Zhang Min, Zhou Yulan, Huang Chao, Chu Qiaoling, Zhang Wenhui, Li Jihong
School of Materials and Engineering, Xi'an University of Technology, Xi'an 710048, China.
Materials (Basel). 2018 Nov 15;11(11):2288. doi: 10.3390/ma11112288.
In this paper, a three-dimensional (3D) finite element model was established by ABAQUS software to simulate the welding temperature field of a Ti-6Al-4V alloy under different welding currents based on a Gaussian heat source model. The model uses thermo-mechanical coupling analysis and takes into account the effects of convection and radiation on all weld surfaces. The microstructure evolution of the molten pool was calculated using the macro-micro coupling cellular automaton-finite different (CA-FD) method. It was found that with the increase of the welding current, the temperature in the central region of the moving heat source was improved and the weld bead became wider. Then, the dendritic morphology and solute concentration of the columnar to equiaxed transition (CET) in the weld molten pool was investigated. It is shown that fine equiaxed crystals formed around the columnar crystals tips during solidification. The coarse columnar crystals are produced with priority in the molten pool and their growth direction is in line with the direction of the negative temperature gradient. The effectiveness of the model was verified by gas tungsten arc welding experiments.
本文基于高斯热源模型，利用ABAQUS软件建立了三维（3D）有限元模型，以模拟不同焊接电流下Ti-6Al-4V合金的焊接温度场。该模型采用热-机械耦合分析，并考虑了对流和辐射对所有焊接表面的影响。利用宏观-微观耦合元胞自动机-有限差分（CA-FD）方法计算了熔池的微观组织演变。研究发现，随着焊接电流的增加，移动热源中心区域的温度升高，焊缝变宽。然后，研究了焊缝熔池中柱状晶向等轴晶转变（CET）的枝晶形态和溶质浓度。结果表明，在凝固过程中，柱状晶尖端周围形成了细小的等轴晶。粗大的柱状晶在熔池中优先产生，其生长方向与负温度梯度方向一致。通过钨极气体保护焊实验验证了该模型的有效性。
