Advances in Multi-Principal Element Alloys II: Structures and Characterization
Sponsored by: TMS Structural Materials Division, TMS Functional Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Alloy Phases Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Yang Ming Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; James Brechtl, Oak Ridge National Laboratory; Gongyao Wang, Globus Medical
Tuesday 8:00 AM
March 21, 2023
Room: Aqua D
Location: Hilton
Session Chair: Tirumalai Srivatsan, The University of Akron; Mitra Taheri, Johns Hopkins University
8:00 AM Invited
Chemical Short-range Order in Multi-principal Element Alloys: Takeshi Egami1; 1University of Tennessee
Multi-principal element alloys (MPAs) are single-phase solid-solutions. But elements are not randomly distributed, forming chemical short-range order (CSRO) which affects various properties including mechanical strength. CSRO is driven mainly by charge-transfer among elements. It is not easy to observe the CSRO because usually constituent elements are close to each other in the atomic number, and their x-ray contrasts are weak. We use x-ray resonance to enhance the x-ray contrast to observe the CSRO. Near the x-ray absorption edge of the element the scattering factor depends strongly on the energy of the incident x-ray due to the x-ray resonance with the core states, providing the information on the structure around a specific element through the variation of the scattering intensity with the energy of the incident x-ray. We show CRSO exists for MPAs of 3d elements, which depends on composition and thermal history. This work was supported by the NSF.
8:20 AM Invited
Role of Local Chemical Order on Phase Stability and Passivation in High Entropy Alloys: Elaf Anber1; Debashish Sur2; Daniel Foley1; Diana Farkas3; Peter Liaw4; John Scully2; Mitra Taheri1; 1Johns Hopkins University; 2University of Virginia; 3Virginia Tech; 4 university of tennessee
High entropy alloys (HEAs) have attracted the major interest due to their novel mechanical and structural properties. Local chemical ordering (LCO) plays an important role in determining thermal and electrical conductivity of solid solutions, diffusion, and passivity of alloys. Here, we examined the role of LCO on orientation relationship (ORs) of BCC precipitates in Al0.3CoCrFeNi via using in-situ and ex-situ TEM heating techniques, where we report a new BCC-ORs due to local chemicalfluctuations. Furthermore, the effect of short-range order (SRO) on alloy passivation will be presented, and the influence of the new BCC-ORs and microstructure changes on the corrosion resistance of HEA will be discussed. These studies were coupled with Extended Electron Energy Loss Fine Structure (EXELFS) and Energy-dispersive X-ray spectroscopy (EDS). Additional insight is obtained from molecular dynamics atomistic simulations that examine the various possible ORs and interface dislocations for the B2 precipitates in these Al containing HEA’s.
8:40 AM Invited
Uncovering Unique Multi-Principal Element Alloy Properties Using Atom Probe Tomography: Jonathan Poplawsky1; Ying Yang1; Xing Wang2; Rui Feng1; 1Oak Ridge National Laboratory; 2Penn State University
Multi-principal element alloys (MPEAs) have become increasingly popular because of improvements in mechanical properties and radiation resistance compared to traditional alloys, which is due to unique microstructures, lattice modification, etc. The microstructures and material properties can be tweaked by the alloy composition, fabrication route (i.e. additive manufacturing, casting, etc.), and processing conditions. For example, an Fe-Ni-Al-Ti medium entropy alloy (MEA) has exceptional strength, work hardening, and ductility due to a unique L12 precipitate structure and matrix composition that allows for austenite retention during quenching that transforms into martensite during plastic deformation. Atom probe tomography (APT) was vital for determining the necessary precipitate sizes and matrix composition needed for this unique physical property. The importance of APT data for the development and characterization of MPEAs will be highlighted with this example along with others. APT was conducted at ORNL's CNMS, which is a U.S. DOE Office of Science User Facility.
