同轴送粉激光增材工艺对温度场及应力场的影响

激光增材制造过程中金属零件能否顺利成形以及成形后组织性能的优劣直接取决于工艺参数的选择。为研究激光工艺参数对增材构件温度场和应力场的影响，本文研究基于顺序热-力耦合有限元方法对在304L基板上进行同轴送粉激光增材GH4169合金粉末的单道单层工艺开展数值模拟研究。在实验验证数值模型有效性的基础上，深入分析激光功率和扫描速度对不同区域的温度场和残余应力的影响，并探讨应力场与温度场之间的关系。在沉积层边缘区域，提高激光功率和降低扫描速度都会明显降低沉积层和基板在降温过程中的温度梯度，且该温度梯度与该位置的横、纵向残余应力呈明显的正比关系。在沉积层内部，扫描速度的变化对横、纵向温度梯度和残余应力影响微小，提高激光功率使得该区域的纵向温度梯度明显降低，但横、纵向残余应力略有增大，熔池中心区域的残余应力和温度梯度不存在明显的正比关系。

Effect of Process Parameters on Temperature and Stress Fields in Laser Additive Manufacturing with Coaxial Powder-Feeding

The forming capability and post-forming quality of metal parts in laser additive manufacturing processes are directly dependent on the choice of process parameters. In order to study the effects of laser process parameters on the temperature and stress fields of additive components, numerical simulation is performed for the single-pass deposition process of GH4169 powder on 304L substrate based on thermo-mechanical sequential coupled finite element method in this paper. The effects of laser power and scanning speed on temperature field and residual stress are investigated in depth on the basis of the experimentally validated numerical model, and the relationship between stress field and temperature field is explored. Both increasing laser power and decreasing scanning speed obviously reduce the temperature gradient during the cooling phase of the deposited layer and substrate near the edge of the deposited layer, and the temperature gradient is proportional to the transverse and longitudinal residual stresses in this region. In the deposition layer, the change of scanning speed has little effect on the transverse and longitudinal temperature gradient and residual stresses. Increasing the laser power makes the longitudinal temperature gradient in this area significantly lower, but leads to a slight increase of transverse and longitudinal residual stresses, which implies that there is no distinct proportional relationship between the residual stress and the temperature gradient in this region.