Phase Transformations and Microstructural Evolution: On-Demand Oral Presentations
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Mohsen Asle Zaeem, Colorado School of Mines; Ramasis Goswami, Naval Research Laboratory; Saurabh Puri, Microstructure Engineering; Eric Payton, University of Cincinnati; Megumi Kawasaki, Oregon State University; Eric Lass, University of Tennessee-Knoxville

Monday 8:00 AM
March 14, 2022
Room: Physical Metallurgy
Location: On-Demand Room

Microstructural Evolution and Nanoprecipitation Behaviour of a Selective Laser Melted, 18% Ni Maraging 300 Steel: Gopi Kompelli1; Angelos Nikolaidis1; David de Castro1; Adriana Eres Castellanos1; Isaac Toda Caraballo1; David San Martin1; Jose Antonio Jimenez1; Esteban Urones Garrote2; Rosalia Rementeria3; Carlos Capdevila1; Francisca Caballero1; 1CENIM-CSIC; 2Universidad Complutense de Madrid; 3ArcelorMittal Global R&D
     Maraging steels are widely applied in the aerospace and tool-manufacturing industries, which often call for geometrically complex components with excellent mechanical properties in relatively small quantities. Compared with other Fe-based alloys, such as 316L stainless steels, Fe-Al steels, and tooling steels, maraging steels are well suited for Selective Laser Melting (SLM), an additive manufacturing method specially developed for 3D printing of metal alloys. It is well known that maraging steels can be age-hardened by intermetallic precipitates. To enhance the progress of this technology, it is necessary to study the precipitation behaviour of SLM maraging steels during age hardening. In this work, microstructural characterization of maraging steels produced by SLM was carried out, paying special attention to the multi-scale complexity and the crystallographic hierarchy of as-built martensitic structures. In addition, X-ray diffraction and high-resolution TEM (HRTEM) analysis were conducted to investigate microstructure evolution and precipitation events during ageing of SLM specimens.

Atomistic Modeling of Phase Stability and Transformations due to the Presence of Precipitates in High and Medium Entropy Alloys: Eva Zarkadoula1; Ying Yang1; Albina Borisevich1; Easo George1; 1Oak Ridge National Laboratory
    High entropy alloys (HEAs) and medium entropy alloys (MEAs) have been increasingly attracting attention because of their unique mechanical and thermal properties. Adding precipitates to HEA and MEA matrices is a way of improving the materials’ strength further. In addition to the materials strength, adding precipitates has been shown to affect the phase transformation of the matrix. Understanding the role of precipitate characteristics, such as volume fraction and interparticle spacing, on the phase transformation and mechanical behavior is critical for the development of design principles for improving the materials’ mechanical behavior. In this work, using molecular dynamics simulations we investigate the role of precipitates in deformation and phase transformation of HEA/MEAs, and compare the results to experimental observations. Work supported by the U.S Department of Energy, Basic Energy Science, Materials Science and Engineering Division.

Influence of Cluster Hardening on Strength and Strain Hardening Behavior of Various Aluminum Alloys: Philip Aster1; Lukas Stemper1; Florian Schmid1; Peter Uggowitzer1; Stefan Pogatscher1; 1Montanuniversität Leoben
    Cluster hardening, i.e. the formation of clusters primarily instead of classical metastable hardening phases, depicts a promising approach for strengthening with a reduced loss of ductility in aluminum alloys. In this context we investigated several alloys, including AlMgSi alloys with different Mg/Si ratios as well as AlMgZn alloys with varying ratios of Mg to Zn. Both alloy types were alloyed with or without Cu. For cluster hardening aging temperatures of 100 °C and lower were applied after solution annealing to prevent the formation of conventional metastable hardening phases. Aging characteristics were evaluated using hardness testing and tensile testing. An advanced interpretation of the tensile testing curves including modelling by the Kocks-Mecking approach was conducted to get insight into the strain hardening behavior. The results show a comparable good aging response in combination with significantly enhanced forming parameters, such as uniform elongation or work hardening.

