Simulation of dissolution and coarsening in the HAZ of 6061 Al- alloy during laser welding

Application of laser beam welding (LBW) in heat treatable aluminum alloys causes softening of the heat affected zone (HAZ). This loss in hardness, reflects the relevant microstructural changes due to dissolution and coarsening of the strengthening precipitates during the weld thermal cycle. The main objective of the present work is the simulation of the microstructural evolution in the HAZ of the 6xxx Al alloys, in order to predict the hardness drop as a function of welding conditions. Towards this scope, bead-on-plate laser welding experiments have been conducted. Weld thermal cycles in the HAZ were determined by the finite element method. The volume fraction and average precipitate size, were calculated by employing the methodology of computational thermodynamics and kinetics for several weld thermal cycles. These microstructural characteristics were incorporated in relevant models in order to predict hardness variation. Calculated hardness profiles in the HAZ are in good agreement with the experimental values. Copyright © 2006 ASM International®