Additive Manufacturing: Microstructure and Material Properties of Titanium-based Materials: Titanium Alloy Microstructure and Properties
Sponsored by: TMS: Titanium Committee
Program Organizers: Ulf Ackelid, Freemelt AB; Ola Harrysson, North Carolina State University; Peeyush Nandwana, Oak Ridge National Laboratory; Rongpei Shi, Harbin Institute of Technology; Yufeng Zheng, University of North Texas
Wednesday 8:00 AM
November 4, 2020
Room: Virtual Meeting Room 8
Location: MS&T Virtual
Session Chair: Peeyush Nandwana, ORNL; Yufeng Zheng, University of North Texas
8:00 AM
Correlating Processing, Structure and Properties for Additively Manufactured Ti-6Al-4V: Jayme Keist1; Selda Nayir1; Todd Palmer1; 1Pennsylvania State University
The mechanical properties of additively manufactured (AM) Ti-6Al-4V components can vary greatly depending on a number of factors and these factors include chemistry, AM processing conditions, and post-processing. In this work, we investigated the underlying mechanisms that drives the resulting mechanical properties and anisotropic behavior observed within AM Ti-6Al-4V. A series of tensile specimens were machined and tested from coupons that were produced via various AM processes that included directed energy deposition and powder bed fusion processes. The microstructure of the AM coupons were characterized to help develop an empirical strength model. Using this model and comparing the mechanical behavior results from Ti-6Al-4V specimens that were produced by various AM processes and in various post-process conditions, a fuller picture was obtained on the significant factors from the AM processing and post-processing that impacted the microstructure and the resulting mechanical behavior.
8:40 AM
Study of Effects from Post-processing on the Fatigue Performances of Laser Powder Bed Fusion Built Parts Using Hydride-dehydride Ti-6Al-4V Powders: Ziheng Wu1; Amir Mostafaei2; Nihal Sivakumar1; Anthony Rollett1; 1Carnegie Mellon University; 2Illinois Institute of Technology
Using hydride-dehydride (HDH) Ti64 powder in powder-based additive manufacturing processes is challenging owing to low packing density with aspherical particles but it can also significantly reduce the feedstock cost. Fabricating highly dense parts using this powder has been shown to be feasible in the laser powder bed fusion (LPBF) process, albeit with smaller hatch spacings than typically used. A more important step going forward is to demonstrate that the HDH parts have comparable fatigue life to standard printed Ti64. Specimens are fabricated in an EOS M290 using HDH Ti6Al4V powders with two different size distributions; additionally, different post-processing treatments are applied to further improve their fatigue lives. This study reports on the high-cycle fatigue performance of these HDH Ti64 parts and understanding how the fracture behaviors correlate with variable pore content as a function of process conditions.
9:00 AM
Mechanical properties, fracture surface and microstructure of additively manufactured Ti6Al4V: Asif Mahmud1; Thinh Huynh1; Le Zhou1; Devin Imholte2; Nicolas Woolstenhulme2; Daniel Wachs2; Yongho Sohn1; 1University of Central Florida; 2Idaho National Laboratory
Mechanical properties, fracture surface and microstructure of Ti6Al4V (Grade 23) tensile rods produced by laser power bed fusion were investigated. Stress-relieved and hot isostatically pressed (HIP) rods were examined for comparison, built both in horizontal (X and Y) and vertical (Z) orientations. The stress-relieved alloy had an average yield strength, tensile strength and elongation of 1158 MPa, 1191 MPa, and 5.9%, respectively, along with more mechanical anisotropy. The HIP rods had an average yield strength, tensile strength and elongation of 946 MPa, 1000 MPa, and 15.5%, respectively. Dimples corresponding to ductile behavior was observed for the HIP rods, and the lack of fusion flaws (i.e., pulled-out powders) were observed in stress-relieved rods. All samples were dense (>99%), but the microstructure, examined by XRD, SEM and TEM, consisted of acicular α’ martensitic needles for stress-relieved rods, while lamellar α + β phases were observed for HIP rods.
9:20 AM
Environmental Degradation of AM-fabricated Ti6Al4V Alloy: Guy Ben Hamu1; 1Sami Shamoon College of Engineering
Additive manufacturing (AM) technologies enable rapid production of parts with complex geometry which cannot be shaped in other conventional methods. The AM-fabricated parts experience rapid solidification and high cooling rates; this leads to formation of atypical microstructure and directly affects the intrinsic properties of the printed part and on its environmental-assisted degradation. In this research, the environmental degradation by means of corrosion and hydrogen embrittlement (HE) of Ti6Al4V produced by AM technologies will be presented.Hydrogen presence is unavoidable in most manufacturing processes and services. Hydrogen can significantly deteriorate mechanical properties and lead to unexpected failure. The hydrogen interaction with the material is strongly dependent on the microstructure, the amount of adsorbed hydrogen and its location in the material. The aim of the research is to provide detail information about the environmental degradation of AM-Ti6Al4V in aggressive service conditions for further application in aircraft, automotive, and marine industries.
9:40 AM
Multiscale Mechanical Studies of Dual-phase Titanium Alloys Made by Additive Manufacturing: Zhiying Liu1; Yu Zou1; 1University of Toronto
The mechanical properties of a laser melting deposited (LMD) Ti–6Al–2Zr–Mo–V alloy are investigated using the nanoindentation and micro-cantilever Bending methods. The results show that hardness and reduced modulus of individual phases made by additive manufacturing are comparable with those made by conventional casting or forging methods. The mechanical difference between α and β phases associated with the crack path will be discussed. This work highlights the comparison of properties of individual phases made by various manufacturing methods and elucidates the relationship between mechanical contrast between phases and corresponded crack propagation mechanisms.
10:00 AM
Study the Effect of Thermal Gradients on the Microstructure and Mechanical Properties of Electron Beam Melting Ti-6Al-4V Builds: Meiyue Shao1; Sriram Vijayan1; Evan Hass1; Kayla Hepler1; Joerg Jinschek1; 1The Ohio State University
Additively manufactured (AM) parts fabricated using electron beam powder fusion (EB PBF) experience complex and cyclic thermal gradients due to the layer by layer fabrication process. These thermal gradients are dependent on AM process parameters, such as input power, beam scan velocities, beam fill patterns, built height, which influence the as built the microstructure and mechanical properties of the build. Here, three different electron beam scan strategies were applied to fabricate Ti-6Al-4V builds. The microstructural variation across the build plane and along the build direction was observed by scanning electron microscopy (SEM) and electron backscattered diffraction (SEM-EBSD) across multiple locations in the build to detect significant trends. Further, Vickers microhardness data were obtained from each sample across the build plane and along the build direction. The results indicate that the microstructure and mechanical properties of Ti64 EBM builds strongly depend on the beam scan strategies.