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D H Kim - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and mechanical properties of Cu-based Bulk Amorphous Alloy billets fabricated by spark plasma sintering
'Elsevier BV', 2019Co-Authors: Ck Kim, D H Kim, Hs Lee, Sy Shin, Jc Lee, Lee SAbstract:In this study, Cu-based Bulk Amorphous Alloy billets were fabricated by a powder metallurgy route, and their microstructure and mechanical properties were investigated. Rapidly solidified Amorphous powders were produced by a conventional N-2 gas atomization method. In order to consolidate Amorphous Alloy billets, a spark plasma sintering (SPS) equipment was set up, and variables for hot consolidation were established. Using the consolidation temperature of 480 degrees C under a pressure of 80 MPa, good quality Amorphous Alloy billets having very few micropores or crystalline phase particles were obtained. Compressive strength of the billet was 1.8 GPa, which was about 6% lower than that of the cast Amorphous Alloy billet. This reduction was associated with the presence of few micropores, crystalline phase particles and thin oxide layers formed along prior powder boundaries in the billets. Amorphous matrix composite billets containing Cu particles homogeneously distributed in the Amorphous matrix were successfully fabricated by the SPS consolidation. These composite billets showed a considerable amount of plastic strain because of the presence of ductile Cu particles, although their compressive strength was lower than that of the Amorphous Alloy billets. (c) 2005 Elsevier B.V. All rights reserved.X1141sciescopu
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mechanical behavior of cu54ni6zr22ti18 Bulk Amorphous Alloy during multi pass warm rolling
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: H J Kim, J K Lee, T S Kim, J C Bae, Eun Sook Park, M Y Huh, D H KimAbstract:Abstract Cu–Ni–Zr–Ti Bulk Amorphous thin strips were produced by multi-pass warm rolling of the Amorphous powder at temperatures in the supercooled liquid region. Process variables for rolling of the Bulk Amorphous strips were properly controlled to prevent onset of crystallization and failure during rolling up to three passes. During rolling of the Amorphous powder, both the deformation and densification took place and the newly developed surface on the deformed Amorphous particles enhances the consolidation leading to an increase in the strength. The strain state during rolling was analyzed by use of the finite element method. FEM results indicate that a high strain rate larger than 10 s −1 prevails during rolling and gradients of the tensile strain rate in the rolling direction may initiate cracks.
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cu based Bulk Amorphous Alloys prepared by consolidation of Amorphous powders in the supercooled liquid region
Intermetallics, 2004Co-Authors: D H Kim, J K Lee, Hyunouk Kim, Sangsoo Shin, Hye Gwang Jeong, J C BaeAbstract:Abstract We report the fabrication of the Cu–Ni–Zr–Ti Bulk Amorphous Alloys by warm rolling of Amorphous powders, which have been prepared by a high-pressure gas atomization. The Cu54Ni6Zr22Ti18 Amorphous powders obtained by a high-pressure He gas atomization method has a wide supercooled liquid region of 53 K. By warm rolling of Amorphous powders in the supercooled liquid state, a fully Amorphous Cu54Ni6Zr22Ti18 Alloy is successfully synthesized. The conditions for rolling are obtained from the time–temperature–transformation curve by measuring the time for the onset of crystallization during isothermal annealing in differential scanning calorimetry. The rolled Bulk Amorphous Cu54Ni6Zr22Ti18 Alloy exhibited high strength about 1.9 GPa, which is against similar to that obtained in the as-cast Bulk Amorphous Alloy.
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ni based Bulk Amorphous Alloys in the ni ti zr si sn system
Journal of Materials Research, 2000Co-Authors: Teahoon Park, D H KimAbstract:New Ni-based Bulk Amorphous Alloys in the Alloy system Ni–Ti–Zr–(Si,Sn) were developed through systematic Alloy design based upon the empirical rules for high glass forming Alloys. Small additions of Si and/or Sn significantly improved the glass forming ability (GFA) of the Alloys Ni 57 Ti 23− x Zr 20 (Si,Sn) x leading to a Ni-based Bulk Amorphous Alloy. The Amorphous ribbons of the Alloys Ni 57 Ti 23− x Zr 20 (Si,Sn) x exhibited very high glass transition temperatures ( T g > 823 K), crystallization temperatures ( T x > 883 K), and large undercooled liquid regions (δ T x > 50 K) implying the high GFA of the Alloys. Fully Amorphous rods with the diameter of up to 2 mm can be fabricated by a copper mold casting method. Development of the new Ni-based Bulk Amorphous Alloys having high T g, T x , and δ T x expands the practical applications of Amorphous Alloys as structural materials.
