Additive Manufacturing: Materials Design and Alloy Development V – Design Fundamentals: 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; Jiadong Gong, Questek Innovations LLC; Orlando Rios, University of Tennessee; Atieh Moridi, Cornell University
Thursday 8:30 AM
March 23, 2023
Room: 24C
Location: SDCC
Session Chair: Behrang Poorganji, Morf3D
8:30 AM
Design and Development of New Metastable Titanium Alloys for Use in Laser Powder Bed Fusion: Zou Zhiyi1; Marco Simonelli1; Adam Clare1; Nesma Aboulkhair1; Richard Hague1; 1University of Nottingham
In this study we present a new strategy to design and develop low-cost titanium metastable alloys for use in Laser Powder Bed Fusion (L-PBF). The work illustrates a computational methodology that integrates CALPHAD and empirical relationships to determine the stability of the ß phase within a Ti-Sn-Cr system. We show how the methodology can be used to identify printable compositions that retain a full metastable ß phase upon rapid solidification. The alloy is also designed to resist solidification and cold cracking and maintain the typical strain-transformable attributes of the metastable ß phase despite the L-PBF thermal cycling. Deformation is then linked to the TRIP and TWIP character of the alloys as a function of solute Sn concentration. Strain transformation is studied using a number of techniques, including SEM in-situ tensile microscopy. Findings support a new strategy that can be extended to other alloy systems and their rapid development.
8:50 AM
Additively Manufactured β-Ti5553 with Laser Powder Bed Fusion: Microstructures and Mechanical Properties of Bulk and Lattice Parts: Margaret Wu1; Marissa Linne1; Thomas Voisin1; Nathan Barton1; Jianchao Ye1; Kavan Hazeli2; Y. Morris Wang3; 1LLNL; 2University of Alabama Huntsville; 3UCLA
Ti5553 (Ti-5Al-5Mo-5V-3Cr wt.%) is a metastable body-centered cubic alloy with aerospace applications due to its high strength-to-weight ratio. Laser powder bed fusion (L-PBF) allows the layer-by-layer fabrication of complex geometries such as lattices which help reduce part weight. Thus, the successful deployment of L-PBF Ti5553 relies on a fundamental understanding of the the hierarchical microstructures and mechanical properties of its bulk and lattice parts. The techniques used include room-temperature tensile tests, nanoindentation, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. The presence of ꙍ nanoprecipitates in the lattice material distinguishes its microstructure from that of the bulk and moreover, indicates the challenges in predicting bulk mechanical response based on lattice properties. The present results provide a starting framework for the successful printing of Ti5553 bulk and lattice parts by comprehensively examining the processing-structure-property-paradigm of the deposited material system.
9:10 AM
Fine-tuning Hierarchy: Targeted In-situ Annealing of Additively Manufactured Titanium Lattices: Connor Rietema1; John Roehling1; William Smith1; Gabe Guss1; Kaila Bertsch1; 1Lawrence Livermore National Laboratory
The design of additively manufactured fault tolerant titanium lattices is an enabling technology across multiple fields including aerospace and biocompatible materials. One approach to realizing complex fault tolerant structures, such as lattices, is to control the printed microstructure in three dimensions. This level of microstructure control could allow the production of lattices with nodes that remain soft and ductile, while the struts provide higher strength without the risk of catastrophic brittle failure. In this work, we show targeted microstructural control of Ti-6Al-4V on a layer-by-layer basis using a custom in-house powder bed fusion laser system equipped with a 2D annealing laser and FLIR thermal imaging system. This work was performed under the auspices of the United States Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract DE-AC52-07NA27344.
9:30 AM
Directed-energy Deposition of Ti-6Al-4V Alloy Using Fresh and Recycled Feedstock Powders under Reactive Atmosphere: Kun Yang1; Geoff de Looze1; Vu Nguyen2; Robert Wilson1; 1Advanced Materials and Processing, CSIRO Manufacturing; 2Materials Characterization and Modelling, CSIRO Manufacturing
This research studies the directed-energy deposition (DED) of Ti-6Al-4V in an argon atmosphere containing oxygen (from air), using both fresh and recycled feedstock powders. The oxygen pickup in the fresh powder build tends to plateau beyond certain oxygen exposure, while the nitrogen pickup keeps increasing. Builds from recycled powder have higher interstitial elements pickup with no apparent saturation. The resulting microstructure comprises full lamellar α+β, formed through the in-situ decomposition of martensite. The α lath thickness is found to increase with air exposure level, due to the increased β transus temperature and martensite start temperature, and the accelerated diffusion-driven phase transformation. Yield strength and ultimate tensile strength models based on oxygen equivalent are proposed. Nitrogen and oxygen in the builds dictate the elongation-to-fracture, with nitrogen content being a more potent factor. Insights into alloy design and microstructure manipulation via interstitial elements addition are provided.
9:50 AM Cancelled
In-situ Design of Compositionally Modulated Ti-alloys for Novel Microstructures and Unprecedented Properties by Additive Manufacturing: Tianlong Zhang1; Chain-Tsuan Liu1; Yunzhi Wang2; 1City University of Hong Kong; 2Ohio State University
AM integrates multiple metallurgical processes into one in which making, shaping, and treating of alloys take place all at once in a single process. However, AM has largely been regarded as a forming technology that produces components near net shape. By building a component flexibly point by point and layer by layer, AM provides the opportunity to create heterogeneous alloys with location-specific compositions and microstructures. In this presentation, we demonstrate an in-situ design approach to make alloys spatially modulated in composition by using laser-powder bed fusion. We show that partial homogenization of two dissimilar alloy melts, Ti-6Al-4V and 316L stainless steel, allows us to produce micrometer-scale concentration modulations. The corresponding phase stability modulation creates a fine scale beta + alpha’ dual-phase microstructure that exhibits a high tensile strength of ~1.3 GPa and a progressive transformation-induced plasticity (TRIP) effect that leads to a uniform elongation of ~9%.