9:00 AM Invited
Study of Microstructural Evolution of Two Magnesium-based Multi-element High Entropy Alloys: Srivatsan Tirumalai1; Khin Tun1; Manoj Gupta1; 1The University of Akron
In this presentation, the results of a recent study on two light weight multi-component high entropy alloys (HEAs) were synthesized and consisted of six constituent elements. The high entropy alloy having a chemical composition of Mg35Al33Li15Zn7Ca5Y5 (atomic percent.) had a density of 2.25 g/cm3, while the high entropy alloy having a chemical composition of Mg35Al33Li15Zn7Ca5Cu5 (atomic percent) had a density of 2.27 g/cm3. The conjoint and mutually interactive influences of non-equiatomic composition, high entropy of mixing and low density was applied to designing the alloy systems. The technique of disintegrated melt deposition (DMD) was used to synthesize the two alloys followed by characterization studies of the as-synthesized alloys. This presentation will examine microstructural development of the two light weight high entropy alloys. The formation and presence of phases and gradual evolution of microstructure was studied by interchanging yttrium and copper. Microstructural observations and microhardness test results will be highlighted.
9:20 AM Invited
Microstructural Evolution and Deformation Mechanisms in Compositionally Complex Alloys: Zachary Kloenne1; Jean-Philippe Couzinié2; Gopal Viswanathan1; William Clark1; Yunzhi Wang1; Hamish Fraser1; 1Ohio State University; 2Univ. Paris Est Creteil, CNRS
Compositionally complex alloys (CCA) have been the subject of considerable study in the recent past. Often, they consist of two or more phases such that refractory versions of the alloys would be expected to exhibit useful creep performance. Here, the alloy AlMo0.5NbTa0.5TiZr has been studied. The microstructure of this alloy after an anneal at 1400°C for 24 hours followed by furnace cooling to room temperature consists of a mixture of two phases, one being a bcc solid solution and the other a B2 intermetallic compound, where the interfaces are essentially coherent. Following aging at 1000°C there is a loss of coherency such that an array of misfit dislocations with b=1/2<111> are present to accommodate the misfit between the two phases. The first part of this talk details the characterization of these interfaces. The second part of the talk presents a determination of the deformation mechanisms operative in this CCA.
9:40 AM Break
10:00 AM Invited
Structure-induced Local Lattice Distortions in a Refractory High-entropy Alloy: Jian Min Zuo1; Haw-Wen Hsiao1; 1University of Illinois
The phase stability of group IV elements (Ti, Zr, and Hf) containing alloys depends sensitively on composition, temperature, and pressure. This sensitivity has been taken to great advantages in tuning a wide variety of properties in titanium alloys to suit applications. Here, using advanced transmission electron microscopy, we examine the interplay between the nanoscale compositional fluctuations and locally varying bcc dynamical instabilities and the formation of structure-induced local lattice distortions at low temperatures, which together with possible chemical short-range ordering (CSRO), are possibly behind the strength and ductility observed in some of refractory high entropy alloys (RHEAs) and brittleness in others. The RHEA we examine here is TaNbHfZrTi. Using scanning electron nanodiffraction, we examine the fluctuations in electron diffuse scattering and determine local lattice distortions. The results reveal characteristic distortional patterns that suggest structural instabilities commonly observed in Ti alloys.
10:20 AM Invited
Powder Properties Characterization of Al0.1CoCrFeNi High-Entropy Alloy Fabricated by Gas Atomization Process: Sung-Jae Jo1; Min-Woo Shin1; Ji-Woon Lee1; Kwangtae Son2; Andy Fan2; Baldur Steingrimsson3; Peter Liaw4; Soon-Jik Hong1; 1Kongju National University(CAMP2); 2Oregon State University; 3Imagars LLC, ; 4University of Tennessee
Al0.1CoCrFeNi alloy is an attractive high-entropy alloy (HEA) with its excellent corrosion resistance and attractive mechanical properties. As the mass-production process of this HEA has not been established yet, low-volume and high-valued processes, e.g., laser powder bed fusion (LPBF), are preferred to produce Al0.1CoCrFeNi products. In an effort to produce high-quality Al0.1CoCrFeNi powders for LPBF, the gas-atomization method was used under argon (or nitrogen) atmosphere. The powder characteristics fabricated by gas atomization are carefully investigated in this study. A powder size determinator was used to assess the powder size distribution, and the powder morphology was characterized, using scanning electron microscope (SEM). Additional compositional analyses employing energy-dispersive x-ray spectroscopy, oxygen/nitrogen determinator were conducted to detect unfavorable impurities like oxygen or to check the composition homogeneity of powders.
