镍基合金TIG焊接熔池及热影响区组织模拟

Simulation of microstructure evolution of weld pool and heat-affected zone during TIG welding of nickel-base alloy

基于枝晶生长动力学和晶粒长大理论,采用元胞自动机法(CA)建立了焊接熔池及热影响区的微观组织演变模型.通过有限元模型计算了TIG焊接过程的温度场分布,并利用插值算法将热循环曲线应用于CA模型,计算了镍基合金TIG焊接熔池凝固过程枝晶生长及热影响区的晶粒长大.结果表明,焊缝边缘的晶核主要以柱状晶的形式向焊缝中心生长,其最终形貌取决于半熔化母材晶粒上的联生结晶及不同取向枝晶间的竞争生长,焊缝中心为等轴晶组织.焊接热影响区的晶粒长大使得熔池凝固形成的柱状晶组织粗大.模拟结果与试验结果吻合较好.

Model for microstructure of molten pool and HAZ was developed based on the dendritic growth kinetics and the grain growth theory using the cellular automaton method.The temperature field during TIG welding process was calculated by the finite element model.And the thermal cycle curves were applied to the CA model to calculate the dendrite growth in the molten pool and grain growth in the heat-affected zone.The simulation results showed that the nuclei at the fusion boundary mainly grows in the form of columnar dendrite toward the center of the weld.The final morphology depends on the partially melted grains of base metal at the fusion boundary and competition growing between dendrite arrays with different orientation.The microstructure at the center of the molten pool was equiaxed dendrites.The grain growth in the heat-affected zone results in the columnar structure of the molten pool coarser.The simulation results agree well with the experimental results.