Benefits of using aluminum

Although aluminum is the most abundant metal in the Earth’s crust, it costs more than some less plentiful metals because of the energy needed to extract the metal from ore. When the electrolytic reduction of alumina (Al2O3) dissolved in molten cryolite was independently developed by CharlesHall in Ohio and Paul Heroult in France in 1886, the first internal-combustion-engine-powered vehicles were appearing,and aluminum would play a role as an automotive material of increasing engineering value. Electrification would requireimmense quantities of light-weight conductive metal for long-distance transmission and for construction of the towersneeded to support the overhead network of cables which deliver electrical energy from sites of power generation. Within afew decades the Wright brothers gave birth to an entirely new industry which grew in partnership with the aluminumindustry development of structurally reliable, strong, and fracture-resistant parts for airframes, engines, and ultimately, formissile bodies, fuel cells, and satellite components. There are many wonderful features in using aluminum for many engineering applications.

High Strength-to-Weight Ratio

Aluminum is the lightest metal other thanmagnesium, with a density about one-third that of steel. The strength of aluminum alloys, however, rivals that of mild carbon steel, and can approach 100 ksi(700 MPa). This combination of high strength and light weight makes aluminum especially well suited to transportation vehicles such as ships, rail cars, aircraft,rockets, trucks, and, increasingly, automobiles, as well as portable structures suchas ladders, scaffolding, and gangways.

Ready Fabrication

Aluminum is one of the easiest metals to form and fabricate,including operations such as extruding, bending, roll-forming, drawing,forging, casting, spinning, and machining. In fact, all methods used to formother metals can be used to form aluminum. Aluminum is the metal most suitedto extruding. This process (by which solid metal is pushed through an openingoutlining the shape of the resulting part, like squeezing toothpaste from the tube) is especially useful since it can produce parts with complex cross sections inone operation. Examples include aluminum fenestration products such as windowframes and door thresholds, and mullions and framing members used incurtainwalls, the outside envelope of many buildings.

Corrosion Resistance

The aluminum cap placed at the top of the WashingtonMonument in 1884 is still there today. Aluminum reacts with oxygen very rapidly,but the formation of this tough oxide skin prevents further oxidation of the metal.This thin, hard, colorless oxide film tightly bonds to the aluminum surface andquickly reforms when damaged. High Electrical Conductivity Aluminum conducts twice as much electricityas an equal weight of copper, making it ideal for use in electrical transmissioncables.

High Thermal Conductivity

Aluminum conducts heat three times as wellas iron, benefiting both heating and cooling applications, including automobileradiators, refrigerator evaporator coils, heat exchangers, cooking utensils, andengine components.

High Toughness at Cryogenic Temperatures

Aluminum is not prone to brittlefracture at low temperatures and has a higher strength and toughness at lowtemperatures, making it useful for cryogenic vessels.Reflectivity Aluminum is an excellent reflector of radiant energy; hence its usefor heat and lamp reflectors and in insulation.Nontoxic Because aluminum is nontoxic, it is widely used in the packagingindustry for food and beverages, as well as piping and vessels used in foodprocessing and cooking utensils.

Recyclability

Aluminum is readily recycled; about 30% of U.S. aluminumproduction is from recycled material. Aluminum made from recycled materialrequires only 5% of the energy needed to produce aluminum from bauxite.Often a combination of the properties of aluminum plays a role in its selectionfor a given application. An example is gutters and other rain-carrying goods, made of aluminum because it can be easily roll-formed with portable equipmenton site and it is so resistant to corrosion from exposure to the elements. Another isbeverage cans, which benefit from aluminum’s light weight for shipping purposes,and its recyclability.

Taken from this wonderful book: The Handbook of Advanced Materials: Enabling New Designs (Hardcover)by James K. Wessel (Editor)

Aluminum Processing Energy Benchmark Report

Different energy used in manufacturing process of aluminum in US

(from US department of energy)

Substantial energy efficiency gains have been made in the aluminum industry over the past forty years, resulting in a 58% decrease in energy utilization. However, as shown in the recently completed U.S. Energy Requirements for Aluminum Production, Historical Perspective, Theoretical Limits, and New Opportunities, room for improvement remains. Overall, the industry is operating at more than three times its theoretical minimum energy requirement. This report provides detailed appendices, statistical data, and descriptions of the fundamental chemistry as well as practical aspects of aluminum production processes. It compares current usage levels and theoretical minimum energy requirements to demonstrate that large energy saving opportunities exist.



