Achievement of defect-free and structurally sound welds based on scientific principles has been an important goal of contemporary welding research. In the welding of aluminum and magnesium alloys, porosity formation and alloying element loss have been two major quality problems. The research to be presented focuses on the alleviation of these problems through quantitative understanding of alloying element loss and porosity formation during laser welding.; The instability of the keyhole was the main cause of macro-porosity formation during laser welding of thin plates of aluminum alloys 5182 and 5754. A computer model was developed to understand the formation and prevention of macroporosity. The stability of keyhole was not a major factor in pore formation during laser welding of die-cast magnesium alloy AM60B. Well controlled remelting of the welded metal led to the removal of gas bubbles and reduced porosity in the welded metal. Loss of alloying elements due to vaporization resulted in significant changes in the composition of the weld metal. Numerical computations of heat transfer and fluid flow and mass transfer were helpful in understanding and controlling compositional changes due to evaporation.; Taken as a whole, the research to be presented is a contribution to the growing quantitative knowledge base in fusion welding. Expansion of this knowledge base is necessary, if not essential, to solve important quality problems in fusion welding based on scientific principles.
展开▼