Seung Yong Shin - One of the best experts on this subject based on the ideXlab platform.
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microstructure and mechanical properties of cu based Bulk Amorphous Alloy billets fabricated by spark plasma sintering
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Seung Yong ShinAbstract:Abstract In this study, Cu-based Bulk Amorphous Alloy billets were fabricated by a powder metallurgy route, and their microstructure and mechanical properties were investigated. Rapidly solidified Amorphous powders were produced by a conventional N 2 gas atomization method. In order to consolidate Amorphous Alloy billets, a spark plasma sintering (SPS) equipment was set up, and variables for hot consolidation were established. Using the consolidation temperature of 480 °C under a pressure of 80 MPa, good quality Amorphous Alloy billets having very few micropores or crystalline phase particles were obtained. Compressive strength of the billet was 1.8 GPa, which was about 6% lower than that of the cast Amorphous Alloy billet. This reduction was associated with the presence of few micropores, crystalline phase particles and thin oxide layers formed along prior powder boundaries in the billets. Amorphous matrix composite billets containing Cu particles homogeneously distributed in the Amorphous matrix were successfully fabricated by the SPS consolidation. These composite billets showed a considerable amount of plastic strain because of the presence of ductile Cu particles, although their compressive strength was lower than that of the Amorphous Alloy billets.
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new cu based Bulk metallic glasses with high strength of 2000 mpa
Materials Science Forum, 2004Co-Authors: Seung Yong Shin, Ha Guk JeongAbstract:New Cu-based Bulk Amorphous Alloys exhibiting a large supercooled liquid region and good mechanical properties were formed in a quaternary Cu-Ni-Zr-Ti systems consisting of only metallic elements. The compositional range for the formation of the Amorphous Alloys that have high glass forming ability (GFA) (> 3 mm diameter) and large supercooled liquid region (> 50 K) is defined in the pseudo-ternary phase diagram Cu-Ni-(Zr, Ti). A Bulk Amorphous Cu54Ni6Zr22Ti18 Alloy with the diameter of 6 mm can be prepared by copper mold casting. The Cu54Ni6Zr22Ti18 Alloy shows glass transition temperature (Tg) of 712 K, crystallization temperature (Tx) of 769 K and supercooled liquid region (ΔTx) of 57 K. The Cu54Ni6Zr22Ti18 Alloy exhibits high compressive fracture strength of about 2130 MPa with a plastic strain of about 1.5 %. The new Cu-based Bulk Amorphous Alloy with high GFA and good mechanical properties allows us to expect the extension of application fields as a new engineering material.
Nj Kim - One of the best experts on this subject based on the ideXlab platform.
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Effects of crystalline particles on mechanical properties of strip-cast Zr-base Bulk Amorphous Alloy
'Elsevier BV', 2019Co-Authors: Jg Lee, Dg Lee, Lee S, Km Cho, Nj KimAbstract:Effects of crystalline phase particles formed in a strip-cast Zr-base Bulk Amorphous Alloy on strength, ductility, and fracture toughness were investigated by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope chamber. The compressive and fracture toughness test results indicated that strength, ductility, and fracture toughness of the strip-cast Amorphous Alloy were higher than those of the as-cast monolithic Amorphous Alloy, although the strip-cast Alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. According to the in situ microfracture observation, crystalline particles were easily cracked under low stress levels, acted as blocking sites of shear band or crack propagation, and provided initiation sites of multiple shear bands. Thus, the improvement of mechanical properties in the strip-cast Alloy could be explained by mechanisms of (1) blocking of crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles. (C) 2004 Elsevier B.V. All rights reserved.X11
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In situ fracture observation and fracture toughness analysis of Zr-based Bulk Amorphous Alloys
