Monte Carlo Simulation Of Grain Growth In The Heat-Affected-Zone Of Laser Welding

The macroscopic behaviours of materials, such as strength, ductility, toughness, corrosion resistance and so on, are strongly determined by their microstructure. Within this scope grain size and texture play an important role. Therefore it is of great interest in material science to understand and to predict grain growth and texture evolution during welding. In this paper, Monte Carlo (MC) technique was used to simulate the grain growth in heat-affected zone in the weld by laser welding, and a programme was developed under C++ Builder. The programme is general-utility, which can be used in general single-phase materials by laser welding. The grain growth process and kinetics were simulated by using grain boundary migration model (GBM) with the programme developed under C++ Builder. The grain size was predicted,and then the kinetic process of grain growth and the topology changes of material microstructure were simulated, and its growth process was made animatedly. The relation of average grain size and Monte Carlo step was established.The temperature field in welding HAZ was studied and analyzed. Considering the effect of the plasma, a mathematical model that divides the heat source into a spot heat source and a line heat source is set up to calculate the hermalcycle of laser welding. At the base of pure grain growth simulation, as an example, the grain growth process and kinetics of ultra-pure ferrite stainless steel (EB26-1) was simulated in this paper. The kinetic model of grain growth in HAZ was established by the thermal properties of materials welded and inducting welding heat cycle curve. The influence of heat pining was successfully simulated because of temperature gradient in HAZ, the phenomenon of grain growth was also simulated under the different heat inputs. Analysing the simulated results, there are close relations between grain size and parameters in HAZ: the lager temperature gradient in, the more little heat input, the smaller is ferrite grain size in the coarse grain of HAZ.