Advances in Titanium Technology: Session III
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 (Shenzhen)
Tuesday 8:00 AM
March 21, 2023
Room: Cobalt 500
Location: Hilton
Session Chair: Stoichko Antonov, National Energy Technology Laboratory
8:00 AM Invited
Tuning the Reversibility of Stress-induced Martensitic Transformation in β-metastable Titanium Alloys by Low Temperature Heat Treatment: Philippe Castany1; Gaëtan Cabon1; Doïna Gordin1; Thierry Gloriant1; 1INSA Rennes
Metastable-β titanium alloys are of increasing interest for biomedical applications because of not only their great biocompatibility but also their potential shape memory or superelastic effects. Usually, shape memory effect is due to the reorientation of pre-existing α” martensite while superelasticity is due to reversible stress-induced martensitic (SIM) transformation from β phase to α” phase. In the present study, an abnormal shape memory effect is found from the non-reversible SIM transformation occurring from a full-β phase microstructure (annealed state) during tensile tests. An additional heat treatment at low temperature from the annealed state leads to a superelastic effect in the same alloy, pointing out the SIM transformation has become reversible. It will be shown by means of transmission electron microscopy (TEM) observations that the reversibility of SIM α” transformation can be tuned by a slight change in the nano-scale precipitation in initial β phase.
8:30 AM Invited
Caracterisation of the Microstructure and the Plastic Deformation in Ti-6al-4v Produced via Directed Energy Deposition: Silvia Lopez-Castaño1; Florence Pettinari-Sturmel2; Samuel Hemery3; Patrick Villechaise3; Philippe Emile4; Claude Archambeau4; Joël Douin2; 1AIRBUS; 2CEMES - Université de Toulouse; 3Pprime Institut, ENSMA - CNRS; 4AIRBUS Operation S.A.S.
Electron Beam Additive Manufacturing (EBAM) is a Wire Directed Energy Deposition (W-DED) process that is recently receiving much more attention than other Additive Manufacturing (AM) techniques, especially in the aeronautical sector for the serial production of metallic parts. EBAM technology allows the production of large metal workpieces with high deposition rates, providing at the same time the advantages of other AM techniques such as cost and environmental impact reduction. In this work, the microstructure obtained in Ti-6Al-4V produced by W-DED is characterized and analyzed using various techniques. Then the deformation mechanisms are investigated using micro-scale mechanical testing and digital image correlation. The impact of the microstructure characteristics on the mechanical properties are also discussed.
9:00 AM
Mechanisms of Grain Boundary α Precipitation in the Metastable β-Titanium Ti-5Al-5Mo-5V-3Cr: Stoichko Antonov1; T.S. Prithiv2; Zachary Kloenne3; Yufeng Zheng4; Rongpei Shi5; Hamish Fraser3; Baptiste Gault2; 1National Energy Technology Laboratory; 2Max-Planck-Institut fur Eisenforschung GmbH; 3The Ohio State University; 4University of Nevada Reno; 5Harbin Institute of Technology (Shenzhen)
We studied the driving force for and precipitation mechanism of the deleterious grain boundary ⍺ phase formed during the aging of the β-titanium alloy, Ti–5Al–5Mo–5V–3Cr–0.5Fe (wt.%). We probed the composition of different grain boundaries and present phases from the as-quenched β condition and after heating and aging using correlative electron microscopy and atom probe tomography. Our analysis reveals strong segregation of some α-stabilizing elements along with a depletion of β-stabilizing elements. Subsequently, multiple α precipitates nucleate along the grain boundary during heating to the aging temperature, and conglomerate during the aging to form the α plates. Interestingly, B and C play very different roles in the nucleation and growth of the α precipitates. This work provides essential insight into the formation of the undesired grain boundary ⍺ layers along prior-β grain boundaries in metastable β-Ti alloys.
9:20 AM Break
9:40 AM
Suppression of ω-phase Formation in Prototypical Metastable β-Ti Alloys: Martin Luckabauer1; Florian Brumbauer2; Wolfgang Sprengel2; Norihiko L Okamoto3; Tetsu Ichitsubo3; 1University of Twente; 2Graz University of Technology; 3Institute for Materials Research, Tohoku University
A critical characteristic of metastable β-Ti alloys is the inevitable formation of ω precipitates during certain heat treatments which leads to embrittlement, or even to a complete loss of ductility. In this work Sn an element known to influence the ω-phase formation was introduced into a β-Ti-Cr alloy to study its influence on the ω-phase formation kinetics in-situ by means of a unique high-precision laser dilatometer. Two Ti-Cr alloys, with and without the addition of Sn which were subjected to similar heat treatments consisting of solution annealing, quenching and subsequent isothermal ageing at various temperatures were studied. For the Ti-Cr alloy, the expected extensive formation of isothermal ω-phase at 250°C was observed. In contrast the addition of 3at% Sn to the alloy decreased the formation rate by more than three orders of magnitude, allowing for a time-temperature processing envelope compatible with all established additive manufacturing techniques.
10:00 AM
Effect of Loading Rate and Applied Potential on the Environment-assisted Cracking Behavior of ST/A Beta-C Titanium Exposed to Marine Environments: Zachary Harris1; James Burns2; 1University of Pittsburgh; 2University of Virginia
The influence of the applied electrochemical potential and loading rate (dK/dt) on the environment-assisted cracking (EAC) behavior of solution-treated and aged Beta-C (Ti-8.3V-5.9Cr-4.4Zr-4.1Mo-3.4Al) in 0.6 M NaCl is assessed via a rising stress intensity (K) testing framework. Experiments demonstrate a strong applied potential dependence on the threshold stress intensity (KTH), which reaches a minimum at -800 mV vs. saturated calomel electrode. The effect of dK/dt on the EAC susceptibility at -800 mV is then assessed over dK/dt ranging from 0.25 to 10 MPa√m/hr, which showed that KTH is largely independent of the applied dK/dt. However, comparison of these data with static K experiments (dK/dt = 0) demonstrate that rising K methods yield conservative EAC metrics with increased efficiency, consistent with observations in other alloy systems. These findings are then discussed in the context of current standardized approaches for quantifying EAC susceptibility and the application of such approaches to Ti alloys.
10:20 AM
Investigation of Fine-scaled Alpha Microstructure in Metastable Beta Titanium Alloys: Deepak Pillai1; Ahsan Habib Munna1; Cameron Tucker1; Dian Li1; Yufeng Zheng1; 1University of Nevada Reno
Due to the combination of great properties such as high strength, low density and great corrosion resistance, metastable beta titanium alloys have been increasingly used as important structural materials in the aerospace industry. The high strength of metastable beta titanium alloys mainly arises from the hcp structured alpha phase precipitates, because the interface between the alpha phase precipitate and the bcc structured beta matrix can act as the barrier for dislocation motion. In this work, the fine-scaled alpha microstructure in two metastable beta titanium alloys, Ti-5Al-5Mo-5V-3Cr-1Zr and TIMETAL18, was quantitatively studied using advanced scanning electron microscopy and the MIPAR image analysis software. It is found that the heating rate before the temperature achieves the isothermal aging temperature plays a critical role in determining the sizescale of alpha precipitate microstructure in these alloys. This work is supported by the NSF CAREER Award, grant DMR-2145844.