Abstract

Processes that use moving point heat sources to temporarily create localized melt pools (metal additive manufacture and fusion welding) have a flow phenomenon due to the surface tension gradient. Surface tension of the liquid metal reduces with temperature and this, coupled with the high temperature gradients associated with point heat sources, creates Marangoni convection in the melt. The Marangoni convection tends to reduce the temperature and change the melt pool geometry (increases width but reduces depth). Computational Fluid Dynamics (CFD) models can simulate the phenomenon of Marangoni convection but are computationally intensive. A simpler thermal model involving heat conduction and latent heat, but with the liquid’s thermal conductivity artificially increased by a constant factor, exhibits similar thermal effects to the Marangoni convection. The heat conduction models are computationally less intensive than CFD, but the trial-and-error exercise needed to obtain an appropriate multiplying factor is time consuming. With an aim to improve the process of factor selection, the present study investigates the correlation between the surface tension gradient and correction factors. For a Ti-6Al-4V under typical additive manufacturing parameters, the corresponding correction factor to be applied to liquid thermal conductivity was 1.76.

抽象的

使用移动点热源临时创建局部熔池的过程（金属添加剂制造和熔焊）由于表面张力梯度而产生流动现象。液态金属的表面张力随温度降低，这与点热源相关的高温梯度相结合，在熔体中产生马兰戈尼对流。Marangoni对流往往会降低温度并改变熔池的几何形状（增加宽度但减小深度）。计算流体动力学（CFD）模型可以模拟Marangoni对流现象，但计算量大。一个更简单的热模型，涉及热传导和潜热，但是随着人为地增加液体的热导率，常数会增加，表现出与Marangoni对流相似的热效应。导热模型的计算强度不如CFD，但要获得适当的乘数所需的反复试验非常耗时。为了改善因素选择过程，本研究研究了表面张力梯度和校正因子之间的相关性。对于在典型增材制造参数下的Ti-6Al-4V，应用于液体导热系数的相应校正系数为1.76。本研究调查了表面张力梯度与校正因子之间的相关性。对于在典型增材制造参数下的Ti-6Al-4V，应用于液体导热系数的相应校正系数为1.76。本研究调查了表面张力梯度与校正因子之间的相关性。对于在典型增材制造参数下的Ti-6Al-4V，应用于液体导热系数的相应校正系数为1.76。