TIG电弧辅助熔滴沉积增材制造中熔滴偏距对熔池形貌的影响机制研究

Influence of the Offset Distance between Droplet and Molten Pool on the Molten Pool Morphology in TIG-assisted Droplet Deposition Manufacturing

针对传统d属熔滴微喷沉积成形中气孔、冷叠等冶金缺陷难抑制的问题,提出一种TIG电弧辅助熔滴沉积增材制造新方法。基于计算流体力学方法,建立铝合金TIG电弧辅助熔滴沉积增材制造过程三维瞬态熔池行为数值模型,对比研究了3组不同熔滴偏距下的熔池行为,通过与堆积层特征尺寸(层高、层宽、熔深)实测值相比较,验证所建熔池行为数值模型的有效性,澄清了单层单道堆积成形中熔滴偏距对熔池热流场和堆积层形貌的影响规律。结果表明:随着熔滴偏距的增加,熔滴与TIG电弧熔池一侧基板表面的接触面积增加,熔池与基板之间的散热效率得到提高,熔池凝固前沿的对称性被打破,进而导致熔滴冲击诱导的熔池热流场与堆积层形貌呈现明显的非对称特征。研究结论可为TIG电弧辅助熔滴沉积增材制造增材技术的工艺参数调控提供理论支撑和依据。

To eliminate metallurgical defects such as porosity and cold lap in the formed parts fabricated by metal droplets deposition manufacturing technology,a novel droplet-based additive manufacturing method,called TIG-assisted droplet deposition manufacturing,for producing three-dimensional metal components is presented.A numerical model based on the computational fluid dynamics(CFD)method is developed to comparatively investigate the effect of the offset distance between the impacting point of droplet and the longitudinal plane of molten pool on the deposition morphology and the impact-induced molten pool behaviors.The numerical model is validated with corresponding experiments for three different lateral offset distances.The results indicated that as the lateral offset distance increases,the amount of liquid metal that contacts with the cooler substrate or the asymmetric pre-solidified bead increased,which leads to exposing more contact area for heat dissipation.Consequently,the symmetry of solidification front morphologies will be broken,an obvious increase of the asymmetry in the thermal-flow fields within the droplet impact-induced molten pool and deposition geometry was observed.The results of this paper can provide theoretical support and basis for the process parameters’controlling and adjusting of TIG-assisted droplet deposition manufacturing.