Advances in Titanium Technology: Session I
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)

Monday 8:30 AM
March 20, 2023
Room: Cobalt 500
Location: Hilton

Session Chair: Yufeng Zheng, University of Nevada Reno


8:30 AM  Invited
Interface and Colony Boundary Sliding as a Deformation Mechanism in Titanium Alloys: Zachary Kloenne1; Gopal Viswanathan1; Hamish Fraser1; 1Ohio State University
    In this research, interface (alpha/beta) sliding has been identified as an active deformation mechanism in the recently developed  titanium alloy Timetal®407 (Ti-0.85Al-3.9V-0.25Fe-0.25Si-0.15O, wt.%). This deformation mechanism has rarely been reported in Ti alloys, in contrast to previous work which has identified grain boundary sliding in some cases. Here, the characterization of this deformation mode will be presented which involves a comparative study of the deformation behaviors in Timetal®407 and Timetal®6-4. Both alloys exhibited slip steps on their surfaces from conventional dislocation activity. However, it has been shown that Timetal®407 may also deform by a mechanism which manifests itself as sliding at alpha/beta interfaces and colony boundaries. In-situ (SEM) deformation has been performed so that the temporal activity of the various deformation mechanisms has been determined. This deformation mechanism is consistent with the ability of the alloy Timetal® 407 to provide significant ductility during very high strain rate testing.

9:00 AM  Invited
New Insights into Oxygen-rich Alpha Titanium Alloys for Structural Applications: Fabienne Amann1; Régis Poulain2; Stéphanie Delannoy1; Ivan Guillot2; Zachary Kloenne3; Guillou Raphaëlle4; Couzinié Jean-Philippe2; Dominique Thiaudière5; Jean-Luc Béchade4; Lartigue Sylvie2; Emmanuel Clouet4; Hamish Fraser3; Frederic Prima1; 1Chimie ParisTech; 2Université Paris Est Créteil; 3The Ohio State University; 4Université Paris-Saclay; 5Synchrotron SOLEIL
     Among the various significant questions affecting titanium metallurgy, the effect of interstitials, more specifically oxygen, on the (mechanical) properties of titanium alloys remains one of the most critical issues. For decades, oxygen has been considered as a detrimental element, leading to drastic embrittlement. However, there is still an important lack of knowledge on underlying mechanisms regarding this effect. This talk proposes a new insight on these facts, based on an extensive work performed on Ti-Zr-O alloys displaying high oxygen concentration (between 0.4 and 1 wt%). Two different aspects of great interest are discussed: (1) the determination of the atomic scale structure of Ti-O alloys, as a function of the chemical composition, with special attention to possible local ordering or local oxygen-driven structural modification. (2) The impact of oxygen content on: (a) the macroscopical properties (resistance/ductility trade-off) and: (b) the operative deformation mechanisms, at room temperature.

9:30 AM  Invited
Pathways to Engineer High Strength Coupled with High Strain Hardenability and Ductility in Metastable β-Titanium Alloys: Abhishek Sharma1; Srinivas Aditya Mantri1; Nartu Mohan Sai Kiran1; Sriswaroop Dasari1; Ravisankar Haridas1; Riyadh Salloom1; Fan Sun2; Frederic Prima2; Hamish Fraser3; Srinivasan Srivilliputhur1; Rajarshi Banerjee1; 1University of North Texas; 2CNRS - PSL Research University; 3The Ohio State University
    Traditionally, increase in the tensile yield strength of Ti alloys is accompanied by substantial reductions in strain-hardenability and ductility. Metastable β-Titanium alloys often exhibit high strain hardenability and ductility due to TRIP/TWIP effects but offer relatively low yield strengths. However, these alloys offer a wide processing window resulting in distinctly differing microstructural templates. While these microstructural templates comprise of various stable and metastable phases (α, αʹ, αʹʹ, ω-phase, etc.) it is their size scale, morphology, and microscopic dispersion in the β matrix that determine the macroscopic mechanical properties. Such microstructures principally involve a β-solutionized microstructure aged below/above the ω solvus temperatures for a short-term/long-term heat-treatment and/or combined with prior/post plastic deformation (cold-rolling). This presentation discusses possible microstructural design pathways towards engineering high yield strength in such systems, while maintaining TRIP/TWIP effects, resulting in a better balance of strength-strain hardenability-ductility.

