Processing-Microstructure-Property Relationships of Titanium and Titanium Alloys: Session II
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
Tuesday 8:00 AM
October 11, 2022
Room: 312
Location: David L. Lawrence Convention Center
Session Chair: Ben Morrow, Los Alamos National Laboratory
8:00 AM Invited
Titanium Alloy Microstructures Produced by Additive Manufacturing and Deformation: Amy Clarke1; Benjamin Ellyson1; Alec Saville1; Chris Jasien1; Jake Benzing2; Adam Creuziger2; Sven Vogel3; Kamel Fezzaa4; Wayne Chen5; John Foltz6; 1Colorado School of Mines; 2National Institute of Standards and Technology; 3Los Alamos National Laboratory; 4Argonne National Laboratory; 5Purdue University; 6ATI Specialty Materials
Titanium (Ti) and its alloys are ubiquitous in the aerospace, defense, and biomedical industries and are often used to realize property and performance gains. Today, state-of-the-art characterization techniques available in the laboratory and at national user facilities are enabling unprecedented, multiscale in-situ/ex-situ studies of Ti alloys and new insights into alloying-processing-microstructure-property-performance relationships. Here we highlight the role of thermals gradients, solidification velocities, and complex thermal cycling on the phases and microstructures developed in commercial and novel Ti alloys under additive manufacturing conditions, revealing possible strategies for microstructure and property control. We also explore the role of phase stability, omega-phase, and transformation- and twinning-induced plasticity, or TRIP/TWIP, on the mechanical response of metastable Ti alloys after/during quasi-static or dynamic testing. These deformation mechanisms can be tailored to design the properties of Ti alloys for high-performance structural applications.
8:30 AM Invited
Insights from Three-dimensional Characterization of Twins in Titanium: Rodney McCabe1; Hi Vo1; Patrick Pinney1; Matthew Schneider1; M. Arul Kumar1; Carlos Tome1; Laurent Capolungo1; 1Los Alamos National Laboratory
Deformation twinning has a significant impact on the evolution of microstructure and mechanical response in hexagonal close packed (hcp) metals. Three dimensional (3D) microstructural neighborhoods influence the local stresses that drive twinning phenomena and have significant effects on evolving twin microstructures. Here we show 3D microstructure effects on twinning in high-purity titanium revealed through two experiments: differential aperture X-ray microscopy and plasma (P)FIB based 3D-EBSD. The differential aperture x-ray microscopy experiment highlights the importance of stress concentrations not only for twin nucleation, but also to the growth process of twins, particularly for low Schmid factor twins. The 3D-EBSD experiments feature the importance of twin-twin interactions in 3D including variant interactions within grains, twin crossings at grain boundaries, and co-nucleation of twins.
9:00 AM Invited
Slip-twinning Interdependency in High-strength Alpha-beta Titanium Alloys: Shaolou Wei1; John Foltz2; Joseph Jankowski2; Bhuvi Nirudhoddi3; Luis Ruiz-Aparicio3; C. Tasan1; 1Massachusetts Institute of Technology; 2ATI Specialty Materials; 3ATI Specialty Rolled Products
Alpha-beta titanium alloys like Ti-6Al-4V are used because of their high specific-strength. In lower strength alloys like Ti-3Al-2.5V, alpha twinning is commonly observed and leads to higher ductility due to increased number of deformation modes. Alloys with yield strengths above 800 MPa typically do not exhibit alpha twinning, and tend to have poor cold-formability. Recent titanium alloys developed by ATI (ATI 425®, ATI Titan 27TM) have demonstrated simultaneously strength above 800 MPa and the activation of twinning in the alpha phase along with interdependent twinning-slip transfer. Interestingly, both alloys contain higher oxygen content than Ti-6Al-4V, and oxygen has previously been linked to suppression of alpha twinning. This presentation primarily aims to explore the micro-mechanical consequences of the interdependent slip-twinning activity, specifically, its influence on plastic strain localization and partitioning. The chemical origin of the twinning mechanism will also be discussed with the assist of density functional theory calculations.
9:30 AM Invited
Role of Oxygen on Phase Stability, Precipitation, and Deformation in Beta Titanium Alloys: Kathleen Chou1; Emmanuelle Marquis1; 1University of Michigan
Titanium’s reactivity with oxygen presents significant challenges to mechanical performance, including embrittlement caused by oxygen in solid solution. Oxygen modifies the phase formation and precipitation sequences in metastable β titanium alloys, which results in novel mechanical behavior suggestive of potential new application spaces. Compositionally-graded microstructures were created using oxidation followed by ageing to understand oxygen’s influence on ω and α phase precipitation kinetics and morphologies in β Ti-Nb, Ti-15-333, and Ti-15Mo alloys. Elevated oxygen levels induced morphology, number density, and size changes for the ω phase and accelerated α nucleation rate. Notably, oxygen partitioning to ω during ageing resulted in increased resistance of ω to precipitate shearing and suppression of catastrophic failure during micropillar compression. Furthermore, oxygen-induced α refinement provides a pathway to obtain fine α laths for accelerated precipitation strengthening of β Ti alloys. These findings provide design strategies to mitigate detrimental effects from interstitial oxygen and ω precipitation.