A Combinatorial Approach to Investigate Abnormal Grain Growth Behavior in Cu-Al-Mn Shape Memory Alloys: Hyoungrok Lee1; Sheng Xu1; Toshihiro Omori1; Ryosuke Kainuma1; 1Tohoku University
    Abnormal grain growth (AGG) can be induced by the cyclic heat treatment (CHT) through the β(bcc) ↔︎ α(fcc) phase transformation in the Cu-Al-Mn system. The subgrain structure formed around the α precipitates serves as a driving force for AGG of the β phase, and thus, the control of subgrain structure is of importance to obtain a large single crystal. In this study, the effect of composition on AGG was investigated through a combinatorial approach in Cu-Al-Mn. Diffusion couples between Cu-14Al-10Mn and Cu-20Al-10Mn (at%) were prepared and subjected to the CHT. The composition profiles were analyzed by EPMA/WDS, and the microstructures were analyzed using EBSD. The α solvus temperature decreased by increasing the Al concentration and the subgrain size also decreased up to 19.5 at%, meaning increase in the driving force for AGG. Furthermore, the optimal Al composition to obtain a large grain was found.

On the Precipitation Behavior of γ-TiAl from a Supersaturated βo-TiAl Matrix in an Intermetallic Ti-44Al-7Mo (at.%) Alloy: Gloria Graf1; Christoph Gammer2; Simon Fellner2; Johanna Byloff1; David Holec1; Helmut Clemens1; Petra Spoerk-Erdely1; 1University of Leoben; 2Erich-Schmid-Institut für Materialwissenschaft der ÖAW
    As lightweight materials with excellent high-temperature properties, intermetallic γ-TiAl based alloys have recently become well established in the aviation industry. In this work, the focus lies on the Ti-44Al-7Mo (in at.%) alloy. Molybdenum, as an alloying element, strongly stabilizes the β/βo phase and yields a (βo + γ) phase-field region at ambient temperatures. Consequently, the precipitation behavior of γ from an ordered βo matrix can be investigated, which is not possible for conventional alloys and therefore not yet well understood. Previous differential scanning calorimetry and high-energy X-ray diffraction investigations raised the questions whether the precipitation of γ-TiAl is preceded by the formation of an intermediate phase and whether the precipitate’s interface type changes during the process. With high-resolution transmission electron microscopy and ab-initio calculations it was proven that the interfaces are first coherent and slowly become incoherent with increasing precipitate radius. No intermediate phase is formed.

Cementite Decomposition in 100Cr6 Bearing Steel during High-pressure Torsion: Influence of Composition, Size, Morphology and Matrix Hardness: Kiranbabu Srikakulapu1; Lutz Morsdorf1; Po-Yen Tung1; Michael Herbig1; 1Max-Planck-Institut für Eisenforschung
     Premature failure of rail and bearing steels by White-Etching-Cracks leads to severe economic losses. This failure mechanism is associated with microstructure decomposition via local severe plastic deformation (SPD). The decomposition of cementite here plays a key role as this hard phase is the most critical obstacle to overcome in the process. Therefore, understanding principal factors effecting cementite decomposition helps in designing damage resistant steels. In this study, the standard 100Cr6 bearing steel microstructure is tailored to create two types of precipitates - spherical and lamellar cementite, surrounded by ferrite matrix. These two types of precipitates differ in size, morphology, and composition (Cr, Mn partitioning). The difference in decomposition behavior upon high-pressure torsion (to model SPD) is examined using multi-scale characterization techniques. We conclude that the cementite size and morphology, as well as the matrix mechanical properties predominantly influence the decomposition behavior of cementite.

Decoupling of Strain and Temperature Effects on Microstructural Evolution during High Shear Strain Deformation: Anqi Yu1; Julian Escobar Atehortua1; Krassimir Bozhilov2; Jia Liu1; Mayur Pole1; Joshua Silverstein1; Sundeep Mukherjee3; Suveen Mathaudhu4; Arun Devaraj1; Bharat Gwalani1; 1Pacific Northwest National Laboratory; 2University of California, Riverside; 3University of North Texas; 4Colorado School of Mines
     While solid phase processing is widely used for advanced materials manufacturing, the effects of strain and the local heating due to process remain implicit. To decouple the effects of shear-strain and temperature, we used a pin-on-disk tribometer to study subsurface microstructural changes in a Cu-Nb binary system under shearing at various temperatures. First, to minimize the frictional heating at the contact surface, low sliding load and velocity were used at room temperature to eliminate the influence of thermal activation during shear induced deformation. Then, external heating was applied during the tribological process to elucidate the coupled effect of shear and temperature. The phase specific strain accommodation as a function of total strain and temperature were characterized using orientation microscopy and transmission electron microscopy, while the compositional changes due to forced mixing were captured using atom probe tomography to understand the transformation pathway during this high strain process.

