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Sunghak Lee - One of the best experts on this subject based on the ideXlab platform.
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high tensile ductility of ti based Amorphous Matrix composites modified from conventional ti 6al 4v titanium alloy
Acta Materialia, 2013Co-Authors: Changwoo Jeon, Choongnyun Paul Kim, Soo Hyun Joo, Hyungmo Kim, Sunghak LeeAbstract:Abstract Three Ti-based Amorphous Matrix composites containing ductile dendrites were fabricated by adding alloying elements of Ti, Zr, V, Ni, Al and Be into a conventional Ti–6Al–4V alloy, and the deformation mechanisms related to the improvement of tensile ductility were investigated by focusing on how the effective size of ductile dendrites affected the initiation and propagation of deformation bands or shear bands. The composites contained ∼73–76 vol.% dendrites ∼63–103 μm in size, and had excellent tensile properties with a yield strength of over 1.3 GPa and an elongation of over 7%. In the composite containing very large dendrites, deformation bands were formed at dendrites in the same direction. In the composite containing small dendrites, however, many deformation bands were actively formed inside dendrites in the several directions, and cross each other to form widely deformed areas. This wide and homogeneous deformation in both dendrites and Amorphous Matrix enhances the tensile ductility, resulting in high strength and elongation occurring simultaneously. In order to theoretically explain the enhanced tensile ductility, a finite-element method (FEM) analysis based on the real microstructures considering dendrite crystal orientations was performed. The FEM simulation results of deformation bands or shear bands were in good agreement with the experimental findings. The reasons for such a good match between the simulation and experimental results are discussed in detail.
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tensile deformation behavior of two ti based Amorphous Matrix composites containing ductile β dendrites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Choongnyun Paul Kim, Sunghak LeeAbstract:Abstract In this study, two Ti-based Amorphous Matrix composites containing Nb and Ta contents were fabricated by a vacuum arc melting method, and deformation mechanisms related to improvement of strength and ductility were investigated by observing the initiation and propagation of deformation bands, shear bands, or twins occurring at ductile dendrites and hard Amorphous Matrix. The two composites contained 60–66 vol.% of coarse dendrites sized by 42–73 μm had excellent tensile properties of yield strength over 1 GPa and elongation over 5%. In the composite having higher Ta content, shear bands were formed first at the Amorphous Matrix, while dendrites were hardly deformed. With further deformation, dendrites were deformed in a band shape as a considerable number of twins were formed inside some dendrites. According to the EBSD analysis result of this composite, parts of β phases were transformed to α phases during the tensile deformation, and twins were formed at phase-transformed α phases. In this composite mixed with α and β phases, β phases could play a role in interrupting the twin formation at α phases, which resulted in the increase in stress required for the twin formation and consequently the increase in yield and tensile strengths.
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microstructure and tensile properties of high strength high ductility ti based Amorphous Matrix composites containing ductile dendrites
Acta Materialia, 2011Co-Authors: Choongnyun Paul Kim, Sunghak Lee, Nack J. KimAbstract:Abstract In the present study, two Ti-based Amorphous Matrix composites containing ductile dendrites dispersed in an Amorphous Matrix were fabricated by a vacuum arc melting method, and deformation mechanisms related to the improvement of strength and ductility were investigated by focusing on how ductile dendrites affected the initiation and propagation of deformation bands, shear bands or twins. Ti-based Amorphous Matrix composites contained 70–73 vol.% coarse dendrites of size 90–180 μm, and had excellent tensile properties of the yield strength (1.2–1.3 GPa) and elongation (8–9%). The Ta-containing composite showed strain hardening after yielding, and reached fracture without showing necking, whereas necking occurred straight after yielding without strain hardening in the Nb-containing composite. The improved tensile elongation and strain hardening behavior was explained by the homogeneous distribution of dendrites large enough to form deformation bands or twins, the role of β phases surrounding α phases to prevent the formation of twins, and deformation mechanisms such as strain-induced β to α transformation.
