Arc Characteristics and Weld Bead Microstructure of Ti-6Al-4V Titanium Alloy in Ultra-high Frequency Pulse Gas Tungsten Arc Welding (UHFP-GTAW) Process

Abstract

To resolve the problem of grain coarsening occurring in the fusion zone and the heat-affected zone during conventional gas tungsten arc welding(C-GTAW) welded titanium alloy, which severely restricts the improvement of weld mechanical properties, welding experiments on Ti-6Al-4V titanium alloy by adopting ultra-high frequency pulse gas tungsten arc welding (UHFP-GTAW) technique were carried out to study arc characteristics and weld bead microstructure. Combined with image processing technique, arc shapes during welding process were observed by high-speed camera. Meanwhile the average arc pressure under various welding parameters were obtained by adopting pressure measuring equipment with high-precision. In addition, the metallographic samples of the weld cross section were prepared for observing weld bead geometry and microstructure of the fusion zone. The experimental results show that, compared with C-GTAW, UHFP-GTAW process provides larger arc energy density and higher proportion of arc core region to the whole arc area. Moreover, UHFP-GTAW process has the obviously effect on grain refinement, which can decrease the grain size of the fusion zone. The results also revealed that a significant increase of arc pressure while increasing pulse frequency of UHFP-GTAW, which could improve the depth-to-width ratio of weld beads.

Study on arc shape, weldment microstructure, and mechanical properties of Ti-6Al-4V welded by FFDP TIG waveform

“…Wang et al [9] quantitatively analyzed the ultrasonic acoustic flow phenomenon in arc plasma at ultrasonic frequency (20kHz~30kHz), revealed the promotion effect of ultrasonic on arc plasma concentration and acceleration. Li et al [10] showed that the heat input of high frequency pulse current was more concentrated. Kumar A. and Chen et al [11,12] analyzed the three-dimensional electromagnetic force through simulation, revealed that high-frequency current can increase arc pressure and promote molten pool flow.…”