Advances in Multi-Principal Elements Alloys X: Structures and Modeling: Structures and Characterization II
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Alcoa Technical Center
Wednesday 8:30 AM
March 2, 2022
Room: 251B
Location: Anaheim Convention Center
Session Chair: Wei Chen, Illinois Institute of Technology; Yi-Chia Chou, National Chiao Tung University
8:30 AM Invited
Microstructural Inversion Accompanied by B2 to hP18 Phase Transformation in a BCC Based Refractory Complex Concentrated Alloy: Abhishek Sharma1; Sriswaroop Dasari1; Vishal Soni1; Oleg Senkov2; Daniel Miracle3; Rajarshi Banerjee1; 1University of North Texas; 2UES Inc.; 3Air Force Research Laboratory
A continuous ordered B2 matrix with discrete cuboidal BCC pockets, like a superalloy microstructure, is often observed in RCCAs or RHEAs. Such a microstructure has been attributed to concomitant spinodal decomposition coupled with chemical ordering within the BCC matrix. The Al0.5Mo0.5NbTa0.5TiZr RCCA exhibits this microstructure at the initial stages when annealed at 800°C. Longer term annealing at 800°C results in a phase inversion into a continuous BCC matrix with discrete B2 precipitates. However, these B2 precipitates appear to be a metastable transition phase which eventually transform to an hP18 ordered phase which is a derivative of the ordered ω type structure. This transformation occurs via collapse of the {111} type planes of the parent B2 structure, a phenomenon well reported in other BCC-based alloy systems such as Zr-Al-Nb and Ti-Al-Nb. Here, the compositional and structural changes associated with this transformation, have been characterized using detailed TEM and APT based techniques.
8:50 AM Invited
Slip Localization in the Refractory High Entropy Alloy HfNbTaTiZr at Room Temperature: Marie Charpagne1; J.C. Stinville1; Fulin Wang2; Tresa Pollock3; 1University of Illinois; 2Jiaotong University; 3University of California Santa Barbara
High-resolution digital image correlation is coupled to electron back-scattered diffraction to probe the strain localization behavior of the HfNbTaTiZr refractory high entropy alloy, at room temperature, during monotonic tensile deformation. Slip activity is studied quantitatively, on a large representative region encompassing a variety of crystallographic orientations, in a statistical manner. Two populations of grains are identified regarding how strain localizes in their interior: a vast majority of the grains exhibit a high density of apparently straight slip bands of low intensity, while the remaining grains show few but very intense and wavy slip bands. This behavior is discussed in regards to dislocation glide and cross-slip processes.
9:10 AM Invited
Microstructure and Mechanical Properties of Medium-entropy Alloys with High-density Nano Precipitates: Che-Wei Tsai1; Hung-Chih Liu1; Pai-Keng Shen1; Jein-Wei Yeh1; Cheng-Yao Huang1; Hung-Wei Yen1; 1National Tsing Hua University, Department of Materials Science and Engineering,
Medium-entropy alloys (MEAs) have attracted considerable research attention because of their excellent mechanical properties. In these, the γ' phase has been utilized as a strengthening phase. However, the η phase has not been widely investigated. Herein, we explain the precipitation behavior of the η phase in a nonequimolar CoCrNiTi MEA. The MEA adopts a face-centered cubic (FCC) matrix upon η phase precipitation. Various characterization techniques were used to analyze the microstructure, phase structure, and phase composition of the as-preparedMEA. The FCC-η interface exhibited semi-coherence. This work facilitates a novel approach to ultrahigh-strength alloy production.