This report provides reliable and comprehensive statistical data over the period 1960 to 2000 for the evaluation of energy trends and issues in the aluminum industry. It should be noted, however, that during the summer of 2001, the extensive heat wave in the western United States produced an increased demand for electricity. Simultaneously, the ability to generate hydroelectric power was reduced due to historically low snowpacks in the Columbia River basin and new regulations mandating the spill of water to aid migrating salmon. The combination of high electricity demand and limited water supply contributed to significant increases to the market price of electricity during this time. This price increase in the Pacific Northwest made it more economical for aluminum smelters to stop production and sell back power from their low-cost, fixed-price electric contracts to aid in minimizing the shortfall in energy supply. As a result, the majority of aluminum smelting capacity in the Pacific Northwest, representing approximately 43% of all U.S. primary aluminum capacity, shut down.



In light of the issues facing aluminum production in the Pacific Northwest. Much of the detailed statistical data for the years 2001 and 2002 are neither finalized nor available. It is currently too early to accurately assess the long-term impact of the shutdown and changing conditions on the aluminum industry. It remains to be seen whether the shutdown will lead to a permanent decline of primary metal production in the Pacific Northwest, or whether the industry will emerge robustly with additional self-generated power capacity and energy efficiency improvements. Whatever the industry’s future, it is clear that the local and global pressures to increase overall energy efficiency will determine its vitality. The energy efficiency opportunities discussed in this report are pertinent to the future of the aluminum industry.

Download the full report from here.

Aluminum alloy for producing high performance shaped castings

Abstract

An aluminum alloy for shaped castings, the alloy having the following composition ranges in weight percent: about 6.0–8.5% silicon, less than 0.4% magnesium, less than 0.1% cerium, less than 0.2% iron, copper in a range from about 0.1% to about 0.5% and/or zinc in a range from about 1% to about 4%, the alloy being particularly suited for T5 heat treatment.

• Patent number: 7087125


• Filing date: Jan 28, 2005


• Issue date: Aug 8, 2006


• Inventors: Jen C. Lin, Cagatay Yanar, Wenping Zhang, Pål S. Jacobsen, Geir Grasmo, Michael K. Brandt, Moustapha Mbaye, Martijn Vos, Michael V. Glazoff, Knut Pettesen, Svein Jorgensen, Terje Johnsen


• Assignee: Alcoa Inc.


• Primary Examiner: George Wyszomierski


• Secondary Examiner: Janelle Morillo


• Attorneys: Greenberg Traurig LLP, Harry A. Hild, Jr.Application number: 11/045,845

Download this patent from Google

Image from http://www.flickr.com/photos/11012311@N07/2143283661/

Different aluminum alloys extrusion

Extruded structural sections are produced by hot extrusion in which a heated cylindrical billet is pushed under high pressure through a steel die to produce the desired structural shape. The extrusion is then fed onto a run-out table where it is straightened by stretching and cut to length. During extrusion, metal flow occurs most rapidly at the center of the ingot resulting in oxides and surface defects being left in the last 10–15% of the extrusion which is discarded.

In general, the stronger the alloy, the more difficult it is to extrude. One of the advantages of the 6XXX (Al-Si-Mg) alloys is that they exhibit good extrudability. On the other hand, the 2XXX (Al-Cu) and 7XXX (Al-Zn) alloys are referred to as “hard” alloys because they are more difficult to extrude.

Alloy Relative extrusion pressure
1100 1.0
3003 1.2
6061 1.6
2014 1.8
7075 2.3

A profile’s shape factor (the ratio of the perimeter of the profile to its area) is an approximate indicator of its extrudability, i.e. the higher the ratio, the more difficult it is to extrude. The extrusion process itself and heat treatable aluminium alloys make it possible to manufacture complex, thin-walled cross-sections with a strength equal to that of ordinary structural steel. The torsional stiffness can be improved by exploiting the advantages of hollow sections.

