High Entropy Alloys V: Poster Session
Sponsored by: TMS Structural Materials Division, TMS Functional 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; Suveen Nigel Mathaudhu, University of California Riverside; Xie Xie, The University of Tennessee, Knoxville; Gongyao Wang, Alcoa Technical Center; E-Wen Huang, National Chiao Tung University
Tuesday 6:00 PM
February 28, 2017
Room: Hall B1
Location: San Diego Convention Ctr
L-86: Annealing Twin Evolution and Grain Boundary Engineering during Recrystallization in CoCrFeNiMn High Entropy Alloys: Christopher Barr1; Elaf Anber1; J. Liu2; Yong Zhang2; Mitra Taheri1; 1Drexel University; 2University of Science and Technology Beijing
The increase in twin and twin-related grain boundaries associated with grain boundary engineering in low stacking fault energy multi-principal element alloys such as CoCrFeNiMn provides a new avenue to tailor the microstructure and grain boundary network. In this study, we explore the goal of finding a repeatable thermomechanical processing route to obtain a traditional GBE microstructure in a fcc stabilized high entropy alloy. Low, medium, and high strain regimes are explored to find the ideal processing route while a discussion is provided into proposed mechanisms of twin formation and twin evolution in the CoCrFeNiMn system. The results indicate that low strain, near the threshold for primary recrystallization, followed by high temperature annealing create large twin-related domains with twin related grain boundary length fractions in excess of 70%. The implications of grain boundary engineered CoCrFeNiMn is discussed in the context of new avenues for improvements of multi-principal elements in extreme environments.
L-87: Atomic-scale Homogenization in an fcc-based High-entropy Alloy via Severe Plastic Deformation: Hao Yuan1; Ming-Hung Tsai2; Gang Sha1; Fan Liu1; Zenji Horita3; Yuntian Zhu4; Jing Tao Wang1; 1Nanjing University of Science and Technology; 2Nantional Chung Hsing University; 3Kyushu University; 4North Carolina State University
The atomic-scale homogenization of a face-centered-cubic-based high-entropy alloy (HEA), Al0.3Cu0.5CoCrFeNi, using severe plastic deformation (SPD) is reported. Atom probe tomography revealed that water quenching from high temperature cannot produce a homogeneous single phase, and clustering of Cu, Al and Ni still exists. Subsequent processing by high-pressure torsion produced nanostructured non-equilibrium single phase with homogeneous elemental distribution at atomic scale. Importantly, such a non-equilibrium single phase is stable at room temperature due to the sluggish diffusion kinetics. These observations suggest that SPD is an effective approach for producing single-phase HEAs for fundamental studies and applications.
L-88: Construction of Pseudo Binary Phase Diagram in FeCoCrNi-Cu High Entropy Alloy System: Kook Noh Yoon1; Khurram Yaqoob2; Je In Lee1; Jin Yeon Kim1; Eun Soo Park1; 1Research Institute of Advanced Materials, Department of Materials Science and Engineering, Seoul National University; 2School of Chemical and Materials Engineering, National University of Sciences and Technology
One of the biggest drawbacks to study on high entropy alloy (HEA) is an absence of precise information on their phase transformation. That is because it is hard not only to expect the exact phase diagram with existing calculation techniques, but also to understand the phase transformation route owing to its complexity of structure. In the present study, we will experimentally draw pseudo binary phase diagram in phase separating FeCoCrNi-Cu high entropy alloy system. In this system, copper will be separated due to its positive ∆H_mix value with other elements. And we carefully figure out the information which is needed to determine the phase diagrams such as invariant reaction compositions, phase transformation temperatures and so on. Through these attempts, we present phase transformation behavior systematically through measuring pseudo-binary phase diagram in FeCoNiCr-Cu phase separating alloy system, which will make an important progress of one step forward in HEA research.
