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针对熔化焊过程建立了宏微观耦合模型,模拟了熔池内不同区域凝固过程中随机取向枝晶的竞争生长过程.通过宏观三维有限元模型计算熔池中瞬态的传热传质过程,利用双线性插值算法将凝固参数传递给微观组织模型.采用元胞自动机法模拟随机取向的枝晶在熔池凝固条件下的竞争生长过程.模拟结果表明,所建立的微观模型能够精确模拟任意生长取向的枝晶.凝固条件中最大温度梯度方向对枝晶竞争过程有明显选择作用,生长方向与最大温度梯度方向相同或接近的枝晶在竞争中具有更大优势.焊缝中的晶粒组织由枝晶簇发展形成,晶粒组织的形貌演变取决于相邻枝晶簇之间的竞争过程,具有择优取向的枝晶簇会逐渐排挤非择优取向的枝晶簇并最终将其阻挡在凝固组织内部,宏观晶粒的取向与其内部枝晶簇的生长方向并不一定相同.熔池中心线附近区域在焊接过程中具有更小的温度梯度、更大的凝固速率以及更大的局部冷却速率,凝固后可以获得更加细小的焊缝枝晶组织.枝晶间距的模拟结果与相应凝固条件下的试验数据符合较好.
A macro-micro coupled model was established for the melt welding process to simulate the competitive growth of randomly oriented dendrites during the solidification in different regions of the molten pool.The transient heat and mass transfer process in the molten pool was calculated by the macroscopic three-dimensional finite element model, The linear interpolation algorithm transfers the solidification parameters to the microstructure model.The cellular automata method is used to simulate the competition and growth process of randomly oriented dendrite in the pool solidification conditions.The simulation results show that the established micro-model can accurately simulate the arbitrary growth Oriented dendrites.The maximum temperature gradient direction in the solidification conditions has obvious choice for the dendritic competition process.The dendrite whose growth direction is the same as or close to the maximum temperature gradient has more advantages in the competition.The grain structure in the weld The dendritic clusters develop and the morphological evolution of the grain structure depends on the competition between adjacent dendritic clusters. Dendritic clusters with preferred orientation gradually crowd out the non-preferentially oriented dendritic clusters and eventually block them in solidification Within the organization, the orientation of the macro-grains is not necessarily the same as the growth direction of the dendrite clusters inside the weld pool Has a smaller temperature gradient, a larger solidification rate and a larger local cooling rate, and the finer weld dendrite structure can be obtained after solidification.The simulation results of dendrite spacing are in good agreement with the experimental data under the corresponding solidification conditions it is good.