Unsymmetric shapes, shapes with sharp corners, profiles with large thickness variations across their cross section, and those that contain fine details are all more difficult to extrude. Generous fillets and rounded corners help to reduce extrusion difficulties.


Data from ASM metals handbook vol. 14

Temper designations for heat-treatable aluminum alloys

Precipitation hardening or age hardening can be applied only to those groups of alloys which are heat treatable (i.e. 2XXX, 6XXX and 7XXX wrought series). Firstly, a supersaturated solid solution (SSSS) is made by solution heat treatment. Secondly the ageing process that occurs after quenching may be accelerated by heating the alloy until second and coherent phase is precipitated. This coherent phase strengthens the alloys by obstructing the movements of dislocations. In heat treatable aluminum alloys, temper designations are shown as follows:

• T1 Cooled from an elevated process temperature and aged (natural aging) at ambient temperature to a substantially stable condition.
• T2 Cooled from an elevated-temperature forming process, cold worked and naturally aged to a substantially stable condition.
• T3 Solution heat treated, cold worked, and naturally aged to a substantially stable condition. Solution heat treatment involves heating the product to an elevated temperature, usually in the 932–1022F (500–5508C) range. At this temperature, the alloy becomes a single-phase solid solution that is cooled rapidly (quenched) so that a second phase does not form. This is designated as the W condition, which is an unstable condition.
• T4 Solution heat treated and naturally aged to a substantially stable condition.
• T5 Cooled from an elevated-temperature forming process and artificially aged (holding for a specific time a temperature above the ambient temperature).
• T6 Solution heat treated and artificially aged. The aging process is usually maintained until maximum or near-maximum strength is achieved.
• T7 Solution heat treated and overaged. Products that have been aged beyond the point of maximum strength to provide some special characteristics, such as improved corrosion resistance or ease of forming, are included in this designation.
• T8 Solution heat-treated, artificially aged, and cold worked.
• T9 Cooled from an elevated-temperature forming process, cold worked, and artificially aged.

This should not be confusing to hardening and tempering as in steels.

Reparability and Auto Insurance Rate for Automobile Made of Aluminum Component

As aluminum use continues to increase in the auto industry, so does the need for understanding and applying "best practices" when repairing automotive aluminum components that will affect on insurance rate of aluminum-intensive car.

A review of both the similarities - and differences - encountered during the repair of aluminum panels compared with those of traditional materials shows that working with aluminum is not difficult; it is merely different.

In fact:

• Some procedures for working with aluminum are easier than with conventional materials
• The majority of tools for working aluminum are similar to those for working conventional materials
• The skills necessary for working aluminum can be learned as easily as the skills required for other materials
• Repair costs are not very different from those of traditional materials
• There are programs currently in place and new programs under development that offer training for repair of aluminum panels

Throughout the past century, body repair shop practices, tools and techniques have been developed to work mainly with automotive steels. As the auto industry looks to the future, however, it is increasingly turning to aluminum as the material of choice for use in automotive body structures and closure panels. As a result, there are a number of repair shops nationwide that are acquiring an expertise in aluminum repair, and their numbers are growing each year.
In fact, comprehensive programs are being put in place that address aluminum’s different characteristics. The development and implementation of repair instructions for specific aluminum vehicles has been led by the manufacturers.
The InterIndustry Conference on Auto Repair (I-CAR)* and others from the auto insurance and repair equipment supply industries have worked side-by-side with experts from the aluminum industry to develop training guides for correct repair of aluminum panels. A nationwide training program which began in 1996; technicians who have attended these programs say working with aluminum is different but not difficult.

Tools for working with aluminum are generally similar to those used for working with steel. However, good practice dictates the same tools should not be used on both metals because of cross-contamination. This causes problems with welding, finishing and potential bimetallic corrosion.
Files, sanding discs and other associated equipment are as effective when working with aluminum as with other metals. Cutting and general working of aluminum is much easier than steel, and the techniques involved are similar to those used in wood-cutting. Reciprocating saws and band saws - both with high blade speeds – are normally used.