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Microstructure and Mechanical Properties of Two Continuous-Fiber-Reinforced Zr-Based Amorphous Alloy Composites Fabricated by Liquid Pressing Process
Metallurgical and Materials Transactions A, 2008Co-Authors: Sang-bok Lee, Sang-kwan Lee, Sunghak Lee, Nack J. KimAbstract:The feasibility to fabricate the tungsten and STS-fiber-reinforced Amorphous alloy Matrix composites was verified by analyses of the thermal stress and cooling behavior between Matrix and metallic fibers. Approximately 50 to 65 vol pct of fibers were homogeneously distributed inside the Amorphous Matrix, although the Matrix of the STS-fiber-reinforced composite contained a small amount of crystalline phases. The compressive test results indicated that the tungsten-fiber-reinforced composite was not fractured at one time after reaching the maximum compressive strength of 2060 MPa, but showed some ductility as the compressive load was sustained by fibers. The STS-fiber-reinforced composite showed the maximum strength of about 1050 MPa, and its strength maintained over 800 MPa until reaching the strain of 40 pct. Both tungsten and STS fibers favorably affected the strength and ductility of the composites by interrupting the propagation of shear bands formed in the Amorphous Matrix, by dispersing the stress applied to the Matrix, and by promoting deformation mechanisms such as fiber buckling. These findings confirmed the possibility to apply the continuous-fiber-reinforced Amorphous alloy Matrix composites to structural materials requiring excellent properties.
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deformation induced nanocrystallization and its influence on work hardening in a bulk Amorphous Matrix composite
Acta Materialia, 2004Co-Authors: Jaechul Lee, Sunghak Lee, Yu Chan Kim, Jaepyoung Ahn, Hyoung Seop Kim, Byeongjoo LeeAbstract:With the development of various processes to produce bulk Amorphous composites with enhanced plasticity, investigations of the mechanical behaviors of the Amorphous alloys in the plastic regime have now become feasible. In addition to dramatically enhanced plasticity, some bulk Amorphous composites have exhibited a work hardening behavior during plastic deformation. Considering that most strengthening mechanisms, such as solid solution hardening, martensitic hardening, etc., operative in crystalline metals are associated with dislocations, the work hardening behavior observed from Amorphous composites, where dislocations do not exist, is of a special scientific interest. We have observed that quasistatic compression imposed to the Amorphous composite induces the homogeneous precipitation of nanocrystallites from the Amorphous Matrix of the composite, which, in turn, leads to strengthening the Amorphous composite. The strengthening mechanism of the Amorphous Matrix composite is investigated as well.
Haifeng Zhang - One of the best experts on this subject based on the ideXlab platform.
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modulating work hardening behaviors and tensile plasticity of in situ formed ductile dendrite ti based bulk metallic glass composites with tailored dendrite composition
Scripta Materialia, 2018Co-Authors: Dingming Liu, Zhengwang Zhu, Long Zhang, Aimin Wang, Hongwei Zhang, Yandong Wang, Haifeng ZhangAbstract:Abstract A novel series of in-situ dendrite Ti-based bulk metallic glass composites (BMGCs) were obtained. The Mo content of the dendrites monotonically increases from nil to 10.5 at% while the dendrite volume fraction and the composition of the Amorphous Matrix remain nearly invariant. It was found that the mechanical behaviors varied tremendously simply by changing the Mo content. Thus, the correlation between the composition and the mechanical behaviors under tension has been determined for in-situ dendrite Ti-based BMGCs for the first time.
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in situ high energy x ray diffraction studies of deformation induced phase transformation in ti based Amorphous alloy composites containing ductile dendrites
Acta Materialia, 2013Co-Authors: Zhengwang Zhu, Yandong Wang, Haifeng Zhang, Yang RenAbstract:Abstract The deformed-induced microstructure evolution and phase transformation behavior of Ti-based Amorphous alloy composites (AACs) containing ductile dendrites in situ formed during solidification were investigated using ex situ transmission electron microscopy (TEM) and in situ high-energy X-ray diffraction (HE-XRD). In situ synchrotron-based HE-XRD experiments provide clear evidence on the deformation-induced phase transformation from β to α″ martensite initiated already in the linear elastic stage of the macroscopic stress–strain curve. Detailed analyses from the diffraction experiments show that the grains that were aligned with [0 0 1] β along the loading direction (LD) were then easily transformed into α″ martensite, whereas the martensitic variants oriented with [1 0 0] α″ along LD were preferentially formed under compression. The current study provides quantitative information about changes in various microstresses between the crystal phase and the Amorphous Matrix during deformation. Enhancement of the macroscopic plasticity of the AACs was mainly attributed to the strain relaxation in the β phase and to the formation of multiple shear bands in the Amorphous Matrix triggered by the deformation-induced phase transformation inside β, knowledge of which greatly deepens understanding of the complex micromechanical behaviors in advanced AACs.