L-89: Hydrogen Effects on the Mechanical Behavior of CoCrFeMnNi High-entropy Alloy: Role of Pre-strain: Yakai Zhao1; Dong-Hyun Lee1; Jung-A Lee1; Jin-Yoo Suh2; Jae-il Jang1; 1Hanyang University; 2Korea Institute of Science and Technology
High-entropy alloys (HEAs) containing five or more elements in almost equal atomic proportions exhibit excellent properties such as high strength, large strain hardening capability, and high toughness, and are hence emerging as an exciting class of new structural materials. Among them, CoCrFeMnNi alloy with face-centered cubic structure is known to have the highest structural stability. To systematically study the effect of hydrogen on the mechanical behavior of HEA, which can be a crucial issue in industrial application of HEA but has not been well understood yet, several different levels of pre-strain were applied to the CoCrFeMnNi HEA to produce various microstructures with different crystalline defects. After hydrogen charging of the pre-strained alloys, subsequent nanoindentation tests and thermal desorption analyses were carried out. The results were analyzed in terms of microstructure changes, hydrogen solubility, and their influences on nanomechanical behavior.
L-90: Mechanical Properties of Entropy Stabilized Oxides: Tyler Harrington1; Matthew Quinn2; William Mellor2; Joshua Gild3; Jian Luo1; Kenneth Vecchio1; 1Department of NanoEngineering and Materials Science and Engineering Program, UC San Diego; 2Department of NanoEngineering, UC San Diego; 3Materials Science and Engineering Program, UC San Diego
The two bulk entropy stabilized oxides of composition (Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)O and (Co0.2Mg0.2Ni0.2Sc0.2Zn0.2)O were investigated to determine the effect of high configurational entropy on thermal and mechanical properties of oxide ceramics. This study focuses on the synthesis of complex oxide systems with a density greater than 95% demonstrating single-phase, solid-solution compounds, along with the mechanical and thermal properties of the multi-metal-component ceramics. Fully dense samples were fabricated through high-energy ball milling and spark plasma sintering at 1100°C and 50MPa. A hardness and compressive strength comparison between the five individual component oxides and the complex oxides was made to determine the role of entropic stabilization and further understanding of the processing-property-microstructure relationships of this new class of materials. Thermal testing was included to find any unique melting temperatures and thermal conductivity that differ between the individual constituents and the complex oxides.
L-91: Precipitation in High-entropy FeNiMnAlCr Alloy: Margaret Wu1; Zhangwei Wang1; Paul Munroe2; Ian Baker1; 1Dartmouth College; 2University of New South Wales
Upon casting, Fe40.4Ni11.3Mn34.8Al7.5Cr6 (at. %) with and without carbon additions up to 1.1 at. % are single-phase, f.c.c. high entropy alloys (HEAs), which can show high strengths, high elongations and high work-hardening rates. After long-term annealing at 973 K, the un-doped HEA exhibits rod-shaped precipitates, while the HEA doped with 1.1 at. % C shows two types of lenticular precipitates. The precipitation is accompanied by increases in hardness in both cases. Interestingly, precipitation is not observed above 1273 K. This presentation will outline the effects of carbon content and various heat treatments on the precipitation kinetics and its influence on the mechanical properties. This research was supported by the US Department of Energy, Office of Basic Energy Sciences grant DE-FG02-07ER46392.
L-92: The Fabrication and Oxidation Behavior of High-entropy Refractory Metal Carbides: Tyler Harrington1; Lavina Backman2; Joshua Gild3; Jian Luo1; Elizabeth Opila2; Kenneth Vecchio1; 1Department of NanoEngineering and Materials Science and Engineering Program, UC San Diego; 2Department of Materials Science and Engineering, University of Virginia; 3Materials Science and Engineering Program, UC San Diego
Bulk samples of high entropy carbides of the composition (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)C, (Hf0.2Nb0.2Ta0.2Ti0.2V0.2)C, and (Nb0.2Ta0.2Ti0.2V0.2W0.2)C were fabricated via high energy ball milling and spark plasma sintering. Further homogenization and greater than 95% theoretical density was achieved via heat treatment at 2500°C following sintering. Virtually single-phase, solid solutions were achieved as determined by EDS and XRD. Oxidation behavior of this new class of ultra-high temperature ceramics was tested using a box furnace for temperatures at or below 1500°C. Ultra-high temperature (T>1500°C) oxidation behavior was tested in controlled environments using a resistive heating apparatus. Oxidation kinetics were determined from the variation of weight and/or oxide thickness with time. Oxide composition and morphology were characterized using XRD, SEM, and EDS. This work serves to further the understanding of a new class high entropy ceramics that are intended to serve in ultra-high temperature applications where oxidation properties are of key importance.
