Laser welding of nickel and its heat affected zone microstructure simulation

A matrix consisting of 200 × 200 sites with 100 possible grain orientations was usedfor simulating the heat affected zone grain structure of nickel during laser welding. Temperature histories measured during welding were substituted into the simulation. The heat affected zone microstructure in the plane were the temperatures were measured, i.e. along the welding direction, were investigated. The material used in the experiment was nickel 270 with purity 99.9% or greater. Type K thermocouples, located in the plane along the welding direction, were used to measure temperatures vertically below the center line of the weld during welding at a sampling rate of 150 Hz. The materials was cold rolled with 50% thickness reduction and then annealed at 700°C for 30 minutes to generate a momogeneous initial grain size. The surface of the specimen was ground using sand paper of 400 grit size to remove oxides and keep the surface conditions consistent, including uniform scratch size, unidirectional scratches parallel to the direction of welding, and uniform surface reflectivity. Both the grain size distribution and grain growth direction throughout the heat affected zone showed reasonable agreement with the experimental results.