When an aluminum part is damaged, the deformed area is work-hardened (strengthened) because of its atomic structure is FCC. Pulling on the part to straighten it will deform undamaged areas, which have not been work-hardened, before correcting the damaged area. Local heating of the damaged area will temporarily soften the heated area so that the damaged area can be corrected. The Aluminum Association provides information on the effects of elevated temperatures on material properties and recommendations for the use of heat for straightening.
A technique known as heat-shrinking can be used to take dents out of aluminum skin panels. When the area around a dent is heated with a torch, the stresses generated by restraining the metal that wants to expand cause the dent to be pushed out.

Another difference between heated aluminum and steel is that aluminum does not change color, even at its melting point. Therefore, it is important to use temperature indicators to keep track of the metal temperature during working. Heat can be used in cases where a technician needs to disassemble an adhesive-bonded joint. As long as the temperature is kept within the recommended range, using heat will soften the adhesive and enable the joint to be chiseled open with less mechanical damage and no long-term effects on material properties.

The most common method used for welding common metals is inert gas (or GMA) welding. Aluminum lends itself very well to this type of welding. Virtually all repair shops possess MIG welders. The more powerful and adaptable machines, required by aluminum, are beginning to penetrate many of the larger repair shops. Lap and fillet welds, butt welds with a backing added for the repair, and MIG plug welds are all approved for replacing other joining methods, as well as to repair original MIG welded joints.

Aluminum panels are finished in the same way as conventional materials, including the use of body fillers. All the major paint suppliers offer aftermarket paint repair systems, which include products designed and tested for specific materials (aluminum, steel, galvanized steel, SMC, etc.). Whatever the material, the supplier will warrantee the quality of the finish provided that the products and procedures for their complete system are used. Most procedures are standard for all the suppliers and the finish systems are warranted as long as directions are followed.

There are few fundamental differences between the repair of steel and aluminum panels and the average repair shop can be outfitted relatively easily for both. The difference between the material costs of steel and aluminum are insignificant in comparison to the cost of replacement parts.
For an experienced technician, the labor time required for aluminum repair is equivalent to that required for steel. To gain appropriate experience, the first step is training. Such training is rapidly spreading, and those who complete instruction are more valued assets to their employers.
As the aluminum content of vehicles increases, more and more repair facilities will learn to better accommodate aluminum-intensive vehicles (AIVs). As AIVs come into the marketplace, repair shops will react - as they always have - to economic pressures and equip themselves to handle damage repairs, much like they did several years ago to adjust to the universal changeover to computer engine controls.

When comparing the relative ease and costs of repairing aluminum and steel, it is clear that aluminum is not more difficult; it is just different. Different techniques are required, as is a clear understanding of the differences between steel and aluminum alloys and how these differences affect the repair process. Such understanding is readily available, as are the necessary specialized tools for proper repair of aluminum. As for training, I-CAR programs have been in existence for several years, and the manufacturers and suppliers are making available the necessary instructional materials to assimilate the repair of aluminum into everyday shop practices.

As the use of automotive aluminum continues to climb due to its performance, safety and environmental advantages, its repair will become as commonplace and routine as that of traditional materials. This factors will definitely affect the insurance rate for aluminum-intensive automobiles.

Source: http://www.autoaluminum.org/

Aluminum part for Apple's family product

Aluminum is well accepted for its recyclability, high strength, light weight, and nice touch. That is why the major and profit-making product lines of Apple, Ipod, are made of aluminum extensively. Both iPod nano and iPod shuffle leverage aluminum casing (either aluminum extrusion for iPod shuffle or aluminum die-casting for iPod nano). Catcher in Taiwan will manufacture both the aluminum extrusion for the new iPod shuffle as well as some other magnesium inner parts spread throughout other model's in Apple's revamped iPod line. Hon Hai (Foxconn) appears to be behind both the manufacturing of Apple's second-generation iPod nano as well the aluminum die-casting for its enclosure. Recently, MacBook Air also features in a highly recyclable-durable aluminum enclosure that should also made by die casting.

It's moving up... it's aluminum.

