RK Shiue | National Taiwan University (original) (raw)

Papers by RK Shiue

Corrosion Science, 2012

ABSTRACT The effect of tungsten inert gas welding and subsequent post-weld heat treatment on the ... more ABSTRACT The effect of tungsten inert gas welding and subsequent post-weld heat treatment on the microstructure evolution and pitting corrosion behavior of duplex stainless steel UNS S31803 was investigated. Detailed microstructure examination demonstrates that ferrite presents higher volume fraction and is easier to suffer attack of pitting corrosion than austenite in the welded zone of as-welded metal. After post-weld heat treatment, the volume fraction of austenite in the heat affected zone and weld metal is elevated significantly. The highest pitting corrosion resistance is obtained at 1080 °C with the highest critical pitting temperature and pitting nucleation resistance.

Key Engineering Materials, 2017

The purpose of this investigation is focused on the direct quench and temper mechanisms of the hi... more The purpose of this investigation is focused on the direct quench and temper mechanisms of the high strength offshore steel. Microstructural analyses of martensite and retained austenite in the direct quenched steel, simulations of martensitic transformation temperatures, Ms/Mf, and morphologies of bainite and ferrite have been evaluated in the experiment. Additionally, carbide formation after temped at various temperatures and microhardness depth profiles after heat treating are also included in the study. The direct quenched steel is primarily comprised of martensite, bainite and a few retained austenite with Vickers microhardness above 300. Tempered martensite, iron carbide and bainite are widely observed from all tempered specimens.

Advanced Materials Research, 2008

Vacuum repair brazing of Inconel 939 using various ratios of DF3 and Rene 80 powder mixtures has ... more Vacuum repair brazing of Inconel 939 using various ratios of DF3 and Rene 80 powder mixtures has been performed in this study. The porosity of the brazed zone is decreased as the amount of DF3 is increased in the powder mixture. At least four phases are observed in the brazed zone including chromium borides, sparse carbides, Ni-rich matrix and eutectic phases. Primary chromium borides are widely observed at the early stage of repair brazing. Dissolution of the Ni from the Rene 80 powder into the molten braze results in isothermal solidification of the residual melt. The chemical composition of the residual melt subsequently moves towards the lowest eutectic temperature, and the eutectic is finally formed in brazing. The oxidation resistance test is performed at 1000oC. Extensive spalling of the oxide film begins at 144 h, and catastrophic failure of the oxide film is observed at 1272 h. The oxidation resistance of the brazed zone is significantly degraded due to the formation of chr...

Active brazing is one of the ideal ways to make metal/ceramic joints. The active braze alloy cont... more Active brazing is one of the ideal ways to make metal/ceramic joints. The active braze alloy contains active element(s), such as: Ti, Zr, Cr.. . etc., reacting and wetting the ceramic surfaces during brazing. Therefore, a strong chemical bonding can be formed after brazing. Cu base active braze alloys are alternatives among active braze alloys. With the aid of additional melting point depressant, Sn, in Cu-Ti alloys, the intermetallic phase in the active braze can be changed. However, its ability to braze structural ceramics, e.g. alumina, needs further study. The purpose of this research is concentrated on the wettability study of the Cu/Sn/Ti alloy on polycrystalline alumina. Based on the experimental results, the minimum Ti content is 6 wt pct in order to effectively wet alumina. Volume fraction of the intermetallic phase in the braze will be greatly increased if the Ti content in the alloy is increased to 12 wt pct. According to sessile drop test results, 70Cu-21Sn-9Ti demonstrates the best wetting ability on alumina. Meanwhile, the Sn content in Cu/Sn/Ti alloy should be less than 21 wt pct in order to maintain proper wettability of the braze. In addition, Cu/Sn/Ti alloys have both lower wetting angle on alumina and lower thermal expansion coefficients than commercial Ticusil ® braze.

Advanced Materials Research, 2012

High-temperature brazing molybdenum using palladium and titanium foils have been investigated in ... more High-temperature brazing molybdenum using palladium and titanium foils have been investigated in the experiment. Successful brazed joints are achieved from using the palladium filler foil. Brazed joints are fully dense and free of any intermetallic phase. Three point bending strengths of 246 and 233 MPa are obtained from joints using 100 m thick palladium filler foil brazed at 1580 and 1610 oC for 600 s, respectively. The application of palladium filler foil shows potential in brazing molybdenum for high-temperature application.

