Additive Manufacturing: Processing, Microstructure and Material Properties of Titanium-based Materials: Session IV
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
Wednesday 8:00 AM
October 20, 2021
Room: A120
Location: Greater Columbus Convention Center
Session Chair: Ola Harrysson, North Carolina State University
8:00 AM
Melt Pool Characterization and Numerical Simulation in Selective Laser Melting of NiTi Powder: Stanislav Chernyshikhin1; Igor Shishkovsky1; 1Skolkovo Institute of Science and Technology
Among the titanium-based materials, the intermetallic NiTi is attracting much attention due to the shape memory or superelasticity effects. The biocompatibility of this material allows utilizing in patient-specific implants which can be produced by Selective Laser Melting. In the relevant papers, there are contradicting condition parameters to obtain near-dense nitinol parts. This research aims to study the melt pool of the NiTi during the SLM process. The results will be useful for optimizing SLM condition parameters, for more accurate prediction of the final geometric dimensions in lattices with thin struts, and the understanding of the printing parameters' influence on the melt pool.Single tracks of the nitinol powder were printed using Trumpf Tru Print 1000. Selected laser power and scanning speed cover the most combinations reported in the literature. A numerical model was established using OpenFOAM software. Microhardness tests were performed directly on the cross-sections of the single tracks.
8:20 AM
Additive Manufacturing of Titanium – Boron Carbide In Situ Composites: Mohan Sai Kiran Nartu1; Srinivas Aditya Mantri1; Thomas Scharf1; Brandon Mc Williams2; Kyu Cho2; Narendra Dahotre1; Rajarshi Banerjee1; 1University of North Texas; 2CCDC U.S. Army Research Laboratory
The present study will focus on detailed microstructural characterization and holistic understanding of the sequence of formation of ceramic phases in Laser engineered net shaping (LENS) processing of in situ Ti-B4C composites for high loading fractions, i.e., 25 wt.% and 35 wt.% B4C. Though, both in-situ composites, Ti-25wt.%B4C and Ti-35wt.%B4C were similarly processed via LENS, their as-processed microstructures were drastically different. Ti-25wt.%B4C exhibited nearly homogeneous microstructure, mainly dominated by TiB, TiC and α-Ti phases. Ti-35wt.% B4C exhibited alternatively-repeating layered microstructure with TiB2 and TiC phases in one layer, and TiB and TiC phases with a small fraction of retained-B4C and α-Ti in another layer. Heipel-Roper theory of weld pool dynamics has been employed to rationalize the mechanism underlying the evolution of these layered composites. Further, results from the hardness, wear and compression tests performed, indicate the potential for the AM processed Ti-B4C composites as wear and abrasion resistant materials.
8:40 AM
Comparison of Mechanical Properties for Ti-Ta Vertically and Horizontally Graded Interfaces in Laser Powder Bed Fusion: Cherish Lesko1; Joseph Walker2; John Middendorf2; Joy Gockel1; 1Wright State University; 2Arctos Technology Solutions
Graded material composition has the ability to adjust the material properties in specific locations towards an improvement in part function. The binary Titanium and Tantalum (Ti-Ta) alloy system is of great interest to many fields of engineering as a result of the unique properties it possesses. However, there remain several challenges in using Ti-Ta alloys for multi-material additive manufacturing (AM), including significantly different thermal behavior. In this work, the mechanical and material characterization of graded interfaces between compositions mixtures of 100% Ti and 52% Ti-48% Ta is explored. The deposition of the material is performed using a custom-built laser powder bed fusion (LPBF) AM machine that allows for both horizontal and vertical compositional grading throughout the powder bed. The ability to grade material composition in multiple directions in LPBF AM provides the capability to fabricate complex geometries with spatially varying functional and structural properties tailored to the desired application.
