Effect of heat input in pulsed Nd:YAG laser welding of titanium alloy (Ti6Al4V) on microstructure and mechanical properties

In the present investigation, titanium alloy Ti6Al4V of 1.4mm thickness has been laser-welded in butt joint configuration using pulsed Nd:YAG laser system. The effects of heat input on weld bead shape, fusion zone width (top, middle, and bottom), heat-affected zone (HAZ) width (top, middle, and bottom), and fusion zone area have been studied. The microstructure and mechanical properties of laser-welded specimens at various heat inputs (43.7-103.5J/mm) have also been investigated. Microstructures of the fusion zone, HAZ, and parent material have been compared at various heat inputs using optical microscope and field emission scanning electron microscope (FESEM). The mechanical properties such as microhardness and tensile strength of the welded joints at varying heat inputs have been studied. Tensile tests of the welded specimen and base metal have been conducted for analyzing ultimate tensile strength and percentage elongation. Surface topography of the tensile fractured specimen of the welded joints and base metal has been examined to analyze the ductile and brittle behavior. EDS analyses of base metal and fusion zone of the welded specimen have been studied. XRD of the as-received base metal and welded specimen have been measured in the range of 30 to 85 degrees to study the crystallographic structure.