9:30 AM
Electron Diffraction-based Studies of Ordering and Mechanical Behavior in FCC and BCC Multi-principal Element Alloys: Daniel Foley1; David Beaudry1; Elaf Anber1; Yevgeny Rakita Shlafstein1; Partha Das2; Simon Billinge3; Andrew Matejunas4; Carolina Frey5; Leslie Lamberson4; Tresa Pollock5; Irene Beyerlein5; Garritt Tucker4; Chris Weinberger6; Mitra Taheri1; 1Johns Hopkins University; 2NanoMEGAS SPRL; 3Columbia University; 4Colorado School of Mines; 5University of California, Santa Barbara; 6Colorado State University
Multi-principle element alloys (MPEAs), and specifically single-phase high entropy alloys (HEAs), offer a unique framework to study fundamental processes of deformation in metallic materials such as dislocation slip and mechanical twinning. Owing to their chemical and structural disorder, the energetic landscape for deformation substructure formation is more complex when compared to conventional alloys. This can lead to different modes microstructural evolution and result in improved mechanical properties. Furthermore, the potential for the existence of short-range order (SRO) in these alloys may further modulate deformation energetics, which would enable tunability and order-based material design. The present work utilizes various electron diffraction-based methods to characterize both the presence of SRO after thermal treatment and the microstructural evolution due to quasistatic and dynamic compression.
9:50 AM Break
10:10 AM
Characterization of High-entropy Titanate Pyrochlore Oxide Single Crystals: Candice Kinsler-Fedon1; Lauren Nuckols1; Anamul Haq Mir2; David Mandrus1; Yanwen Zhang1; William Weber1; Veerle Keppens1; 1The University of Tennessee, Knoxville; 2University of Huddersfield
Research on multi-principal element materials has expanded exponentially to include compounds with various structures and properties with the promise of discovering unique property combinations and advanced applications. The area of compositionally complex ceramics, otherwise known as high entropy oxides, is a particular subset of this research that is showing continuous growth in the number of possible compositions that can be synthesized and characterized. High entropy pyrochlore oxides have recently gained recognition for their low thermal conductivity and tunable mechanical capabilities, but further investigation of their properties compared to standard pyrochlores is still warranted. Our group has successfully grown and characterized large, bulk single crystals of high entropy titanate pyrochlore oxides to determine their mechanical and radiation resistant properties. Resonant ultrasound spectroscopy, Raman spectroscopy, electron microscopy and ion-channeling have been employed in this study. The results obtained on these multi-component pyrochlores are compared to those of their single-component counterparts.
10:30 AM
Size Effects in a Dual Phase High Entropy Alloy: Junaid Ahmed1; Matthew Daly1; 1UIC
Reports of transformation-induced plasticity in FeMnCoCr-based high entropy alloys have generated great interest within the materials science community. As a duplex microstructure, many important mechanical properties can be traced back to size effects in the parent austenite phase and the morphology of martensitic laths. Here, we use high temperature annealing to explore the microstructure evolution and associated changes in size effects in a Fe50Mn30Co10Cr10 TRIP alloy. Post-heat treatment characterization revealed an anticipated increase in the austenite FCC grain size, combined with an increase in the HCP martensite phase fraction and decrease in lath spacing. Interestingly, mechanical testing showed an insensitivity in the yield strength to parent FCC grain growth. Our interpretation is that grain-growth induced weakening is counterbalanced by strengthening from the reduction in martensite lath spacing. In this regard, this alloy shows a remarkable resiliency to grain growth, which may be leveraged for applications in extreme temperatures.
10:50 AM
A High-throughput Investigation of Microstructure-property Relationships in NbVZr: Katharine Padilla1; Mu Li1; Zhaohan Zhang1; Rohan Mishra1; Katharine Flores1; 1Washington University in St. Louis
Many studies of refractory complex concentrated alloys (RCCA) focus on identifying equiatomic, single-phase solid solution alloys with high ductility and other favorable mechanical properties. However, multiphase alloys offer an additional degree of design flexibility and the potential for superior performance. In this work, we apply a high-throughput synthesis technique to investigate the microstructure-mechanical property relationship in equiatomic NbVZr as a model RCCA. We use direct laser deposition to rapidly synthesize microstructural libraries under a wide range of heating and cooling rates. BCC dendrites are observed separated by two Laves phases, cubic C15 and hexagonal C14, which grow finer with decreasing heat input. Dendrite size, spacing, and morphology are correlated with the laser power and travel speed. Nanoindentation experiments are performed to investigate the relationship between microstructure and mechanical properties at temperatures up to 600 C.