'Elsevier BV', 2019Co-Authors: Jg Lee, Lee S, Nj Kim, Ks Sohn, Cp KimAbstract:The fracture property improvement of Zr-based Bulk Amorphous Alloy containing ductile crystalline particles was explained by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber. Strength and apparent fracture toughness measured from the in situ fracture test of the Amorphous Alloy containing crystalline particles were lower than those of the monolithic Amorphous Alloy, whereas its ductility was higher. According to the microfracture observation, shear bands were initiated from ductile crystalline particles, and the propagation of the shear bands or cracks was blocked by crystalline particles, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the Alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching. (c) 2007 Elsevier B.V. All rights reserved.X1
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FABRICATION OF Bulk Amorphous Alloy SHEETS BY STRIP CASTING
'Trans Tech Publications Ltd.', 2019Co-Authors: Jg Lee, Ss Park, Sb Lee, Ht Chung, Nj KimAbstract:A study has been made to fabricate the Bulk Amorphous Alloy sheets by strip casting. Simulation of the solidification behavior of the Zr-base Amorphous forming Alloy during strip casting shows that fast enough cooling rate can be achieved by strip casting to form Amorphous structure through the thickness of sheet. Two Alloys with different glass forming abilities were subjected to actual strip casting, which shows that both Zr-base Alloy with high GFA and Cu-base Alloy with much less GFA can be strip cast forming Amorphous structure. The results indicate that the strip casting is a viable process for continuous fabrication of sheets of Bulk Amorphous Alloys with a wide range of critical cooling rates.112sciescopu
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CONTINUOUS FABRICATION OF Bulk Amorphous Alloy SHEETS BY TWIN-ROLL STRIP CASTING
'Elsevier BV', 2019Co-Authors: Jg Lee, Lee S, Lee H, Nj KimAbstract:Twin-roll strip casting was utilized to fabricate the sheet products of Zr- and Cu-base Bulk Amorphous Alloys with quite different glass forming abilities (GFAs). Simulation of the solidification behavior of the these Amorphous forming Alloys during twin-roll strip casting shows that suitable cooling rate can be achieved by twin-roll strip casting to form Amorphous structure through the thickness of sheet. Optimum twin-roll strip casting conditions have been suggested based on the simulation results. Actual twin-roll strip casting shows that both Zr-base Alloy with high GFA and Cu-base Alloy with much less GFA can be strip cast forming Amorphous structure. The results indicate that the twin-roll strip casting is a viable process for continuous fabrication of sheets of Bulk Amorphous Alloys with a wide range of critical cooling rates. (c) 2006 Elsevier Ltd. All rights reserved.1115sciescopu
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Effects of crystalline particles on mechanical properties of strip-cast Zr-base Bulk Amorphous Alloy
'Elsevier BV', 2019Co-Authors: Jg Lee, Dg Lee, Lee S, Km Cho, Nj KimAbstract:Effects of crystalline phase particles formed in a strip-cast Zr-base Bulk Amorphous Alloy on strength, ductility, and fracture toughness were investigated by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope chamber. The compressive and fracture toughness test results indicated that strength, ductility, and fracture toughness of the strip-cast Amorphous Alloy were higher than those of the as-cast monolithic Amorphous Alloy, although the strip-cast Alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. According to the in situ microfracture observation, crystalline particles were easily cracked under low stress levels, acted as blocking sites of shear band or crack propagation, and provided initiation sites of multiple shear bands. Thus, the improvement of mechanical properties in the strip-cast Alloy could be explained by mechanisms of (1) blocking of crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles. (C) 2004 Elsevier B.V. All rights reserved.X1117sciescopu
Lee S - One of the best experts on this subject based on the ideXlab platform.
