Effect of Laser Welding on Intermetallic Phase Formation between Aluminium Alloys Foam and Steel Bulk Skin

Metal foams are conquering an increasing interest in the industrial stage. Aluminium foams have a high potential for use in weight-sensitive construction parts. The stiffness to weight ratio is the main criteria for material selection in light-weight design. Many processes are available to manufacture metal foams classified according to the state in which the metal is processed (liquid, solid, vapour or a solution of metal ions) and similarly different techniques can be applied to join the foam to bulk elements. In this context, the aim of this work is to perform an experimental study of laser welding for realising parts with an aluminium foam core (AlSi10 and AlSi0.6Mg1) and a steel external skin. The goal of the paper is to point out the feasibility of the process with the formation of an intermetallic phase between steel and aluminium and then the influence of the main process parameters. The experimentation was carried out in two steps: a preliminary study about an overlapped joint between steel and foam sheets and then the joining of steel hollow profile and aluminium foam obtained by a precursor material foamed directly inside the profile. A full factorial plan was designed by varying different process parameters referred to the laser (power of the laser source, execution speed, heat input and focal distance of the laser beam) while, except the precursor material, all the factors relative to the foam were kept constant. As results an intermetallic phase formation between aluminium foams and a stainless steel sheets and moulds have been obtained observed by micrograph examination.