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A 14 kW CO2 laser and reflective optics were utilized to produce specimens for obtaining typical joint properties associated with laser beam welds of automotive aluminum alloys. The results of static and dynamic testing of these welds indicated that the laser beam welding process is capable of producing high quality welds. In all cases, the measured yield strength of butt welds exceeded the minimum yield strength of base material specified for these alloys. Post weld aging of the heat treatable alloys resulted in a moderate increase in strength of butt welds but virtually no effect on joint strength of lap welds. Butt welds produced with filler metal additions on the non-heat treatable alloys exhibited improved joint strength in comparison to welds produced autogenously. Butt welds displayed, as expected, displayed significantly higher fatigue endurance when compared to lap welds.

A method for improving resistance spot weldability is proposed based on creating a differential surface resistance between the sheet surfaces. The differential in surface resistance is achieved by an anodizing technique. Relationships between electrode life, differential surface resistance and differential oxide thickness have been established. Under the conditions used, optimum electrode life is achieved with a differential oxide thickness of some 330Å. This corresponds to a differential in surface resistance of approximately 50 × 103 micro-ohms. The treatment also produces an improvement in the consistency of weld performance. Although the method has so far only been tested and evaluated on a laboratory scale it is felt that the results offer sufficient insight into the mechanisms of aluminum spot welding to merit publication. The possibility of developing a commercial process based on these findings for the production of improved autobody sheet is under investigation.