Browsing by Author "Huang, E-Wen"

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A study of lattice elasticity from low entropy metals to medium and high entropy alloys
(2015-05-01)
Huang, E-Wen
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Yu, Dunji
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Yeh, Jien-Wei
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Lee, Chi
;
An, Ke
An equal-molar CoCrFeMnNi, face-centered-cubic high-entropy alloy system and a face-centered-cubic stainless steel described as a medium-entropy system, are measured by in situ neutron-diffraction experiments subjected to continuous tension at room and several elevated temperatures, respectively. With spallation neutron, the evolution of multiple diffraction peaks is collected simultaneously for lattice-elasticity study. Temperature variation of elastic stiffness of a single face-centered-cubic-phase Ni and a single face-centered-cubic-phase Fe are compared as low-entropy metals. The CoCrFeMnNi high-entropy alloy shows distinct lattice anisotropy. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Calcitriol exerts a mineralization-inductive effect comparable to that of vitamin C in cultured human periodontium cells
(2019-01-01)
Hong, Hsiang-Hsi
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Hong, Adrienne
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Wang, Chun-Chieh
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Huang, E-Wen
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Chiang, Cheng-Cheng
This study inspected whether calcitriol could exert a mineralization-inductive effect comparable to that of vitamin C in cultured human periodontium cells (hPDCs). The mRNA expression of the mineralization-related biomarkers core-binding factor subunit alpha-1 (Cbfal), collagen 1 alpha l (Col-l), alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP), osteocalcin (OCN), vitamin D receptor (VDR), cementum protein 1 (CEMP-1), cementum attachment protein (CAP), interleukin 6 (IL-6), transforming growth factor-beta 1 (TGF-beta 1) and osteoprotegerin (OPG) was surveyed after incubation of hPDCs with vitamin C and calcitriol for 2 weeks. Translational expression information from ALP activity and CEMP-1 and CAP immunofluorescence assays was acquired from hPDCs at the second and third weeks. Extracellular calcifications were confirmed by von Kossa staining, Alizarin Red staining and synchrotron transmission X-ray microscopy (TXM) at the fourth and fifth weeks. It was found that both vitamin C and calcitriol not only increased mineralization-related mRNA fold-changes but also enhanced ALP activity, CEMP1 immunofluorescence, von Kossa and Alizarin Red staining and TXM-associated calcifications. Generally, 10(-8) M calcitriol displayed greater mineralization significance than 10(-7) M calcitriol in the assays tested. However, vitamin C stimulated lower Cbfal, Col-1, ALP, OPN, BSP, OCN, VDR, CEMP-1 and IL-6 mRNA fold-changes than 10(-8) M calcitriol. Finally, TXM analysis indicated that a 10(-8) M calcitriol treatment stimulated greater calcifications than vitamin C treatment. Therefore, the analytical results confirmed the osteo-inductive potential of vitamin C in cultured hPDCs. In contrast, 10(-8) M calcitriol could potentially function as a substitute because it stimulates a greater mineralization effect than vitamin C or 10(-7) M calcitriol.
Characterization of Deformation and Wear Mechanisms During Indentation Scratching on Pure Zinc
(2020-01-01)
Gokhale, Aditya
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Jain, Jayant
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Prasad, Rajesh
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Huang, E-Wen
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Lee, Soo Yeol
Scratch testing using nanoindentation helps to characterize material's wear resistance and the accompanying material removal, and deformation mechanism. The effect of load and repeated scratching on pure zinc was investigated in this study. Surface examination post scratching revealed the formation of long chips at lower loads, which can be attributed to ductile-like behavior. Ploughing dominated at higher loads, while micro-cutting was active at lower loads. The material removal factor (f(ab)) is an indicator of the prevailing wear mechanism. A good correlation appeared between the observed wear mechanism and the calculated fab, wherein interplay of ploughing and micro-cutting was observed. The decrease in wear rate as the number of passes increased and the decreasing value of fab are indicative of the strain hardening behavior during repeated scratching. The presence of intergranular fracture slip and twinning on the deformed surface is indicative of the material's response to induced stress.
Comparing Cyclic Tension-Compression Effects on CoCrFeMnNi High-Entropy Alloy and Ni-Based Superalloy
(2019-08-01)
Lam, Tu-Ngoc
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Chou, You-Shiun
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Chang, Yao-Jen
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Sui, Tsung-Ruei
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Yeh, An-Chou
An equal-molar CoCrFeMnNi, face-centered-cubic (fcc) high-entropy alloy (HEA) and a nickel-based superalloy are studied using in situ neutron diffraction experiments. With continuous measurements, the evolution of diffraction peaks is collected for microscopic lattice strain analyses. Cyclic hardening and softening are found in both metallic systems. However, as obtained from the diffraction-peak-width evolution, the underneath deformation mechanisms are quite different. The CoCrFeMnNi HEA exhibits distinct lattice strain and microstructure responses under tension-compression cyclic loadings.
