightful information regarding the extrusion of RE-free Mg alloys but also inspire the development of new Mg extrusion technologies.     

Effects of high niobium addition on the mechanical properties and high-temperature deformability of gamma TiAl alloy

The effects of Nb on the mechanical properties, high-temperature deformability and some other basic properties of TiAl–Nb alloys were investigated over a wide compositional range, and an appropriate composition for high-temperature applications was investigated for both wrought and cast materials. The lattice parameter of Ti–50Al–xNb alloy, which is a γ single phase alloy, shows an anisotropic variation with Nb content. This lattice distortion is assumed to be responsible for the strengthening and embrittlement of high-Nb ternary alloys. In the case of wrought materials, no appropriate composition exists in the high-Nb content region since wrought materials require good forgeability and high-temperature strength which are properties of antithesis. In the case of cast materials, however, an appropriate composition exists in the vicinity of Ti–46Al–7.5Nb (at.%).     

Rendering wrought aluminium alloys castable by means of minimum composition adjustments

Wrought alloys have low fluidity and are prone to hot tearing, which make them difficult to cast. The presence of eutectic-forming elements in the alloy composition lessens these effects. For this reason, the constituents of casting alloys tend to include a eutectic portion. Typically, silicon is added to aluminium alloys to provide casting ability by forming the aluminium–silicon eutectic. However, the presence of silicon in aluminium alloys is associated with a number of issues that do not allow these alloys to reach their full potential. In this publication we report results of our investigation of three alternative eutectics: Al–6.1Ni, Al–1.8Fe, and Al–1.75Fe–1.25Ni. Our results indicate that these eutectics have satisfactory fluidity and resistance to hot tearing and higher strength than the aluminium–silicon eutectic. We also found that introducing these eutectic compositions into 7075 wrought alloy results in a castable composition with yield strength comparable to that of the wrought alloy.     

The development and potential applications of a Pb-Al Alloy

Although widely used in batteries, lead alloys are heavy and have poor creep properties. To develop a lighter, more creep resistant battery alloy, the possibility of alloying lead with aluminum has been explored. Although aluminum and lead are immiscible, rapid solidification and mechanical alloying techniques allow the production of an alloy with uniformly distributed phases. Aluminum additions have been demonstrated to improve creep resistance and increase electrical conductivity, as well as reducing density. Ongoing work is aimed at optimizing the processing, structure and properties of Pb-Al alloys.     

金胜铝业公司的工业挤压材专用合金

简要介绍金胜铝业公司研发的几种生产工业挤压材的专用铝合金的化学成分和性能,它们是超高强度的H755铝合金、无粗晶环的H601铝合金、高蠕变性能的MO34铝合金、绿色的可高速切削的M662铝合金和有特色的6063型铝合金。这几种铝合金在替代同类传统铝合金生产某些工业挤压材时表现出了优越性。     

Magnesium alloy applications in automotive structures

The use of magnesium alloys in structural applications has great potential for the lightweighting of transportation vehicles. Research within the CAST Cooperative Research Centre has tackled some of the important issues related to the use of magnesium in structural applications. To this end, a new alloy with extrudability and properties similar to 6000 series aluminum alloys has been developed. Furthermore, a method of laser heating magnesium alloys before self-piercing riveting has enabled high-integrity joining between magnesium components or between magnesium and dissimilar metals. In this paper, new technologies and improved understanding of the deformation behavior of wrought magnesium alloys are discussed in light of key metallurgical features such as alloy composition, grain size, and work hardening rate. All are part of CAST Co-operative Research Centre.