L-93: The Role of Mass Scattering on Thermal Transport across Multiple Component Systems: Ashutosh Giri1; Jeffrey Braun1; Mina Lim2; Zsolt Rak2; Donald Brenner2; Patrick Hopkins2; 1University of Virginia; 2North Carolina State University
The role of mass scattering on thermal conductivity in multiple component systems is investigated via nonequilibrium molecular dynamics (NEMD) simulations. The Lennard-Jones (LJ) potential is used to describe the interatomic interactions, where the different species only vary in mass. The model systems are useful to get general physical properties of multi-component systems but do not give insight into material specific properties. We also use NEMD simulations to compare the thermal boundary conductance across an ordered LJ-alloy/homogeneous LJ-based crystal interface to that across a disordered LJ-based alloy/homogeneous LJ-based crystal to gain insight into the role of disorder in thermal conductance across an alloy/homogeneous crystal interfaces.
L-94: Microstructure and Properties of the VNbMoTaW High Entropy Alloy Prepared Powder Metallurgy: Jong Hwa Lim1; Ki Buem Kim2; Jin Kyu Lee3; 1Kongju National University; 2Sejong University; 3Kongju National University
High entropy alloys have been reported to form in many alloys systems with nearly equiatomic ratios and exhibits high temperature strength, excellent wear resistance, high thermal stability and outstanding oxidation resistance. Therefore high entropy alloys are suitable for a wide range of engineering applications. Combination of mechanical alloying(MA) and spark plasma sintering(SPS) has been developed to prepare bulk high entropy alloys, which is a promising method to obtain high performance bulk high entropy alloys. In the study, we report the microstructure and properties of the VNbMoTaW high entropy alloy prepared powder metallurgy. The MA process was carried out using planetary high-energy ball mill and the as-milled powders were consolidated by SPS process. Structural characterization was performed using X-ray diffractometry(XRD) and scanning electron microscopy(SEM) with energy dispersive spectometry(EDS). Compressive properties were measured at room temperature with a strain rate of 1x10-4s-1.
L-95: A Combinatorial Assessment of AlxCrCuFeNi2 (0 < x < 1.5) Complex Concentrated Alloys: Microstructure, Microhardness, and Magnetic Properties: Bharat Gwalani1; Tushar Borkar1; Deep Choudhuri1; Rajarshi Banerjee1; 1University of North Texas Denton
A novel combinatorial approach for assessing composition-microstructure-microhardness-magnetic property relationships, using laser deposited compositionally graded AlxCrCuFeNi2 (0<x<1.5) complex concentrated alloys as a candidate system is studied. The composition gradient has been achieved from CrCuFeNi2 to Al1.5CrCuFeNi2 over a length of ∼25mm, deposited using the laser engineered net shaping process from a blend of elemental powders. With increasing Al content, there was a gradual change from a fcc-based microstructure (including ordered L12 phase) to a bcc-based microstructure (including the ordered B2 phase), accompanied with an increase in microhardness. Interestingly, with increasing paramagnetic Al content, saturation magnetization as-well-as coercivity increases and reaches a maximum value when x = 1.3, indicating the tunability of magnetic properties by a paramagnetic element in this system. Such graded alloys are highly attractive candidates for investigating the influence of systematic compositional changes on microstructural evolution and concurrent physical and mechanical properties in high entropy alloys.