10:00 AM Break
10:20 AM
Conventional Ti Alloys for Aeroengines And Aircraft Landing Gear Beams—a Data-driven Analysis for Selection of Ti-based Alloys and Future Directions: Ramachandra Canumalla1; Tanjore Jayaraman2; 1Weldaloy Specialty Forgings; 2University of Michigan-Dearborn
Titanium alloys find diverse aerospace applications owing to their superior combination of corrosion resistance, lightweight, mechanical properties, and so forth. We analyzed the available data, in the literature, of the titanium alloys for two critical applications: aeroengines and landing gear beams. We applied fundamental statistical analysis (FSA), principal component analysis (PCA), and multiple-attribute decision making (MADM) to unearth the voice of the data. The ranks assigned by several MADMs, including ROVM (range of value method), ARAS (additive ratio assessment method)), and MEW (multiplicative exponent weighing), were consistent. FSA and PCA consolidated the MADM ranks of the alloys and identified similar top-ranked alloys. The investigations highlight similarities (and differences) across several grades/variants of the alloys, suggest potential replacement or substitute for the existing alloys, weed out some of the heavier alloys and consequently help in reducing the weight, and provide possible directions for improvement and/or development of these alloys.
10:40 AM
Dilatometric Study of Phase Transformations in Ti-407: Marco Ponce1; 1Centro de investigación de estudios avanzados del instituto politécnico nacional
In the present work, the study of the phase transformations in the Ti-407 alloy will be carried out, in particular, the effects of the initial microstructure and the heating rate on the phase transformations that give rise to the formation of the β phase and the cooling rate on the stability and transformation behavior of said phase. The manufacture of this type of engineering components from Ti-407 alloy represents considerable savings since this material is significantly easier to process and machine, since it exhibits a better combination of ductility and resistance. The solution heat treatment affects the distribution of elements in the initial microstructure, consequently, the dilatometric curves behave very differently during heating, dissolving the alloying elements differently.Based on the analysis of the dilatometric curves during constant heating, it was determined that the β-transus temperature starts from ~815°C for the Ti-407 alloy.
11:00 AM
Enhancing Low-cycle Fatigue Life of Commercially-pure Ti By Deformation At Cryogenic Temperature: Geonhyeong Kim1; Seyed Amir Arsalan Shams1; Jae Nam Kim1; Jong Woo Won2; Seong Woo Choi2; Jae Keun Hong2; Chong Soo Lee1; 1Pohang University of Science and Technology (POSTECH); 2Korea Institute of Materials Science (KIMS)
In this study, the low-cycle fatigue behavior of a cryogenic-rolled commercially pure titanium alloy was investigated, and compared with those of undeformed and room-temperature rolled variants. The amounts of deformation twins increased to over 70% after cryogenic temperature rolling, and to 27% after room temperature rolling. Strain-controlled low-cycle fatigue tests were performed at various total strain amplitudes from 0.4% to 1.2%. The Coffin-Manson and hysteresis energy-based models confirmed that low-cycle fatigue resistance was remarkably improved with increasing the volume fraction of deformation twins by pre-deformation. As the proportion of deformation twins in the microstructure increased, the hysteresis loop area decreased, and the severity of crack-deflection behavior increased. At total strain amplitude of 0.4%, dislocation recovery was inhibited in the pre-deformed microstructure, so cyclic behavior was stable. However, at total strain amplitude from 0.8% to 1.2%, the recovery actively occurred, so well-defined cell structures formed and cyclic softening became dominant behavior.
11:20 AM
Microstructure Evolution and Mechanical Behaviour of Two Phase (α+β) Ti-6Al-4V Alloy : An Effect of Heat Treatment Temperature and Duration: Jagadeesh Babu S M1; Manjesh Kumar Mishra2; 1REVA University; 2Malaviya National Institute of Technology (MNIT) Jaipur
In the present study, effect of heat treatment on the microstructure evolution and mechanical behaviour of the Ti-6Al-4V (α+β) alloy was investigated. The samples of Ti-6Al-4V alloy were heat treated at the temperature of 900 °C for the duration 1hr-to-6 hrs followed by water quenching. Room temperature tensile tests were conducted for as-received and heat-treated samples at the strain rate of 1×10-3 s-1.Vickers hardness of the as received and heat treated Ti-6Al-4V alloy was measured using the load of 500g for the dwell time 10 sec. Microstructure examinations were made using optical and scanning electron microscopy (SEM), which revealed morphological changes (banded structure to equiaxed structure) and also the modification in volume fraction of alpha and beta phases. It also found that, there is a occurrence of grain growth with increase in the duration of heat treatment. The tensile strengths of the samples were ranged from ~750 N/mm2 to ~960 N/mm2, hardness values ranged from ~350 HV to ~485 HV depending upon duration of heat treatment. The stress-strain behaviour could be explained with the help of changes in grain morphology and the volume fractions of the alpha and beta phases.