Advances in Titanium Technology: Advanced Manufacturing of Ti Alloys
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Yufeng Zheng, University of North Texas; Zachary Kloenne, Ohio State University; Fan Sun, Cnrs Umr 8247 - Chimie Paristech Psl; Stoichko Antonov, National Energy Technology Laboratory; Rongpei Shi, Harbin Institute of Technology
Wednesday 2:00 PM
March 2, 2022
Room: 252A
Location: Anaheim Convention Center
2:00 PM
Microstructure Evolution in Additively Manufactured Ti-5Al-5Mo-5V-3Cr Alloy: Veronica Anghel1; Ramon Martinez1; Jillian Bennett1; William Anderson1; John Carpenter1; Ben Brown2; 1Los Alamos National Laboratory; 2Kansas City National Security Campus
Titanium alloy Ti5553 (Ti-5Al-5Mo-5V-3Cr) is an excellent candidate for structural applications and additive manufacturing processes. Ti5553 is a heat treatable metastable beta titanium-alloy desirable for structural applications due to the high strength and low density. This relatively new β-stabilized alloy provides strength, ductility, fatigue resistance, and toughness advantages over other alloys. Work described here is part of a larger effort to develop strength models across strain rates for additively manufactured materials of interest to the NNSA complex. Electron Backscatter Diffraction characterization of Ti5553 microstructures produced powder bed fusion are used to study the impact of heat treatment on microstructure, mechanical properties, and dynamic performance. The difference in material response to deformation is discussed in the context of morphological and textural differences in as-built, β-solution treated, and β-solution treated and aged material. Development of damage under dynamic testing conditions is also discussed in relation to microstructural differences among these material flavors.
2:20 PM
Using Defects to Inform on Physical Phenomena in EBM Ti-6Al-4V across Scanning Strategies: Katie O'Donnell1; Maria Quintana1; Matthew Kenney1; Peter Collins1; 1Iowa State University
The manufacture of structurally sound parts through additive manufacturing is usually achieved by reducing or avoiding defects during manufacture or post-processing heat treatments. However, defects can be used to study the physical mechanisms at play during additive manufacturing processes. Examining regions around defects in Ti-6Al-4V samples from across three different EBM scan strategies, using compositional, crystallographic, and microstructural characterization methods, have revealed information not only about defect formation mechanisms, but also residual stresses present in the build, fluid flow dynamics within melt pools before solidification, preferential vaporization of select elements, and grain growth. The free surfaces of both spherical pores and lack-of-fusion defects can also provide information on solid-state phase transitions and the timelines of defect formation. Spot-melting techniques specifically resulted in fewer overall spherical pores, as well as smaller spherical pores, leading toward techniques that might help mitigate the formation of these pores in future builds.
2:40 PM
Thermohydrogen Refinement of Microstructure of AM Titanium Components: Michael Hurst1; James Paramore1; Brady Butler1; Daniel Lewis1; Laura Moody1; 1United States Army Research Laboratory
Thermohydrogen refinement of microstructure (THRM) is a hydrogen-based heat treatment for titanium components, particularly well-suited to metal AM. Introduction of hydrogen into the Ti-6Al-4V system enables unique phase transformations and microstructural engineering. Additionally, hydrogen accelerates self-diffusion in transition metals, alloying defects (i.e. pores) to heal during the heat treatment without requiring applied pressure. Finally, hydrogen has a very high diffusion rate in titanium and the hydrogenation reaction is easily reversible, allowing subsequent removal to < 10 ppm H via a vacuum or inert gas anneal. THRM results in tunable fine-grained and wrought-like Ti-6Al-4V microstructures and isotropic mechanical properties (> 1 GPa strength and > 20 %EL) without requiring mechanical working. This deformation-free aspect makes the process particularly applicable to components created in near-net-shape processes. This talk will present results from applying THRM to Ti-6Al-4V components produced by various metal AM technologies.
3:00 PM
Thermohydrogen Refinement of Microstructure (THRM) to Improve the Performance of Material Extrusion Additively Manufactured Ti-6Al-4V: Brady Butler1; Daniel Lewis2; Michael Hurst1; James Paramore1; 1US Army Research Laboratory; 2Texas A&M University
Additive manufacturing of titanium alloys has generated significant interest for prototyping, small production runs, and producing complex components that are not feasible to manufacture by traditional processes. However, the high costs associated with feedstock powders, equipment capital, and long production cycles severely limit the widespread adoption of these techniques in all but a few niche fields. Material extrusion additive manufacturing is based on mature powder metallurgy practice, offering significant opportunities to reduce cost while maintaining the versatility of additive manufacturing in general. Although powder metallurgy techniques show many benefits over melt-based processing, high sintering temperatures are typically required to achieve full density, and the resulting coarse lamellar microstructures have significant property and performance limitations. This study utilizes a hydrogen-based thermochemical heat treatment to improve the microstructure and mechanical behavior of Ti-6Al-4V alloy components fabricated by material extrusion manufacturing.
