A non-conventional technique for evaluating welded joints based on the electrical conductivity

Recent studies showed that electrical conductivity is a valuable technique to identify the different zones of solid-state welded joints with a good correlation with the microstructure and hardness. This is a relevant result since this technique is expedite and, in some cases, non destructive. The concept was applied to other welding processes as the ones involving fusion and to a wide range of materials. For this, a comprehensive study was performed using friction stir welding, tungsten inert gas (TIG) and gas metal arc (MAG) welding processes in either bead on plate or butt joints in: carbon steel, magnesium and titanium. Eddy current non-destructive testing (NDT) was used to measure the electrical conductivity at different depths in transverse sections of the processed materials. The obtained profiles were compared to the hardness profiles in the same sections. As a result, a good correlation was observed in most materials welded by solid state and by fusion processes. The variation of the electrical conductivity closely follows the one detected in the hardness. Another interesting conclusion is that, even for fusion welding of carbon steels, the technique has potential to complement the hardness measurements and microstructural observations, allowing to identify the distinct zones of welds in materials commonly used in industry. © 2014 Trans Tech Publications, Switzerland.