Metallurgical and Materials Transactions A, 2012

Journal of Alloys and Compounds, 2004

The microstructural evolution and shear strength of the infrared brazed Cu and Ti with two silver... more The microstructural evolution and shear strength of the infrared brazed Cu and Ti with two silver-based braze alloys are studied. The dissolution between the molten braze and Cu substrate is much more prominent than that of Ti substrate. For specimens infrared brazed with pure Ag, the molten braze is separated into Ag-, Cu-and Ti-rich liquids. The Ag-rich liquid overflows out of the joint, so only the liquid rich in Cu and Ti is left in the joint. The joint is primarily comprised of Cu 4 Ti and Cu 2 Ti phases, and three interfacial reaction layers, CuTi 2 , CuTi and Cu 4 Ti 3 are observed after infrared brazing. For specimens infrared brazed with 72Ag-28Cu, the microstructural evolution is well elucidated by the Ag-Cu-Ti ternary alloy phase diagram, and its shear strength is strongly related to the presence of interfacial phases between Ti and the braze alloy.

Materials Letters, 2007

Great efforts have been made in brazing high-strength α-β titanium alloys below their beta-phase ... more Great efforts have been made in brazing high-strength α-β titanium alloys below their beta-phase transformation temperature in order to obtain optimized mechanical properties. The brazing temperature of the cold roll-bonded Ti-20Zr-20Cu-20Ni foil is roughly 70°C lower than that of Ti-15Cu-15Ni filler metal. Moreover, the detrimental Cu-Ni and Cu-Ni-Zr rich Ti phases can be greatly reduced or eliminated by properly choosing the brazing thermal cycle. This research demonstrates the potential application of Ti-20Zr-20Cu-20Ni foil in brazing titanium alloys.

The ductile to brittle transition temperature (DBTT) of the modified 9Cr-lMo steel and its laser ... more The ductile to brittle transition temperature (DBTT) of the modified 9Cr-lMo steel and its laser welds was studied. The increase in grain size of the weld structure ascended the DBTT of the steel significantly. The transformation of retained austenite at martensite interlath boundaries into untempered and/or twinned martensite could also contribute to increased DBTTs of the steel and its welds tempered at 540℃.

Metallurgical and Materials Transactions A, 2002

Metallurgical and Materials Transactions A, 2012

Acta Materialia, 2003

TiAl intermetallic alloy joined by infrared brazing using BAg-8 braze alloy was investigated. The... more TiAl intermetallic alloy joined by infrared brazing using BAg-8 braze alloy was investigated. The microstructural evolution of the brazed joint, shear strength and reaction kinetics across the joint was comprehensively evaluated. According to the experimental observations, silver would not react with the TiAl substrate, but copper reacted vigorously with the TiAl, forming continuous reaction layer. The consumption of copper from molten braze during infrared brazing resulted in depletion of the copper content from the braze. Therefore, chemical composition of the braze deviated from Ag-Cu eutectic into hypoeutectic with increased brazing time and/or temperature. Both AlCuTi and AlCu 2 Ti phase were observed at the interface between BAg-8 and TiAl substrate for the specimen brazed at 950°C. By increasing the brazing temperature and time, the growth rate of AlCuTi phase was much faster than that of AlCu 2 Ti phase. The maximum shear strength achieved 343 MPa for the specimen infrared brazed at 950°C for 60 s. Further increasing the brazing time resulted in excessive growth of brittle AlCuTi reaction layer, which greatly deteriorated the shear strength of the joint.

Archives of Metallurgy and Materials, 2018

Advanced Materials Research, 2014

The purpose of this investigation is focused on two high strength low alloy steels for offshore a... more The purpose of this investigation is focused on two high strength low alloy steels for offshore application. TTT, CCT curves, Vickers depth profiles and microstructures of direct water quenched steels are evaluated in the experiment. Microhardness of the direct quenched surface is as high as 400 Hv, and the central region hardness of water quenched specimen is above 250 Hv. Martensite dominates the microstructure of quenched surface. In contrast, the mixture of martensite, bainite and ferrite is widely observed from the center of quenched specimen.