Processing Electroceramics in the Transmission Electron Microscope: Jenna Wardini1; Jairo Gonzalez1; George Harrington2; William Bowman1; 1University of California Irvine; 2Kyushu University
    We explore a unique electroceramic thermal processing approach that leverages the small thermal-mass of electron-transparent thin-films to apply rapid heating/cooling cycles in situ, in the transmission electron microscope (TEM). The emergent microstructures, crystallized from amorphous mixed-metal oxide thin-films, are iteratively evolved and characterized with a range of electron imaging, diffraction, and spectroscopy techniques to establish a relationship between characteristics of the evolving microstructure and the temperature-dependent electrical behavior, with particular interest placed on the effect of the grain boundary network on O2- transport. However, additional complexity in the phase-space is encountered under these processing conditions, leading to the formation of an abundance of unique phases. We explore ways to control the film phase, microstructure, and morphology that develops under in situ processing by investigating the effects of oxygen partial pressure and annealing temperature.

Phase Field Simulations of Direct Aging of a Rapidly Solidified Ni-Fe-Nb Alloy: Bala Radhakrishnan1; Sarma Gorti1; Ranadip Acharya2; 1Oak Ridge National Laboratory; 2Collins Aerospace Applied Research and Technology
    Standard heat treatments developed for wrought Ni-base alloys cannot be used for AM alloys. Extensive homogenization of as-built microstructures not only results in increased energy consumption but also the destruction of fine microstructural scale obtained through rapid solidification during AM. Direct aging of as-built microstructures could result in the formation of undesirable phases. The research focuses on designing a custom heat treatment to achieve the optimum microstructure in AM parts. This approach is demonstrated through large scale, phase field simulations of solid-state precipitation in a model Ni-Fe-Nb ternary. The simulations capture the effect of solute gradient and dislocation strain fields in the AM microstructure on precipitation. Research sponsored by the Advanced Manufacturing Office of the U.S. Department of Energy under the High-Performance Computing for Energy Innovation (HPC4EI) program and performed at the Oak Ridge National Laboratory managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.

Role of Phosphorus in Irradiated Microstructure Evolution of a Binary Fe-P Model Alloy by TEM In Situ Irradiation: Patrick Warren1; Wei-Ying Chen2; Ling Wang3; Janelle Wharry1; 1Purdue University; 2Argonne National Laboratory; 3Materials Science and Technology Division
    The objective of this study is to understand the role of phosphorus (P) in irradiation-induced defect clustering and loop nucleation. High-strength steels rely on solid solution strengthening from P additions. But ab initio studies have predicted strong self-interstitial atom trapping by P in Fe, potentially leading to enhanced defect formation under irradiation in Fe-P alloys. This study utilized transmission electron microscopy (TEM) in situ irradiation with 1 MeV Kr2+ ions at 370°C of an Fe-4at%P alloy. The alloy contains a multiphase microstructure of bcc-Fe matrix with dilute P, and bct Fe3P intermetallic phases. The threshold nucleation dose for dislocation loops, radiation-assisted precipitation and coarsening increases with distance from pre-existing interphase boundaries. The greater susceptibility to irradiation damage near the Fe3P phases is attributed to higher local P concentration due to ballistic dissolution of the P-rich Fe3P phase. This study provides evidence that cluster evolution is dependent on local P concentration.

The Effect of Low-temperature Aging on the Microstructure and Mechanical Behavior of Martensitic Ti-Nb Alloy: Marissa Linne1; Rohini Sankaran1; Sharon Torres1; Joseph Mckeown1; Amanda Wu1; 1Lawrence Livermore National Laboratory
     Nb-lean martensitic Ti-Nb has been given less attention than β-stable alloys, despite demonstrating similarly low elastic stiffness at a lower cost and weight. In this work, the low-temperature thermal stability of martensitic Ti-Nb is investigated, as it is less well understood and is important for developing processing parameters for achieving desired mechanical properties. Ti- 20 wt % Nb α'' martensite was aged at 250 °C, 400 °C and 550 °C for time intervals ranging from 10 minutes to 10 days. The effects on structure and mechanical behavior were assessed using X-ray diffraction, microhardness and electron backscatter diffraction. These experimental results contribute to a better understanding of (1) how the martensite microstructure evolves during aging at temperatures low enough to avoid austenitic transformation to the β phase and (2) how these changes affect deformation mechanism activity.This work was performed by LLNL under Contract DE-AC52-07NA27344.

