This work aimed to (i) understand conventional & pulse gas tungsten arc welding (GTAW) of AZ31B, and (ii) explore high frequency welding (100 Hz to 1500 Hz). GTA welding with alternating current (AC) & direct current electrode positive (DCEP) polarities yielded crack-free partial penetration welds for 6 mm thick AZ31B alloy sheet. Welding under direct current electrode negative (DCEN) polarity with identical parameters as that for AC & DCEP resulted in full penetration welds that had microcracks. Defect-free full-penetration welds could be accomplished with pulse GTA welding using DCEN polarity at a pulse frequency of 1 Hz with a pulse duration ratio of 1:1. The resultant DCEN P 1:1 weld metal had a microstructure finer than the conventional DCEN weld. Welds produced with pulse duration ratios of 1:2 & 1:4 lacked penetration but had a much finer microstructures because of the lower heat input. The arc constriction by the high frequency pulsing in the ActivArc®-High frequency (AA-HF) mode welding was responsible for deeper penetration. Welds produced under DCEN pulsing and AA-HF conditions had hardness higher than conventional DCEN, DCEP & AC GTA welds, attributed to the finer microstructure. AA-HF GTA welding produced defect free deeper penetration welds with good microstructural features/mechanical properties and also gave an advantage of 50% enhanced productivity when welded at 1500 Hz.