焊接熔池快速凝固过程的微观组织演化数值模拟

基于晶粒形成原理和枝晶生长动力学特点,建立了焊接熔池凝固过程中的形核、枝晶生长、溶质再分配及扩散的二维数学物理模型,对焊接熔池快速凝固过程中柱状晶向等轴晶的转变以及不同的冷却速度对这一转变过程的影响进行了模拟.结果表明,焊接熔池在快速冷却凝固过程中,溶质再分配与扩散明显;柱状晶向等轴晶转变时,熔池中心等轴晶凝固排出的溶质使柱状晶尖端浓度急剧升高,抑制了柱状晶的生长;冷却速度越大,柱状晶越容易向等轴晶转变,且转变所需时间越短.

Microstructure numerical simulation of weld pool in rapid solidification

Based on grain formation principle and kinetics characteristics of dendrite growth,two-dimensional mathematical and physical model of nucleation,dendrite growth,redistribution and diffusion of the solute were established to simulate the columnar- to-equiaxed transition in rapid solidification process of welding molten pool and the influence of different cooling rate on this transition process was also studied.The results show that, the solute redistribution and diffusion are evident in the process of rapid cooling.When the columnar grains transform into equiaxed grains,the discharged solute makes concentration sharply increased at the tip of columnar grain,which inhibits the growth of columnar crystals.Moreover,the change will be more likely to occur at higher cooling rate,and the required time will be also shorter.