Materials Chemistry and Physics, 2004

The fatigue crack growth behavior of AISI 304 stainless steels annealed by a CO 2 laser was inves... more The fatigue crack growth behavior of AISI 304 stainless steels annealed by a CO 2 laser was investigated in the study. For the laser-annealed specimen prior to introducing a notch, the residual tensile stress was obtained around the center of the laser-annealed zone (LAZ), and the residual stress field changed gradually from tensile into compressive stress with increasing the distance away from the centerline of LAZ. Based on the experimental result, the laser-annealed specimen tested under low K had a higher resistance to fatigue crack growth in the region preceding the LAZ after introducing a notch perpendicular to the LAZ. In contrast, the retardation of fatigue crack growth disappeared for the laser-annealed specimen stress-relieved at 850 • C for one hour. The presence of residual compressive stress field ahead of the crack tip resulted in the decreased fatigue crack growth rate (FCGR). Moreover, residual compressive stresses enhanced the effect of crack closure, and led to the formation of rubbed marks on the fatigue-fractured surface. As the fatigue crack propagated further into the LAZ, the residual tensile stress field ahead of crack tip did not accelerate the crack growth. The results indicated that tensile stress field ahead of the crack tip had little effect on the FCGR of the ductile 304 stainless steel.

A CO 2 laser was applied for dissimilar welding of Ti–15V–3Cr–3Al–3Sn (Ti–15–3) to Ti–6Al–4V (Ti–... more A CO 2 laser was applied for dissimilar welding of Ti–15V–3Cr–3Al–3Sn (Ti–15–3) to Ti–6Al–4V (Ti–6–4) alloys. The microstructures and notched tensile strength (NTS) of the dissimilar welds were investigated in the as-welded and post-weld heat treatment (PWHT) conditions, and the results were compared with Ti–6–4 and Ti–15–3 homogeneous laser welds with the same PWHT. The results indicated that predominant α″ with a few α and β phases was formed in the as-welded fusion zone (FZ). Furthermore, the FZ hardness was susceptible to the PWHT and showed a plateau for the specimens aged in the temperature range from 426 to 482 °C/4 h. In comparison with the homogeneous Ti–15–3 weld under the same PWHT conditions, the dilution of Ti–15–3 with Ti–6–4 caused a slight increase in the Al equivalent (Al EQ ) of the FZ, resulting in a further rise in FZ hardness. With the PWHT at/below 538 °C, the dissimilar welds were associated with low NTS or high notch brittleness.

Infrared dissimilar brazing of α 2 -Ti 3 Al and Ti–6Al–4V using Ti–15Cu–25Ni and Ti–15Cu–15Ni fil... more Infrared dissimilar brazing of α 2 -Ti 3 Al and Ti–6Al–4V using Ti–15Cu–25Ni and Ti–15Cu–15Ni filler metals has been performed in this study. The brazed joint consists primarily of Ti-rich and Ti 2 Ni phases, and there is no interfacial phase among the braze alloy, α 2 -Ti 3 Al and Ti–6Al–4V substrates. The existence of the Ti 2 Ni intermetallic compound is detrimental to the bonding strength of the joint. The amount of Ti 2 Ni decreases with increasing brazing temperature and/or time due to the depletion of Ni content from the braze alloy into the Ti–6Al–4V substrate during brazing. The shear strength of the brazed joint free of the blocky Ti 2 Ni phase is comparable with that of the α 2 -Ti 3 Al substrate, and strong bonding can thus be obtained.

Dissimilar welding of the Ti–6Al–4V (Ti-6-4) to Ti–6A1–6V–2Sn (Ti-6-6-2) alloys was performed by ... more Dissimilar welding of the Ti–6Al–4V (Ti-6-4) to Ti–6A1–6V–2Sn (Ti-6-6-2) alloys was performed by CO 2 laser in this work. The effect of post-weld heat treatment (PWHT) on the notched tensile strength (NTS) of the dissimilar weld was evaluated. Moreover, the results were also compared with the homogeneous laser welds with the same PWHT. Similar to the Ti-6-4 welds, the NTS of the FZ for dissimilar welds was less sensitive to PWHT conditions; the NTS of the FZ for distinct dissimilar welds fell within the range of 1060–1180 MPa. The results indicated a minor rise in the Mo equivalent of the titanium alloy promoted the formation of fine α + β microstructures in the form of basket weave in the welds, which resulted in high hardness accompanied with low NTS of the welds.

