Innovative Fabrication Design for In Situ Martensite Decomposition and Enhanced Mechanical Properties in Laser Powder Bed Fused Ti6Al4V Alloy

Abstract

Ti6Al4V alloy (Ti64) is a popular material used in the aerospace, medical, and automotive industries due to its excellent mechanical properties. Laser Powder Bed Fusion (LPBF) is a promising manufacturing technique that can produce complex and net-shaped components with comparable mechanical properties to those produced using conventional manufacturing techniques. However, during LPBF, the rapid cooling of the material can limit its ductility, making it difficult to achieve high levels of ductility while maintaining the required tensile strength for critical applications. To address this challenge, this study presents a novel approach to controlling the microstructure of Ti64 during LPBF by using a border design surrounding the main parts. It is hypothesized that the design induces in situ martensitic decomposition at different levels during the fabrication process, which can enhance the ductility of the material without compromising its tensile strength. To achieve this aim, a series of Ti64 samples were fabricated using LPBF with varying border designs, including those without borders and with gaps from 0.5 to 4 mm. The microstructure, composition, and mechanical properties of the Reference sample were compared with those of the samples fabricated with the surrounding border design. It was found that the latter had a more homogenized microstructure, a higher density, and improvements in both ductility and tensile strength. Moreover, it was discovered that the level of property improvement and martensitic transformation can be controlled by adjusting the gap space between the border and the main part, providing flexibility in the fabrication process. Overall, this study presents a promising approach for enhancing the mechanical properties of Ti64 produced via LPBF, making it more suitable for critical applications in various industries.

In Situ Microstructure Modification Using a Layerwise Surface-Preheating Laser Scan of Ti-6Al-4V during Laser Powder Bed Fusion

“…Reference samples (non-preheated) were fabricated using only a melting laser scan with the default process parameters. The default laser parameters for melting were recommended by the manufacturer and defined as a laser power of 280 W, a scan speed of 1300 mm/s, a hatch spacing of 120 µm, and a layer thickness of 40 µm, resulting in an energy density of 44.87 J/mm 3 [54]. The laser spot size was 100 µm and has a Gaussian-distributed energy.…”

Microstructure Tailoring for High Strength Ti-6Al-4V without Alloying Elements through Optimized Preheating and Post-Heating Laser Scanning in Laser Powder Bed Fusion

“…A 3D printer, EOS M290 (EOS GmbH, Electro Optical Systems, Krailling, Germany) equipped with Ytterbium fiber laser power of 400 W was utilized for the fabrication of the samples. Fabrication parameters of Ti-6Al-4V by the manufacturer are 280 W laser power, 1300 mm/s scan speed, 120 µm hatch spacing, 100 µm laser spot size with a Gaussian distribution of energy, and 40 µm of layer thickness with 47 • angle stripes scanning strategy (used for the reference specimen process parameters) [27]. These parameters were obscured by the printer's proprietary software, EOS Print (version 2.6; EOS GmbH, Krailling, Germany).…”

“…Despite its capability for complex lightweight geometry fabrication and superior mechanical properties, LPBF-fabricated Ti-6Al-4V has a challenging microstructure that limits the engineering application of this technology and still needs to be fully addressed. There are studies seeking solutions to address these issues through optimization of the process parameters [15,26,27]. In addition to these, there are a great number of reported studies investigating the impact of post-HT [28][29][30][31][32][33].…”