Page 94 - MSAM-2-3

Materials Science in Additive Manufacturing Validation of a novel ML model for AM-PSP

typical beam sizes range from 0.1 – 0.5 mm, with layer scattering and dissipation of electron beams that occur in
thicknesses between 20 and 75 μm when employing a laser the atmospheric environment, electron beaming systems
source in an inert atmosphere, and 0.2 – 1 mm with layer are operated in a vacuum environment (10 Mbar in the
−3
thicknesses of approximately 75 – 125 μm for an electron chamber and 10 Mbar in the gun column). Compared to
−6
beam source within a vacuum environment. In the DED laser-based AM processes, the EB-PBF process is operated
process, the typical beam sizes range from 2 – 4 mm, at higher working temperatures without the risk of oxygen
with layer thicknesses between 500 and 1000 μm within uptake due to excellent thermal isolation and the desired
a shielding gas or vacuum environment. The parameters vacuum environment. Higher chamber temperatures
employed in the DED process result in a coarse surface lead to lower residual stress compared to laser-based AM
finish [2-6] . In recent years, several studies have explored systems, and parts processed using EB-PBF can be used
the application of machining learning and deep learning without secondary stress-relieving. Furthermore, the
methods to create the process-structure-property (PSP) EB-PBF process involves a preheating step before melting,
linkages [7-11] . Figure 1 shows the workflow of the Ti-6Al-4V which partially sinters the powder layer to increase
process-structure-property linkage study. thermal conductivity during a melting pass, reducing
the temperature gradient and preventing the formation
1.1. PBF AM methods for metals of thermal cracks [4,13] . The preheating process also holds

The electron beam melting (EB-PBF) process is a PBF powder particles together, which can act as supports.
AM process known for its ability to produce full-density Therefore, in the EB-PBF process, support structures are
functional parts. This is achieved using a high-energy often employed for heat conduction. After the melting pass,
electron beam and “hot-bed” metal powder. Throughout the entire build plate is heated again with an electron beam
the manufacturing process, the entire build tank is (higher velocity and lower current) before the next power
maintained at an elevated temperature under a vacuum layer is spread. The EB-PBF process includes an “in-built”
environment. The electron beam is powered by a high- heat treatment step, where the machine is allowed to cool
voltage electron beam (30 – 60 kV), as shown in Figure 2. down to room temperature in an inert atmosphere before
The EB-PBF can process multiple conductive material the build chamber is accessed.
systems such as stainless steel (316), tool steel (H13), Ti-based Laser PBF (L-PBF) process, also known as selective
superalloys (Ti-6Al-4V), Ni-based superalloys (Inconel 718), laser sintering, selective laser melting (SLM), direct
Co-based superalloys (Stellite 21), low-expansion alloys metal laser sintering, direct metal laser melting, uses a
(Invar), hard metal, intermetallic compounds, aluminum, high-power laser beam to selectively fuse powder within
copper, niobium, and beryllium [4,12,13] . To eliminate the an inert atmosphere, as shown in Figure 3. This process

Figure 1. This research presents a validated machine learning model to predict process-structure-property linkage in additive manufacturing of Ti-6Al-4V.
Abbreviations: CNC: Computer numerical control; DED: Directed energy deposition; EB-PBF: Electron beam-powder bed fusion; EBSD: Electron
backscattered diffraction analysis; L-PBF: Laser powder bed fusion; PBF: Powder bed fusion; PCA: Principal component analysis; PSP: Process-structure-
property; SEM: Scanning electron microscopy; XRD: X-ray diffraction analysis.

Volume 2 Issue 3 (2023) 2 https://doi.org/10.36922/msam.0999