Corrosion Science, 2012

ABSTRACT The effect of tungsten inert gas welding and subsequent post-weld heat treatment on the ... more ABSTRACT The effect of tungsten inert gas welding and subsequent post-weld heat treatment on the microstructure evolution and pitting corrosion behavior of duplex stainless steel UNS S31803 was investigated. Detailed microstructure examination demonstrates that ferrite presents higher volume fraction and is easier to suffer attack of pitting corrosion than austenite in the welded zone of as-welded metal. After post-weld heat treatment, the volume fraction of austenite in the heat affected zone and weld metal is elevated significantly. The highest pitting corrosion resistance is obtained at 1080 °C with the highest critical pitting temperature and pitting nucleation resistance.

Key Engineering Materials, 2017

The purpose of this investigation is focused on the direct quench and temper mechanisms of the hi... more The purpose of this investigation is focused on the direct quench and temper mechanisms of the high strength offshore steel. Microstructural analyses of martensite and retained austenite in the direct quenched steel, simulations of martensitic transformation temperatures, Ms/Mf, and morphologies of bainite and ferrite have been evaluated in the experiment. Additionally, carbide formation after temped at various temperatures and microhardness depth profiles after heat treating are also included in the study. The direct quenched steel is primarily comprised of martensite, bainite and a few retained austenite with Vickers microhardness above 300. Tempered martensite, iron carbide and bainite are widely observed from all tempered specimens.

Advanced Materials Research, 2008

Vacuum repair brazing of Inconel 939 using various ratios of DF3 and Rene 80 powder mixtures has ... more Vacuum repair brazing of Inconel 939 using various ratios of DF3 and Rene 80 powder mixtures has been performed in this study. The porosity of the brazed zone is decreased as the amount of DF3 is increased in the powder mixture. At least four phases are observed in the brazed zone including chromium borides, sparse carbides, Ni-rich matrix and eutectic phases. Primary chromium borides are widely observed at the early stage of repair brazing. Dissolution of the Ni from the Rene 80 powder into the molten braze results in isothermal solidification of the residual melt. The chemical composition of the residual melt subsequently moves towards the lowest eutectic temperature, and the eutectic is finally formed in brazing. The oxidation resistance test is performed at 1000oC. Extensive spalling of the oxide film begins at 144 h, and catastrophic failure of the oxide film is observed at 1272 h. The oxidation resistance of the brazed zone is significantly degraded due to the formation of chr...

Active brazing is one of the ideal ways to make metal/ceramic joints. The active braze alloy cont... more Active brazing is one of the ideal ways to make metal/ceramic joints. The active braze alloy contains active element(s), such as: Ti, Zr, Cr.. . etc., reacting and wetting the ceramic surfaces during brazing. Therefore, a strong chemical bonding can be formed after brazing. Cu base active braze alloys are alternatives among active braze alloys. With the aid of additional melting point depressant, Sn, in Cu-Ti alloys, the intermetallic phase in the active braze can be changed. However, its ability to braze structural ceramics, e.g. alumina, needs further study. The purpose of this research is concentrated on the wettability study of the Cu/Sn/Ti alloy on polycrystalline alumina. Based on the experimental results, the minimum Ti content is 6 wt pct in order to effectively wet alumina. Volume fraction of the intermetallic phase in the braze will be greatly increased if the Ti content in the alloy is increased to 12 wt pct. According to sessile drop test results, 70Cu-21Sn-9Ti demonstrates the best wetting ability on alumina. Meanwhile, the Sn content in Cu/Sn/Ti alloy should be less than 21 wt pct in order to maintain proper wettability of the braze. In addition, Cu/Sn/Ti alloys have both lower wetting angle on alumina and lower thermal expansion coefficients than commercial Ticusil ® braze.

Advanced Materials Research, 2012

High-temperature brazing molybdenum using palladium and titanium foils have been investigated in ... more High-temperature brazing molybdenum using palladium and titanium foils have been investigated in the experiment. Successful brazed joints are achieved from using the palladium filler foil. Brazed joints are fully dense and free of any intermetallic phase. Three point bending strengths of 246 and 233 MPa are obtained from joints using 100 m thick palladium filler foil brazed at 1580 and 1610 oC for 600 s, respectively. The application of palladium filler foil shows potential in brazing molybdenum for high-temperature application.

