Laser beam welding of dissimilar materials

In modern industrial fields, there is a tendency that more and more components or structures are compositely made of dissimilar materials, which offers challenges to the joining technology. In this paper, a review of laser beam welding of some dissimilar materials is presented based on our research. The dissimilar material combinations include W-Cu PMM/stainless steel, brass/copper, brass/steel, aluminium/titanium, and aluminium/copper. To join W-Cu PMM and stainless steel, the laser welding process with filler powder was conducted. Firm welds free of cracks are successfully obtained using Ni35 as the filler material. Laser deep penetration welding is achieved in the joining of brass and copper with a Nd:YAG laser, adopting lap joint with brass on the right side, by utilizing the easily vaporizing of the zinc element in brass. For the joining of dissimilar materials with great differences in the melting temperature and metallurgical properties, such as brass-steel, aluminium-titanium, and aluminium-copper, a so-called laser penetration brazing (LPB) process has been proposed and researched. The substrate with lower melting temperature is penetratingly melted by the focused laser beam while the substrate with higher melting temperature is still kept in the solid state. The melted metal wets the butt joint surface of the solid substrate to form a brazing joint.