3:20 PM Break
3:40 PM
Titanium Metal Matrix Composites via Selective Laser Melting: William Hixson1; Howard Stone2; James Coakley1; 1University of Miami; 2University of Cambridge
Titanium metal matrix composites (MMCs) exhibit high strength and stiffness compared to conventional metal alloy materials and present a notable opportunity to gain mass efficiencies in applications where these characteristics can be beneficial such as the aerospace industry. Likewise, the development of metal additive manufacturing techniques has paved the way towards making these uniquely hard and lightweight materials increasingly viable in a manufacturing setting by permitting in-situ fabrication of delicate or complex geometries in these materials. In this work, we target eutectic compositions of Ti-B, Ti-Si, Ti-C and Ti-Fe based materials in an effort to minimize solidification cracking during selective laser melting, and will present the effect of composition on microstructure-mechanical property relationships of the MMCs developed to date.
4:00 PM
Triggering New Deformation Mechanisms in Ti Alloys by Heat Treatments: A Step Forward into the Improvement of the Ductility and Work-hardening of 3D Printed Parts: Odeline Dumas1; Loïc Malet1; Frédéric Prima2; Stéphane Godet1; 1Universite Libre De Bruxelles; 2PSL Research University, Chimie ParisTech, CNRS, Institut de Recherche de Chimie Paris
The plastic behavior of Ti alloys remains a major drawback: “classical” Ti-based materials usually display a low work hardening, bringing rapid strain localization and low ductility level. Moreover, with the lightning growth of 3D printing, the damage tolerance criterion becomes critical since fabricated alloys contain defects inherent to the process, leading to early damage upon loading. In that context, a quenching strategy has been used to promote α + α’ dual-phase microstructures capable to induce martensite reorientation-induced plasticity, rather usually associated to the orthorhombic α’’ martensite. The occurrence of such non classical deformation mechanism was shown to be highly efficient to improve the work-hardening and the ductility of Ti-alloys while keeping a high mechanical resistance. The present study provides a fundamental understanding of the crystallography and the microscale behavior of such martensite. The critical influence of the chemical enrichment, the texture and the morphology of α’ on reorientation is highlighted.
4:20 PM
Microstructural Scale Evolution of Titanium Alloys during Additive Manufacturing: Alec Saville1; Adam Creuziger2; Jake Benzing2; Sven Vogel3; Amy Clarke1; 1Colorado School of Mines; 2National Institute of Standards and Technology; 3Los Alamos National Laboratory
Microstructural scale in additively manufactured titanium alloys can vary drastically between different alloys and build processes. Varying thermal conditions during solidification and thermal cycling can refine or coarsen as-solidified microstructures, influencing the final microstructural condition. Cooling rates experienced in the solid state may also impact the scale and morphology of as-transformed microstructures, leading to challenges in controlling microstructural development in the as-built condition. A greater understanding of these phenomenon is required in relation to processing parameters and local conditions to advance microstructural control in metallic alloy additive manufacturing of titanium alloys. This work highlights recent efforts in understanding how thermal conditions and phase transformations influence microstructural scale, and how these insights can be used to tailor titanium builds with additive manufacturing.
4:40 PM
Mechanical Behavior of Ti Alloys in Relation to the Microstructure across Lengthscales: Anais Huet1; Thomas Yvinec1; Tiphaine Giroud1; Azdine Nait-Ali1; Joseph Wendorf2; Jean-Charles Stinville2; McLean Echlin2; Tresa Pollock2; Jonathan Cormier1; Loic Signor1; Patrick Villechaise1; Mikael Gueguen1; Samuel Hemery1; 1Institut Pprime; 2UCSB
Grain scale micromechanics have received significant research efforts to determine active deformation processes and how they govern the mechanical behavior. In this presentation, we report a major role of “ghost” structures inherited from the processing history that govern the deformation behavior at the mesoscale in Ti alloys. Several examples of deformation heterogeneities at the mm scale, resulting from the scanning strategy in additively manufactured materials, from microtextured regions in α+β alloys and from β grains in metastable β alloys, were experimentally characterized using in situ testing in scanning electron or optical microscopes. The relation with the macroscopic mechanical behavior is discussed and a mechanistic understanding of the experimental observations is provided using advanced computational and microstructure generation techniques.