Additive Manufacturing of Large-scale Metallic Components: Titanium and Nickel-based Alloys/Modeling
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee
Program Organizers: Sneha Prabha Narra, Carnegie Mellon University; Sougata Roy, University of North Dakota; Andrzej Nycz, Oak Ridge National Laboratory; Yousub Lee, Oak Ridge National Laboratory; Chantal Sudbrack, National Energy Technology Laboratory; Albert To, University of Pittsburgh

Wednesday 2:00 PM
March 2, 2022
Room: 263A
Location: Anaheim Convention Center

Session Chair: Jonathan Pegues, Sandia National Laboratories; Jonah Klemm-Toole, Colorado School of Mines

2:00 PM  Invited
Heat Treatment Effects on Mechanical Properties of Wire Arc Additive Manufactured and Electron Beam Additive Manufactured Ti-6Al-4V: Jonathan Pegues1; Shaun Whetten1; Andrew Kustas1; William Dannemann1; 1Sandia National Laboratories
    Directed energy deposition (DED) is an attractive additive manufacturing (AM) process for large structural components. The rapid solidification and layer-by-layer process associated with DED results in non-ideal microstructures, such as large grains with strong crystallographic textures, resulting in severe anisotropy and low ductility. Despite these challenges, DED has been identified as a potential solution for the manufacturing of near net shape Ti-6Al-4V preforms. In this work, we explore several heat treatment processes, including HIP, and their effects on tensile properties of wire arc additively manufactured (WAAM) and electron beam additively manufactured (EBAM) Ti-6Al-4V. A high throughput tensile testing procedure was utilized to generate statistically relevant data sets related to each specific heat treatment and sample orientation. Results are discussed in the context of microstructural evolution and the resulting fracture behavior for each condition as compared to conventionally processed Ti-6Al-4V.

2:40 PM  
Process-structure-property Study on CP-Ti (Grade 2) Produced via High Deposition AM Laser-hot Wire: 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. Single bead deposits were used to produce a process map that analyzed the effects of laser power, travel speed, and wire feed speed. From this process map several combinations of parameters were used to deposit multibead wall prints. The fatigue and fracture behaviors of each of the multibead deposits were analyzed in this study using Charpy bar samples excised from the walls in different orientations. Hardness testing, fatigue crack growth testing, and fracture toughness testing were conducted, followed by optical and scanning electron microscopy. Additionally, large scale electron backscatter diffraction was performed to document the grain structure development throughout the entire build. The effect of build parameters, sample orientation, and resulting microstructure/defects on the fracture properties will be presented and compared to more conventionally processed CP-Ti.

3:00 PM  
Prior-β Grain Structure Control of Ti-6Al-4V WAAM in the As-deposited Condition: James Wainwright1; Stewart Williams1; Jialuo Ding1; Alec Davis2; 1Cranfield University; 2University of Manchester
    Deposition of Ti-6Al-4V in a plasma wire + arc additive manufacturing process typically produces a prior-β columnar grain structure exhibiting anisotropic mechanical properties. To achieve the formation of equiaxed grain structures which provide isotropic properties requires additional process steps. This research demonstrates a process for controlling the prior-β grain structure in the as-deposited condition through process parameters, removing the need for additional post-processing steps to enable columnar to equiaxed transition. EBSD analysis of deposited Ti-6Al-4V samples illustrates the refinement of the prior-β grain structure when there is a reduction in the specific energy density of material deposited and associated layer height increase. The application of pyrometry to measure the melt pool temperature during deposition identifies a repeatable reduction in the thermal gradient across the melt pool enabling microstructural evolution. Consequently, a solidification map is generated permitting microstructural refinement to be selected in terms of deposition parameters.