10:40 AM Invited
Defect Detection and Characterization of Additively Manufactured Al0.1CoCrFeNi High Entropy Alloy: Kwangtae Son1; Andy Fan1; Baldur Steingrimsson2; Peter Liaw3; Soon-Jik Hong4; Ji-Woon Lee4; 1Oregon State University; 2Imagars LLC; 3University of Tennessee, Knoxville; 4Kongju National University
Laser powder bed fusion (LPBF) has been investigated in both industrial and academic areas due to its potential to process poor-machinability alloys, such as Al0.1CoCrFeNi high entropy alloy (HEA). One important requisite for LPBF processing of a new alloy like Al0.1CoCrFeNi is to optimize the LPBF process parameters to reduce defect formation. As a fundamental approach to parameter optimization, in-situ monitoring of the Al0.1CoCrFeNi process was conducted, using a multi-sensor system consisting of an infrared camera, acoustic sensor, and spectrometer. Those obtained in-situ sensor data were correlated with the ground truth information from the computational tomography (CT) data. The comparison of sensor data to the ground truth information helped realize the direct defect detection from in-situ sensor signals. Artificial intelligence/machine learning-based software tools are being developed to improve the reliability of the defect identification from sensor data, which is based on the ground truth information of CT data.
11:00 AM
Characterizing Deformation Mechanisms in BCC/B2 Refractory Multi-principal Element Alloys via a Model BCC/B2 Alloy in the Fe-Al-Ni System: Bryan Crossman1; Milan Heczko1; Veronika Mazanova1; Junxin Wang1; Julian Brodie1; Loic Perriere2; Jean-Philippe Couzinie2; Michael Mills1; Maryam Ghazisaeidi1; 1The Ohio State University; 2Institute of Chemistry and Materials Science (ICMPE)
Refractory multi-principal element alloys (RMPEAs) with BCC/B2 phase microstructures are a promising field of study with microstructure akin to γ/γ’ Ni-based super alloys while maintaining strength at higher temperatures. Despite their promise, the deformation mechanisms of BCC/B2 RMPEAs are only just beginning to be characterized, as seen in recent work on Al0.5NbTa0.8Ti0.5 V0.2Zr [1]. In this work, the deformation mechanisms and microstructural evolution of a model BCC/B2 alloy in the Fe-Al-Ni system are characterized via diffraction contrast and high-resolution STEM techniques. The BCC/B2 Fe-Al-Ni system’s microstructure is highly tailorable, which is an ideal characteristic for analysis of dislocation transmission between BCC and B2 phases. The obtained results for this Fe-Al-Ni model system are then compared to existing BCC/B2 RMPEAs [1] assisting in their optimization and future development. [1] Couzinie, Heczko, Mazanova, et al. "High-temperature deformation mechanisms in a BCC+B2 refractory complex concentrated alloy." Acta Materialia 233 (2022).
11:20 AM Invited
Lattice Distortion and Phase Transitions in AlxCoCrFeNi HEAs under Pressure: Qiaoshi Zeng1; 1Hpstar
Polymorphism and polymorphic transitions are attracting considerable interest due to their significant effects on phase stability, switchable properties, and the atomic rearrangement mechanism in materials. Here, by employing in situ high-pressure synchrotron x-ray diffraction in a diamond anvil cell, we reveal rich polymorphic transitions in the AlxCoCrFeNi high-entropy alloy (HEA) up to tens of GPa during compression and decompression. Much severe lattice distortion has developed under high pressure in the original body-centered cubic (bcc) phase compared to the initial face-centered cubic phase (fcc) phase. Lattice distortion affects the transition pressure, transition path, reversibility, stability at ambient conditions, etc. Our results demonstrate that the complex chemistry and the pressure-tuned lattice distortion may play a key role in introducing and stabilizing the rich polymorphs in the HEA, which could be a tuning knob to develop HEAs with novel structures and properties.