# Effect of Ultrasonic Frequency Pulse Current on the Microstructure and Mechanical Properties of Ti6Al4V TIG Welded Joints

## TL;DR

This paper shows that using ultrasonic frequency pulse current during welding improves the strength and microstructure of titanium alloy joints.

## Contribution

The novel use of ultrasonic frequency pulse current in TIG welding refines grain structure and enhances mechanical properties of Ti6Al4V joints.

## Key findings

- Ultrasonic frequency pulse current refines grains to an average size of 0.54 μm in Ti6Al4V welds.
- The average hardness of the fusion zone increases to 350 HV with ultrasonic welding.
- Ultrasonic TIG welding improves yield strength and elongation compared to conventional methods.

## Abstract

To enhance the performance of Ti6Al4V titanium alloy joints, ultrasonic frequency pulsed TIG welding was employed. The microstructure and mechanical properties of the joints were systematically investigated. Results show that the weld microstructure is predominantly composed of acicular α phase, lath α phase, and a minor amount of β phase. Compared with conventional TIG welding, the application of ultrasonic frequency pulse current effectively refined the grains, achieving an average grain size of 0.54 μm. Concurrently, the proportion of high-angle grain boundaries increased from 96.1% to 97.6%. The average hardness of the fusion zone exceeded that of the base metal and was significantly increased by the ultrasonic frequency pulse current, reaching 350 HV compared to 330 HV for conventional welds. Furthermore, the ultrasonic frequency pulsed TIG joints exhibited higher yield strength and elongation than their conventional welds. These findings demonstrate that introducing ultrasonic frequency current during TIG welding effectively improves the properties of Ti6Al4V welded joints.