Evolution of molten pool during selective laser melting of Ti–6Al–4V

Abstract

The characteristics of molten pools provide valuable insight into the complexity of the metal additive manufacturing process, which has a significant influence on the quality of the parts built using this process. In our work, we develop a three-dimensional multiphysics finite element model of a selective laser melting (SLM) process on a Ti-6Al-4V alloy. The dynamic characteristics of the molten pool are studied by multiphysics simulation with consideration of phase transitions, recoil pressure, surface tension, and Marangoni effect. The results show the time-evolution of temperature distribution, flow field, and surface morphology of a single track during the SLM process. The recoil pressure caused by evaporation plays a significant role in molten pool dynamics and induces a depression at the head of the molten pool. As a result of the backward Marangoni flow, the material is shifted to the tail region and a vortex is generated. In addition, a protrusion is presented at the middle and start points of the scanned track, while a depression is formed at both sides and at the terminal point. The simulation and the experimental results on the surface morphology of the molten track during the SLM process are in good agreement. Furthermore, it is found that metal evaporation may take place not only on the surface of the molten pool but also inside it, due to the drop in pressure. This is a significant contributor to the formation of porosity in SLM parts.

3D printed cobalt-chromium-molybdenum porous superalloy with superior antiviral activity

“…The process parameters influence the phases, recoil pressure, surface tension, Marangoni effect, and hydrodynamics that affects the size, and shape of the melt pool. When the laser beam leaves the melt area, the melt pool starts to cool down and solidifies [58,59]. As such the creation of a stable melt pool with a regular shape and geometrical characteristics, the powder characteristics of Co-Cr-Mo and laser processing parameters are the significant factors.…”

Powder bed fusion additive layer manufacturing of titanium alloys

“…They found that in addition to process parameters, thermal [59]. (e) Schematics of melt pool simulation [54].…”

Effects of the powder, laser parameters and surface conditions on the molten pool formation in the selective laser melting of IN718

“…In most cases, many simplifying assumptions were necessary to reduce the computational cost or to enable the application of the models. For instance, the powder bed was often assumed as a homogeneous and continuous material layer (Zhang et al, 2018), or as a homogenized porous (partly solid, partly gaseous) layer (Heeling et al, 2017). Highly sophisticated simulations that represent individual powder particles, as done by Khairallah et al (2016), Chen et al (2020) and Qiu et al (2015), on the other hand, are too costly for extensive studies that would provide relations between process parameters and MP formation for a wide range of parameters.…”