3:20 PM Break

3:40 PM  
Formation of Multiple Necks in Wire-based Electron Beam Additively Manufactured Ti-6Al-4V Pulled in Uniaxial Tension: Daniel Lewis1; Michael Hurst2; James Paramore2; Brady Butler2; 1Texas A&M University; 2Army Research Lab
    Developed for utilization in space, Wire-based Electron Beam Additive Manufacturing (Wire EBAM) offers a novel method of producing large components or in-situ repairs under vacuum. Due to the large cooling rates associated with melt-based additive manufacturing processes, a martensitic microstructure is expected to form. To address undesirable microstructural features, Thermo Hydrogen Refinement of Microstructure (THRM) was implemented to achieve a microstructure comparable to that of wrought titanium. However, as THRM produces a hierarchical microstructure, the large, columnar beta grains initially created maintain their form as large prior-beta grains. Mechanical testing along an axis transverse to the build direction resulted in the formation of multiple necks. Although similar phenomena have been reported for Ti-6Al-4V, they are at either high strain rates or elevated temperatures. This study aims to deduce the mechanisms responsible for forming multiple necks in standard inch tensile specimens at a strain rate of 1e-5 at room temperature.

4:00 PM  
The Effects of CoAl2O4 on the Microstructural Evolution of Inconel 718 Processed by Direct Energy Deposition: Dhruv Tiparti1; I-ting Ho1; Tilo Buergel2; Fred Carter2; Sammy Tin3; 1Illinois Institute of Technology; 2DMG Mori Advanced Solutions; 3University of Arizona
    Processing of Inconel 718(IN718) mixed with CoAl2O4 grain refiners via direct energy deposition (DED) has revealed some unintended microstructural modification effects. The physical presence of these oxides within the melt pool suggests a decrease in convective heat transfer due to increased fluid viscosity induced by a nano/micro particle slag. This decrease in convective flow is accompanied by increased melt pool penetration depth which has consequences of earlier onset of large columnar grains extending across multiple layers. Due to the low and heterogeneous distribution of strain energy within DED processed material; recrystallization kinetics are hindered by a potent Zenner pinning effect that leads to retention of the as-built microstructure even following aggressive heat treatment of 1200 oC up to 4 Hrs. The minor addition of oxide particles shows potential avenues for increased microstructural control of additive materials. Further detail of the results and accompanying discussion will be presented.

4:20 PM  
Design for Metal Large-scale Additive Manufacturing: Mitigation of Bending Deformation on Curved Sheet: Yousub Lee1; Andrzej Nycz1; Srdjan Simunovic1; Luke Meyer1; Derek Vaughan1; William Carter1; 1Oak Ridge National Laboratory
    Wire-arc based metal are additive manufacturing (mBAAM) is a potential disruptive manufacturing process for creating large-scale metal parts. Owing to its superior feature of high deposition rate and minimal material waste, mBAAM enables one to print a part up to approximately 10 feet tall. For this technology to be widely adopted for manufacturing critical structural component, a tight control of process is required. Under dynamic printing conditions and complex geometries, part deformation is primarily associated with varying thermal cycles influencing internal stress buildup. This can lead to unfavorable part deformation during printing. In this study, a large scale thermo-mechanical simulation using finite element method (FEM) has used to manage part distortion and deformation on curved-sheet geometry. The transient part deflection is tracked in the simulation and then compared to untracked case for in-depth understanding on the deformation mechanism. Ultimately, potential solutions will be suggested to avoid undesired part deformation.

4:40 PM  
NOW ON-DEMAND ONLY - Process Optimization in Metal Additive Manufacturing Using Image Processing and Statistical Analysis : Faiyaz Ahsan1; Jafar Razmi1; Leila Ladani1; 1Arizona State University
    Additive manufacturing has attracted widespread attention due to its ability to produce parts with complicated design and less waste because of the additive nature of the process. Process optimization to obtain high quality parts is still a concern which is impeding full scale production of materials. This work focus on gaining useful information such as contact angle, porosity, voids, melt pool and keyhole area from experimentally obtained bead geometry produced using laser powder bed fusion (LPBF) additive manufacturing technique. These features are identified and quantified using process learning (ImageJ) that pertains to different process parameters including laser power and scan speed along with their underlying physics. Finally, a full factorial design will be employed that allows to estimate the effect of the process parameters on the output features. Both single and multi-response analysis are applied to observe the output response individually as well as in a collective manner.