L-96: An Assessment of the Lattice Strain in the CrMnFeCoNi High-Entropy Alloy: Lewis Owen1; Ed Pickering2; Helen Playford3; Howard Stone1; Matthew Tucker4; Nicholas Jones1; 1University of Cambridge; 2University of Manchester; 3STFC ISIS Facility; 4Spallation Neutron Source
The formation of single-phase solid solutions from equiatomic combinations of multiple elements, with differing atomic radii, has led to the suggestion that the lattices of high-entropy alloys (HEAs) must be severely distorted. Whilst a lattice of this type might be considered thermodynamically unstable, it is argued that the high configurational entropy of these systems is sufficient to allow such distortions to exist. Significant solid solution strengthening is believed to be derived from these strained lattices, but experimental studies have yet to verify these hypotheses. In this study, neutron total scattering and pair distribution function (PDF) analysis have been used to assess the level of local lattice strains in the exemplar HEA CrMnFeCoNi. The results are compared with similar data from five compositionally simpler materials within the same system to determine whether the HEA lattice can be considered to contain anomalously high levels of local distortion.
L-97: Deformation Behavior and Solid Solution Hardening of Al-containing Refractory High-entropy Alloys: Hans Chen1; Alexander Kauffmann1; Bronislava Gorr2; Daniel Schliephake1; Christoph Seemüller1; Julia Wagner3; Hans-Jürgen Christ2; Martin Heilmaier1; 1Karlsruhe Institute of Technology (KIT); 2University of Siegen; 3University of Stuttgart
High temperature structural materials have to provide good oxidation behavior, a high melting point and outstanding specific mechanical properties. Al-containing refractory high-entropy alloys may fulfill these requirements. The high-melting refractory metals Nb and Mo, the passivating metals Cr, Ti and Al as well as the low density of the last two elements perfectly meet the needs. Hence, we present the microstructural and mechanical characterization of the equiatomic alloy Nb-Mo-Cr-Ti-Al. A quasi-homogeneous microstructure was achieved by arc-melting and subsequent homogenization at 1300 °C for 20 h. Mechanical properties at high temperatures were obtained by compression tests at 800 °C-1200 °C. The altering of the microstructure during deformation was investigated by SEM and EBSD, which aid to reveal the underlying deformation mechanism. In addition, the impact of the number of elements and changing atomic size differences on the deformation behavior is compared to quaternary and senary alloys such as Mo-Cr-Ti-Al or Zr-Nb-Mo-Cr-Ti-Al.
L-98: Development of Lightweight High Entropy Alloys using a CALPHAD Approach: Xuejun Huang1; Weihua Sun1; Alan Luo1; 1The Ohio State University
Lightweight high entropy alloys were designed based on CALPHAD (CALculation of PHAse Diagrams) calculations and prepared using melting and casting method. XRD (X-Ray Diffraction) and SEM/EDS (Scanning Electron Microscope/Energy Dispersive X-ray Spectroscopy) were used to characterize the as-cast microstructures. Heat treatment schedule was developed based on CALPHAD modeling results. The observed microstructures were used to validate the CALPHAD calculations. It is demonstrated that the CALPHAD approach is an effective way in developing lightweight high entropy alloys.
L-101: Exploring the Effects of Grain Refinement in Non-equiatomic High Entropy Alloys: Benjamin MacDonald1; Zhiqiang Fu1; Baolong Zheng1; Weiping Chen2; Julia Ivanisenko3; Yizhang Zhou1; Horst Hahn3; Enrique Lavernia1; 1University of California Irvine; 2South China University of Technology; 3Karlsruhe Institute of Technology
The underlying phenomena governing mechanical behavior and thermal stability in nanostructured high entropy alloys (HEAs) was studied within a non-equiatomic composition of FeNiCoCuMn. The HEA was first synthesized via ingot casting and then fully homogenized through subsequent heat treatments to produce a coarse grain microstructure with a single face centered cubic phase, which was confirmed by x-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Baseline mechanical behavior and thermal stability in the coarse-grained FeNiCoCuMn HEA were examined through tensile tests and differential scanning calorimetry, respectively. Severe plastic deformation was utilized as a secondary processing route to achieve significant grain refinement in the homogenized non-equiatomic FeNiCoCuMn HEA. Assessments of the thermal stability and microstructure evolution of these nanostructured samples, specifically grain size, phase formation, and dislocation density, are used to explain the mechanical behavior at ambient and elevated temperatures.