Lattice Point Defects: A Vacancy in Phase Transformation Models: Estelle Meslin1; Maylise Nastar1; Lisa Belkacémi1; Marie Loyer-Prost1; 1Cea
     From a joint experimental and modeling study, we show the role of point defects in the stability of phases in alloys and in unforeseen phase transformations [1]. The creation or removal of lattice sites is an accommodation mechanism of the coherency loss and even a precipitation driving force. We report the formation of a fcc Ni-rich phase in this purely bcc Fe-Ni metallic system under irradiation. The characterisation of the Ni-enriched fcc phase has been performed by complementary atomic-scale techniques (HR-TEM, STEM/EDX and APT) [2]. In this presentation, we introduce a thermodynamic approach that rationalizes the selection of phases resulting from chemical and crystallographic constraints in relation to point defect properties. [1] M. Nastar, L.T. Belkacemi, E. Meslin, M. Loyer-Prost, Communications Materials 2, 1–11 (2021) ;[2] L.T. Belkacemi, E.Meslin, B.Décamps, B. Radiguet, J.Henry, Acta Materialia 161, 61–72 (2018).

Thermoelastic Martensitic Transformation in Mn-rich Mn-Cu-Al BCC Alloys: Tatsuya Ito1; Xiao Xu1; Toshihiro Omori1; Ryosuke Kainuma1; 1Tohoku University
    Cu-Al-Mn ternary alloys are known as the first discovered Heusler alloys, and the BCC structure has a broad region of solid solution. These alloys show thermoelastic martensitic transformations from the BCC to the monoclinic or tetragonal structures in the Cu-rich regions. They exhibit shape memory effect and superelasticity, which have been utilized for applications such as medical clips for ingrown nails. However, the research has been limited to the Cu-rich region because the martensitic transformation temperature decreases by the addition of either Mn or Al. In this work, we investigated the phase equilibria, microstructures and crystal structures in Mn-rich Mn-Cu-Al alloys. As a result, we found a thermoelastic martensitic transformation for the first time near the BCC/FCC phase boundary. The martensitic transformation temperatures and crystal structures will be reported in this presentation.

Kinetics of γ’ Evolution in a Model Ni-based Alloy: Govindarajan Muralidharan1; Shivakant Shukla1; Donovan Leonard1; Balasubramaniam Radhakrishnan1; Jonathan Poplawsky1; Matt Frith2; Jan Ilavsky2; 1Oak Ridge National Laboratory; 2Argonne National laboratory
    High performance Ni-based alloys are required for use in exhaust valve applications in the next generation, high efficiency automotive engines. These alloys are expected to be as low as possible in cost while being able to perform at temperatures up to 950°C in an exhaust gas environment. The work will highlight the use of transmission electron microscopy, atom probe tomography, USAXS, and phase field modeling in understanding microstructural evolution in a model Ni-Fe-Cr alloy. *Research sponsored by the U.S.DOE, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. This work used resources of the Advanced Photon Source, a U. S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Atom Probe Tomography was conducted at the Center for Nanophase Materials Sciences, a DOE Office of Science User Facility.

Z-phase Formation in a 12% Cr Tempered Martensite Ferritic Steel during Long Term Creep: Johan Westraadt1; William Goosen1; Aleksander Kostka2; Hongcai Wang2; Gunther Eggeler2; 1Nelson Mandela University; 2Ruhr-Universität
    The formation of Z-phase in a 12% Cr tempered martensite ferritic (TMF) steel subjected to interrupted long term creep testing at 550 °C and 120 MPa was investigated. Four samples were tested up to defined creep-strain values of 0.5%, 1.0%, 1.6%, and 11.9% (failure-139 kh). Z-phase and MX precipitates were quantified from EFTEM elemental maps taken on thin-foils prepared from the (non-deformed) gauge and grip sections. Z-phase precipitated in both the gauge (fv: 0.4%) and grip regions (fv: 0.3%) of the sample tested to failure. The formation of Z-phase was accompanied by a progressive dissolution of the important creep-strengthening MX precipitates, which decreased from an initial fv of 0.17% to less than 0.05% in the gauge section of the sample tested to failure. The preferred nucleation sites, MX/Z-phase transformation mechanism, and the effects of stress (gauge vs grip) and creep-deformation in the failure zone on Z-phase formation will be discussed.

