AbstractLaser beam welding is currently used in the welding of steels, aluminium alloys, thin sheets, and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, deep penetration, narrow bead and heat affected zone (HAZ) widths, and low distortion compared to other conventional welding processes. However, the metallurgical and mechanical properties of laser welds and the response of conventional materials to this new process are not yet fully established. The welding process may lead to drastic changes in the microstructure with accompanying effects on the mechanical properties and, hence, on the performance of the joint. The thermal cycles associated with laser beam welding are generally much faster than those involved in the conventional arc welding processes. This leads to the formation of a rather small weld zone that exhibits locally a high hardness in the case of C–Mn structural steels owing to the formation of martensite. It is currently difficult ...