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Effects of crystalline particles on mechanical properties of strip-cast Zr-base Bulk Amorphous Alloy
'Elsevier BV', 2019Co-Authors: Jg Lee, Dg Lee, Lee S, Km Cho, Nj KimAbstract:Effects of crystalline phase particles formed in a strip-cast Zr-base Bulk Amorphous Alloy on strength, ductility, and fracture toughness were investigated by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope chamber. The compressive and fracture toughness test results indicated that strength, ductility, and fracture toughness of the strip-cast Amorphous Alloy were higher than those of the as-cast monolithic Amorphous Alloy, although the strip-cast Alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. According to the in situ microfracture observation, crystalline particles were easily cracked under low stress levels, acted as blocking sites of shear band or crack propagation, and provided initiation sites of multiple shear bands. Thus, the improvement of mechanical properties in the strip-cast Alloy could be explained by mechanisms of (1) blocking of crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles. (C) 2004 Elsevier B.V. All rights reserved.X11
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In situ fracture observation and fracture toughness analysis of Zr-based Bulk Amorphous Alloys
'Elsevier BV', 2019Co-Authors: Jg Lee, Lee S, Nj Kim, Ks Sohn, Cp KimAbstract:The fracture property improvement of Zr-based Bulk Amorphous Alloy containing ductile crystalline particles was explained by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber. Strength and apparent fracture toughness measured from the in situ fracture test of the Amorphous Alloy containing crystalline particles were lower than those of the monolithic Amorphous Alloy, whereas its ductility was higher. According to the microfracture observation, shear bands were initiated from ductile crystalline particles, and the propagation of the shear bands or cracks was blocked by crystalline particles, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the Alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching. (c) 2007 Elsevier B.V. All rights reserved.X1
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CONTINUOUS FABRICATION OF Bulk Amorphous Alloy SHEETS BY TWIN-ROLL STRIP CASTING
'Elsevier BV', 2019Co-Authors: Jg Lee, Lee S, Lee H, Nj KimAbstract:Twin-roll strip casting was utilized to fabricate the sheet products of Zr- and Cu-base Bulk Amorphous Alloys with quite different glass forming abilities (GFAs). Simulation of the solidification behavior of the these Amorphous forming Alloys during twin-roll strip casting shows that suitable cooling rate can be achieved by twin-roll strip casting to form Amorphous structure through the thickness of sheet. Optimum twin-roll strip casting conditions have been suggested based on the simulation results. Actual twin-roll strip casting shows that both Zr-base Alloy with high GFA and Cu-base Alloy with much less GFA can be strip cast forming Amorphous structure. The results indicate that the twin-roll strip casting is a viable process for continuous fabrication of sheets of Bulk Amorphous Alloys with a wide range of critical cooling rates. (c) 2006 Elsevier Ltd. All rights reserved.1115sciescopu
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Effects of crystalline particles on mechanical properties of strip-cast Zr-base Bulk Amorphous Alloy
'Elsevier BV', 2019Co-Authors: Jg Lee, Dg Lee, Lee S, Km Cho, Nj KimAbstract:Effects of crystalline phase particles formed in a strip-cast Zr-base Bulk Amorphous Alloy on strength, ductility, and fracture toughness were investigated by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope chamber. The compressive and fracture toughness test results indicated that strength, ductility, and fracture toughness of the strip-cast Amorphous Alloy were higher than those of the as-cast monolithic Amorphous Alloy, although the strip-cast Alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. According to the in situ microfracture observation, crystalline particles were easily cracked under low stress levels, acted as blocking sites of shear band or crack propagation, and provided initiation sites of multiple shear bands. Thus, the improvement of mechanical properties in the strip-cast Alloy could be explained by mechanisms of (1) blocking of crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles. (C) 2004 Elsevier B.V. All rights reserved.X1117sciescopu
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Microstructure and mechanical properties of Cu-based Bulk Amorphous Alloy billets fabricated by spark plasma sintering
'Elsevier BV', 2019Co-Authors: Ck Kim, D H Kim, Hs Lee, Sy Shin, Jc Lee, Lee SAbstract:In this study, Cu-based Bulk Amorphous Alloy billets were fabricated by a powder metallurgy route, and their microstructure and mechanical properties were investigated. Rapidly solidified Amorphous powders were produced by a conventional N-2 gas atomization method. In order to consolidate Amorphous Alloy billets, a spark plasma sintering (SPS) equipment was set up, and variables for hot consolidation were established. Using the consolidation temperature of 480 degrees C under a pressure of 80 MPa, good quality Amorphous Alloy billets having very few micropores or crystalline phase particles were obtained. Compressive strength of the billet was 1.8 GPa, which was about 6% lower than that of the cast Amorphous Alloy billet. This reduction was associated with the presence of few micropores, crystalline phase particles and thin oxide layers formed along prior powder boundaries in the billets. Amorphous matrix composite billets containing Cu particles homogeneously distributed in the Amorphous matrix were successfully fabricated by the SPS consolidation. These composite billets showed a considerable amount of plastic strain because of the presence of ductile Cu particles, although their compressive strength was lower than that of the Amorphous Alloy billets. (c) 2005 Elsevier B.V. All rights reserved.X1141sciescopu
Jg Lee - One of the best experts on this subject based on the ideXlab platform.