Nucleation of Coupled Body-centered-cubic and Closed-packed Structures in Liquid Ni-Cr Alloys: Deep Choudhuri1; 1New Mexico Institute of Mining and Technology
     In the last four decades, the structure of pre-critical solid nuclei within a liquid phase of single-component face-centered-cubic (FCC) materials has been extensively investigated. These studies demonstrated that formation of equilibrium-FCC is mediated by metastable-body-centered-cubic (BCC) structured pre-critical nucleus. However, it is unknown if such nucleation mechanism is applicable to multi-component structural alloys that forms FCC and BCC structures as equilibrium phases. We have investigated this matter using Ni-35at.\%Cr and Ni-50at.\%Cr binary alloys via molecular-dynamics simulations. Our results indicated that the pre-critical and critical nucleus comprised coupled Cr-rich BCC and Ni-rich closed-packed (FCC and hexagonal-closed-packed) structures. Formation of such multi-structured pre-critical nucleus was facilitated by prior phase-separation of alloy-melt into Cr-rich and Ni-rich liquid-pockets. BCC and closed-packed regions inside the nucleus formed with non-equilibrium compositions that evolved over time. Thus, a non-conventional nucleation mechanism in concentrated Ni-Cr alloys allows them to solidify into FCC-BCC microstructures.

Effect of Micro-segregation of Alloying Elements on the Precipitation Behaviour in Laser Surface Engineered Alloy 718: Srinivas Aditya Mantri1; SriSwaroop Dasari1; Abhishek Sharma1; Mangesh Pantawane1; Narendra Dahotre1; Rajarshi Banerjee1; Srikumar Banerjee2; 1University of North Texas; 2Homi Bhabha National Institute, Bhabha Atomic Research Centre
    Micro-segregation of alloying elements in the fusion zone of laser surface melted Alloy 718 samples has been found to have a strong influence on the local precipitation behavior. The dendritic structure produced by rapid melting and solidification has shown three distinct zones – a) core and b) periphery of dendrites, and c) the inter-dendritic channel. While precipitation of γ’ dominates in the core, the periphery is decorated by γ” and composite γ’/γ” precipitates, all in the γ matrix. The inter-dendritic channel, rich in Nb, Mo, and C, contains discretized aggregates of Laves phase and carbides, which act as preferential nucleation sites for the equilibrium δ phase. Microscopic examinations at different length scales using SEM, site-specific TEM (both diffraction contrast and phase contrast) and APT have revealed several hitherto unknown features of precipitation processes in a compositionally inhomogeneous Alloy 718, which are invariably encountered in components produced by laser additive manufacturing.

Investigating the Dynamic Precipitation of AZ91 Alloy during Friction Stir Processing (FSP): Xiaolong Ma1; Hrishikesh Das1; David Garcia1; Ethan Nickerson1; Timothy Roosendaal1; Mageshwari Komarasamy1; Glenn Grant1; 1Pacific Northwest National Laboratory
    Friction stir processing (FSP) is a powerful solid-state processing technique to modify the local microstructure via severe strain and resultant temperature. Starting with a super-saturated solid solution, FSP will introduce dynamic precipitation along with recrystallization, providing a kinetic pathway and morphology evolution of precipitates that is different from their static aging counterpart. In this study, the dynamic precipitation behavior of AZ91 alloy during FSP is investigated in detail, emphasizing its differing characteristics at various processing conditions. Its difference from static precipitation, relationship with the concurrent dynamic recrystallization and implication on the mechanical properties will be discussed.

Multiscale Model for Colony Breakdown Prediction in Two-phase Titanium Alloys: Benjamin Begley1; Victoria Miller1; 1University of Florida
    For two-phase titanium alloys, predicting the evolution of texture during deformation processing is key to developing highly efficient strategies for colony and microtexture breakdown. This work develops a “open-box” framework linking DEFORM, a commercial finite element model for deformation processing, and the viscoplastic self-consistent (VPSC) model, which predicts texture evolution during plastic deformation. Matched sets of physical deformations and DEFORM simulations are used to validate the microstructure predictions and better parameterize the VPSC model. Additional model rules are integrated through a modular approach, including non-equilibrium phase transformation calculations, variant selection of transformed α grains, and temperature-dependent deformation properties. The new framework is coupled with modern electron microscopy to investigate the orientation dependence of colony breakdown during complex thermomechanical processes, with the goal of developing a simple parameter for predicting resulting microtexture severity as a function of the starting microstructure and the processing pathway.

