Effect of sheet thickness on the fusion zone temperature distribution, melt pool dimensions, mechanical properties, and microstructure in laser welding of Ti6Al4V alloy

Generally, sheet thickness plays a significant role in the selection of appropriate process parameters in order to produce high quality weld joint in the laser welding process. The heat sink capacity and weld penetration are known as two criteria that are mainly influenced by sheet thickness. In this study, the effect of sheet thickness, welding speed, nozzle distance, and laser power were investigated in order to determine the temperature distribution near the melt pool, dimensions of molten pool through experimental and numerical analysis. The weld joint mechanical characterization was determined via elongation rate and tensile strength. The highest value of tensile strength is about 80% of the typical base metal and the elongation of the welded samples achieved about 40% of the base metal. The thinner sheets showed more sensitivity related to the elongation of the joint by increasing the welding speed. Also, the temperature rise with increasing laser power near the melt pool for the thinner sheet was about 200 °C in comparison to the 3 mm sheet, which is about 90 °C. The obtained simulation results for the maximum temperature discrepancy at near the melt pool was 12 °C and 4 °C for 1 and 3 mm thickness orderly, which depicts good agreement with the temperature experimental results.