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Effects of crystalline particles on mechanical properties of strip-cast Zr-base Bulk Amorphous Alloy
'Elsevier BV', 2019Co-Authors: Jg Lee, Dg Lee, Lee S, Km Cho, Nj KimAbstract:Effects of crystalline phase particles formed in a strip-cast Zr-base Bulk Amorphous Alloy on strength, ductility, and fracture toughness were investigated by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope chamber. The compressive and fracture toughness test results indicated that strength, ductility, and fracture toughness of the strip-cast Amorphous Alloy were higher than those of the as-cast monolithic Amorphous Alloy, although the strip-cast Alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. According to the in situ microfracture observation, crystalline particles were easily cracked under low stress levels, acted as blocking sites of shear band or crack propagation, and provided initiation sites of multiple shear bands. Thus, the improvement of mechanical properties in the strip-cast Alloy could be explained by mechanisms of (1) blocking of crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles. (C) 2004 Elsevier B.V. All rights reserved.X11
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In situ fracture observation and fracture toughness analysis of Zr-based Bulk Amorphous Alloys
'Elsevier BV', 2019Co-Authors: Jg Lee, Lee S, Nj Kim, Ks Sohn, Cp KimAbstract:The fracture property improvement of Zr-based Bulk Amorphous Alloy containing ductile crystalline particles was explained by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber. Strength and apparent fracture toughness measured from the in situ fracture test of the Amorphous Alloy containing crystalline particles were lower than those of the monolithic Amorphous Alloy, whereas its ductility was higher. According to the microfracture observation, shear bands were initiated from ductile crystalline particles, and the propagation of the shear bands or cracks was blocked by crystalline particles, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the Alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching. (c) 2007 Elsevier B.V. All rights reserved.X1
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FABRICATION OF Bulk Amorphous Alloy SHEETS BY STRIP CASTING
'Trans Tech Publications Ltd.', 2019Co-Authors: Jg Lee, Ss Park, Sb Lee, Ht Chung, Nj KimAbstract:A study has been made to fabricate the Bulk Amorphous Alloy sheets by strip casting. Simulation of the solidification behavior of the Zr-base Amorphous forming Alloy during strip casting shows that fast enough cooling rate can be achieved by strip casting to form Amorphous structure through the thickness of sheet. Two Alloys with different glass forming abilities were subjected to actual strip casting, which shows that both Zr-base Alloy with high GFA and Cu-base Alloy with much less GFA can be strip cast forming Amorphous structure. The results indicate that the strip casting is a viable process for continuous fabrication of sheets of Bulk Amorphous Alloys with a wide range of critical cooling rates.112sciescopu
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CONTINUOUS FABRICATION OF Bulk Amorphous Alloy SHEETS BY TWIN-ROLL STRIP CASTING
'Elsevier BV', 2019Co-Authors: Jg Lee, Lee S, Lee H, Nj KimAbstract:Twin-roll strip casting was utilized to fabricate the sheet products of Zr- and Cu-base Bulk Amorphous Alloys with quite different glass forming abilities (GFAs). Simulation of the solidification behavior of the these Amorphous forming Alloys during twin-roll strip casting shows that suitable cooling rate can be achieved by twin-roll strip casting to form Amorphous structure through the thickness of sheet. Optimum twin-roll strip casting conditions have been suggested based on the simulation results. Actual twin-roll strip casting shows that both Zr-base Alloy with high GFA and Cu-base Alloy with much less GFA can be strip cast forming Amorphous structure. The results indicate that the twin-roll strip casting is a viable process for continuous fabrication of sheets of Bulk Amorphous Alloys with a wide range of critical cooling rates. (c) 2006 Elsevier Ltd. All rights reserved.1115sciescopu
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Effects of crystalline particles on mechanical properties of strip-cast Zr-base Bulk Amorphous Alloy
'Elsevier BV', 2019Co-Authors: Jg Lee, Dg Lee, Lee S, Km Cho, Nj KimAbstract:Effects of crystalline phase particles formed in a strip-cast Zr-base Bulk Amorphous Alloy on strength, ductility, and fracture toughness were investigated by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope chamber. The compressive and fracture toughness test results indicated that strength, ductility, and fracture toughness of the strip-cast Amorphous Alloy were higher than those of the as-cast monolithic Amorphous Alloy, although the strip-cast Alloy contained a considerable amount (4.5 vol.%) of hard, brittle crystalline particles. According to the in situ microfracture observation, crystalline particles were easily cracked under low stress levels, acted as blocking sites of shear band or crack propagation, and provided initiation sites of multiple shear bands. Thus, the improvement of mechanical properties in the strip-cast Alloy could be explained by mechanisms of (1) blocking of crack propagation, (2) formation of multiple shear bands, and (3) crack deflection by crystalline particles. (C) 2004 Elsevier B.V. All rights reserved.X1117sciescopu