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liquid phase separation and microstructure characterization in a designed al based Amorphous Matrix composite with spherical crystalline particles
Journal of Alloys and Compounds, 2010Co-Authors: Baijun Yang, Jiuzhou Zhao, Haifeng ZhangAbstract:The solidification process of the immiscible alloys exhibit a unique opportunity in designing the composites with the spherical crystalline particles dispersed in the Amorphous metal Matrix. The typical Al–Pb immiscible alloy and the additional elements Ni, Y and Co were selected, and the Al82.87Pb2.5Ni4.88Y7.8Co1.95 multicomponent immiscible alloy has been designed. The ribbon samples of the multicomponent alloy were prepared by using the melt spinning technique. The ribbons were characterized by the scanning electron microscopy (SEM). The phase constitution and transformation were studied by the X-ray diffraction (XRD) and the differential scanning calorimeter (DSC). It was revealed in the as-quenched ribbons the Al-based metallic glass Matrix is embedded by the spherical crystalline Pb-rich particles. The microstructure evolution, the glass formation and the thermal stability of the as-prepared composite have been discussed in detail. A method has been developed based on the mechanism of the liquid–liquid phase transformation in the miscibility gap of the multicomponent immiscible alloy to produce the spherical crystalline particles in the Amorphous Matrix.
Akihisa Inoue - One of the best experts on this subject based on the ideXlab platform.
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formation stability and ultrahigh strength of novel nanostructured alloys by partial crystallization of high entropy fe0 25co0 25ni0 25cr0 125mo0 125 86 89b11 14 Amorphous phase
Acta Materialia, 2019Co-Authors: Fengwu Wang, Akihisa Inoue, F L Kong, Shengli Zhu, E Shalaan, F Almarzouki, W J Botta, C S Kiminami, Yu P Ivanov, A L GreerAbstract:Abstract Heating-induced crystallization of high-entropy (HE) (Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)86‒89B11‒14 Amorphous (am) alloys is examined to develop new structural materials with low B contents. The crystallization of 11B alloy occurs in three stages: first nanoscale bcc precipitates form in the Amorphous Matrix, second nanoscale fcc precipitates form, and the residual Amorphous phase disappears in the third stage which yields borides in addition to the bcc and fcc phases. Crystallization of 14B alloy is the same, except that the order of appearance of bcc and fcc is reversed. The bcc and fcc particle diameters are 5–15 nm and remain almost unchanged up to ∼960 K. On annealing, ultrahigh hardness of 1500–1550 (unprecedented for boride-free structures) is attained just before the third crystallization stage. This hardening and the thermal stability of the novel [am + bcc + fcc] structures are remarkable at such low boron content and encouraging for development as ultrahigh-strength alloys. The results are interpreted in terms of the nature and extent of partitioning of elemental components between the bcc/fcc phases and the Amorphous Matrix, and the size and defect structures of the bcc and fcc precipitates. The magnetic flux density at room temperature increases by precipitation of bcc and decreases by appearance of fcc. Slower quenching of the 11B alloy shows a pseudo-polymorphic crystallization that may be characteristic of multicomponent HE systems.
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metal semiconductor Amorphous and nanoscale ge phase composites produced by rapid solidification and by devitrification of an Amorphous Matrix
Journal of Electronic Materials, 2006Co-Authors: D V Louzguineluzgin, Akihisa InoueAbstract:In the current paper, we review our recent studies and present new data on Ge- and Si-based Amorphous and composite alloys containing nanoscale semiconductive Ge or Ge(Si) solid solution particles homogeneously distributed in a conductive Amorphous Matrix formed by rapid solidification or by devitrification of an Amorphous single phase. Ge-rich alloys containing up to 70 at. % Ge were produced in Ge−Al−Cr-RE (RE, rare earth elements) systems, while Si-based Amorphous alloys containing up to 60 at.% Si were produced in Si−Al-TM (TM, transition metals) systems by the melt-spinning technique. The samples are ribbons 10–100 μm thick. Nanocomposites in Si−Al-TM-Ge and some Ge−Al−Cr-RE alloys were produced directly by rapid solidification, while in the Ge55Mg35Y10 alloy they were produced by devitrification of the glassy phase on heating. The semiconductive nanoparticles exhibit homogeneous distribution, and their sizes vary from ∼7 nm to 20 nm. The structure, phase transformations, and properties of the samples are discussed.