Physical and Chemical Characteristics of Aluminium for Welding

There are many considerations during welding aluminum alloys because of their unique physical and chemical characteristics of aluminium, contrasted with those of more familiar steel. Here are some comprehensive lists excerpted from the wonderful book "The welding of aluminium and its alloys" by G. Mathers:

• The difference in melting points of the two metals and their oxides. The oxides of iron all melt close to or below the melting point of the metal; aluminum oxide melts at 2060°C, some 1400°C above the melting point of aluminum. It is essential to remove and disperse this oxide film before and during welding in order to achieve the required weld quality.

• The coefficient of thermal expansion of aluminium is approximately twice that of steel which can mean unacceptable buckling and distortion during welding or high residual stress on welds.

• The coefficient of thermal conductivity of aluminum is six times that of steel. The result of this is that the heat source for welding aluminium needs to be far more intense and concentrated than that for steel. This is particularly crucial for thick sections, where the fusion welding processes can produce lack of fusion defects if heat is lost too rapidly. Preheating is usually important.

• The specific heat of aluminium – the amount of heat required to raise the temperature of a substance – is twice that of steel.

• Aluminum has high electrical conductivity, only three-quarters that of copper but six times that of steel. This is a disadvantage when resistance spot welding where the heat for welding must be produced by electrical resistance.

• Aluminum does not change colour as its temperature rises, unlike steel. This can make it difficult for the welder to judge when melting is about to occur, making it imperative that adequate retraining of the welder takes place when converting from steel to aluminum welding.

• Aluminum is non-magnetic which means that arc blow is eliminated as a welding problem.

• Aluminum has a modulus of elasticity three times that of steel which means that it deflects three times as much as steel under load but can absorb more energy on impact loading.

• The fact that aluminum has a face-centred cubic crystal (FCC) structure means that it does not suffer from a loss of notch toughness as the temperature is reduced. In fact, some of the alloys show an improvement in tensile strength and ductility as the temperature falls, EW-5083 (Al Mg 4.5 Mn) for instance showing a 60% increase in elongation after being in service at -200 C for a period of time.

• Aluminium does not change its crystal structure on heating and cooling, unlike steel which undergoes crystal transformations or phase changes at specific temperatures.This makes it possible to harden steel by rapid cooling but changes in the cooling rate have little or no effect on the aluminium alloys. However, for heat treatable alloys, it is important for the loss of mechanical properties from overaging problem.

Fluxing of Aluminum Alloys

Fluxes should be used when melting aluminum because this alloy rapidly forms a layer of oxide (primarily alumina) on all surfaces exposed to an oxygen-containing atmosphere. In aluminum melting, and especially in the remelting of returns or other scrap, oxide formation and nonmetallic impurities are common. Impurities appear in the form of liquid and solid inclusions that persist through melt solidification into the casting. Inclusions can originate from dirty tools, sand and other molding debris, sludge (iron-chromium-nickel intermetallic compounds commonly found in die casting alloys), metalworking lubricant residues, and the oxidation of alloying elements and/or the base metal. Oxidation accelerates as temperature increases. Fine oxide particles in molten aluminum tend to remain suspended because its density is close to that of aluminum and its high specific surface area slows both flotation and settling. Moreover, oxides that separate from the melt tend to envelop substantial amounts of usable metallic aluminum.

The term fluxing, in the broadest sense, applies to a treatment technique to the melt containing such impurities and inclusions as those mentioned above. Fluxing of the melt facilitates the agglomeration and separation of such undesirable constituents from the melt.

Fluxing is temperature dependent. The temperature must be high enough to achieve good physical separation or the desired chemical reaction. At sufficiently high temperatures, the fluidity of both the metal and the fluxing agent is likely to be very high, which provides for good contact between the two and better reactivity.