Deformation Enabled Precipitation in Magnesium Alloys during Hot Compression: Suhas Eswarappa Prameela1; Yannick Hollenweger2; Peng Yi1; Steven Lavenstein1; Roshan Plamthottam1; Alec Davis3; Joey Chen1; Joseph Robson3; Jaafar El-Awady1; Michael Falk1; Dennis Kochmann2; Timothy Weihs1; 1Johns Hopkins University; 2ETH Zurich; 3The University of Manchester
    Simple aging of Magnesium alloys often yields inadequate precipitation hardening response compared to Aluminum alloys. Deformation-enabled precipitation is one viable strategy to overcome this problem. Using defects, one can severely alter the nucleation and growth of desired second phases and thereby tune their number density, size, shape, orientation, and spatial distribution. Through simple compression experiments on rolled, large-grained Magnesium-Aluminum alloys, we show how solid-solid phase transformations are altered in grain interiors and along grain boundaries after only 10% plastic strain and at four, relatively low temperatures (25C, 100C, 150C, and 200C). With ex situ TEM, we detail the nanoscale Mg17Al12 intermetallic precipitates that form within a fully solutionized Mg-9Al matrix after compression. With crystal plasticity simulations, we link the inhomogeneity of these nano precipitates to the heterogeneity of deformation gradients within the samples. Finally, we explore the underlying mechanisms behind this deformation-induced precipitation.

High Speed Rotational Diamond Anvil Cell for in situ Analysis of Shear Deformation Induced Microstructural Evolution and Phase Transformation: A Multimodal Experimental and Computational study: Arun Devaraj1; Tingkun Liu1; changyong Park2; Stanislav Sinogeikin3; Matthew Olszta1; Bharat Gwalani1; lei li1; wenkai Fu1; Qin Pang1; Nanjung Chen1; Ayoub Soulami1; Yulan Li1; shenyang Hu1; Peter Sushko1; Suveen Mathaudhu1; Cynthia Powell1; 1Pacific Northwest National Laboratory; 2argonne national laboratory; 3DAC tools
    Development of scalable shear deformation-based solid phase processing methods critically depends on obtaining better predictive understanding of the fundamental atomic scale mechanisms of mass and energy transfer in materials under shear deformation. Hence to improve the predictive mechanistic understanding of dynamic microstructural evolution of materials during shear deformation, we developed a first of its kind high-speed rotational diamond anvil cell (HSRDAC) and implemented it at the Advanced Photon Source synchrotron beamline. HSRDAC provided time resolved synchrotron-based XRD results of lattice strain evolution and spatial variation of shear deformation induced defect density, and alloying in Cu-Ni binary system. The in situ synchrotron XRD results were then correlated with multimodal ex situ characterization and multiscale computational simulations to provide a comprehensive description of morphology, structure, composition and defects evolution at multiple length scales. Ultimately, this study provides new insights on how interfacial mass transfer can be accelerated in materials under shear deformation.

Quantitative Assessment of Short-range Order in Fe-Al and Fe-Ga Alloy Single Crystals: Rahulkumar Sunil Singh1; Andrew Laroche1; Travis Willhard1; Sivaraman Guruswamy1; 1University of Utah
    Rare earth free α-Fe based Fe-Al alloys show a good combination of high strength, ductility, low-cost, moderate low-field magnetostriction, and wide range of operating temperatures, making them attractive for use in actuators and sensors. This study focuses on the quantitative assessment of short-range ordering (SRO) and its correlation with magnetostriction in Fe-Al alloy single crystal prepared using a vertical Bridgman growth process. SRO coefficients were obtained using the diffuse scattering peaks in the high resolution theta-2 theta scans of [100]-oriented (i) as-grown and (ii) high-temperature annealed Fe-16.4 at.% Al single crystals. XRD examinations of [220]- and [111]-oriented single crystals were also carried out to understand the nature of ordering. The SRO coefficients in Fe-16.4 at.% Al alloy single crystal samples were correlated with magnetostriction and compared with SRO coefficients for Fe-15 at.% Ga and Fe-20 at.% Ga with similar thermal histories.