Metallurgical and Materials Transactions A, 2012

Journal of Alloys and Compounds, 2004

The microstructural evolution and shear strength of the infrared brazed Cu and Ti with two silver... more The microstructural evolution and shear strength of the infrared brazed Cu and Ti with two silver-based braze alloys are studied. The dissolution between the molten braze and Cu substrate is much more prominent than that of Ti substrate. For specimens infrared brazed with pure Ag, the molten braze is separated into Ag-, Cu-and Ti-rich liquids. The Ag-rich liquid overflows out of the joint, so only the liquid rich in Cu and Ti is left in the joint. The joint is primarily comprised of Cu 4 Ti and Cu 2 Ti phases, and three interfacial reaction layers, CuTi 2 , CuTi and Cu 4 Ti 3 are observed after infrared brazing. For specimens infrared brazed with 72Ag-28Cu, the microstructural evolution is well elucidated by the Ag-Cu-Ti ternary alloy phase diagram, and its shear strength is strongly related to the presence of interfacial phases between Ti and the braze alloy.

Materials Letters, 2007

Great efforts have been made in brazing high-strength α-β titanium alloys below their beta-phase ... more Great efforts have been made in brazing high-strength α-β titanium alloys below their beta-phase transformation temperature in order to obtain optimized mechanical properties. The brazing temperature of the cold roll-bonded Ti-20Zr-20Cu-20Ni foil is roughly 70°C lower than that of Ti-15Cu-15Ni filler metal. Moreover, the detrimental Cu-Ni and Cu-Ni-Zr rich Ti phases can be greatly reduced or eliminated by properly choosing the brazing thermal cycle. This research demonstrates the potential application of Ti-20Zr-20Cu-20Ni foil in brazing titanium alloys.

The ductile to brittle transition temperature (DBTT) of the modified 9Cr-lMo steel and its laser ... more The ductile to brittle transition temperature (DBTT) of the modified 9Cr-lMo steel and its laser welds was studied. The increase in grain size of the weld structure ascended the DBTT of the steel significantly. The transformation of retained austenite at martensite interlath boundaries into untempered and/or twinned martensite could also contribute to increased DBTTs of the steel and its welds tempered at 540℃.

Metallurgical and Materials Transactions A, 2002

Metallurgical and Materials Transactions A, 2012

Acta Materialia, 2003

TiAl intermetallic alloy joined by infrared brazing using BAg-8 braze alloy was investigated. The... more TiAl intermetallic alloy joined by infrared brazing using BAg-8 braze alloy was investigated. The microstructural evolution of the brazed joint, shear strength and reaction kinetics across the joint was comprehensively evaluated. According to the experimental observations, silver would not react with the TiAl substrate, but copper reacted vigorously with the TiAl, forming continuous reaction layer. The consumption of copper from molten braze during infrared brazing resulted in depletion of the copper content from the braze. Therefore, chemical composition of the braze deviated from Ag-Cu eutectic into hypoeutectic with increased brazing time and/or temperature. Both AlCuTi and AlCu 2 Ti phase were observed at the interface between BAg-8 and TiAl substrate for the specimen brazed at 950°C. By increasing the brazing temperature and time, the growth rate of AlCuTi phase was much faster than that of AlCu 2 Ti phase. The maximum shear strength achieved 343 MPa for the specimen infrared brazed at 950°C for 60 s. Further increasing the brazing time resulted in excessive growth of brittle AlCuTi reaction layer, which greatly deteriorated the shear strength of the joint.

Archives of Metallurgy and Materials, 2018

Advanced Materials Research, 2014

The purpose of this investigation is focused on two high strength low alloy steels for offshore a... more The purpose of this investigation is focused on two high strength low alloy steels for offshore application. TTT, CCT curves, Vickers depth profiles and microstructures of direct water quenched steels are evaluated in the experiment. Microhardness of the direct quenched surface is as high as 400 Hv, and the central region hardness of water quenched specimen is above 250 Hv. Martensite dominates the microstructure of quenched surface. In contrast, the mixture of martensite, bainite and ferrite is widely observed from the center of quenched specimen.

