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The paper summarises work which has been carried out to establish the sensitivity of the Alcan AVT weld-bonding system to manufacturing process variability. The robustness of the joint-line to factors such as panel fit-up, bondline thickness, adhesive fillet size and missing adhesive is discussed and their effects demonstrated. Manufacturing factors, such as pretreatment damage during part forming and the cure-cycle window for the adhesive, are considered and their effects on performance are indicated. Finally the effect of a series of manufacturing shortfalls and environmental factors have been put together in one experiment and the resulting strength and fatigue performance of bonded joints has been established.

The recycling and reclamation of metal-matrix composites (MMC's) are critical aspects of the commercialization process. By recycling, we mean the economic processing of MMC scrap for reuse as composite. Reclamation refers to the separation and recovery of the individual components of the composite, i.e., the various aluminum alloys and ceramic particles. Three forms of MMC wrought alloy scrap have been considered; i.e., D. C. (direct chill) cast log ends, extrusion butts, and cut extrusion scrap. Recycling each of these forms of scrap back into D. C. cast extrusion billet has been demonstrated. This has been accomplished by recycling the scrap back through the basic mixing process. Various ratios of scrap to virgin composite have been explored and optimum blends are being studied. Similarly, for MMC foundry alloy (high silicon) gates and risers produced in shape-casting, fluxing and degassing techniques have been developed so these may be recycled back into useful castings.

The need to reduce or contain a weight increase in new automobile designs is leading to the use of more and more aluminum and, in particular, to the adoption of aluminum outer body panels in a number of volume production vehicles. This has been made possible by improvements in the properties of heat treatable aluminum sheet materials and also from a better understanding of the issues related to part design and manufacturing. The alloy AA6111 has become the material of choice due to its unique combination of formability and paint bake strengthening and is used, for example, in the deck lids of the current Ford Crown Victoria, Grand Marquis and Taurus/Sable models. A modified process for this alloy has now been developed which significantly increases its paint bake strengthening and can be used either to obtain even better dent resistance or to reduce the gauge and hence obtain cost and weight savings.

An A356T61 cast aluminum lower suspension control arm has been put into production for the Lincoln Mark VIII. The mechanical requirements which drive the design for a critical part like this are discussed, together with some of the background knowledge needed to address the issues surrounding alloy and process selection. Particularly as it must be realized that the process impacts the degree to which the potential of the alloy can be realized. With this in mind, some of the research activities which have been spawned in parallel with the production activities are briefly covered. The sequence of events involved in the design and prototyping of the part itself are outlined, as is the implementation of a specialized low pressure casting line to produce the part. Part performance to date has been excellent and the quality controls and test methods which have been put in place to see that this remains so are also covered.

Due to the inherently superior corrosion resistance of aluminum compared to automotive steels, phosphating and electrocoating are not necessarily required to provide good corrosion protection to aluminum intensive vehicles. This allows the potential for significant cost savings in the overall finishing process by eliminating these steps. Advantage can also be taken of the movement towards the use of powder primer surfacers to reduce solvent emissions in that the powder coating can be applied directly to a suitably pretreated aluminum surface. Pretreatments which are optimized for aluminum and much simpler to control than phosphating were chosen for trials based upon discussions with chemical suppliers. In this paper, the adhesion and corrosion characteristics of these selected pretreatment/powder primer systems were compared to standard phosphated and electrocoated AA6111 automotive closure sheet.

This paper will describe the main features of two newly-developed enabling technologies for the future establishment of an integrated system to recover the full value of the aluminum from scrapped aluminum intensive vehicles. These technologies are fluidized bed decoating and alloy sorting using analysis by laser induced optical emission spectroscopy. Aluminum Intensive Vehicles will employ substantial quantities of sheet material, most of which will have fairly heavy paint coatings and possibly adhesives. While it may be possible to remove and segregate some of the closure panels and the major aluminum castings, the main body structure will need to be shredded to facilitate both the separation of the various aluminum and other materials and also the subsequent thermal decoating of paint films and adhesives. The decoating is necessary to ensure complete pyrolysis of the coatings and to avoid the excessive dross losses encountered when as-painted scrap is remelted.

