Advances in Welding Metal Alloys, Dissimilar Metals and Additively Manufactured Parts

Nowadays, strong, light-weight, multi-functional, high performing products are key for achieving success in the worldwide markets. Meeting those requirements calls for enabling technologies that lead to innovative and sustainable manufacturing [1]. A joint technique is one or a combination of the available mechanical, chemical, thermal processes to create a bond between materials with a number of combinations and geometries. Welding processes of metal alloys use a thermal energy source that can either melt materials of similar compositions and melting points or produce coalescence at temperatures essentially below the melting point of the base materials being joined. Such well-known welding processes include thermal fusion joining processes and solid-state joining processes; the latter are gaining renewed interest. Among the thermal fusion joining processes, the most common process is electric arc welding. Several methods use the electric arc approach for fusion welding of steel [2], aluminum [3], titanium [4] and magnesium alloys [5]. The selection of filler material is critical for the quality of the dissimilar metal welds [6]. Laser beam and electron beam welding are high-energy beam welding methods that can operate in either melt-in/conduction or keyhole mode. In the latter mode, the laser beam is highly effective at welding metals. Similar and dissimilar weld can be produced for appliance, automotive, and aerospace applications [7–9]. Brazing and soldering involve a filler material, heated to its melting temperature, and applied between the mating parts, which do not melt. Recently, laser autogenous brazing has enabled the selective use of the unique properties exhibited by biocompatible materials such as stainless steel and shape memory materials, such as NiTi, to tailor the properties of implantable medical devices [10]. Important mid-temperature thermoelectric materials such as Pb Te-based alloys can be successfully brazed to form a thermoelectric module [11]. Resistance spot welding, which dominates the steel body-in-white production, involves a strong current through the metal combination that heats up and finally melts the metals at localized points. A force is applied before, during and after the application of the current to confine the contact area at the weld interfaces and, in some applications, to forge the workpieces. Similar [12] and dissimilar [13] weld can be easily produced. Within the solid-state joining process, friction stir welding has gained a prominent position. Invented in 1991, it uses a non-consumable tool to join two facing workpieces without melting the workpiece material. Heat is generated by friction between the rotating tool and the workpiece material. This welding method has great capability at welding lightweight [14] and dissimilar weld [15]. Otherwise, friction welding is a process where the two pieces are moved relatively by means of an upsetting force. The relative motion heats the two pieces to a plastic-state. Two friction welding processes are available: linear friction welding and rotary friction welding [16]. Ultrasonic welding uses high frequency ultrasonic vibration for joining materials, such as in lithium-ion battery manufacturing, carbon fiber reinforced polymer–aluminum weld and dissimilar joining of aluminum to copper [17].