Flux Composition

The specific compounds or chemical reagents used in fluxes depend on the specific purpose of the flux. Most fluxing compounds consist of inorganic salt mixtures. The various constituents of these salts or other materials in the flux serve to:

· Form low-melting high-fluidity compounds at use temperature, as is the case with sodium chloride (NaCl)-potassium chloride (KCl) mixtures
· Decompose at use temperature to generate anions, such as nitrates, carbonates, and sulfates, capable of reacting with impurity constituents in the melt. This creates impurity metal oxides or other compounds with densities different from that of the base melt and facilitates physical separation
· Act as fillers to lower the cost per pound or to provide a matrix or carrier for active ingredients or adequately cover the melt

· Absorb or agglomerate reaction products from the fluxing action

Excellent book on aluminum melt treatment is Treatment of Liquid Aluminum-Silicon Alloys by John E. Gruzleski, Bernard Closset.

How will aluminum take on the low-cost car?

Toyota will be building a low-cost car undercutting Renault's emerging-market Logan through a "radical" rethink in design and production, the president of the fast-growing Japanese automaker said.

"The focus is on low-cost technology," Toyota president Katsuaki Watanabe told Britain's Financial Times newspaper in an interview published Monday. He declined to set a price for a low-cost car but said it would be "at least" less than the Logan.

Renault has started production of the Logan, which will cost from 5,000 euros (6,200 dollars) on up, touted as a budget model for consumers in emerging economies such as China and Russia that conforms to European standards. Watanabe said that Toyota could slash the price by targetting costs throughout production. Everything from design to production methods will be radically changed and we are thinking of a really ultra-low-cost way of designing, using ultra-low-cost materials, even developing new materials if necessary," he said.

The plan would create a new challenge to struggling US automakers. Toyota is set this year to overtake General Motors as the world's largest automaker.The Japanese automaker has cashed in by pioneering environmentally friendly hybrid cars and has also seen success with its luxury Lexus line.

Recently, Tata will also join this emerging market as reported in here. The Tata people's car was aimed to sell for about $2,500--the cheapest, by far, ever made.

(Agence France Presse, January 22, 2007) Picture from http://www.dancewithshadows.com/

Wear behaviour of cast hypereutectic aluminium silicon alloys

Wear behaviour of cast hypereutectic aluminium silicon alloys

Dheerendra Kumar Dwivedi

Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee 247 667, India

Abstract

In the present paper, influence of alloying elements on wear behaviour of binary (Al–17%Si) and multi-component (Al–17Si–0.8Ni–0.6Mg–1.2Cu–0.6Fe) cast hypereutectic aluminium alloys has been reported. Experimental alloys were prepared via foundry technique. Wear behaviour of Al–17Si and Al–17Si–X {X = Ni, Cu, Mg, Fe} alloys was studied using pin on disc (ASTM: G99) type of friction and wear testing machine. Dry sliding wear tests were performed at various sliding speeds (0.2–4.0 m/s) and contact loads (10–30 N) against hardened ground steel disc (hardness 60 HRC). It was observed that the addition of alloying element not only reduces the wear rate in mild oxidative wear condition but also increases the transition load. Temperature of wear pin near the sliding surface was measured and it was related to wear and friction behaviour of experimental alloys. Increase in hardness was also noticed due to alloying. SEM study of wear surface and wear debris was conducted to analyse the mode of wear and wear mechanism.

doi:10.1016/j.matdes.2004.11.029

Residual stresses in aluminum castings

Residual stresses in aluminum castings

J.E. Wyatt, J.T. Berry, and A.R. Williams

Abstract

The majority of manufacturing processes induce residual stresses in the surface of the component produced. These residual stresses can be either beneficial or in some cases detrimental to the performance of the component in question. This investigation involves the use of a previously described new low-cost method to determine the superficial residual stresses in a casting of A356 aluminum alloy. The technique concerned involves the measurement of the change in spacing of previously applied pairs of micro-hardness indentations which occurs upon stress relief. In the case of a compressive residual stress, this spacing will increase after stress relief. In estimating the strain concerned it should be noted that the equivalent ‘original gage length’ will be the relaxed spacing measurement. This strain multiplied by the modulus of elasticity will indicate the corresponding stress for a uniaxial stress state. The special 3 bar test frames that were employed had their residual stresses measured using both a cutting and a thermal stress relief technique. From the results it can be seen that the use of cutting is probably applicable to the more localized stresses that occur in the vicinity of the cutting zone. However, the stresses that remain in the frame redistribute themselves to maintain equilibrium, and are not measurable until the cut frame is stress relieved thermally. It was noted that the levels of strain measured were unusually high. This may be related to the occasional spontaneous failure of the castings on removal from their molds. The current paper describes the results of on-going research in this area.

