A team of researchers from the Ohio State University has developed a new explosion welding technique able to join dissimilar metals. The process leverages a strong electric impulse to sublimate a small aluminium foil. The rapidly expanding gas pushes the flyer plate against the target plate at a speed of several hundred meters per second, solidly joining the two metals. This process is called Vaporized Foil Actuator Welding (VFAW).
To generate a strong yet short current pulse, a capacitor bank is used. The energy required by this process is 80% less than traditional spot welding, but joins are up to 50% stronger. The energy consumption is about 1.2 kilojoule, but researchers of the Ohio State University are aiming to reach an energy as low as 1 kJ, at the quick pace of one weld per second.
The main advantage is the possibility to weld metals that cannot be joined with techniques commonly in use. The researchers have been able to weld copper, aluminum, magnesium, mild steel, nickel, titanium, and even high-strength steel. Joints do not melt, hence there is no weakening of the material. In some cases, the welded zone becomes stronger than base metal. Traditional welding generates a Heat-Affected Zone (HAZ) that damages the mechanical and chemical characteristics of an alloy. This technique would therefore be highly useful to avoid corrosion and weakening.
Apart from welding, this technology can be used for sheet metal deformation, similar to what is acheived through hydroforming or stamping. Welding and deformation processes can therefore be carried in a single step, speeding up and simplifying the production of even complex pieces.