Advances in Titanium Technology: Phase Transformation and Deformation in Titanium Alloys
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Don Li, Howmet Engineered Products; Yufeng Zheng, University of North Texas; Peeyush Nandwana, Oak Ridge National Laboratory; Matthew Dunstan, US Army Research Laboratory
Wednesday 2:00 PM
March 17, 2021
Room: RM 30
Location: TMS2021 Virtual
Session Chair: Yufeng Zheng, University of Nevada Reno
2:00 PM
Hierarchical Twinning Microstructure in Beta Titanium Alloys: Dian Li1; Wenrui Zhao1; Zachary Kloenne2; Stoichko Antonov3; Dong Wang4; Yipeng Gao2; Yunzhi Wang2; Hamish Fraser2; Yufeng Zheng1; 1University of Nevada, Reno; 2Ohio State University; 3Max-Planck-Institut für Eisenforschung; 4Xi’an Jiaotong University
Twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) play an important role in determining the ductility of beta titanium alloys. However, the microstructure evolution during the deformation and the mechanism involved in the TWIP and TRIP in beta titanium alloys remain controversial. In this work, the microstructure before and after the cold rolling of beta titanium alloys, e.g., Ti-24Nb-4Zr-8Sn (wt.%, Ti-2448) and Ti-5Al-5Mo-5V-3Cr (wt.%, Ti-5553), were systematically investigated using scanning electron microscopy, transmission electron microscopy and aberration-corrected scanning electron microscopy. Nano-scale metastable athermal omega phase and O’ phases were observed in the beta titanium alloys before deformation. Hierarchical twinning microstructure, including primary {332}<113> deformation twin and secondary {112}<111> deformation twin, was characterized in Ti-2448 in detail. Interestingly, various metastable phases were observed at different twin boundaries. In addition, a novel {10 9 3} <331> type deformation twin characterized in the cold-rolled Ti-5553 for the first time will be introduced.
2:20 PM
How Microtextured Regions Influence the Early Slip Activity in Ti Alloys: Samuel Hemery1; Azdine Naït-Ali1; Loic Signor1; Patrick Villechaise1; McLean Echlin2; Joseph Wendorf2; Jean-Charles Stinville2; Tresa Pollock2; Mikael Gueguen1; 1ISAE-ENSMA; 2UCSB
Processing of α/β Ti alloys produces mm-scaled microstructural regions with a sharp local texture. These microtextured regions, also called macrozones, have detrimental effects on mechanical properties for various loading conditions including fatigue and dwell-fatigue. In situ SEM tensile tests combined with EBSD were employed to experimentally monitor the onset of slip activity at the grain scale and to observe pronounced stress and strain heterogeneities in relation to MTRs. Fast-Fourier transform based crystal plasticity simulations of very large 3D polycrystalline aggregates were also carried out to obtain a mechanistic understanding. Experimentally captured 3D microstructures as well as synthetic microstructures were employed to isolate the influence of the degree of microtexture on the deformation behavior. In particular, polycrystalline aggregates containing MTRs with different sizes and geometries were instantiated in order to obtain predictive insights into the detrimental effect of MTRs.
2:40 PM
Influence of Microtextured Regions on Early Plasticity in Ti64: Joseph Wendorf1; Jean-Charles Stinville1; Marie-Agathe Charpagne1; McLean Echlin1; Andrew Polonsky1; Paul Dawson2; Tresa Pollock1; 1University of California Santa Barbara; 2Cornell 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. Grains that begin to yield far below the macroscopic yield strength are predicted via linear elastic finite element techniques operating on such a dataset, and these results are validated against experimental DIC measurements. The influence of extreme hard and soft grain neighborhoods found within MTRs as well as the importance of soft grains embedded in otherwise hard oriented MTRs will be discussed.
