Processing-Microstructure-Property Relationships of Titanium and Titanium Alloys: Session I
Sponsored by: TMS: Titanium Committee
Program Organizers: Yufeng Zheng, University of North Texas; Rongpei Shi, Harbin Institute of Technology; Benjamin Morrow, Los Alamos National Laboratory; Sriram Vijayan, Michigan Technological University; Keyou Mao, Florida State University
Monday 8:00 AM
October 10, 2022
Room: 328
Location: David L. Lawrence Convention Center
Session Chair: Yufeng Zheng, University of Nevada Reno; Sriram Vijayan, The Ohio State University
8:00 AM Invited
Design of New Metastable Ti Alloys and Determinations of Their Deformation Mechanisms Active during Tensile Deformation: Brian Welk1; Nevin Taylor1; Zachary Kloenne1; G. Babu Viswanathan1; Hamish Fraser1; 1The Ohio State University
Metastable Ti alloys are those for which their microstructures, when heat-treated above the beta transus and quenched to room temperature, consist entirely of the beta phase rather than the formation of martensite commonly observed in quenched (alpha+beta) alloys (e.g., Ti64 (Ti-6Al-4V). Interestingly, the retained beta phase in the metastable beta alloys consists of a number of structural and compositional instabilities, most common being the omega and O’ phases. These latter phases influence the nucleation of the alpha phase such that extremely refined distributions of this latter phase may be obtained by tailored heat-treatments. In this paper, we report on the design of some new metastable beta alloys containing a variety of alpha distributions, differing in scale. The tensile properties of these new alloys will be listed, and the results of studies of the deformation mechanisms active in these refined microstructures will be reported.
8:30 AM Invited
Tailoring Martensitic Transformation in Metastable Beta-Ti Alloys: Yunzhi Wang1; 1Ohio State University
Martensitic transformation (MT) is a fundamental carrier of both elastic (reversible) and plastic (irreversible) strains and can offer many novel physical, mechanical and functional properties that conventional elasticity and plasticity carriers cannot, including superelasticity, shape memory effect, Invar and Elinvar anomalies, TRIP effect and excellent work-hardening capacity. However, the strain release by a MT is usually highly nonlinear, taking place in an avalanche fashion within a narrow temperature or stress range, which is difficult to control. In this presentation, we give an overview on recent efforts devoted to regulating and utilizing MTs in metastable beta-Ti alloys for controlled strain release under an applied load. In particular, we discuss several means that have been proven effective to turn the sharp, strongly first-order MT into a broadly smeared, apparently continuous transformation, including spatial variation of beta-phase stability induced by concentration modulation, nano shuffle-domain regulated MT, and deformation twin boundary regulated MT.
9:00 AM Invited
Approaches to Improving Yield-strength without Compromising Strain-hardenability in β-Titanium Alloys: Srinivas Aditya Mantri1; Mohan Sai Kiran Nartu1; Abhishek Sharma1; Sriswaroop Dasari1; Riyadh Salloom1; Ravisankar Haridas1; Fan Sun2; Frederic Prima2; Hamish Fraser3; Srinivasan Srivilliputhur1; Rajarshi Banerjee1; 1University of North Texas; 2Chimie ParisTech; 3The Ohio State University
Metastable β-Titanium alloys offer wide range of processability, multiple microstructures and hence, impressive mechanical properties. A β-solutionised microstructure may be aged below or above the ω solvus temperatures for either a short-term or a long-term heat-treatment. The effect of plastic deformation (cold-rolling) prior to such heat-treatment has also been realized recently. Large tonnage commercial usage of these alloys for safety critical applications makes such observations important as they may help design more robust and economically efficient processing routes. In the present talk, we discuss some of these approaches which lead to substantial increase in yield strength without any significant compromise to strain-hardening or ductility. Using experiments in commercial alloy systems coupled with DFT studies in modal binary beta-Titanium alloys we show how to realize this goal and with detailed investigation of the associated deformation-mechanisms we provide insights for a wider application of such approaches.
