Laser Welding of Automotive Aluminum Allow to Achieve Defect-Free, Structuralh Sound and Reliable Welds

I. TECHNICAL PROGRESS The objective of this program was to seek improved process control and weldment reliability during laser welding of automotive aluminum alloys while retaining the high speed and accuracy of the laser beam welding process. In particular, we undertook a comprehensive experimental and theoretical research to understand the effects of various welding variables on the loss of alloying elements and the formation of porosity and other geometric weld defects such as underfill and overfill. The major achievements and findings fiom the work are summarized below: 1-1. Alloying elements loss a) We developed a comprehensive model that can predict the weld pool geometry, vaporization rates, and weld metal compositional changes during conduction mode laser welding of aluminum alloys. The model can serve as a basis for the quantitative understanding of influences of various welding parameters on fluid flow and heat transfer, vaporization of alloying elements, and weld metal composition change during laser welding. b) The vaporization rate of magnesium was found to be about two orders of magnitude greater than that of aluminum during conduction mode laser welding of aluminum alloy 5182. The significant magnesium loss fiom the weld pool resulted in a lower magnesium concentration in the weld metal than present in the base metals for all welding conditions. The vaporization rate increased with an increase in laser power. However, the higher loss was compensated by an equivalent increase in the melting rate and, as a result, the concentration of magnesium in the weld metal, although lower than found in the base metal, was not significantly affected by changes in the laser power. The DOE Patent Clearance Granted