Weldability of metal foams using different processes: A review

Foam materials, especially aluminum-based, have peculiar properties as a consequence of their intrinsic porous structure. The unusual physical-mechanical properties of metal foams make this class of materials highly promising for application in various branches of industry: low weight constructions, energy and vibrations absorbers, soundproofing systems and many others. The extensive application of metal foam is possible just producing high-quality joints and from this point of view it is extremely important to investigate the weldability of this kind of material, developing suitable joining technologies. Until today Al and its alloys, Ti, Cu, Fe, Ni, stainless steel foams have been successfully manufactured. Sandwich panels and filled tubes have been considered too. Problems in the production of metal foams usually arise due to the lack of knowledge about controlling the process parameters, dealing in many cases with a gas dispersed in a liquid unstable phase. The results are frequently uneven and unpredictable variations in the structure and properties of semi products and final products have been experienced. Similar problems arise also during metal foams joining due to the cellular structure. Different joining technologies (FSW, laser, ultra-sonic spot, arc-welding) are detailed in this chapter. A comprehensive review of common and less common joining processes are described. The main problems have been focused and solved thanks to some technological modifications applied to consolidated processes. Welding of metal foams allows the manufacturing of novel geometries, complex structures and customized parts with minimum waste. Continuous researches and development in joining techniques, including novel materials, design methods, welding and brazing technologies have helped to overcome many challenges and increase the industrial applications. The research results have been focused on the improvement of the joining processes; current issues and open problems are highlighted too.