**1. Introduction**

Resistance spot welding (RSW) or simply spot welding is widely employed in automotive and aeronautical industries. This type of welding employs a tremendous amount of current and a very low voltage. Numerous types of metals like different grades of steels, aluminum (Al), magnesium (Mg), titanium (Ti), copper (Cu), and their alloys. Generally, thin sheets of similar or dissimilar metals are joined by RSW in lap joint configuration. RSW also suffers from a few limitations like liquation cracking, voids, misalignment, electrode wear, etc. Thicker sheets of metals are generally difficult to weld by RSW because the heat flows into the surrounding metal very easily.