L-102: High Throughput Exploration of High Entropy Alloys for High Temperature and Nuclear Applications via Diffusion Multiples: Owais Waseem1; Soon Hyung Hong1; Ho Jin Ryu1; 1Korea Advanced Institute of Science and Technology
Conventional one-alloy-at-a-time approach consumes hundreds of alloy samples prior to the possible discovery of a candidate alloy with useful properties. In order to carry out high throughput exploration, diffusion multiple approach is being utilized, in which an alloy sample having diversified compositions is developed and screened for trends in desired engineering characteristic. In present research work, diffusion multiple approach has been utilized to explore the potential of various high entropy alloy compositions having W, Ta, Ti, V and Cr. Diffusion multiple samples with compositional gradients have been successfully produced by sintering multiple layers of unary and multi-component powder mixtures together. Microstructures of the diffusion layers have been analyzed by scanning electron microscope (SEM). Characterization of compositional gradient has been carried out by electron dispersive spectroscopy (EDS). The potential HEA compositions for high temperature and nuclear applications have been explored by screening hardness of the diffusion couples under micro-Vickers hardness tester.
L-103: Liquid Phase Separation in Equiatomic High-entropy Alloys Containing Copper: Nicholas Derimow1; Abraham Munitz2; Reza Abbaschian1; 1University of California, Riverside; 2Nuclear Research Center-Negev
Since the discovery of high-entropy alloys, the mechanism for single phase formation still remains to be completely understood. In this presentation, we report on our recent investigation to understand the role Cu plays in the liquid phase separation (LPS) in the CoCrCu, CoCrCuFe, and CoCrCuFeV HEA systems. The LPS of the arc-melted samples were investigated using electromagnetic levitation melting (EML) and rapid solidification techniques. EML allows for observation of solidification in a containerless environment, as well as probe the LPS at different undercoolings. The microstructures of arc-melted and EML solidified samples were investigated using SEM and EDX to elucidate the effect of Cu on liquid phase separation. The HEA samples underwent a melt separation into Cu-rich and Cu-lean liquids. Secondary melt separation was also observed as spheres of the Cu-rich and Cu-lean liquids present in the other’s primary melt separation.
L-104: Microstructural Investigations of a Nanocrystalline TiZrHfNbTa High-entropy Alloy: Benjamin Schuh1; Jean-Philippe Couzinié2; Verena Maier-Kiener1; Bernhard Völker1; Anton Hohenwarter1; 1Montanuniversität Leoben; 2CNRS & Université Paris-Est
An equiatomic TiZrHfNbTa high-entropy alloy was subjected to severe plastic deformation using high-pressure torsion, leading to a substantial refinement of the microstructure and a grain size well below 100 nm. Isochronal heat treatments performed for 1 hour resulted in a significant hardness increase from approximately 420 HV1 for the as-processed state to ~ 530 HV1 for an annealing temperature of 500°C, while for higher temperatures the hardness starts to decrease due to the onset of grain growth. In order to clarify this unexpected annealing response comprehensive analysis of selected microstructural states was performed utilizing electron microscopy as well as mechanical testing such as nanoindentation and compression testing to gain further information on microstructure-property relationships. The changes in mechanical properties could be related to the formation of new phases during low temperature annealing, therefore the obtained results give new valuable insights into the phase-stability of the TiZrHfNbTa high-entropy alloy.
