Ti-6Al-4V alloy weld joint by variant of TIG welding method: Characterization and mechanical performance evaluation

Abstract

Ti-6Al-4V alloy is an advance engineering material with excellent mechanical and metallurgical characteristic. However, joining of Ti-6Al-4V alloy by fusion welding methods has always been challenging because of its high affinity towards oxygen and nitrogen above 550 °C temperature. Therefore, shielding of weld pool during and after the welding process becomes essential for joining of Ti-6Al-4V alloy. In this work, autogenous butt weld joint of 3 mm thick Ti-6Al-4V alloy plate was performed by different variant of TIG welding, i.e., conventional TIG welding, pulse TIG welding and activated TIG welding methods with the aid of in-house fabricated shielding arrangements. The mechanical and metallurgical properties of the weld joints were analyzed through various characterization techniques and mechanical testing. The analysis of the weld bead geometry and microstructure was executed through optical microscopy and identification of metallurgical phase transformation, assessment of residual stress generated due to spatial thermal gradient and the texture evolution in the weldment were performed by X-ray diffraction (XRD) technique. The micro-hardness values of the weld joints at different locations were measured through Vickers micro indentation method. The tensile and flexural properties of the weld joints were analyzed through universal testing machine and the fracture surfaces were evaluated through scanning electron microscopy (SEM).
The experimental analysis revealed that with the use of pulse current, and TiO2 activated flux during TIG welding the mechanical properties of the weld joint improved significantly, which affirms that the proposed methods with appropriate parametric conditions can be adopted for industrial application of Ti-6Al-4V alloy.