9:00 AM
Multi-scale Strain, Microstructure, and Solidification Behavior of Ti-5553 Architected Lattice Melt Pools: Caleb Andrews1; Maria Strantza2; Tae Wook Heo2; Nicholas Calta2; Rongpei Shi2; Manyalibo Matthews2; Mitra Taheri1; 1Johns Hopkins University; 2Lawrence Livermore National Laboratory
Laser powder bed additive manufacturing (L-PBF AM) enables the manufacture of advanced materials, like architected lattices or functionally graded structures, thanks to its ability to shape materials at the microscale. We demonstrate how the melt pool environment within a single Ti-5553 architected lattice strut can be altered by changes in strut angle and laser parameters through in situ X-ray imaging measurements. We relate these alterations to microstructure and stress development across length scales within these Ti-5553 lattice struts by utilizing HR-EBSD cross correlation, dynamical Kikuchi pattern simulation, and phase field modeling. We provide a nano-to-microscale approach to understanding how residual strain and microstructure formation within AM produced architected lattices are tied to the melt pool and solidification environment at the scale of a single lattice strut. Thus, we hope to further elucidate the mechanisms of residual stress formation in L-PBF and produce more robust and reliable architected materials.
9:20 AM
Effects of Process Parameters on Fracture and Fatigue of High Deposition Rate Laser Hot Wire Processed CP-Ti Grade 2: Hannah Sims1; John Lewandowski1; 1Case Western Reserve University
CP-Ti Grade 2 has been produced via a wire-based additively manufactured laser hot wire process using biomedical grade CP-Ti Grade 2 wire. Several iterations of builds have been deposited and analyzed in order to determine the optimum process parameter window. Metallography and large-scale electron backscatter diffraction were performed to document the grain structure development throughout the entire build. Hardness testing, fatigue crack growth testing, and fracture toughness testing were conducted on Charpy-sized samples excised from the as-deposited material in different orientations, followed by optical and scanning electron microscopy of fracture surfaces. The effects of build parameters, sample orientation, and resulting microstructure/defects on the fracture properties will be presented and compared conventionally processed CP-Ti Grade 2.
9:40 AM
Mechanical Properties as a Function of Material State for Additively Manufactured Ti-5Al-5V-5Mo-3Cr: Andrew Temple1; Madison Harrington1; Peter Collins1; 1Iowa State University
Titanium alloys are commonly sought for their specific strength and used in applications where weights savings may be achieved with only a moderate reduction in strength. Following heat treatments, this work has demonstrated that the uniaxial tensile properties, specifically the yield and tensile strengths, of metastable beta titanium alloy Ti-5Al-5V-5Mo-3Cr produced via selective laser melting begins to surpass those of high strength steels. The yield strengths range from 924-1535 MPa for 28 selective laser melted samples that experienced post-deposition heat-treatments. The wide range of measured mechanical properties can be rationalized through careful observation and analysis of the heat-treated microstructures. The observations, including detailed characterization, and a new equation to predict the strength of Ti-5553 will be presented.
10:00 AM
Performance of Titanium Alloy Lattice Structures in Quasi-static and High Strain Rate Environments: John Carpenter1; Ben Brown2; Nathan Johnson3; Don Brown1; David Jones1; Borys Drach4; Jonathan Pegues5; Manyalibo Matthews6; 1Los Alamos National Laboratory; 2Kansas City National Security Campus; 3SLAC National Accelerator Laboratory; 4New Mexico State University; 5Sandia National Laboratories; 6Lawrence Livermore National Laboratory
Additively manufactured metal lattices are uniquely positioned to address current and emerging lightweight needs through unprecedented design freedom and manufacturing responsiveness. In this talk, the results of in situ, diffraction-based quasi-static compression studies on lattice structures fabricated out of Ti5553 are presented and connected with predictive FE-based modeling. It was found that incorporation of CT-based surface roughness and diffraction-based residual stress measurements are required in order to develop a predictive mechanical model. In addition, high strain rate tests on Ti5553 lattice structures built using Renishaw and SLM systems will be presented in a case study on the impact of differing AM technologies on dynamic performance. The combined results presented are used to help mature our understanding of the process-structure-property-performance relationships in metal lattice structures.