Materials Chemistry and Physics, 2004

The fatigue crack growth behavior of AISI 304 stainless steels annealed by a CO 2 laser was inves... more The fatigue crack growth behavior of AISI 304 stainless steels annealed by a CO 2 laser was investigated in the study. For the laser-annealed specimen prior to introducing a notch, the residual tensile stress was obtained around the center of the laser-annealed zone (LAZ), and the residual stress field changed gradually from tensile into compressive stress with increasing the distance away from the centerline of LAZ. Based on the experimental result, the laser-annealed specimen tested under low K had a higher resistance to fatigue crack growth in the region preceding the LAZ after introducing a notch perpendicular to the LAZ. In contrast, the retardation of fatigue crack growth disappeared for the laser-annealed specimen stress-relieved at 850 • C for one hour. The presence of residual compressive stress field ahead of the crack tip resulted in the decreased fatigue crack growth rate (FCGR). Moreover, residual compressive stresses enhanced the effect of crack closure, and led to the formation of rubbed marks on the fatigue-fractured surface. As the fatigue crack propagated further into the LAZ, the residual tensile stress field ahead of crack tip did not accelerate the crack growth. The results indicated that tensile stress field ahead of the crack tip had little effect on the FCGR of the ductile 304 stainless steel.

A CO 2 laser was applied for dissimilar welding of Ti–15V–3Cr–3Al–3Sn (Ti–15–3) to Ti–6Al–4V (Ti–... more A CO 2 laser was applied for dissimilar welding of Ti–15V–3Cr–3Al–3Sn (Ti–15–3) to Ti–6Al–4V (Ti–6–4) alloys. The microstructures and notched tensile strength (NTS) of the dissimilar welds were investigated in the as-welded and post-weld heat treatment (PWHT) conditions, and the results were compared with Ti–6–4 and Ti–15–3 homogeneous laser welds with the same PWHT. The results indicated that predominant α″ with a few α and β phases was formed in the as-welded fusion zone (FZ). Furthermore, the FZ hardness was susceptible to the PWHT and showed a plateau for the specimens aged in the temperature range from 426 to 482 °C/4 h. In comparison with the homogeneous Ti–15–3 weld under the same PWHT conditions, the dilution of Ti–15–3 with Ti–6–4 caused a slight increase in the Al equivalent (Al EQ ) of the FZ, resulting in a further rise in FZ hardness. With the PWHT at/below 538 °C, the dissimilar welds were associated with low NTS or high notch brittleness.

Infrared dissimilar brazing of α 2 -Ti 3 Al and Ti–6Al–4V using Ti–15Cu–25Ni and Ti–15Cu–15Ni fil... more Infrared dissimilar brazing of α 2 -Ti 3 Al and Ti–6Al–4V using Ti–15Cu–25Ni and Ti–15Cu–15Ni filler metals has been performed in this study. The brazed joint consists primarily of Ti-rich and Ti 2 Ni phases, and there is no interfacial phase among the braze alloy, α 2 -Ti 3 Al and Ti–6Al–4V substrates. The existence of the Ti 2 Ni intermetallic compound is detrimental to the bonding strength of the joint. The amount of Ti 2 Ni decreases with increasing brazing temperature and/or time due to the depletion of Ni content from the braze alloy into the Ti–6Al–4V substrate during brazing. The shear strength of the brazed joint free of the blocky Ti 2 Ni phase is comparable with that of the α 2 -Ti 3 Al substrate, and strong bonding can thus be obtained.

Dissimilar welding of the Ti–6Al–4V (Ti-6-4) to Ti–6A1–6V–2Sn (Ti-6-6-2) alloys was performed by ... more Dissimilar welding of the Ti–6Al–4V (Ti-6-4) to Ti–6A1–6V–2Sn (Ti-6-6-2) alloys was performed by CO 2 laser in this work. The effect of post-weld heat treatment (PWHT) on the notched tensile strength (NTS) of the dissimilar weld was evaluated. Moreover, the results were also compared with the homogeneous laser welds with the same PWHT. Similar to the Ti-6-4 welds, the NTS of the FZ for dissimilar welds was less sensitive to PWHT conditions; the NTS of the FZ for distinct dissimilar welds fell within the range of 1060–1180 MPa. The results indicated a minor rise in the Mo equivalent of the titanium alloy promoted the formation of fine α + β microstructures in the form of basket weave in the welds, which resulted in high hardness accompanied with low NTS of the welds.