Defect and Phase Transformation Pathway Engineering for Desired Microstructures: Experiment and Characterization
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Yufeng Zheng, University of North Texas; Rongpei Shi, Harbin Institute of Technology; Yipeng Gao, Jilin University; Timofey Frolov, Lawrence Livermore National Laboratory; Stoichko Antonov, National Energy Technology Laboratory; Jessica Krogstad, University of Illinois at Urbana-Champaign; Bin Li, University Of Nevada, Reno
Wednesday 8:30 AM
March 17, 2021
Room: RM 55
Location: TMS2021 Virtual
Session Chair: Stoichko Antonov, Max Planck Insitut fur Eisenforschung GmbH
8:30 AM
Grain Boundary Segregation for Thermal Stability in Ternary Nanocrystalline Alloys: Sebastian Kube1; Wenting Xing2; Arvind Kalidindi2; Sungwoo Sohn1; Amit Datye1; Dor Amram2; Christopher Schuh2; Jan Schroers1; 1Yale University; 2Massachusetts Institute of Technology
Nanocrystalline alloys can be stabilized through selective grain boundary segregation of specific solute element additions. Increasing attention is paid to ternary and higher order systems, where complex interactions govern segregation. To efficiently study the large composition spaces of such systems, we apply a high-throughput combinatorial technique revealing nanocrystalline stability through composition-grain-size maps. We compare two systems with distinct interactions: In Pt–AuAg both binaries are expected to be stable, whereas in Pt–AuPd the Pt–Pd binary is unstable and Au-induced co-segregation of Pd was previously reported. For ternary Pt–AuAg we find excellent thermal stability throughout. The Pt–AuPd system, by contrast, divides into an unstable regime, where Pd solute dominates and precipitates, and a stable regime, where Au solute dominates and retains Pd in the grain boundary. Overall, by combining current theory and the introduced combinatorial approach, stable multicomponent nanocrystalline composition spaces can be rapidly determined.
8:50 AM
Tuning Fine-scale Alpha Microstructures via Nano-scale Structural and Compositional Non-uniformities in Beta Titanium Alloys: Dian Li1; Rongpei Shi2; Rajarshi Banerjee3; Yunzhi Wang4; Hamish Fraser4; Yufeng Zheng1; 1University of Nevada, Reno; 2Lawrence Livermore National Laboratory; 3University of North Texas; 4Ohio State University
The microstructures in beta titanium alloys mainly contain the hcp alpha precipitates and the bcc beta matrix, generated by the precipitation reaction during the aging treatment. In general, alpha precipitates prefer to nucleate along the beta grain boundary and form a thick layer of grain boundary alpha microstructure. However, by introducing different defects into the interior of beta grains, e.g., nano-scale compositional and structural non-uniformities via the intermediate phases, various fine-scale intragranular alpha microstructures can be produced in the beta titanium alloys. In this work, the influence of nano-scale intermediate phases on the local structure and composition was investigated using aberration-corrected S/TEM and atom probe tomography. The extra driving force from these structural and compositional non-uniformities for the subsequent alpha precipitation was studied using phase field modeling. Various fine-scale intragranular alpha microstructures produced using different effects of these intermediate phases will be introduced in detail.
9:10 AM
Exploring the Microstructure of Sputtered Nanotwinned Alloys and Its Role in the Study of Dislocation-Twin Interactions: Francisco Andrade Chávez1; Orcun Koray Calebi1; Ahmed Sameer Khan Mohammed1; Huseyin Sehitoglu1; Jessica Krogstad1; 1University of Illinois at Urbana-Champaign
Nanotwinned alloys demonstrate superior mechanical properties and have the potential to warrant an optimum combination of high strength, ductility and cracking resistance. This remarkable performance is attributable to dislocation-twin interactions, but full control over the nature and structure of nanotwins is yet to be achieved. To develop a fundamental understanding of the mechanisms involved in achieving such control, we use a combination of magnetron sputtered nickel-titanium films and molecular statics simulations. Through manipulation of sputtering parameters, alloy chemistry and substrate interfacial strain, we aim to control the stacking fault energy and thereby the likelihood for twinning. Further, the use of compliant substrates allows for the deformation and study of our films. Preliminary results show that twin density and orientation can be modified through alloy chemistry and interfacial strain modulation. Gaining control over the microstructure of deposited films will enable a detailed and systematic investigation of dislocation structure and dislocation-twin interactions.
