Additive Manufacturing of Titanium-based Materials: Processing, Microstructure and Material Properties: Ti-alloys
Program Organizers: Ulf Ackelid, Freemelt AB; Ola Harrysson, North Carolina State University
Wednesday 8:00 AM
October 12, 2022
Room: 305
Location: David L. Lawrence Convention Center
Session Chair: Ulf Ackelid, Freemelt
8:00 AM Invited
Hybrid Strategies to Increasing the Throughput of Electron Beam Selective Melting of Ti-alloys: Moataz Attallah1; Riccardo Tosi1; Alex Leung2; Emmanuel Muzangaza1; Xipeng Tan3; 1University of Birmingham; 2University College London; 3NUS, Singapore
The presentation covers two investigations that are aimed towards increasing the throughput of electron beam selective melting (EBSM). The first investigation involves the integration of the build to the substrate, generating an EBSM-forged material structure, focusing on the impact of surface preparation on the joint integrity. The second approach investigates the use of in-situ shelling, through the use of EBSM to build shells that are subsequently subjected to hot isostatic pressing (HIPping) to reduce the process time. The presentation also explores other challenges associated with EBSM, including post-processing for powder removal from complex cooling channels.
8:40 AM
Additive Manufacturing of Titanium – Boron Carbide In-situ Composites: Mohan Sai Kiran Nartu1; Srinivas Aditya Mantri1; Thomas W. Scharf1; Narendra Dahotre1; Rajarshi Banerjee1; 1University of North Texas
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.
9:00 AM Cancelled
Multi-stage Modeling of Fatigue of Ti-6Al-4V Fabricated by Different Additive Manufacturing Techniques: Lionardo Lado1; Mohammad Mahtabi1; 1University of Tennessee Chattanooga
In this study, the multi-stage fatigue behavior of the Ti-6Al-4v fabricated using different AM methods were compared. These include Laser Engineered Net Shaping (LENS), Electron Beam Melting (EBM), and Selective Laser Melting (SLM). Microstructural data was collected from the public literature on Ti-6Al-4V. This data includes characteristic of the particle, pore size and porosity. Scanned Electron Microscopy (SEM) images were used to examine the fracture surfaces of the AM specimens’ defects responsible for fatigue failure. A Multi-Stage Fatigue (MSF) model was used to study the different stages of fatigue failure in AM Ti-6Al-4V. With an emphasis on the microstructurally small crack growth and long crack growth, a comparison was made after calibrating the parameters for each of the AM process. The results determine which of the fatigue resistance governing parameters for all AM Ti-6Al-4V depend on the process. Therefore, improving the efficiency of the fatigue modeling for additive manufactured Ti-6Al-4V.
9:20 AM
Transmission Electron Microscopy Analysis of Cellular Structure of Laser Processed Metastable Ti-Nb Alloy: Wenhao Lin1; Eric Hoglund1; Helge Heinrich1; Ji Ma1; 1University of Virginia
Laser powder bed fusion (LPBF) can promote novel microstructures. Because of the unstable BCC β phase, metastable titanium-niobium alloy after rapid solidification can generate uncommon local lattice distortions as well as several unexpected metastable phases. In this study, we perform line scans on a Ti-25 at% Nb substrate. Then transmission electron microscopy (TEM) samples are extracted across the melt pool boundary. Techniques such as SAED, HR(S)TEM, and 4D STEM are used for structure analysis. We found that the microstructure of the melt pool consists of nano-cells with an unusually large elastic strain field, sandwiched between nearly strain-free inter-cellular boundaries. Despite the inter-cellular regions remain as β phase, the lattice in the cells is an unfamiliar orthorhombic structure. Moreover, another uncommon o^' phase is also found in the melt pool at the room temperature. These results imply metastable β-Ti, unlike conventional alloys, appears to have a different response to thermal stress.