Efforts towards weight reduction are leading towards increasing use of aluminum components on automobiles. Although aluminum on its own has inherently superior corrosion resistance to steel, galvanic action between the aluminum and steel or galvanized parts can lead to severe corrosion. Straightforward and effective methods of preventing galvanic corrosion from the subject of this paper. Since many aluminum components are connected to steel structures by mechanical fasteners, protective coatings on fasteners were evaluated as well. Galvanic test couples were prepared in a manner simulating typical automotive assembly conditions while incorporating features which would lead to enhanced corrosion. A variety of chemical treatments and coatings on the fasteners as well as barriers between the dissimilar metals were evaluated for corrosion prevention between the aluminum and cold rolled or galvanized steel. Comparison between neutral salt spray and cyclic corrosion tests is provided.

The movement towards extended warranties in the automobile industry has focussed attention on corrosion performance of many components, particularly cast aluminum wheels. Filiform corrosion is of particular concern since it can severely affect the appearance of the wheel. The appearance and the choice of wheel design are the most attractive features to customers. In order to enhance the filiform corrosion resistance of cast aluminum wheels, cleaning, pretreatment, coating and alloy parameters are critical and need to be optimized. In this paper, the effects of alloy composition and condition on filiform corrosion are reviewed. A series of cast discs were prepared with variations in iron, zinc and copper levels around the standard A356.2 alloy composition. Apart from composition, certain specimens were subjected to different heat treatment and ageing conditions. The effects of porosity and different machining procedures were also evaluated.

A co-operative program initiated by the Automotive Aluminum Alliance and supported by USAMP continues to pursue the goal of establishing an in-laboratory cosmetic corrosion test for finished aluminum auto body panels that provides a good correlation with in-service performance. The program is organized as a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee. Initially a large reservoir of test materials was established to provide a well-defined and consistent specimen supply for comparing test results. A series of laboratory procedures have been conducted on triplicate samples at separate labs in order to evaluate the reproducibility of the various lab tests. Exposures at OEM test tracks have also been conducted and results of the proving ground tests have been compared to the results in the laboratory tests. Outdoor tests and on-vehicle tests are also in progress. An optical imaging technique is being utilized for evaluation of the corrosion.

This work outlines the evaluation of static and dynamic dent resistance of medium scale structural assemblies fabricated using AA6111 and AA5754. The assemblies fabricated attempt to mimic common automotive hood designs allowing for a parametric study of the support spacing, sheet thickness and panel curvature. Closure panels of AA6111, of two thicknesses (0.8, and 0.9mm), are bonded to re-usable inner panels fabricated using AA5754 to form the structural assemblies tested. While normal practice would use the same alloy for both the inner and the outer, in the current work, AA5754 was adopted for ease of welding. Numerical simulations were performed using LS DYNA. A comparison of experimental and numerically simulated results is presented. The study attempts to establish an understanding of the relationship between structural support conditions and resulting dent depths for both static and dynamic loading conditions.

Process consistency and long electrode-life are essential requirements for users of resistance spot welding (RSW) in the automotive industry. RSW is the dominant joining process for manufacturing automotive body structures from sheet materials. The technique is cost effective (particularly in high-volume production), makes joints rapidly, is easy to automate, and it has no per-joint consumables. These beneficial attributes apply equally to RSW of aluminium automotive structures. However, there has been some reluctance in the industry to embrace spot welding for aluminium. This is because the electrode-life is much shorter than that experienced when welding traditional uncoated, plain-carbon steels, and there is a general lack of confidence in the consistency of the process. This paper describes a potentially non-intrusive method that addresses these concerns.