Confined martensitic phase transformation kinetics and lattice dynamics in Ni-Co-Fe-Ga shape memory alloys
(2016-05-15)
Cong, Daoyong
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Rule, Kirrily Clair
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Li, Wen-Hsien
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Lee, Chi-Hung
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Zhang, Qinghua
Insights into the phase transformation kinetics and lattice dynamics associated with the newly discovered confined martensitic transformation are of great significance to the in-depth understanding of the phase transformation behavior responsible for the rich new physical phenomena in shape memory alloys and could shed light on the design of novel multifunctional properties through tuning the confined martensitic transformation. Here, we employ in-situ elastic and inelastic neutron scattering techniques to reveal the characteristics of transformation kinetics and lattice dynamics in two Ni55-xCoxFe18Ga27 magnetic shape memory alloys with x = 5.5 and 6.5. With a remarkable difference in transformation temperature, these two alloys show similar vibrational properties. Phonon softening of the TA(2)[xi xi 0] phonon branch, manifested as a dip at xi similar to 033 on the phonon dispersion curves, was disclosed by inelastic neutron scattering experiments; but this phonon softening is much less pronounced than that observed in stoichiometric Ni2MnGa or near-stoichiometric Ni-Fe-Ga Heusler alloys. The dispersion curves for the TA(2)[xi xi 0] phonon branch are only weakly dependent on temperature. The less pronounced phonon softening and very weak temperature dependence of the phonon dispersion curves could be attributed to the martensitic transformation which is confined by local inhomogeneities. This confined martensitic transformation shows a sluggish nature and occurs in a broad temperature range. The sluggish transformation was evidenced by the existence of residual austenite at low temperatures far below the martensitic transformation start temperature. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Control of Dopant Distribution in Yttrium-Doped Bioactive Glass for Selective Internal Radiotherapy Applications Using Spray Pyrolysis
(2019-03-25)
Tesfay, Abadi Hadush
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Chou, Yu-Jen
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Tan, Cheng-Yan
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Bakare, Fetene Fufa
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Tsou, Nien-Ti
In this study, we demonstrate the fabrication of Y-doped bioactive glass (BG), which is proposed as a potential material for selective internal radiotherapy applications. Owing to its superior bioactivity and biodegradability, it overcomes the problem of yttrium aluminosilicate spheres that remain in the host body for a long duration after treatment. The preparation of Y-doped BG powders were carried out using a spray pyrolysis method. By using two different yttrium sources, we examine the change of the local distribution of yttrium concentration. In addition, characterizations of phase information, particle morphologies, surface areas, and bioactivity were also performed. The results show that both Y-doped BG powders are bioactive and the local Y distribution can be controlled.
Crystal plasticity modeling and neutron diffraction measurements of a magnesium AZ31B plate: Effects of plastic anisotropy and surrounding grains
(2020-02-01)
Wang, Huamiao
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Lee, Soo Yeol
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Huang, E-Wen
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Jain, Jayant
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Li, Dayong
This study used in-situ neutron diffraction measurements and Elastic ViscoPlastic Self-Consistent polycrystal plasticity model, which incorporates a Twinning and DeTwinning scheme (denoted by EVPSC-TDT), to examine the macro-and micro-mechanical behaviors of a rolled AZ31B plate subjected to uniaxial tension. Three specimens were specifically designed for minimum, maximum and intermediate twinning: (1) loading along the rolling direction, (2) loading along the plate normal, and (3) loading along the direction 45 degrees with respect to the plate normal. Apart from the macroscopic stress strain response, the measured diffraction intensities and internal elastic strains were obtained to examine the activities of the deformation modes at the grain level. The diffraction intensity evolution signaled the volume fraction change of twinning, while the internal elastic strain evolution designated the stress partitioning among the grain orientations. The effect of the surrounding grains on the development of the internal elastic strain was investigated by identifying the corresponding deformation mechanisms. Notably, the corresponding modeling work revealed that the EVPSC-TDT model permitted the prediction of the strain hardening and anisotropic behavior along the directions with minimum, maximum and intermediate twinning at the macroscale, and the evolution of the diffraction intensities and internal strains at the microscale. The results provide a physical understanding of the effects of the load direction, texture and surrounding grains on the role of the deformation modes in hexagonal close-packed polycrystalline materials. (C) 2019 Elsevier Ltd. All rights reserved.
