APPLICATION OF THERMAL MODELING TO LASER-BEAM WELDING OF ALUMINUM-ALLOYS

A thermal model has been developed for laser welding which describes t he heat input in terms of point and line sour ces. The model was used to generate weld profiles which closely matched those found by Experim ent. Outputs of the model (the thermal gradient GL and the growth rate R) were used to describe the macroscopic grain structure found along the weld centreline. Columnar structures were predicted at low welding speeds thigh G(L)/R ratio) and equiaxed structures at high welding sp eeds (low G(L)/R ratio), Using the thermal model, cooling rates of sim ilar to 1500 K s(-1) were estimated for the lowest welding speed, whic h increased by an order of magnitude for the highest welding speed con sidered There was excellent agreement between the dendrite secondary a rm spacings measured by experiment and those predicted using the therm al model.