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gold as an alloying element promoting formation of a nanoicosahedral phase in a cu based alloy
Journal of Alloys and Compounds, 2003Co-Authors: Dmitri V Louzguine, Akihisa InoueAbstract:Abstract The present paper presents a new application field of Au as an alloying element in Cu-based glassy alloys with a tendency to form nanoscale icosahedral particles having quasicrystalline symmetry upon devitrification. Nanoicosahedral particles with a size below 10 nm are formed in the Amorphous Matrix of Cu55Zr30Ti10Au5 glassy alloy in the initial stage of the devitrification process. The paper also illustrates structure changes on heating studied by X-ray diffraction, transmission electron microscopy, differential scanning and isothermal calorimetry methods.
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is cu60ti10zr30 a bulk glass forming alloy
Applied Physics Letters, 2003Co-Authors: Jianzhong Jiang, Junji Saida, H Kato, Tetsu Ohsuna, Akihisa InoueAbstract:The microstructures of Cu60Ti10Zr30 alloys fabricated by using two different methods, (rods of 2.5 mm in diameter prepared by a copper-mold casting method, and ribbons of about 0.03 mm in thickness prepared by the melt-spinning method), have been investigated by transmission electron microscopy and high-resolution transmission electron microscopy. Surprisingly, we found that the alloy in both geometries contains cubic nanometer-sized crystals of about 5–7 nm in diameter with a lattice parameter of 0.45 nm for ribbons and 7–15 nm in diameter with a lattice parameter of 0.42 nm for rods. Nanocrystals with a significant volume fraction are randomly distributed in the Amorphous Matrix. The copper element is enriched in nanocrystals while a slightly high zirconium content is found in the Matrix. We classify that the Cu60Ti10Zr30 alloy prepared by both of the aforementioned methods is a nanocomposite: Nanocrystals embedded in an Amorphous Matrix.
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Nanocrystalline composites with high strength obtained in Zr–Ti–Ni–Cu–Al bulk Amorphous alloys
Applied Physics Letters, 1999Co-Authors: Dmitri V Louzguine, Chunfei Li, Akihisa InoueAbstract:Nanocrystalline composites with the grain size less than 10 nm were produced by annealing of Cu-mold cast Zr70−x−yTixNi10Cu20Aly (X=5–7.5 and Y=10–15 at %) bulk Amorphous alloys. The nanostructured alloys show increased tensile strength at the volume fraction of nanoparticles less than 30%. The microstructure of the Amorphous alloys was found to contain medium range order (MRO) domains, which uniformly distributed in the Amorphous Matrix. We suggest that MRO domains provide nucleation sites for precipitation of the primary crystals and lead to the formation of nanocrystalline composites.
J W Qiao - One of the best experts on this subject based on the ideXlab platform.
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corrosion behavior and pitting susceptibility of in situ ti based metallic glass Matrix composites in 3 5 wt nacl solutions
Applied Surface Science, 2017Co-Authors: A D Lan, J W Qiao, Huimin Yang, Peide HanAbstract:Abstract The Ti62Zr12V13Cu4Be9, Ti58Zr16V10Cu4Be12, Ti46Zr20V12Cu5Be17, and Ti40Zr24V12Cu5Be19 metallic glass Matrix composites (MGMCs) were prepared by copper mould casting. The corrosion resistance and the pitting susceptibility of Ti-based MGMCs were tested on their cross-sectional areas in 3.5 wt.% NaCl solutions by potentiodynamic polarization measurements. The composites with lower Ti contents (Ti40Zr24V12Cu5Be19 and Ti46Zr20V12Cu5Be17) exhibit a low resistance to the chloride induced pitting and local corrosion. The preferential dissolution of Amorphous Matrix is explained by the high chemical reactivity of beryllium element compared to that of stable dendrites and by the detected lower Ti and V contents. However, fairly good passivity was found in the composite with higher Ti contents (Ti62Zr12V13Cu4Be9). XPS measurements revealed that protective Ti-enriched oxide film was formed on the composite surface, additionally, lower content of beryllium element in Amorphous Matrix hinder the selective corrosion of Amorphous Matrix. The assessment of experimental observation leads to a proposed corrosion mechanism involving selective dissolution of Amorphous Matrix and chloride induced pitting process.