Deviatoric deformation kinetics in high entropy alloy under hydrostatic compression
(2019-07-05)
Huang, E-Wen
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Lin, Chih-Ming
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Juang, Jenh-Yih
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Chang, Yao-Jen
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Chang, Yuan-Wei
An equiatomic CoCrFeMnNi high-entropy alloy under hydrostatic compression is investigated using insitu angular-dispersive X-ray diffraction to explore the polymorphism in high entropy alloy systems. The metallic system is of face-centered-cubic structure at ambient condition and applied hydrostatic pressures up to 20 GPa via diamond anvil cell. The angle-resolved diffraction-intensity evolutions of multiple diffraction peaks were collected simultaneously to elucidate the phase stability examinations. The phase transformation from face-centered-cubic to hexagonal-close-packed structure was evidently observed in CoCrFeMnNi alloy accompanied by a deviatoric strain subjected to the hydrostatic compression. We found lattice-asymmetric crossover before and after the phase transformation subjected to hydrostatic compression surroundings. Deviatoric strain triggers fcc-hcp phase transformation as local heterogeneity-driven lattice distortion is significant for CoCrFeMnNi alloy. (c) 2019 The Authors. Published by Elsevier B.V.
Dynamic Strain Evolution around a Crack Tip under Steady- and Overloaded-Fatigue Conditions
(2015-12-01)
Lee, Soo Yeol
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Huang, E-Wen
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Woo, Wanchuck
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Yoon, Cheol
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Chae, Hobyung
Element Effects of Mn and Ge on the Tuning of Mechanical Properties of High-Entropy Alloys
(1970-01-01)
Tu-Ngoc Lam
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Tsai, Che-Wei
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Chen, Bo-Kai
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Lai, Bo-Hong
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Liu, Hung-Chih
Substitution of Ge for Mn increases the elastic moduli of different {h k l} orientations of the CoCrFeMnNi-based high-entropy alloy. Our findings indicate that tuning minor element compositions may result in improved strength-ductility combination. The underlying deformation mechanisms of CoCrFeNiGe(0.3)were examined byin situneutron diffraction and analysis of the associated diffraction profiles during tensile deformation. The strain-hardening response of CoCrFeNiGe(0.3)exhibited a dominant mechanism of mechanical twinning at moderate and large strains at room temperature. The evolution of the bulk work hardening rate was consistent with the convolutional multiple whole profile fitting results, which exhibited a continuous increase in twin formation probability. The microstructural development was also investigated by transmission electron microscopy, which revealed the formation of huge amounts of deformation twins in CoCrFeNiGe(0.3)at room temperature.
Element Effects on High-Entropy Alloy Vacancy and Heterogeneous Lattice Distortion Subjected to Quasi-equilibrium Heating
(2019-10-15)
Huang, E-Wen
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Chou, Hung-Sheng
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Tu, K. N.
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Hung, Wei-Song
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Tu-Ngoc Lam
We applied Simmons-Balluffi methods, positron measurements, and neutron diffraction to estimate the vacancy of CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs) using Cu as a benchmark. The corresponding formation enthalpies and associated entropies of the HEAs and Cu were calculated. The vacancy-dependent effective free volumes in both CoCrFeNi and CoCrFeMnNi alloys are greater than those in Cu, implying the easier formation of vacancies by lattice structure relaxation of HEAs at elevated temperatures. Spatially resolved synchrotron X-ray measurements revealed different characteristics of CoCrFeNi and CoCrFeMnNi HEAs subjected to quasi-equilibrium conditions at high temperatures. Element-dependent behavior revealed by X-ray fluorescence (XRF) mapping indicates the effect of Mn on the Cantor Alloy.
Fatigue-Crack-Growth Behavior of Two Pipeline Steels
(2016-12)
Chen, Bilin
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Wang, Gongyao
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Chen, Shuying
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Muralidharan, Govindarajan
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Stalheim, Doug
The fatigue-crack-growth behavior of two types of pipeline steels, Alloy B [Fe-0.05C-1.52Mn-0.12Si-0.092Nb, weight percent (wt%)] and Alloy C (Fe-0.04C-1.61Mn-0.14Si-0.096Nb, wt%), have been investigated. Compact-tension (CT) specimens have been tested at various frequencies (10, 1, and 0.1 Hz) and different R ratios (0.1 and 0.5, R = P-min/P-max where P-min is the minimum applied load, and P-max is the maximum applied load) in air. It is concluded that higher R ratios lead to faster crack-growth rates (FCGRs), while frequency does not have much influence on FCGRs. Moreover, Alloy B tends to have better fatigue resistance than Alloy C under various test conditions in air.