10:10 AM Break
10:25 AM
Selective Phase Transformation Behavior in the Heterogeneous Microstructured Ti-Zr-Nb-Sn Alloy Manufactured by Directed Energy Deposition: Jung Gi Kim1; Yukyeong Lee1; Shuanglei Li1; Eun Seong Kim2; Dong Jun Lee3; Jae Bok Seol1; Hyokyung Sung1; Hyoung Seop Kim2; Taekyung Lee4; Jung Seok Oh1; Tae-Hyun Nam1; 1Gyeongsang National University; 2Pohang University of Science and Technology; 3Korea Institute of Materials Science; 4Pusan National University
Adjusting the phase transformation behavior in metallic alloys is important for controlling both the strengthening capability and the shape memory effect. Because phase transformation usually occurs in high interfacial energy regions, heterogeneous microstructures with inclusions have a potential to induce a localized phase transformation behavior. In this study, transformation-induced plasticity in a heterogeneous microstructured Ti-Zr-Nb-Sn alloy was investigated. The high interfacial energy between the unmelted Nb particles and the β-Ti matrix supports the initiation of deformation-induced α′′ martensite, while phase transformation was suppressed at grain boundaries. This result indicates that the heterogeneous microstructure design with laser-based additive manufacturing is helpful for manipulating phase transformation at specific regions, which allows the adjustment of the local shape memory effect or plastic deformation in metallic alloys.
10:45 AM
Effect of Stress Relief Temperature on Microstructure and Mechanical Behavior of Additively Manufactured Ti-5Al-5Mo-5V-1Cr-1Fe: Mohammad Salman Yasin1; Shuai Shao1; Nima Shamsaei1; 1Auburn University
Although stress relief is commonly used for residual stress removal from additively manufactured parts, it sometimes can impact their microstructures and thus mechanical properties. This study analyzed the influence of stress relief temperature on the microstructure and mechanical behavior of laser powder bed fused (L-PBF) Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511). L-PBF round bars were stress relieved at two temperatures (700°C and 900°C for an hour, respectively) and machined into test specimens. Defect evolution as the result of stress relief was also studied through X-ray computed tomography. Although the as-built microstructure primarily comprised β and ω phases, they were mostly converted to lamellar α after exposure at 700°C (with ~13% β and ~8% ω remaining). After the 900°C stress relief, only 0.2% of β and ω remained in total, leaving relatively coarser α laths. Both tensile and fatigue tests will be performed and the measured properties will be correlated to the micro-/defect- structures
11:05 AM
Microstructural Engineering of Metastable Ti-Al-V-Fe Alloy via In Situ Alloying during Laser Powder Bed Fusion: Ming Chen1; Steven Van Petegem1; Zhiyi Zou2; Marco Simonelli2; Yau Yau Tse3; Helena Moens-Van Swygenhoven1; 1Paul Scherrer Institute; 2University of Nottingham; 3Loughborough University
The application of blended powders in Laser Powder Bed Fusion offers considerable freedom to print alloys and tune phase composition. β-Ti phase is stabilized in Ti6Al4V-based alloys by adjusting chemical composition of powder mixtures to obtain desired mechanical properties. We demonstrate that using a blended powder consisting of Ti6Al4V with Fe particles, as-built microstructures and phase composition are varied from almost complete α’ to β dominant by simply decreasing the volume energy density in the L-PBF process. Synchrotron operando X-ray diffraction demonstrate the phase evolution and temperature profiles for different energy inputs and show the direct stabilization of β phase to ambient temperature even under rapid cooling (106 K/s). β-Ti phase dominant samples show high strength and enhanced ductility in as-build conditions. Our study offers an effective method to engineer site-specific microstructures and mechanical properties by simply tuning locally laser parameters, while using the same blended powder for entire sample.
11:25 AM
Suppressing Large Columnar Grain Structures in Ti Alloys Processed with Laser Wire Directed Energy Deposition: Alexander Hansen1; Emma Vetland2; John Potter2; Chad Henry2; Jonah Klemm-Toole1; Zhenzhen Yu1; 1Colorado School of Mines; 2GKN Aerospace
Many titanium alloys processed with additive manufacturing suffer from anisotropy due to the formation of highly textured, large, columnar grains caused by large thermal gradients during solidification. In this study, large columnar grains were suppressed through the addition of alloying elements with high growth restriction factors, increasing the compositional undercooling of the alloy system, and inoculants, acting as heterogeneous nucleation sites. Utilizing powder core wires, novel compositions of alpha-beta and near beta titanium alloys were developed; their as-deposited microstructures were analyzed and compared to a Ti-6Al-4V control deposition. The compositions studied are categorized as having high or low growth restriction and high or low nucleation potential. A columnar to equiaxed transition model was developed for each composition to determine the potential to suppress large columnar grains. As-solidified grain size and morphology comparisons were made by reconstructing prior beta grains, revealing a measurable impact on size and morphology.