Additive Manufacturing: Materials Design and Alloy Development IV: Rapid Development: Titanium Alloys
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Behrang Poorganji, Morf3d; Hunter Martin, HRL Laboratories LLC; James Saal, Citrine Informatics; Orlando Rios, University of Tennessee; Atieh Moridi, Cornell University; Jiadong Gong, Questek Innovations LLC
Wednesday 8:30 AM
March 2, 2022
Room: 261A
Location: Anaheim Convention Center
Session Chair: Jiadong Gong , QuesTek
8:30 AM
High Speed In-situ Alloying of Ti34Nb via Laser Powder Bed Fusion: Sheng Huang1; R. Lakshmi Narayan2; Joel Heang Kuan Tan3; Swee Leong Sing1; Wai Yee Yeong1; 1Nanyang Technological University; 2Indian Institute of Technology Delhi; 3Freelance
Research on in-situ alloyed Ti alloys with biocompatible β stabilizer(s) manufactured via Laser Powder Bed Fusion has been trending due to the need of compositional optimization. However, the β-stabilizers consist mostly of refractory metals which has led to the issue of porosity-inclusion tradeoff. Combining top-hat laser profile and tailored scanning path along with high power high speed scan, unique melt pool that travels perpendicularly to the laser scan direction was created and enabled pore-free in-situ alloyed Ti34Nb with significantly reduced un-melted Nb inclusions. {100} fiber texture was also achieved, which has the ideal combination of strength and elastic modulus. With the support of simple thermal finite element analysis, Kurz-Giovanola-Trivedi model and experimental validations, the “stray” grains formation is explained. These findings can be extended to other powder-mix systems, expanding the conventional belief of processing window and offering a new dimension for rapid compositional prototyping.
8:50 AM
Hydrogen-aided Microstructural Engineering of Additively Manufactured Ti-6Al-4V Alloy: Lara Draelos1; Peeyush Nandwana2; James Paramore3; Brady Butler3; Ankit Srivastava1; 1Texas A&M University; 2Oak Ridge National Laboratory; 3Army Research Laboratory
Additive manufacturing of Ti-6Al-4V alloy via Electron beam melting (EBM) produces unconventional microstructures and defects. Thus, the as-fabricated material is in general subjected to hot isostatic pressing during which the pressure aids in pore closure while the heat-treatment impacts the resulting microstructure. This heat-treatment can be carried out below or above the beta-transus temperature. The sub-transus heat-treatment, however, does not mitigate the adverse effects of the unconventional microstructure while super-transus heat-treatment leads to lamellar microstructures that are prone to strain localization. Herein, we demonstrate that hydrogen-aided heat-treatment is an effective way to engineer the unconventional microstructure of the EBM processed Ti-6Al-4V alloy. Specifically, we show that hydrogen-aided heat-treatment produces wrought-like microstructures without compromising the ductility of the material. Furthermore, since hydrogen reduces the beta-transus temperature it allows us to carry out microstructure engineering at relatively lower temperatures.
9:10 AM
In Situ Monitoring and Post Operando Analysis of Additive Manufactured Dissimilar Alloys: AlSi10Mg and Ti6Al4V: Caterina Iantaffi1; Yunhui Chen1; Maureen Fitzpatrick1; Marta Majkut2; Bratislav Lukic2; Alexander Rack2; Kudakwashe Jakata2; Martina Meisnar3; Thomas Rohr3; Eral Bele1; Peter D. Lee1; 1University College London; 2ESRF; 3ESA-ESTEC
Metal Additive Manufacturing (AM) is an emerging technique that offers unprecedent design flexibility and customizability. Engineered parts comprising bi-metallic and compositionally graded hybrid materials can also be manufactured; however, mismatch in thermo-physical properties and intermetallic phase formation at the interface can lead to poor interfacial bonding and delamination. In situ synchrotron X-ray observation of directed energy deposition (DED) AM of AlSi10Mg on Ti6Al4V substrate revealed the melt flow dynamics and solidification mechanisms of Al-Ti blending. The results suggest methods of maximising bonding along the interface whilst minimising defects when melting dissimilar alloys. At the interface, Ti aluminide formation by exothermic reaction caused higher heat release increasing diffusion, enhancing the gradual transition from alpha/beta Ti phases to alpha Al matrix. The results elucidate the process-microstructure-properties relationships during additively manufacturing Al-Ti bimetallic structures and help identify improved industrial practice to help avoid the use of intermediate bond layers.