3:00 PM
Localization of Plastic Strain in Microtextured Regions of Ti-6Al-4V: Jonathan Cappola1; Jean-Charles Stinville2; Marie-Agathe Charpagne2; Patrick Callahan3; McLean Echlin2; Tresa Pollock2; Adam Pilchak4; Matt Kasemer1; 1University of Alabama; 2University of California, Santa Barbara; 3US Naval Research Laboratory; 4Air Force Research Laboratory
Microtextured regions (or macrozones) in Ti-6Al-4V have been witnessed to facilitate the formation of long-range strain localization prior to the onset of macroscopic yield, which affects the mechanical performance of the material. The character of microtexture that leads to this behavior has not been widely studied. In this study, a crystal plasticity finite element solver is employed to simulate the deformation response of a suite of samples exhibiting microtextured regions, where both the nominal orientation and the intensity of microtexture are parameterized. Additionally, scanning electron microscope digital image correlation experiments are performed on a sample exhibiting a strong microtextured region. The heterogeneity of plastic strain within the simulated and experimental microtextured regions is calculated, providing a quantitative assessment of degree of strain localization. Results - specifically the microtexture conditions which facilitate the formation of long-range strain localization, and the underlying micro-mechanical influences - are discussed.
3:20 PM
Anomalous c+a Dislocation Activity in TIMETAL-407 (Ti-407): Zachary Kloenne1; Gopal Viswanathan1; Bo Pang2; Stephen Fox3; Michael Loretto2; Hamish Fraser1; 1Ohio State University; 2University of Birmingham; 3TIMET
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-0.85Al-3.9V-0.25Si-0.25Fe-0.15O (wt.%, Ti-407) was studied and compared with Ti-6Al-4V (wt.%). Whilst Ti-64 was shown to deform by c+a dislocations only in hard grains, Ti-407 exhibited c+a activity in both hard and soft grains. Initial CRSS measurements show a similar trend in Ti-407 as Ti-64. Preliminary atomic resolution imaging of Ti-407 shows a deviation in the ideal interface structure. A combination of CTEM, aberration corrected HRSTEM, and additional micropillar testing was performed to elucidate the source of anomalous c+a dislocation activity in Ti-407.
3:40 PM
Colony Orientation Dependence in the Deformation and Spheroidization of Two-Phase Titanium Alloys: Benjamin Begley1; Cameron Frampton1; Thomas Spradley1; Jennifer Perez1; Adam Pilchak2; Victoria Miller1; 1University of Florida; 2Air Force Research Laboratory
The lamellar colony microstructure of two-phase titanium alloys dramatically affects the deformation mechanics as a result of the Burgers orientation relationship (BOR) between the alpha and beta phases, which aligns certain slip systems in each phase to form a stable interface. Thermomechanical processing to break down this microstructure is a critical processing step for many applications. In certain initial colony orientations, plastic deformation promotes rotation away from BOR, increasing the driving force for spheroidization and recrystallization, while other orientations fail to disrupt the BOR. We hypothesize that the orientation dependence of colony breakdown can be predicted by such plastic rotation arguments for a variety of loading schemes (uniaxial compression, plane strain). The viscoplastic self-consistent model is used to examine plastic rotation under various processing parameters, coupled with electron backscattered diffraction and transmission electron microscopy to elucidate the microscale relationships between colony orientation and spheroidization not captured by the model.
4:00 PM
Effect of Grain Orientation on Slip Transmission in Titanium: An Analysis of Strain Localization within Slip Bands: Behnam Ahmadikia1; Irene Beyerlein1; 1University of California, Santa Barbara
Stress-based conditions that enhance the propensity for slip transmission across a boundary in commercially pure titanium (CP-Ti) are studied in this work. A novel full-field fast Fourier transform (FFT)-based elasto-viscoplastic model that accounts explicitly for discrete slip bands in crystals (SB-FFT) is presented and applied to investigate the effect of grain neighbor orientation on the slip band development in CP-Ti. Then, this model along with a new slip band tip stress-based criterion to predict the propensity of slip transmission are validated using experiments on HCP metals. Finally, the effect of grain neighbor orientation on slip transmission is studied through numerous simulations, each with a unique c-axis misorientation between two neighboring crystals. Calculations reveal that while transmission likelihood is not clearly associated with geometric factors, there is a correlation between c-axis misorientation of two contiguous grains and the type of system onto which a slip band is anticipated to transmit.