Hardening steels by the generation of transient phase using additive manufacturing
(2019-06-01)
Huang, E-Wen
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Lee, Soo Yeol
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Jain, Jayant
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Tong, Yang
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An, Ke
In the present work, the tensile properties of 15-5 PH steel fabricated by selective laser melting (SLM) were examined with respect to the transient austenite phase. Compared with the 8%-transient-phase sample, the 18%-transient-phase one shows higher ultimate tensile strength and relatively low yield strength, as well as hardening behavior. We conducted in-situ neutron-diffraction study to examine the microstructure evolution for mechanistic understanding. After applying the external load, most non-equilibrium, retained austenite in the 8% transient-phase sample transforms before the yield strength, whereas in the 18%-transient-phase sample only 50% of the austenite transforms. Accompanying with the phase transformation, a decrease in the dislocation density and the dislocation strain energy-assisted phase transformation of the ferrite phase are found in the 8%-transient-phase sample even before yielding, which, however, is not the case in the 18%-transient-phase sample. The study demonstrates the SLM enables tuning the amount of transient-phase ratio and coherency between phases to realize a mechanical property control for additive manufactured steel.
High-temperature materials for structural applications: New perspectives on high-entropy alloys, bulk metallic glasses, and nanomaterials
(2019-11-01)
Huang, E-Wen
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Liaw, Peter K.
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材料科學與工程學系
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Department of Materials Science and Engineering
Tougher, lighter, and more formable and machinable metals for broader ranges of applications at higher temperatures are needed now more than ever. High-performance computing, high-resolution microscopy, and advanced spectroscopy methods, including neutrons and synchrotron x-rays, together with advances in metallurgy and metal mixology, reveal the potential of multicomponent advanced metals, such as multicomponent bulk metallic glasses and advanced high-entropy alloys. The development of new experimental approaches relates bulk properties and voxel-associated optimized properties throughout structures with high resolution. The correlations from in situ measurements greatly improve crystal plasticity-based models. This issue of MRS Bulletin overviews recent progress in the field, and this article highlights the importance of these new perspectives. The latest progress and directions in the science and technology for prospective high-temperature metals for structural applications are reported.
In-situ neutron diffraction studies on high-temperature deformation behavior in a CoCrFeMnNi high entropy alloy
(2015-07-01)
Woo, Wanchuck
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Huang, E-Wen
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Yeh, Jien-Wei
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Choo, Hahn
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Lee, Chi
An equiatomic, face-centered-cubic, CoCrFeMnNi high-entropy alloy was tensile tested at 800 K and 1,000 K with a nominal strain rate of 6.7 x 10(-6) s(-1). In addition to the macroscopic (bulk) behavior, mesoscopic (lattice) phenomena during the pseudo-creep deformation were investigated simultaneously using in-situ neutron diffraction. The evolutions of lattice strains, peak widths, and intensities of several hkl reflections suggest that the dominant deformation mode is the dislocation glide at 800 K and diffusion-controlled dislocation creep at 1,000 K. (C) 2015 Elsevier Ltd. All rights reserved.
Irreversible phase transformation in a CoCrFeMnNi high entropy alloy under hydrostatic compression
(2018-03-01)
Huang, E-Wen
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Lin, Chih-Ming
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Jain, Jayant
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Shieh, Sean R.
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Wang, Ching-Pao
An equal-molar CoCrFeMnNi, face-centered-cubic high-entropy alloy system is investigated using in-situ angular-dispersive X-ray diffraction under hydrostatic compression up to 20 GPa via diamond anvil cell. The evolutions of multiple diffraction peaks are collected simultaneously to elucidate the phase stability field. The results indicated that an irreversible phase transformation had occurred in the high entropy alloy upon decompression to ambient pressure. A reference material (n-type silicon-doped gallium arsenide) was investigated following the same protocol to demonstrate the different deformation mechanisms. It is suggested that the atomic bonding characteristics on the phase stability may play an important role in the high entropy alloys.
