扫描路径对选区激光熔化温度场的影响

Influence of Scanning Path on the Temperature Field in Selective Laser Melting

对平行于长边和平行于短边的两种"Z"形扫描路径进行有限元仿真。综合考虑热传导、热对流、热辐射效应和温度对合金粉末材料热物性参数和相变潜热的影响,建立瞬态选区激光熔化(SLM)温度场有限元模型并与实验测得的残余应力数据和金相图进行对比。结果表明:在SLM过程中,短边扫描形成的温度场更均匀,温度标准差和温度梯度更小,成形件的残余应力和孔隙更小;在扫描过程中,扫描区域边界点的温度梯度大于扫描区域中点的温度梯度,残余应力峰值出现在成形件边界处;通过预热基板,可以使温度场更均匀,减少温度标准差和温度梯度,达到减小成形件残余应力和孔隙的目的,提高成形质量。研究扫描路径对温度场的影响,可为提高SLM技术水平提供参考。

The finite element simulation is used to investigate two different Z-shaped scanning paths parallel to the long and short sides.Considering the effects of heat conduction,heat convection,heat radiation,and temperature on the thermal properties of alloy powder materials,the finite element model of the transient selective laser melting(SLM)temperature field is established.Then,the established model is compared with the experimentally measured residual stress data and metallographic diagram.It is determined that in the SLM process,the temperature field formed by short-side scanning is more uniform;the temperature standard deviation,the temperature gradient,the residual stress,and the porosity of the formed part are smaller than those in the long-side scanning.During the scanning process,the temperature gradient at the boundary point of the scanning region is greater than that of the scanning region,and the residual stress peak appears at the boundary of the formed part.By preheating the substrate,the temperature field can be more uniform,and both the standard deviation and the gradient of the temperature field can be reduced.Therefore,the residual stress and the porosity of the formed part are reduced,and the forming quality is improved.The investigation of the influence of scanning path on the temperature field provides the reference for the improvement of the SLM technique.