Effect of reducing heat input on autogenous TIG welding of Ti–6Al–4V alloy

3 mm-thick Ti–6Al–4V alloy plates were welded in butt joint configuration through autogenous TIG welding method using a trailing gas shielding arrangement. After attaining full penetrated weld joint with appropriate heat input, subsequent experiments were conducted by reducing the heat input, which was obtained through combination of higher welding current and scan speed. An in-depth microstructural analysis of the weld joint executed under different heat input conditions shows a strong correlation with the microhardness, tensile strength, and flexural strength of the weld joint. A significant improvement in the mechanical properties of the weld joint was perceived for employing lower heat input. Alteration in the primary-α, primary-β, and martensite-α phases, due to the variation in heat input, amended the mechanical properties of the weld joint under lower heat input condition. With the reduction of heat input from 0.406 to 0.232 kJ/mm, the tensile and flexural strengths of the weld joint increased from 1020 to 1070 MPa, and from 1015 to 1950 MPa, respectively. The tensile strength of the joint reached up to 98% of the base material at minimum heat input (0.232 kJ/mm). The experimental results show the potential of TIG welding for joining Ti–6Al–4V alloy under low heat input condition.