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Resolving ensembled microstructural information of bulk-metallic-glass-Matrix composites using synchrotron x-ray diffraction
Applied Physics Letters, 2010Co-Authors: J W Qiao, Ewen Huang, Feng Jiang, Tamás Ungár, Gábor Csiszár, Yang Ren, Peter K. Liaw, Yong ZhangAbstract:The microstructural characterization of the Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0 bulk-metallic-glass-Matrix composites is investigated using high-energy synchrotron x-ray diffraction. The convoluted diffraction-intensity distribution in the azimuthal direction is naturally yielded from the spatial arrangements of the crystalline dendrites and their Amorphous Matrix. We facilitate the area selection and the intensity integration of the diffraction collected from a two-dimensional detector to characterize the diffraction intensity of the Amorphous Matrix. The results enable us to apply the modified Williamson–Hall plots for using the peak width to study the microstrain and micromechanism of the deformation of the crystalline phase.
Choongnyun Paul Kim - One of the best experts on this subject based on the ideXlab platform.
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high tensile ductility of ti based Amorphous Matrix composites modified from conventional ti 6al 4v titanium alloy
Acta Materialia, 2013Co-Authors: Changwoo Jeon, Choongnyun Paul Kim, Soo Hyun Joo, Hyungmo Kim, Sunghak LeeAbstract:Abstract Three Ti-based Amorphous Matrix composites containing ductile dendrites were fabricated by adding alloying elements of Ti, Zr, V, Ni, Al and Be into a conventional Ti–6Al–4V alloy, and the deformation mechanisms related to the improvement of tensile ductility were investigated by focusing on how the effective size of ductile dendrites affected the initiation and propagation of deformation bands or shear bands. The composites contained ∼73–76 vol.% dendrites ∼63–103 μm in size, and had excellent tensile properties with a yield strength of over 1.3 GPa and an elongation of over 7%. In the composite containing very large dendrites, deformation bands were formed at dendrites in the same direction. In the composite containing small dendrites, however, many deformation bands were actively formed inside dendrites in the several directions, and cross each other to form widely deformed areas. This wide and homogeneous deformation in both dendrites and Amorphous Matrix enhances the tensile ductility, resulting in high strength and elongation occurring simultaneously. In order to theoretically explain the enhanced tensile ductility, a finite-element method (FEM) analysis based on the real microstructures considering dendrite crystal orientations was performed. The FEM simulation results of deformation bands or shear bands were in good agreement with the experimental findings. The reasons for such a good match between the simulation and experimental results are discussed in detail.
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tensile deformation behavior of two ti based Amorphous Matrix composites containing ductile β dendrites
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Choongnyun Paul Kim, Sunghak LeeAbstract:Abstract In this study, two Ti-based Amorphous Matrix composites containing Nb and Ta contents were fabricated by a vacuum arc melting method, and deformation mechanisms related to improvement of strength and ductility were investigated by observing the initiation and propagation of deformation bands, shear bands, or twins occurring at ductile dendrites and hard Amorphous Matrix. The two composites contained 60–66 vol.% of coarse dendrites sized by 42–73 μm had excellent tensile properties of yield strength over 1 GPa and elongation over 5%. In the composite having higher Ta content, shear bands were formed first at the Amorphous Matrix, while dendrites were hardly deformed. With further deformation, dendrites were deformed in a band shape as a considerable number of twins were formed inside some dendrites. According to the EBSD analysis result of this composite, parts of β phases were transformed to α phases during the tensile deformation, and twins were formed at phase-transformed α phases. In this composite mixed with α and β phases, β phases could play a role in interrupting the twin formation at α phases, which resulted in the increase in stress required for the twin formation and consequently the increase in yield and tensile strengths.
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microstructure and tensile properties of high strength high ductility ti based Amorphous Matrix composites containing ductile dendrites
Acta Materialia, 2011Co-Authors: Choongnyun Paul Kim, Sunghak Lee, Nack J. KimAbstract:Abstract In the present study, two Ti-based Amorphous Matrix composites containing ductile dendrites dispersed in an Amorphous Matrix were fabricated by a vacuum arc melting method, and deformation mechanisms related to the improvement of strength and ductility were investigated by focusing on how ductile dendrites affected the initiation and propagation of deformation bands, shear bands or twins. Ti-based Amorphous Matrix composites contained 70–73 vol.% coarse dendrites of size 90–180 μm, and had excellent tensile properties of the yield strength (1.2–1.3 GPa) and elongation (8–9%). The Ta-containing composite showed strain hardening after yielding, and reached fracture without showing necking, whereas necking occurred straight after yielding without strain hardening in the Nb-containing composite. The improved tensile elongation and strain hardening behavior was explained by the homogeneous distribution of dendrites large enough to form deformation bands or twins, the role of β phases surrounding α phases to prevent the formation of twins, and deformation mechanisms such as strain-induced β to α transformation.