Influence of Powder Bed Temperature on the Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Fabricated via Laser Powder Bed Fusion

Abstract

Laser powder bed fusion (LPBF) is being increasingly used in the fabrication of complex-shaped structure parts with high precision. It is easy to form martensitic microstructure in Ti-6Al-4V alloy during manufacturing. Pre-heating the powder bed can enhance the thermal field produced by cyclic laser heating during LPBF, which can tailor the microstructure and further improve the mechanical properties. In the present study, all the Ti-6Al-4V alloy samples manufactured by LPBF at different powder bed temperatures exhibit a near-full densification state, with the densification ratio of above 99.4%. When the powder bed temperature is lower than 400 °C, the specimens are composed of a single α′ martensite. As the temperature elevates to higher than 400 °C, the α and β phase precipitate at the α′ martensite boundaries by the diffusion and redistribution of V element. In addition, the α/α′ lath coarsening is presented with the increasing powder bed temperature. The specimens manufactured at the temperature lower than 400 °C exhibit high strength but bad ductility. Moreover, the ultimate tensile strength and yield strength reduce slightly, whereas the ductility is improved dramatically with the increasing temperature, when it is higher than 400 °C.

Additive Manufacturing of AlSi10Mg and Ti6Al4V Lightweight Alloys via Laser Powder Bed Fusion: A Review of Heat Treatments Effects

“…At 470 °C, the α′ → α decomposition occurs according to the study on phase transformation of Ti6Al4V conducted by Kaschel et al [ 227 ]. The authors reported TEM results indicating the decomposition temperature at 400 °C, as also shown by Xing et al [ 228 ], and a full decomposition at 700 °C. Sallica-Leva et al [ 229 ] reported, however, an exothermic peak related to the martensite decomposition between 760 and 850 °C.…”

Special Issue: The Science and Technology of 3D Printing

“…This Special Issue contains eleven articles, including three reviews [ 3 , 4 , 5 ], one perspective article [ 6 ], and seven research articles [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ] from leading institutes in the United States, China, Australia, Germany, Sweden, the Netherlands, Slovakia, the Czech Republic, Egypt, and United Arab Emirates. These articles cover the 3D printing of diverse materials such as metallic materials [ 5 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ], composites [ 4 , 6 ], and soft materials [ 3 ].…”

“…The articles in this Special Issue cover a wide variety of experimental [ 8 , 9 , 10 , 11 , 13 ], theoretical [ 12 ], and data-science [ 7 ]-based research on the science and technology of 3D printing. For example, experimental investigations were performed to identify the most important factors that affect the microstructure and properties of Ti-6Al-4V parts printed using powder bed fusion [ 9 , 11 ]. In particular, the effects of powder morphology, preheating temperature, and post-process heat treatment on the size of α-grains, the hardness, and the tensile properties were studied.…”

Microstructure Evolution of Al6061 Alloy Made by Additive Friction Stir Deposition

“…This demands strict requirements on the weldability of feedstock. For this reason, only limited types of metallic materials are suitable for laser–powder-based AM processes, i.e., Inconel 718 alloy [ 8 ], Inconel 625 alloy [ 9 ], stainless steel 316 L [ 10 ], Ti-6Al-4V alloy [ 11 ], and CuCrZr alloy [ 12 ]. Another undesirable feature of the laser–powder-based AM strategy is the well-known anisotropic mechanical properties caused by epitaxial solidification (columnar grains growing along the build direction), as isotropic mechanical properties are typically needed for structural applications [ 13 ].…”