Advances in Titanium Technology: Deformation Behavior in Ti Alloys II
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Yufeng Zheng, University of Nevada-Reno; Zachary Kloenne, Ohio State University; Fan Sun, CNRS - PSL Research University; Stoichko Antonov, National Energy Technology Laboratory; Rongpei Shi, Lawrence Livermore National Laboratory

Wednesday 8:30 AM
March 2, 2022
Room: 252A
Location: Anaheim Convention Center

Session Chair: Zachary Kloenne, Ohio State University

8:30 AM  
Anomalous c+a Dislocation Activity in TIMETAL-407: Zachary Kloenne1; Gopal Viswanathan1; Michael Loretto2; Hamish Fraser1; 1Ohio State University; 2University of Birmingham
    Typically, two types of Burgers vectors are possible for glissile dislocations in Ti: b = [a] and b = [c+a], with the former gliding on the prismatic, basal, or first-order pyramidal planes. Previous studies have shown a large difference in CRSS between [a] slip and [c+a] slip, with the latter only being activated with close alignment of the c-axis and tensile direction. In this study, the dislocation behavior of Ti-1Al-4V-0.25Si-0.25Fe-0.15O (wt.%, Ti-407) was studied and compared with Ti-6Al-4V (wt.%). While Ti-64 was shown to deform by [c+a] dislocations in hard grains, Ti-407 exhibited [c+a] activity in both hard and soft grains. Initial CRSS measurements (micro-compression testing) show a similar trend in Ti-407 and Ti-64. FIB foils were extracted from said micropillars and studied further. It was determined that misfit dislocations at the alpha/beta interface were responsible for anomalous [c+a] activity in Ti-407, which were studied further via CTEM and HRSTEM.

8:50 AM  
Heterogeneous and Cooperative Deformation in Two-phase Titanium Alloys: Slip Initiation, Transfer, and Their Effects on Strain Localization : Shaolou Wei1; Cem Tasan1; 1Massachusetts Institute of Technology
    The diverse microstructural combinations in two-phase titanium alloys have enabled fruitful pathways to tailor the macroscopic load-bearing responses. However, plastic deformation coordination between alpha- and beta-phases, especially the underlying deformation micro-events that lead to strain localization and partition still remain elusive and are deem detailed considerations. In this presentation, by studying a Ti-Al-V-Fe alloy and its processing variants through integrated in-situ DIC, in-situ synchrotron X-ray diffraction, and crystallographic calculation, we aim to showcase the exploration of the following three fundamental topics: (1) what are the deformation micro-events that governing strain localization inception? (2) how do strain localization and/or its partition evolve with respect to plastic straining? (3) how do the foregoing deformation micro-events affect damage nucleation and thereby macroscopic failure? Broader indications for mechanistically-guided microstructural design will also be included.

9:10 AM  
Strengthening of Ti-6Al-4V/TiC Composites: Pavlo Markovsky1; Dmytro Savvakin1; Olexandr Stasyuk1; Matthew Mecklenburg2; Vianey Ellison3; Sergey Prikhodko3; 1G.V. Kurdyumov Institute for Metal Physics, NAS of Ukraine; 2University of Southern California, Los Angeles; 3University of California Los Angeles
    Titanium alloys reinforced with additional phase and fabricated using powder metallurgy attract significant attention due to the simplicity of intentional hardness increase and exceptional wear resistance. In this study the metal-matrix composites of Ti-6Al-4V alloy reinforced with TiC (up to 80%, vol.) were fabricated via blended elemental powder metallurgy using hydrogenated Ti as the base of powder blends. Post-sintering solution treatment at 880 and 1000 C followed by the water quenching and aging at 550 C were employed to modify the microstructure and properties of metallic matrix. For the duration of thermal exposure throughout the sintering followed by solution treatment and subsequent aging the matrix and reinforcement phase underwent distinct structural changes that significantly increase the hardness of composites. It was shown that the combined effect from the additional phase reinforcement and the applied treatment of fabricated materials can increase their hardness in two times compared to as-sintered alloy.

9:30 AM  
The Effect of Sample Size and Plastic Behavior on the Validity of Sub-scale Mechanical Testing of Titanium Alloys: James Paramore1; Laura Moody1; Xinzhu Zheng2; Ankit Srivastava2; Brady Butler1; 1US Army Research Laboratory; 2Texas A&M University
    Today’s technological landscape is increasingly driving the demand for reliable property data from small specimens. Sub-scale techniques are useful for testing near-net-shape components, rapidly producing large data sets for data-driven modeling and machine learning, and other applications. However, the mechanical behavior of most materials tends to depart significantly from the bulk as the testing scale is decreased. In this talk, the effect of thickness on the mechanical properties of mm-scale flat tensile bars is presented for two wrought alloys – commercially pure titanium (CP-Ti) and Ti-6Al-4V. While it might be expected that the more ductile CP-Ti would be less susceptible to sample size, the opposite effect was observed. The relationship between sample thickness and ductility was found to be more significant for CP-Ti by a substantial margin. The underlying mechanisms for this observed behavior and the implications for sub-scale testing of these and other titanium alloys will be discussed.

9:50 AM  
Modeling Local Stress States Near Microtextured Regions in Ti64 and Implications on Dwell Fatigue Life: Joseph Wendorf1; Jean-Charles Stinville1; Marie-Agathe Charpagne1; McLean Echlin1; Andrew Polonsky2; Paul Dawson3; Tresa Pollock1; 1University of California Santa Barbara; 2Sandia National Laboratories; 3Cornell University
    Titanium alloys have been extensively used throughout the cold section of jet engines for several decades due to their high strength to weight ratio and excellent fatigue performance. However, many titanium alloys develop microtextured regions (MTRs) during forging which significantly reduce dwell fatigue life. 3D EBSD datasets collected via Tribeam tomography enable characterization of the overall millimeter scale 3D structure of MTRs at high enough resolution to also study the micron scale structure of individual grains and grain neighborhoods. Finite element analysis is performed on experimentally collected 3D microstructures of microtextured Ti64 to model the deformation behavior of MTRs and predict likely dwell fatigue crack initiation sites based on several mechanical metrics. The influence of MTR orientation and arrangement on these metrics, as well as the role of MTR boundaries and misoriented grains within MTRs will be discussed.