9:30 AM
Pseudo-in situ Characterization of Phase Transformation in an Al-Cu-Mn-Zr Alloy Using Atom Probe Tomography: Bharat Gwalani1; Jia Liu1; Jonathan Poplawsky2; Amit Shyam2; Arun Devaraj1; 1Pacific Northwest National Laboratory; 2Oak Ridge National Lab
Aluminum (Al) alloys with improved high-temperature mechanical properties (up to 350oC) are needed to enable the next generation of higher efficiency, affordable vehicle engines. A significant challenge with traditional Al alloys is that at high temperatures the metastable, semi-coherent θ′ (Al2Cu) transforms to θ (Al2Cu), the presence of which deteriorates mechanical properties. The compositionally optimized Al-Cu-Mn-Zr (ACMZ) alloys developed at ORNL can be used at >325oC by utilizing an enveloping co-precipitation around θ′ (Al2Cu) precipitates to extend the θ′ metastability. These co-precipitates could underpin the development of higher performance alloys (375-400oC). The current study investigates the θ′ coherent and semi-coherent interfacial evolution with temperature and time, both compositionally and structurally. To have a detailed understanding of the coprecipitation mechanism, a novel in situ-atom probe tomography (APT) technique coupled with transmission electron microscopy (TEM) were used to probe early stage aging at 300 oC in an ultra-high vacuum environment.
9:50 AM
High-temperature Bulk Dislocation Dynamics in Aluminum: Leora Dresselhaus-Marais1; 1Lawrence Livermore National Laboratory
Establishing the appropriate thermal pathways to tune a metal’s microstructure and generate the appropriate continuum response requires a quantitative view of high-temperature annealing. The dislocation motion and interactions that are known to dictate microstructural changes in metals depend strongly on temperature, however, the necessary time-resolved measurements have been elusive, especially near the melt. We use time-resolved dark-field X-ray microscopy to directly image dislocation motion at temperatures spanning the final 7% to Tm. Our real-time movies resolve the creep-dominated dislocation motion and interactions deep beneath any surface in single-crystal, showing dynamics that has previously been limited to theory. Quantitative analysis of the temperature-dependent dislocation mobility in these findings present opportunities to test and refine dislocation models that have previously relied on indirect measurements and multi-scale models for validation. This work was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
10:10 AM
Interaction between Martensite Transformation and Ion-induced Damage in Shape Memory Alloys: Alejandro Hinojos1; Daniel Hong1; Nan Li2; Khalid Hattar3; Peter Anderson1; Michael Mills1; 1The Ohio State University; 2Los Alamos National Labs; 3Sandia National Labs
Traditional efforts in modifying the activation barriers for the martensitic transformation in shape memory alloys have utilized microstructural control through thermal processing and deformation processing. Ion irradiation damage could also create crystallographic defects on important length scales, such as vacancies, dislocations, and voids. Martensite transformation may be controlled through a combination of ion implantation and transformation defects with unique defect templates. The work here will probe the interplay between Ni-ion implantation and irradiation of Ni-rich NiTi through SEM, TEM, and nanoindentation. Thermally cycled and uncycled NiTi were irradiated with several ion irradiation doses in order to understand the interaction between transformation and irradiation induced defects. In-situ observations will enable the observation of the martensitic morphology upon transformation. In-situ cooling experiments will be performed to observe the effects of these defect templates on the martensite morphology upon the forward and reverse transformation.
10:30 AM
Microstructural Evolution of Nanotwinned Al-Zr Alloy with Significant 9R Phase Stabilization: Nick Richter1; Yifan Zhang1; Ruizhe Su1; Tongjun Niu1; Qiang Li1; Sichuang Xue1; Haiyan Wang1; Xinghang Zhang1; 1Purdue University
Aluminum (Al) alloys have a multitude of structural applications, notably in the automotive and aerospace industries. Despite their widespread use, Al alloys suffer from low mechanical strength, significantly lower than most high strength steels. It has been demonstrated that nanotwins can drastically improve the mechanical strength of metals while retaining ductility. However, due to a high stacking fault energy, it remains difficult to form nanotwins in Al. Here, we report on Al-Zr alloy films with an abundance of incoherent twin boundaries and 9R phase. These films also show an extended solid solubility of Zr in Al, retaining a columnar nanograined structure among incoherent twin boundaries, up to 10at% Zr. These nanotwinned Al-Zr alloys exhibit a high hardness (4.5 GPa) and good deformability as shown by micropillar compression tests