Effect of fast-frequency pulsed waveforms on the microstructure and mechanical properties of Ti–6Al–4V alloy welded by FFP-TIG

Abstract

Ti–6Al–4V alloys have been widely adopted because of their good mechanical properties. TIG welding is a common method for Ti–6Al–4V alloys. However, the high heat input of conventional TIG can lead to a coarsening of grains within Ti–6Al–4V and thus a weaker Ti–6Al–4V weld. This study presents a novel fast-frequency pulsed tungsten inert gas (FFP-TIG) welding technology to fabricate a high-reliability Ti–6Al–4V weld. The effects of fast-frequency pulsed waveforms on microstructures and mechanical properties of Ti–6Al–4V weld samples were uncovered. The arc core diameter of FFP-TIG technology was reduced by 32%–36% compared with that of conventional TIG. The adoption of FFP-TIG decreased the average grain sizes and acicular martensite α′ within the Ti–6Al–4V weld by 47.7% and 40.5%, respectively, which further enhanced the mechanical properties of the corresponding weldments. The hardness, tensile strength, and elongation of Ti–6Al–4V weldments obtained by FFP-TIG were improved by 10.35%, 13.84%, and 304.61% compared with those obtained by conventional TIG, achieving the highest value of 373 HV, 1018.97 MPa, and 4.301%, respectively. This study provides fresh insight into the development and application of high-reliability titanium alloy weldments commonly used in the aviation industry.