L-105: Positron Annihilation Study on Equiatomic Multicomponent Alloys: Shuhei Yoshida1; Tilak Bhattacharjee1; Yu Bai1; Kazuki Sugita2; Masataka Mizuno2; Hideki Araki2; Nobuhiro Tsuji3; 1Kyoto University; 2Osaka University; 3Kyoto University / Elements Strategy Initiative for Structural Materials (ESISM)
A novel design concept called high entropy alloys (HEAs) has been getting attention owing to their superior properties such as high strength, high ductility, high corrosion resistance, etc. However, recently, some reports questioning the role of “high entropy” have been published, which indicate that the origin of the outstanding properties is still unclear. In this study, we focus on vacancy diffusion in equiatomic multicomponent alloys. Various kinds of FCC single phase equiatomic multicomponent alloys composed of Co, Cr, Fe, Ni, Mn (e.g., FeNi, CoFeNi, CoCrFeNi, etc.) were fabricated by using vacuum arc-melting furnace. The formation energy and migration energy of vacancies were determined using positron annihilation spectroscopy as a vacancy probe. The contribution of entropy and enthalpy to the properties of CoCrFeNiMn HEA and its subsystems will be discussed to understand the essential characteristics of equiatomic multicomponent alloys from a viewpoint of point defects.
L-107: Structural and Mechanical Characterization of Refractory High Entropy Alloys: Boliang Zhang1; Yang Mu2; Yi Zhang2; Bin Zhang2; Wen Jin Meng2; Shengmin Guo2; 1Louisiana State University ; 2Louisiana State University
Refractory high entropy alloys (HEAs) promise high strength and ductility, due to atomic misfits of the solid solution phases. In refractory HEAs, compositional segregation often exists in different BCC structured grains at the micron scale. To understand their mechanical behaviors, the structure and mechanical properties of several refractory HEA systems with BCC structures are investigated by XRD, TEM, and in-SEM instrumented nanoindentation. The HEA systems examined include MoNbTaVW, CrMoNbTaVW and TiMoNbTaVW. Site-specific indentation experiments are carried out on both the dendritic and inter-dendritic grains, both with BCC structures and very similar lattice parameters, but severe compositional segregation. Strain rate effects are explored. The current study offers new data and provides insights into the structure-property relationships for refractory HEAs.
L-108: Synthesis of High-entropy Metal Diborides and Fluorite Oxides: Joshua Gild1; Yuanyao Zhang1; Tyler Harrington1; Kenneth Vecchio1; Jian Luo1; 1University of California, San Diego
Several equimolar, five-component, metal diborides were fabricated via high-energy ball milling and spark plasma sintering. The majority of them possess virtually one solid-solution boride phase of hexagonal AlB2 structure, while a few of compositions also have minor secondary boride phases. Revised Hume-Rothery size-difference factors are proposed and used to rationalize the formation of high-entropy solid solutions in metal diborides. Greater than 92% of the theoretical densities have been generally achieved with largely uniform compositions (albeit some Nb clustering in selected specimens) with simple spark plasma sintering at 2000 ˚C for 5 minutes. Further studies have been conducted to use sintering aids to improve the densities and prolonged annealing at high temperature to further homogenize the specimens. More recently, high-entropy oxides of the cubic fluorite structure have also been synthesized and characterized. These materials represent new classes of ultra-high temperature ceramics as well as new types of high-entropy materials.
L-109: Thermal Properties of Entropy Stabilized Oxides: Jeffrey Braun1; Ashutosh Giri1; Zsolt Rak2; Mina Lim2; Christina Rost2; John-Paul Maria2; Donald Brenner2; Patrick Hopkins1; 1University of Virginia; 2North Carolina State University
High-entropy alloys (HEAs) have been demonstrated to exhibit exceptional mechanical properties and thermal stability. The emergence of five-component oxides containing high configurational entropy, created by populating a single sublattice with many distinct cations, promises to extend such properties to oxide based systems. In these novel materials, thermal characterization is essential for understanding and predicting performance at elevated temperatures. Moreover, these systems provide a unique opportunity to study the nature of thermal transport and phonon scattering in multicomponent high-entropy materials. In this study, we experimentally investigate the thermal conductivity and heat capacity of thin-film 5- and 6-component oxides using time- and frequency-domain thermoreflectance to reveal a strong reduction in thermal conductivity with inclusion of more components. Finally, we compare experimental results to analytical and computational results to understand the phonon scattering mechanisms driving these findings.
