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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。
In order to study the effect of electromagnetic stirring on the solidification process of laser fusion pool, the finite volume method was used to simulate the three-dimensional magneto-thermo-coupling process of TA15 titanium alloy before and after laser application. The influence of magnetic field on the laser flow field, the temperature distribution of the fused single channel and its surrounding substrates, the temperature gradient at solid-liquid interface and the solidification rate were studied. The simulation results were verified by experimental means. The simulation results show that the maximal velocity of the molten pool is increased by about 20% with electromagnetic stirring, and the intensified convection accelerates the heat exchange in the molten pool and decreases the maximum temperature. The temperature gradient at the solid-liquid interface decreases greatly and the solidification rate increases slightly , Which favors the columnar crystal-equiaxed crystal transition (CET) at the top of the weld pool. The experimental results show that there is an equiaxed grain structure at the top of the melt layer after the magnetic field is applied, and as the distance from the center of the magnetic field increases, the electromagnetic force increases and the equiaxed grain area has an expanding trend. The test results are in good agreement with the simulation results.