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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.

The use of aluminium alloys for automotive heat exchangers has increased considerably in the last 15-20 years and, in parallel, new alloys have been developed to meet the increased demand for strength and improved corrosion resistance. A non-heat treatable Al-Mn alloy, X800, has been developed by Alcan to significantly increase the corrosion resistance of radiator tubes when subjected to typical service environments. The alloy development employed considerable microstructural understanding to provide heat exchanger manufacturers with an improved product that readily attained enhanced performance during any brazing cycle. A similar philosophy has been adopted to address the issue of increased mechanical performance, higher intrinsic sheet strength, both during and after brazing, provides the opportunity for sheet downgauging and thus lightweighting of components.

The application of aluminium alloy materials for automotive heat exchangers, including engine cooling and air conditioning systems, is now widespread. To meet the industry demands of both extended service life and improved reliability for heat exchanger components, it is important that the critical factors influencing corrosion behaviour are properly understood, particularly with the trend towards downgauging of materials. To maximise resistance to waterside corrosion, manufacturers have adopted the approach of using an internal cladding, commonly a high purity or zinc - containing alloy, to provide sacrificial protection of the core material. Recent studies have shown that the presence of an internal cladding can, under certain conditions, promote rapid localised attack of the core alloy.

The need to reduce the weight of automobiles has favored the widespread use of aluminum in automotive ventilation and cooling systems. Space, weight restrictions, the need for increased thermal efficiency, and recycling legislation have all contributed to new designs for heat exchangers. In many cases there has been a move to using extruded tube rather than seam-welded tube, leading to a reliance on the relatively more expensive clad fin. A new process, NOCOLOK™ Sil flux brazing, offers the potential for materials cost savings through the use of “in-situ” filler metal generation. This eliminates the need for using clad brazing materials. It can be applied to a number of alloy systems and product forms. This new technology is firmly rooted in the well established NOCOLOK™ non-corrosive aluminum brazing flux system.

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 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 development of a durable adhesive bonding technology for joining of aluminium automotive structures requires a full understanding of the importance of the environment on the chemistry of the adhesively bonded system. This paper describes the accelerated testing procedures used by Alcan to provide information on the significance of environmental factors on adherend surface, the bonding interface and adhesive and so establish the best combination of adhesive and surface pretreatment for good long term durability. The stress/humidity test provides information on adhesive and interface performance, while the neutral salt spray test illustrates durability and corrosion resistance of the pretreatment. Outdoor exposure testing provides the means of comparing the accelerated tests with real life durability.