Laser weldability of brass open cell foams

Brass materials are widely used as engineering materials in industry because of their high strength, high corrosion resistance, high electrical and thermal conductivity. For the brass, the conventional fusion welding has some obvious limitations. The main problem of these alloys in fusion welding is the evaporation of the zinc during the welding process Therefore, it loses its physical and chemical properties. Using fiber laser welding effectively reduce this problem. In this study, fiber laser technology was used for welding foams in lap joint configuration, where 1 mm thick plate was welded on the top surface of the foam itself. Because of the difficulties for the presence of the pores, lap-joint configuration looks to be one of the most suitable welding configuration without the addition of filler material. The investigations of this work include technological, metallurgical and mechanical analysis. Welding tests were carried out by means of varying the welding speed and its effect was correlated to the size of the welded beads. The most of the work was concentrated on the characterization of the beads, present in the plate, because more repeatable than the joints in the foams. In details, in the first part of this work, the metallurgical analysis was taken into account: the presence of different microstructures were revealed by optical and scanning electronic microscopy. Additionally, the chemical composition of the beads was analysed by means of energy diffraction spectroscopy as well as the determination of the crystalline structure and crystal orientations was carried out by using back electron scattering diffraction analysis. In the second part of this work, mechanical examinations of the beads was performed in terms of microhardness cross the beads and tensile testing of the samples under different conditions. It was seen that the laser weldability of brass appears to be good from the point of view of both the microstructure and the mechanical properties, even if the welded beads realized cannot be considered continuous along the welding direction. It was found that the thermal damages of the welded beads indicates a very limited heat affected zone and a larger softened area; back electron scattering diffraction analysis has shown that the high cooling rates, characteristic of laser welding, can induce the generation of dual phase structure, even if the initial material was pure  phase.