L-110: Thermodynamic Approach for Designing New FCC High Entropy Alloy: Won-Mi Choi1; Seungmun Jung1; Yong Hee Jo1; Sunghak Lee1; Byeong-Joo Lee1; 1POSTECH
High-entropy alloys (HEAs) are multi-component single-phase alloys. Many studies have been carried out to develop new HEAs with superior mechanical properties in cryogenic conditions. CALPHAD approach allows to calculate multicomponent phase diagrams by using thermodynamic properties of their sub-systems. Therefore, it can be an efficient way to develop a new HEA system within a compositional range. In the present study, HEA constitution map demonstrating compositional range where single solid solution exists is developed. New fcc HEAs are developed with this constitution map. They have similar or better cryogenic mechanical properties compared with well-known Cantor alloy. This constitution map can be used for another new HEA alloy design.
L-111: Thermomechanical and Nanoindentation Study of High Entropy Alloys Derived from Equilibrium Solidification: Artashes Ter-Isahakyan1; John Balk1; 1University of Kentucky
Equilibrium solidification of an equiatomic CrMnFeCoNiCu alloy resulted in a composite material containing Cr-rich needle precipitates in a Cr-poor single-phase high entropy alloy matrix. Mn 17 Fe 22 Co 24 Ni 24 Cu 13 and Cr 11 Mn 16 Fe 21 Co 21 Ni 19 Cu 12 compositions were identified from the matrix phase and were selected for arc melting of new alloys. Wedge-shaped samples were fabricated and cold rolled. Upon annealing, a microstructural gradient as a function of initial strain was produced, which allowed the annealing behavior of the alloys to be studied. Nanoindentation hardness measurements were taken along the gradient to evaluate mechanical properties with respect to recrystallized grain size. These results will be discussed in the context of size effects in mechanical behavior, and effects of rolling strain on recrystallization behavior and microstructural features of new grains.
L-113: Microstructures and Properties of As-Cast AlCrFeMnV, AlCrFeTiV, and AlCrMnTiV High Entropy Alloys: Prithvi Narayana1; Keith Knipling2; Lily Nguyen2; 1Thomas Jefferson High School for Science and Technology; 2U.S. Naval Research Laboratory
High-entropy alloys (HEAs) typically contain five or more principal elements in nearly equiatomic proportions. HEAs can be formed from a virtually limitless combination of elements, creating millions of possible alloy combinations. Using thermodynamic modelling, Senkov et al.  recently predicted the equilibrium phases and properties of thousands of three- four-, five- and six-component alloys. The present study tests these predictions by casting three equimolar AlCrFeMnV, AlCrFeTiV, and AlCrMnTiV alloys, which were chosen as potential replacements for titanium alloys due to their predicted increased elastic modulus for structural applications and use in potentially corrosive environments. We present the measured the density of the alloys, the elastic modulus measured by nanoindentation, and estimations of the yield strength by Vickers microhardness. These properties are correlated to the underlying microstructures, as measured by X-ray diffraction, scanning electron microscopy, and atom probe tomography.1. Senkov ON, Miller JD, Miracle DB, Woodward C. CALPHAD 50 pp. 32–48 (2015).
L-112: Microstructural Details and Indentation Behavior of Microcrystalline and Nanocrystalline Ti-Ni-Cr-Co-Fe High-entropy Alloy: Abhijit Abhijit1; G. Madhusudhan Reddy1; Koteswararao Rajulapati1; 1University of Hyderabad
High-entropy alloys (HEA) usually form simple solid solutions with fcc and/or bcc structures with no intermetallic compounds and hence have emerged as a new class of advanced materials. A multi-component TiNiCrCoFe HEA was synthesized using vacuum arc melting. Structural details were probed using optical microscopy, XRD, SEM and TEM. Subsequently the as-cast HEA was milled for 30 hours to attain nanocrystalline structure. Subsequently nanocrystalline TiNiCrCoFe HEA was sintered using spark plasma sintering (SPS) at 0.5TM and 0.6TM. Mechanical properties, in all conditions, were evaluated using Vickers microindentation and nanoindentation. The results of both microcrystalline and nanocrystalline Ti-Ni-Cr-Co-Fe HEA will be compared and discussed in detail in this paper.