红外与激光工程, 2017, 46(9): 0906006, 网络出版: 2017-09-01
Effect of electromagnetic stirring on melt flow velocity of laser melt pool and solidification structure
沈阳航空航天大学 航空制造工艺数字化国防重点学科实验室, 辽宁 沈阳 110136
电磁搅拌 激光熔凝 磁流体动力学模型 CET转变 electromagnetic stirring laser melting magnetohydro dynamics model columnar-to-equiaxed transition
为了研究电磁搅拌对TA15钛合金激光熔池的影响, 构建了一种三相三极旋转式电磁搅拌器作用下微小熔池内部的磁流体力学数学模型。运用该模型计算了不同激励电流情况下磁场中心处的磁感应强度和熔池内熔体周向流速, 分析了其对熔池温度分布和组织形成的影响。并采用试验手段对分析计算结果进行了验证。结果表明: 电磁力驱使熔体作周向运动, 且随着远离磁场中心, 洛伦兹力越大, 周向流速越大。随着激励电流的增大, 磁感应强度增强, 熔质周向流速增大。流速加剧能够降低熔池内温度及凝固界面处的温度梯度, 有利于等轴晶的增多。试验证明施加磁场后熔池顶部组织出现等轴晶, 且随着远离磁场中心, 熔池顶部的等轴晶数量逐渐增多, 与计算结果的分析趋势相吻合。
In order to study the effect of electromagnetic stirring on laser melt pool solidification of TA15 titanium alloy, A MHD mathematical model was established on minimal melt pool under the three-phase three-pole rotating electromagnetic stirrer. This model was used to calculate magnetic induction intensity in the center of magnetic field and the melt circumferential flow velocity in melt pool under different exciting current. The influence of circumferential flow velocity on temperature field and solidification structure formation were analyzed. At last the analysis results were verified by experiment method. The results showed that the electromagnetic force drived melt to flow circumferentially. Farer from the magnetic field center, lorentz force was larger which promoted the circumferential flow velocity of melt. Magnetic induction intensity was rising with the increase of exciting current, which caused more faster circumferential flow velocity. The enhance of flow velocity resulted in temperature going down in melt pool and temperature gradient on solid-liquid interface, which were good for generation of the equiaxed crystal. The experiment results testified that equiaxed grains were generated at the top of melt layer with the magnetic field. The number of the equiaxed grains were rising with an increase of the distance from magnetic field center. The tendency of analysis results are in good agreement with the experimental results.