9:30 AM
Microstructure Investigation of Ti15Mo and Compositionally Graded Ti+Ti15Mo Alloys Prepared by Additive Manufacturing: Tomas Krajnak1; Miloš Janeček1; Dalibor Preisler1; Josef Stráský1; Michal Brázda2; Jaroslav Vavřík2; Jan Džugan2; 1Charles University; 2COMTES FHT a.s.
The present study characterises the microstructure of homogenous Ti15Mo and compositionally graded Ti+Ti15Mo alloys prepared by direct energy/laser deposition. The composition in the gradient material varied from Ti(70%)-Ti15Mo(30%) to Ti(30%)-Ti15Mo(70%) by 5% in the adjacent layers. Microstructure investigations in the vertical cut were performed by precise microhardness mapping and complemented by microstructural observations by SEM and energy dispersive spectroscopy (EDS). It was found that microhardness of gradient Ti+Ti15Mo alloy varied in the range of 300-550 HV in contrast to the almost constant HV value of ~330 HV in the Ti15Mo sample. On the other hand, the microstructure of both alloys consists mostly of columnar grains of similar size, orientated perpendicular to the plotted layers. In addition, the influence of the phase composition on the HV values is discussed in detail.
9:50 AM Break
10:05 AM
Tailored Microstructures in a Laser-processed Metastable Beta-Ti Alloy Using Enforced Epitaxial Growth: Wenhao Lin1; Ji Ma1; 1Mse/University of Virginia
Laser additive manufacturing demonstrates the capability of controlling microstructure via altering the process parameters. In this study, metastable Ti-25Nb(at.%) samples are processed using laser powder bed fusion (LPBF) showing a “ladder-like” microstructure with high density of melt pool boundaries that align with the building direction and cellular solidification boundaries perpendicular to the melt pool boundaries. The epitaxial growth is locally enforced due to the small hatch distance such that only parallel cellular structures develop due to high G/R ratio are maintained, while the rest are erased from remelting. The result is a microstructural composite formed with melt pool boundaries and cellular structures that alters the mechanical properties and anisotropy of the part.
10:25 AM
Understanding the Effect of Solute Elements on the Evolution of Equiaxed and Columnar Grains in AM Processed Beta Titanium Alloys: Mohan Sai Kiran Nartu1; Srinivas Aditya Mantri1; Brian Welk2; Narendra Dahotre1; Hamish Fraser2; Rajarshi Banerjee1; 1University of North Texas; 2Ohio State University
Virtually, all additive manufacturing (AM) processes involving complete melting of metal powders/wires produce significantly textured columnar grains along build direction, which are deleterious for mechanical properties. Therefore, understanding growth and texture of these columnar grains becomes crucial for AM alloys. Significant research in the last decade has been focused on extending the concept of growth restriction factor (GRF) (a classical theory originally developed for conventional casting) to AM. However, there are some critical concerns regarding the applicability of GRF model to AM and there is a need to understand and validate this model.Current work analyzes the evolution of grain morphology and texture in few commercial as well as model metastable beta titanium alloys processed via AM. Results indicate that the GRF model fails to interpret the grain growth behavior in these alloys. Alternatively, an approach based on solidification range has been proposed for the first time to rationalize the observations.
10:45 AM
Powder Blown Directed Energy Deposition of Nickel-titanium Shape Memory Alloys: Process-structure-property Relationship: Dyuti Sarker1; Samad Firdosy2; Nicholas Ury2; James Tsangarides1; Lauren Holm1; Aaron Stebner1; 1Georgia Institute of Technology; 2NASA Jet Propulson Laboratory
Additive manufacturing of nickel-titanium (NiTi)_ shape memory alloys has attained much attention as such technology promises the ability for 3D printing multi-functional thermomechanical systems. Much of the AM focus to date has been on the development of laser powder bed fusion process parameters. However, powder blown directed energy deposition (DED) has several desirable characteristics including easier grading of material composition by controlling mixing of powders from multiple compositions into the powder blown gas stream during manufacture to enable local control of martensitic transformation temperatures. Here, we report upon new characterizations of porosity and cracking, microstructures, martensitic phase transformation temperatures, and superelastic performances as a function of DED process parameter and post-process heat treatment variations. Through a methodical production approach, the relationship between process parameters, microstructural characterizations, and defect formation mechanisms are correlated to maximizing functional performance.