Advances in Titanium Technology: Session III
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Rongpei Shi, Harbin Institute of Technology; Yu Zou, University of Toronto; Iman Ghamarian, The University of Oklahoma; Yu Lung Chiu, University of Birmingham; Yufeng Zheng, University of North Texas
Tuesday 8:00 AM
March 5, 2024
Room: Plaza Int'l G
Location: Hyatt
Session Chair: Yu-Lung Chiu, University of Birmingham
8:00 AM Keynote
2024 Institute of Metals Lecture/Robert Franklin Mehl Award: Optimization of Microstructure of Titanium Alloys Processed Using Additive Manufacturing: Mohan Nartu1; Brian Welk2; Srinivas Mantri3; Nevin Taylor2; Gopal Viswanathan2; Rajarshi Banerjee4; Narendra Dahotre4; Hamish Fraser2; 1PNNL; 2Ohio State University; 3ANL; 4University of North Texas
When processing Ti alloys using additive manufacturing, the resulting microstructure often exhibits coarse columnar grains (in the direction of deposition) with attendant deficits in properties. The solution adopted involved the application of computational thermodynamics to identify which alloying additions to titanium alloys result in an increase in the freezing range of the given alloy base, such that a columnar to equiaxed transition (CET) may be effected. These alloying additions, mainly eutectoid formers, have been found, at critical concentrations, to cause a CET to occur, resulting in a relatively fine equiaxed microstructure. The amount of solute addition for these elements usually exceeds their solubility limit in the various titanium alloys, and a further effort involving alloy development is required. Two types of alloys are being developed, the first with essentially identical properties as the (given) base alloy, and the second, alloys with enhanced properties. These various efforts will be discussed.
8:30 AM
Novel Bainitic Ti Alloys Designed for Additive Manufacturing: Duyao Zhang1; Ryan Brooke1; Dong Qiu1; Mark Gibson1; Mark Easton1; 1RMIT University
A novel bainitic titanium alloy system has been designed specifically for additive manufacturing (AM). The Ti-xCu-yFe alloys take advantage of constitutional supercooling to suppress the growth of large columnar grains usually associated with AM Ti alloys. The bainitic microstructure shows refined α-phase within a matrix of β-phase. The intermetallic Ti2Cu forms prevalently on the edge of the α-phase and within the β matrix. The high strength of these materials in the as-built condition is attributed to the high prevalence of fine α-phase and Ti2Cu particle as well as significant solid solution hardening. This work demonstrates a viable way to fabricate structural components with unique and excellent properties using low-cost elemental powders with AM.
8:50 AM
Microstructure Transition Gradients in Next-generation Alloy-Alloy-Composite Titanium AM Aerospace Components: Alec Davis1; Albert Smith2; Jack Donoghue1; Vivek Sahu1; Dongchen Hu1; Jacob Kennedy3; Armando Caballero4; Romali Biswal4; Philip Prangnell1; 1University of Manchester; 2TESCAN; 3Institut Jean Lamour; 4Cranfield University
Additively manufactured (AM) aerospace multi-alloy components (alloy-alloy composites or AACs) have the potential to increase weight savings and fuel efficiency. These components exploit AM layer-by-layer deposition to print dissimilar alloys in different locations for site specific properties, by switching the feedstock in situ. Therefore, AAC parts can be designed with greater freedom than their wrought counterparts that must instead rely on detrimental fastenings or welds to meet component specifications. However, in high deposition rate AM parts required for aerospace industries, significant dissimilar-alloy melt-pool mixing occurs during deposition of AACs and results in microstructure ‘transition gradients’, which continue across many layers, exhibiting a stepwise change in alloying elements separated by steep local gradients at each layer boundary. In this work, two AAC case-study combinations were studied: 1) Ti-6Al-4V → Ti-5Al-5V-5Mo-3Cr (wt.%) and 2) Ti-6Al-4V → Ti-6Al-2Sn-4Zr-2Mo. The transition gradients in these test samples were characterised and their graded micromechanical behaviour investigated.
9:10 AM
Additive Friction Stir Deposition of a Metastable β-titanium Alloy: Anurag Krishnakedar Gumaste1; Abhijeet Dhal1; Ravi Sankar Haridas1; Rajiv S. Mishra1; 1University of North Texas
Friction-stir-based additive manufacturing (AM) technology has shown promising developments. Additive friction stir deposition (AFSD) is a solid-state AM process that uses frictional heating to plasticize workpiece material and deposit it in a layer-by-layer fashion to fabricate 3-dimensional structures. The AFSD process yields a fully dense wrought-like microstructure with minimal distortion and material wastage. AFSD state of the art has been well established for softer metallic materials like aluminum and magnesium. However, adaptation of AFSD for high-temperature materials is still challenging due to limited tool endurance and oxidation proneness. In this work, a feasibility study has been carried out to deposit a metastable β-Ti-5553 alloy using AFSD. Process-structure-property correlation has been established on the as-deposited alloy via detailed microstructural and mechanical property investigation. Further, mechanical property enhancement of the as-deposited alloy has been achieved by optimized post-process heat treatment.
