金属熔滴连续沉积、凝固重叠工艺及实验验证

Experimental investigation of the Overlap Process inSuccessive Deposition and Solidification

摘要:

金属熔滴均匀连续沉积是一种新型的3D打印技术和快速原型(RP)技术。本文系统研究了铝熔滴连续沉积到基板表面的瞬态传热传质现象,沉积机理主要包括金属熔体的毛细现象及固液界面的传热、凝固、搭接和重熔。采用VOF方法对连续沉积的金属熔滴在水平固定铝基板表面沉积进行3D建模。针对凝固传热过程中不同参数下熔滴在铝基板表面沉积、凝固进行了研究,通过数值计算与实验验证,各种工艺参数的影响,如喷射速度、基板温度、熔滴直径与碰撞最大铺展因子的影响,显示了很好的一致性。基于上述研究,成形形貌和内部微观结构之间的定量关系进一步验证了金属熔滴连续沉积、凝固重叠工艺的可行性。此工艺为金属微沉积制造实施有效的过程控制提供指导。

Abstract:

Successive deposition of uniform metal droplet is a new kind of 3D printing and rapid prototyping (RP) technology. This paper presents a systematic numerical investigation of the transient transport phenomenon during the overlap of successive aluminum droplets impinging onto a substrate surface. The physical mechanisms of the overlap process, including the bulk liquid, capillarity effects at the liquid-solid interface, heat transfer, and solidification, are identified and quantified numerically. The 3D models based on a volume of fluid (VOF) method were developed to investigate the successive deposition of molten metal droplets on a horizontally fixed aluminum substrate surface. The numerical models are validated with experiments. The comparison between numerical simulations and experimental findings shows a good agreement. The effects of various parameters such as impact velocity, substrate temperature, droplet diameters on the maximum spread factor during impacting and spreading with solidification of a molten droplet onto an aluminum surface under different parameters was studied. Based on the above research, a semi-quantitative relationship between external morphology and internal microstructure was proposed, which was further certified by investigating the piled overlap of successive droplets. This investigation is essential to implement effective process control in metal micro-droplet deposition manufacture.