电磁搅拌对激光熔凝TA15钛合金熔池凝固研究

为了研究电磁搅拌作用对激光熔凝熔池凝固过程的影响,采用有限体积法对施加磁场前后激光单道动态熔凝TA15钛合金过程进行三维磁-热耦合数值模拟。研究了磁场对激光熔池流场、熔凝单道及其周边基材温度分布、固液界面处温度梯度和凝固速度的影响,并采用试验手段对模拟结果进行了验证。模拟结果表明:电磁搅拌作用使激光熔池最大流速增加了约20%,对流加剧促进了熔池热交换作用,使其最高温度下降,固液分界面处温度梯度大幅降低,凝固速度小幅增大,从而有利于熔池顶部组织发生柱状晶-等轴晶转变(CET)。试验结果显示施加磁场后熔凝层顶部有等轴晶组织生成,且随着远离磁场中心,电磁力增大,等轴晶区有扩大趋势。试验结果和模拟结果一致性较好。

Effect of Electromagnetic Stirring on Melt Pool Solidification of Laser Melting TA15 Titanium Alloy

In order to study the effect of electromagnetic stirring on melt pool solidification, a three-dimensional magnetic-thermal coupling numerical simulation was conducted on the process of single-pass laser melting TA15 titanium alloy with and without the magnetic field based on the finite volume method. The influence of electromagnetic field on temperature field, flow field, temperature gradient and solidification rate were analyzed. Then the numerical simulations were verified by experiment method. The results of numerical simulations showed that the melt pool maximum flow velocity increased by 20%, which promoted the function of heat exchange resulting in going down of the highest temperature of melt pool and temperature gradient on solid-liquid interface, and meanwhile the small rise in solidification rate, which were good for columnar-to-equiaxed transition at the top of melt pool. The experiment results indicated some equiaxed grains were generated at the top of melt layer with the magnetic field. Electromagnetic force was enlarged with an increase of the distance from magnetic field center, which causes equiaxed grain zone had a tendency to expand. The numerical simulations were in good agreement with the experimental results.