Lattice distortion effect on elastic anisotropy of high entropy alloys
(2020-03-25)
Yen, Chao-Chun
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Huang, Guan-Rong
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Tan, Yun-Cheng
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Yeh, Han-Wen
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Luo, Da-Ji
The superior mechanical properties of high-entropy alloys (HEAs) have made an outstanding success in materials science and engineering. Studies to date have been devoted to what the severe lattice distortion induces. However, most researchers focus on its stimulation to plastic deformation instead of scrutinizing the variations on elasticity. Compared with conventional alloys, HEAs may perform disproportionate elasticity with uneven local lattice strain resulting from the severe lattice distortion. Therefore, it is necessary to survey its influence on the mechanical properties of HEAs systematically. In this study, the Lennard-Jones (LJ) potential, the embedded atom method (EAM) potential, and the modified embedded atom method (MEAM), are respectively conducted to investigate the lattice distortion effect on Young's modulus E (hkl) and Poisson's ratio nu (hkl, theta) along [100], [110], and [111] loading directions for several fcc metals composed of 1 similar to 5 atomic types, including Ni, Ni98W2, Ni96W4, FeCrNi, and CoNiCrFeMn HEAs. Also, a method is used to analyze the performance of the individual element on the elastic properties in the HEA environment. As a result, it can be unveiled that the effect of electron density inconsistency is more dominant than the effect of lattice distortion associated with the atomic size difference. The electronic configuration in the HEA environment plays a major role in elastic anisotropy while the difference of the atomic radii does the minor one. The anisotropy of CoNiCrFeMn HEA analyzed by this work is also consistent with in-situ neutron diffraction measurements. (C) 2019 Elsevier B.V. All rights reserved.
Mechanical and Magnetic Properties of the High-Entropy Alloys for Combinatorial Approaches
(2020-03-01)
Huang, E-Wen
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Hung, Guo-Yu
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Lee, Soo Yeol
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Jain, Jayant
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Chang, Kuan-Pang
This review summarizes the state of high-entropy alloys and their combinatorial approaches, mainly considering their magnetic applications. Several earlier studies on high-entropy alloy properties, such as magnetic, wear, and corrosion behavior; different forms, such as thin films, nanowires, thermal spray coatings; specific treatments, such as plasma spraying and inclusion effects; and unique applications, such as welding, are summarized. High-entropy alloy systems that were reported for both their mechanical and magnetic properties are compared through the combination of their Young's modulus, yield strength, remanent induction, and coercive force. Several potential applications requiring both mechanical and magnetic properties are reported.
Micro-Layer and Lattice Structure Effects on Impedance of Titanium Oxide Phthalocyanine
(2018-07-01)
Lam, Tu-Ngoc
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Huang, Wei-Jie
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Wang, Chun-Chieh
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Chuang, Wei-Tsung
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Su, Ya-Wen
In this study, the authors employ synchrotron techniques to characterize multi-scale microstructure in elucidating how the modified crystal lattices at angstrom level and molecular stacking at micrometer scale of titanium oxide phthalocyanine (TiOPc) thin film tuning the impedance. The a and c lattice lengths of the TiOPc reveal a positive correlation with the impedance because of the - stacking distances of TiOPc molecules arrangements. Our results suggest a promising dip coating method to tailor the charge storage capability of TiOPc through controlling the crystal lattice sizes of TiOPc.
Multi-scale mapping for collagen-regulated mineralization in bone remodeling of additive manufacturing porous implants
(2019-05-15)
Tsai, Pei-I.
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Lam, Tu-Ngoc
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Wu, Meng-Huang
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Tseng, Kuan-Ying
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Chang, Yuan-Wei
Long term success of metallic fusion cages depends on mechanobiological processes through the bone incorporation and rich osseointegration. An optimal configuration of porous titanium-aluminum-vanadium (Ti-6Al-4V) implant fabricated via the additive manufacturing was evaluated in complimentary structure examinations to investigate the growth of autologous osseous at multi-length scales. X-ray microcomputed tomography (micro-CT) and transmission X-ray microscopy (TXM) using newly-built analysis method indicate the porous Ti-6Al-4V is much better for bone ingrowth compared to commercially non-porous titanium (Ti) and porous tantalum (Ta) implants at the ultramicrostructural level. The evolution of bone formation and remodeling acquired by nano X-ray Laue diffraction mapping exhibits the isotropic orientation and low crystallinity of all newly formed bone whereas mature bone in Ti-6Al-4V discloses the preferential alignment and higher crystallinity volumes of constituent hydroxyapatite (HA) crystallites. The high degree in mineral crystallinity of the fully mature bone suggests additive manufactured Ti-6Al-4V pores enhance the collagen-regulated mineralization.