9:30 AM Break
9:50 AM Invited
Ultrastrong Nanotwinned Titanium Alloys Through Additive Manufacturing: Aijun Huang1; Yuman Zhu1; 1Monash University
Additive manufacturing(AM) is leading a new era in metal fabrication across aerospace, automotive, biomedical and energy sectors due to its design freedom that can fabricate almost any geometrical part. Titanium alloys are presently the leading AMed metal components for the aerospace industry. However, most commercially available titanium alloys made by AM do not have satisfactory properties for many structural applications. In this talk, we will present our recent breakthrough that ultrastrong and thermally stable titanium alloys can be produced by AM, which may be directly implemented in service. As demonstrated in a commercial titanium alloy, after simple post heat treatment, adequate elongation and tensile strengths over 1600 MPa are achieved - resulting in the highest strength-to-weight among all AM alloys to date. The excellent properties are attributed to the unusual formation of dense, stable and internally-twinned nanoprecipitates, that are rarely observed in the traditionally processed titanium alloy.
10:15 AM
Novel Twinning in Shock Loaded Additive Metastable Ti5553: Tim Ruggles1; Josh Kacher2; Paul Kotula1; Brittany Branch1; Paul Specht1; 1Sandia National Laboratories; 2Georgia Institute of Technology
This work documents a new twinning mode in a β titanium alloy subjected to shock loading. The material was additively manufactured Ti5553 in the as-built condition, resulting in a metastable β microstructure. It was loaded in a gas-gun with a sapphire impactor to create a peak load of 2.1 GPa. Significant spall nucleated in the test specimen, but it remained intact for postmortem characterization. Twinning was found near the spall plane, but not the {332}<113> twinning mode typical of metastable β titanium or on the {112}<111> twinning that is typical of other BCC materials. This novel twin is investigated using electron backscatter diffraction (EBSD) analysis and transmission electron microscopy. The misorientation relationship is approximately a 20⁰ about the <110> axis and the twin is believed to be {811}<441>, an unreported twinning mode. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525
10:35 AM
Microstructural Manipulation of LPBF Ti-6Al-4V by Hydrogen Heat Treatment: Matthew Dunstan1; Matthew Vaughn1; James Paramore1; Brady Butler1; Kevin Hemker2; Andelle Kudzal3; 1US Army Research Laboratory; 2Johns Hopkins University; 3Naval Surface Warfare Center Carderock Division
In laser powder bed fusion additive manufacturing (AM) of Ti-6Al-4V, the resulting microstructure in the as-printed state is martensitic in nature due to the rapid cooling rates and thermal cycling which results in high strength, low ductility tensile properties. Post AM heat treatments can be used to decompose these martensitic microstructures and improve the ductility, but due to the continuous network of retained β phase the manipulation of these microstructures is limited. In this work, the effects of maximum temperature of a post-processing heat treat utilizing a hydrogen atmosphere are explored as a method to manipulate the microstructure and to improve tensile ductility of extra low interstitial Ti-6Al-4V produced by laser powder bed fusion. Low maximum temperatures coupled with an inert globularization heat treatment are found to produce tensile properties comparable with hot isostatic pressing reaching ultimate strengths of 1 GPa and 19% elongation at failure.
10:55 AM
Effect of Electropulsing on Ti-6Al-4V Fabricated by Selective Laser Melting: Seong Ho Lee1; Jinyeong Yu2; Seho Cheon1; Jung Gi Kim3; Taekyung Lee1; 1Pusan National University; 2Pusan National University (PNU); 3Gyeongsang National University
Selective laser melting (SLM) enables to fabricate a complex 3D product using Ti-6Al-4V alloy powders. Microstructural inhomogeneity, such as a columnar structure, in SLM Ti-6Al-4V leads to deterioration in mechanical properties. This study verified electropulsing treatment (EPT) to eliminate the columnar structure to exploit its rapid heating capability. The microstructural evolution was compared to that caused by the traditional method of furnace heat treatment (FHT). The rapid heating achieved by EPT effectively suppressed a grain growth. In addition, this work also investigated the effect of electropulsing anisotropy on microstructural evolution. It is noted that the columnar structure disappeared by EPT along the building direction at a current density of 16 A·mm−2, whereas the disappearance occurred at a higher density of 20 A·mm−2 along the scanning direction. Both thermal and athermal effects were discussed to elucidate the role of EPT in increasing the microstructural homogeneity.
11:15 AM
Solid Phase Recycling of Titanium Scrap by Friction Extrusion: Mageshwari Komarasamy1; Scott Taysom1; Anthony Reynolds1; Scott Whalen1; 1Pacific Northwest National Laboratory
Titanium scrap is highly recyclable but requires the addition of titanium sponge during vacuum arc remelting to achieve the desired properties. If the need for fresh sponge and re-melting could be eliminated during recycling, then energy consumption, carbon footprint, and sustainability could be dramatically improved. In this project, a solid phase processing methodology known as friction extrusion was used to recycle Ti-6Al-4V scrap into rods. Feedstock consisting of machining chips with varying oxygen levels was successfully extruded. Both optical and electron microscopy was used to investigate the evolved microstructures and to understand the breakage and distribution oxide particles. Additionally, the effect of intense strain and temperature on the microstructure evolution was discussed. To quantify the structural integrity of the rods, tensile testing, and hardness measurements were carried out. This investigation suggests friction extrusion as a potential pathway for recycling Ti-6Al-4V scrap without remelting or introducing fresh titanium sponge.