In this paper, the feasibility of using a fiber laser to perform a dissimilar metal joining was explored. AZ31B magnesium and 316 stainless steel were autogenously joined in butt configuration. The weldability between different materials is often compromised by a large difference in thermal properties and poor metallurgical compatibility. Thus, the beam was focused onto the top surface of the magnesium plate, at a certain distance from the interfaces (offset), and without using any interlayer or groove preparation. Such a method was called laser offset welding (LOW). Results proved a very good capability. The ultimate tensile strength exceeded the value of 100 MPa, since a resistant and thin layer of hard intermetallic compounds is formed within the fusion zone. The rupture was observed within the magnesium side, far from the centerline. The metallurgy of fusion zone indicated the effectiveness of phases coalescence, without mixing at liquid states. LOW was demonstrated to be a promising technique to join dissimilar metal welds, being capable to produce an effective bonding with good tensile strength

Welding between Fe and Al alloys is difficult because of a significant difference in thermal properties and poor mutual solid-state solubility. This affects the weld microstructure and causes the formation of brittle intermetallic compounds (IMCs). The present study aims to explore the weld microstructure and those compounds over two different technologies: the laser offset welding and the hybrid laser-MIG (Metal inert gas) welding. The former consists of focusing the laser beam on the top surface of one of the two plates at a certain distance (offset) from the interfaces. Such a method minimizes the interaction between elevated temperature liquid phases. The latter combines the laser with a MIG/MAG arc, which helps in bridging the gap and stabilizing the weld pool. AISI 316 stainless steel and AA5754 aluminum alloy were welded together in butt configuration. The microstructure was characterized and the microhardness was measured. The energy dispersive spectroscopy/X-ray Diffraction (EDS/XRD) analysis revealed the composition of the intermetallic compounds. Laser offset welding significantly reduced the content of cracks and promoted a narrower intermetallic layer.

Friction Stir Welding (FSW) has demonstrated a significant potential for joining low melting point non-ferrous metals in several joint configurations. During FSW metals are joined in the solid state due to the heat generated by the friction and flow of metal by the stirring action of a pinned tool.This paper reports an experimental investigation on the effects of geometry and surface coating of the tool shoulder on the defectiveness, the microstructure and the microhardness of a 3 mm thick 5754H11 aluminium alloy butt weld.During the experiments the diameter and slope of the shoulder varied. Moreover a tungsten carbide coated was tested. The pin geometry and dimensions were kept constant. Four different tools for shoulder geometry and coating condition were tested.The weld was characterized in terms of the bead morphology and the grain size.The weld microhardness profile was measured for all the microstructural zones of the friction stir welding process.The obtained results provide a deeper knowledge of the effect of the tool shoulder geometry and surface condition on the aluminium alloy weldability