Analysis of mass transport during laser welding

Lasers, though developed only about a quarter century ago, are now being routinely used in automotive, aerospace and other industries to produce superior quality, high speed autogenous welds with narrow heat affected zones in a number of alloys. However, at present lasers cannot be used to successfully weld certain important structural alloys due to a change in weld composition resulting from selective mass transport of certain alloying elements from the laser melted region. The loss of alloying element leads to a degradation in mechanical properties of laser welded structures. Extensive experimental and theoretical research has previously been conducted to develop a better understanding and control of mass transport that takes place during high energy laser welding. In light of the possible use of high energy lasers for deep penetration welding of certain hard to weld structural alloys used in Navy vessels, the approach and results of these mass transport studies has been applied to evaluate the suitability of lasers for welding alloys used by the U.S Navy. Details of the study will be discussed in this paper.