**4. GTAW**

GTAW is also known as tungsten inert gas (TIG) welding, in which heat from an electric arc is used. The arc sparks between a tungsten non-consumable electrode and the workpiece [1]. The molten pool is shielded by an inert gas such as argon, helium, and nitrogen. The shield‐ ing gas prevents the molten pool from atmospheric contamination. The heat produced by the arc melts the samples' edges. The filler rod can be used if required, especially in welding aluminum. GTAW produces a high quality weld of most metals because it does not use flux. An externally supplied shielding gas is necessary because of high temperatures involved to prevent metal from oxidation. Direct current is typically used, and its polarity is important as this welding method still uses current and voltage as critical parameters. Given that the tungsten electrode is not consumed during welding, a stable and constant arc is preserved at a constant current level. The filler metals used are usually similar to the parent metals to be welded, without using flux. The shielding gas used is normally argon or helium (or a mixture of gases). GTAW is used for a wide variety of metals and applications. Metals that usually can be welded by GTAW are aluminum, magnesium, titanium, and copper and its alloy. The tungsten electrode is usually in contact with a water-cooled copper tube (contact tube), which is connected to the welding cable from the terminals. Both the weld current and electrode must be cooled to avoid overheating during welding.