9:30 AM Invited
Microstructure-based Equivalent Initial Flaw Size (m-EIFS) Distributions for Airframe Structural Components: Adam Pilchak1; Manisha Banker1; Michelle Harr1; Joshua Shaffer1; Thomas Carmody1; Nathan Crosby2; Juan Ocampo3; Harry Millwater4; Ayman Salem1; 1Materials Resources LLC; 2Aeromatter; 3Aeromatter and St. Mary's University; 4University of Texas San Antonio
The damage tolerance sustainment philosophy was introduced in the late 1970’s. A key parameter in this methodology is the equivalent initial flaw size (EIFS). While the approach has proven successful, it has failed in certain cases where micromechanical phenomena overshade continuum mechanics. One such example is the case of beta-annealed titanium alloys which exhibit coarse lamellar microstructures with large colony sizes. In such situation small crack effects may persist to physically large crack sizes. Here we demonstrate a mechanism-based methodology for establishing an initial flaw size distribution from microstructure characterization data that is segmented based on observed fatigue damage mechanisms and which can be used in fatigue life prediction of beta-annealed titanium alloys. The approach is demonstrated within the probabilistic damage tolerance code SMART | DT and represents an improvement over existing fracture mechanics methods which may lead to anticonservative predictions.
10:00 AM Invited
Using Synchrotron X-ray Characterization to Understand Slip Processes in Titanium Alloys: Darren Pagan1; 1Pennsylvania State University
A challenge for understanding and predicting hexagonal titanium alloy deformation is the availability of different families of slip systems to accommodate plastic deformation, each with their own strengths, hardening behaviors, and rate sensitivities. Traditional single crystal mechanical testing has long struggled with deconvolving the activity of various slip systems leading to deficiencies in micromechanical modeling efforts. The advent of various synchrotron X-ray diffraction techniques, including high-energy diffraction microscopy (HEDM) which can probe large numbers of crystals and loading conditions in situ, is providing a new means to address this challenge. Here a series of efforts to understand the microscale crystallographic slip behavior of titanium alloys using synchrotron X-ray measurements will be presented.
10:30 AM Break
10:45 AM
Hierarchical Twinning Microstructure in the Metastable β Titanium Alloys: Dian Li1; Yufeng Zheng1; 1University of Nevada, Reno
Due to the combination of great properties such as high specific strength, excellent fracture toughness, and good corrosion resistance, metastable β titanium alloys have been increasingly used as structural materials in the aerospace and biomedical industries. The room-temperature ductility of the metastable β titanium alloys can be improved by promoting the twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) effects. In this work, the micro- and nano-scale substructure of the deformation induced twinning in the metastable β Ti-24Nb-4Zr-8Sn and Ti-5Al-5Mo-5V-3Cr alloys was studied using scanning electron microscopy, transmission electron microscopy and aberration-corrected scanning transmission electron microscopy. High-index primary twin has been characterized in both alloys, with the nano-scale secondary twin formed in the interior and the nano-scale metastable phase layer formed at the twin boundary. The characteristics of these high-index deformation twins with hierarchical substructures will be introduced. This work is supported by the National Science Foundation, grant CMMI-2122272.
11:05 AM Cancelled
Nanoindentation Studies and Bulk Mechanical Properties of Additively Manufactured Titanium Alloys: Yu Zou1; 1University of Toronto
Laser-based directed energy deposition (LDED) enables rapid near-net-shape fabrication of large-scale titanium components for aerospace applications. However, the poor tensile ductility of most as-deposited titanium alloys, particularly near-á alloys, hinders their wide usage for critical load-bearing structures. Here we report that a high density of microscale shear bands (MSBs) can be activated in an LDED-produced Ti-6Al-2Zr-Mo-V alloy with dispersed microscale á colonies to enhance its tensile ductility. Using high-speed nanoindentation and in situ scanning electron microscopy tensile tests, we correlate the local micromechanical properties and global mechanical behaviour of such a LDED-produced titanium alloy.Our study demonstrates that activating the MSBs provides a new opportunity to effectively enhance the ductility of LDED-produced titanium alloys and expedite the adoption of this additive manufacturing technology for critical structural applications.