10:00 AM Break

10:20 AM  
Adiabatic Heating and Phase Transformation in Serrated Chips of Ti-6Al-4V during Turning: Jiawei Lu1; Thomas Bieler1; Ryan Khawarizmi1; Patrick Kwon1; 1Michigan State University
    The wear rate on tools when machining titanium alloys increases dramatically with increasing cutting rate. This may result from transformation from alpha to beta phase at the chip-tool interface where beta more aggressively attacks the tool. Chips from turning experiments at 1, 1.5, and 2 m/s (61, 90, 122 m/min) were examined using EBSD mapping to identify mechanisms causing serrated chips, along with 2-D simulations using a Johnson-Cook model in DEFORM to assess local strain and temperature history in the tool and chip. Temperatures exceed 800 C where the fastest tool wear occurs. The stress tensor where shear instabilities commence was used to assess likely slip system activation in chips with and without cracks; those with cracks had orientations that favored <c+a> slip. Chips were heat treated to use recovery and recrystallization to infer the internal state of shear bands, and evidence for transformation to the beta phase is assessed.

10:40 AM  
Investigation of Grain Boundary Precipitation in Titanium Alloys using 3D Computational Simulation and Experimental Characterization: Dian Li1; Rongpei Shi2; Yufeng Zheng1; 1University of Nevada-Reno; 2Harbin Institute of Technology (Shenzhen)
    In order to achieve the optimum combination of the strength and ductility in titanium alloys, it is of significant importance to study the critical factors determining the alpha microstructure. In this work, the 3D computational simulation and experimental characterization are used to study the grain boundary precipitation in titanium alloys. The nucleation and growth of grain boundary alpha precipitates was simulated using 3D phase field modeling. The 3D morphology of grain boundary alpha precipitates was characterized by the FIB serial sectioning and reconstructed using the MIPAP image analysis software. The influence of the inclination angle between the habit plane of the selected variant for grain boundary alpha and the hosting grain boundary plane in determining the morphology of grain boundary precipitates will be introduced. This work is supported by the National Science Foundation, grant CMMI-2122272.

11:00 AM  
Exploring the Potential of Ti-Fe-X Systems for Design of Novel Titanium-based Superalloys: Rosie Mellor1; Nicholas Jones1; Howard Stone1; 1University of Cambridge
    Synergistic benefits can be derived in alloys by the inclusion of superlattice precipitates. Such benefits include hardening through reduced dislocation mobility in the ordered structure and retained ductility through a coherent precipitate interface. In this research, the concept of superlattice precipitate reinforcement in Ti-Fe alloys is explored. Whilst the lattice misfit between the A2 and B2 phases in binary Ti-Fe alloys is relatively large, it can be reduced with ternary additions. However, ternary Ti-Fe-X systems are poorly documented in the literature. As a result, insufficient information is known about the extent of the A2 + B2 two-phase field and how the lattice misfit may be tuned through compositional modification. In this talk, we will present on the phase equilibria and lattice constants of a range of Ti-rich Ti-Fe-X alloys in order to assess the potential of these systems and facilitate the design of future Ti-based superalloys.

11:20 AM  
Grand Canonical Optimization of Grain Boundary Structure in Hexagonal Close-packed Titanium: Enze Chen1; Timofey Frolov2; Mark Asta1; Tae Wook Heo2; Brandon Wood2; 1University of California, Berkeley; 2Lawrence Livermore National Laboratory
    Due to its high specific strength and good corrosion resistance, titanium (Ti) and its alloys feature in several technologically important applications including aerospace, biomedicine, and hydrogen storage. For many of these applications, grain boundaries (GBs) profoundly impact the material’s properties including strengthening, solute segregation, phase transformations, and diffusion kinetics. Recent work has shown the existence of competing phases at GBs in hexagonal close-packed Ti (α-Ti), which offers another pathway toward engineering desirable alloy properties by optimizing the GB structure. We build on previous work and perform an evolutionary, grand-canonical structure search for GB phases across a wide range of misorientation angles and tilt axes in α-Ti, whose interfacial phases are less explored than those in other face-centered cubic and body-centered cubic metals. We compare the resulting structures with the literature and discuss the consequences for GB mobility and hydrogen segregation in α-Ti.

11:40 AM  
Understanding the Role of Dual-phase Interface on the Alpha Precipitation in Metastable Beta Titanium Alloy: Dian Li1; Yufeng Zheng1; 1University of Nevada, Reno
    In metastable beta titanium alloys, alpha microstructure of different morphologies, size scales and distributions can be tuned via different phase transformation pathways. One non-conventional transformation pathway is the nucleation of fine scaled alpha precipitates associated with the pre-formed omega phase. For example, super-fined alpha microstructure with a number density of 35-40 Ct/μm2 can be achieved during slow heating and isothermal aging process. In this work, we studied the alpha nucleation at the pre-formed dual-phase interface between omega phase and beta matrix in a metastable beta Ti-5Al-5Mo-5V-3Cr (wt%, Ti-5553) alloy using isothermal aging treatment. When isothermally aged at 300°C, alpha nucleation occurs closely associated with the pre-formed isothermal omega phase that the alpha precipitates were observed at the omega/beta interface using diffraction contrast TEM and z-contrast aberration-corrected S/TEM. The role of dual-phase interface on the alpha precipitation will be presented. This work is supported by the National Science Foundation, grant CMMI-2122272.