doi:10.1016/j.jmatprotec.2007.03.018

Effect of casting imperfections on the fatigue life of 319-F and A356-T6 Al–Si casting alloys

Effect of casting imperfections on the fatigue life of 319-F and A356-T6 Al–Si casting alloys

H.R. Ammara, A.M. Samuela and F.H. Samuel, a, aDépartement des Sciences Appliquées, Université du Québec à Chicoutimi, 555 Boulevard de l’Université, Chicoutimi, Québec G7H 2B1, Canada

Abstract

Casting imperfections, such as porosity, in cast aluminum components greatly influence their fatigue properties. The effect of porosity on the fatigue life of 319-F and A356-T6 aluminum alloys was studied, where the porosity characteristics on the fracture surfaces of fatigue-tested samples were examined using SEM and image analysis. The results show that porosity has the greatest detrimental effect on fatigue life: 92% of all tested samples fractured as a result of porosity which acted as the main crack initiation site. In the absence of casting imperfections, other microstructural aspects such as slip bands may be held responsible (4%). Porosity was investigated in terms of the pore size at the sample fracture surface. It was found that fatigue life decreases as the size of the surface pore increases. A comparison was made between the fatigue behavior of low-pressure-permanent mold-cast 319 alloy and lost foam-cast A356-T6 alloy. The results show that the 319 alloy provides greater fatigue strength compared to the 356 alloy, which may be explained by taking into consideration the nature of the surface porosity (single pore versus multiple shrinkage pores) that initiated the fatigue crack in the two alloys. The microstructural characteristics are of secondary importance in this regard.

doi:10.1016/j.msea.2007.03.112

Aluminum Recycling

Aluminum Recycling

By Mark E. Schlesinger

Product Description
Even though over 30% of the aluminum produced worldwide now comes from secondary sources (recycled material), there are few books that cover the recycling process from beginning to end. Meeting the need for a comprehensive treatment of the aluminum recycling process, Aluminum Recycling explores the technology and processing strategies required to convert scrap aluminum and its alloys into new aluminum products and mixtures. The book details the collecting, sorting, and separating of scrap aluminum as well as the processing and upgrading equipment used. It first describes the aluminum alloys that are contained in the ore body and the various "mines" where aluminum scrap is found, followed by a discussion of the procedures for separating scrap aluminum from other materials. Subsequent chapters review the furnaces used for remelting the recovered scrap and the refining techniques that improve its purity and quality. The book also discusses the economics of scrap recycling and outlines the structure of the recycling industry. The final chapter addresses the unique environmental and safety challenges that recycling operations face. Although the benefits of recycling are numerous, aluminum recycling presents a series of unique challenges. Aluminum Recycling expertly leads you through the sequences of scrap aluminum recycling to provide a solid foundation for overcoming these obstacles.

Product Details
Published on: 2006-11-01
Number of items: 1
Binding: Hardcover
248 pages

Designing Aluminum Alloys for a Recycling-Friendly World

I found this interesting article on the Internet on how to design aluminum alloys for better recyclability.

Abstract

Recycling aluminum alloys has been shown to provide major economic benefits. As a result, it is appropriate for the aluminum industry and the U.S. as a whole to identify, develop, and implement all technologies that will optimize the benefits of recycling.This paper will focus primarily on alloy design for optimizing the reuse of recycled metal; this is both the most forward looking area as we move toward a more recycle friendly world, and the most overlooked for its potential in maximizing the recycle loop. Some specific approaches to alloy design for recycling are put forth, and some specific compositions for evaluation are proposed.Options for moving forward to further capitalize on the advantages of aluminum recycling are also addressed.

Download the full paper here:
Designing Aluminum Alloys for a Recycling-Friendly World, S.K. Das, Light Metal Age, June 2006. Nominated for Best Paper Award, Sloan Industry Centers.