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Effects of heat treatments on microstructures of TiAl alloys
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作者 Wen Yu Jianxin Zhou +5 位作者 Yajun Yin Zhixin Tu Xin Feng Hai Nan junpin lin Xianfei Ding 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2022年第6期1225-1230,共6页
This study aims to investigate the effects of heat treatments on the microstructure ofγ-TiAl alloys.Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat trea... This study aims to investigate the effects of heat treatments on the microstructure ofγ-TiAl alloys.Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat-treated in two types of heat treatments.Their microstructures were studied by both optical and scanning electron microscopies.The chemical compositions of two ingots were determined as well.The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within1270 to 1185℃.A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures.They are distributed at grain boundaries when holding at a higher temperature,such as 1260℃.However,B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185℃.Furthermore,the effects of heat treatments on grain refinement and other microstructural parameters are discussed. 展开更多
关键词 TiAl alloys MICROSTRUCTURE heat treatment CASTING
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Mechanical Properties of Interface between U-0.75Ti Alloy and TiC
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作者 Yong Zhang junpin lin +2 位作者 Guoliang Chen Gengchen Sun Guanxing Li (State Key Laboratory for Advanced Metals and Materials, UST Beijing, Beijing 100083, China)(Institute of Mechanics Research, Sinica Academy of Science, Beijing, China)(202 Plane Baotou, C 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 1998年第1期41-43,共3页
The microhardness and modulus changes of the interface between U-0.75Ti alloy and TiC before andafter heat treatment were studied by SEM and Nano Indenter II, and the results show that the hardness and modulusof the i... The microhardness and modulus changes of the interface between U-0.75Ti alloy and TiC before andafter heat treatment were studied by SEM and Nano Indenter II, and the results show that the hardness and modulusof the interface are greatly increased after 820℃, 2 h water quenching and 450℃, 6 h aging. This result probablycomes from much more U2Ti and U6Ni precipitates along the interface. 展开更多
关键词 U-0.75Ti alloy TIC INTERFACE hardness and modulus
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Densification behavior of high Nb containing TiAl alloys through reactive hot pressing
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作者 Yanhang Wang junpin lin +2 位作者 Yuehui He Yanli Wang Guoliang Chen 《Journal of University of Science and Technology Beijing》 CSCD 2007年第3期251-255,共5页
Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400°C could reach a near full density of ... Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400°C could reach a near full density of 98.37%. However, the densification abnormality was observed at 1500°C. The diffusion of elemental Nb during microstructural evolution is an important aspect affecting densification, which will form pore nests. With the increase of hot pressing temperature, the diffusion of Nb becomes more adequate. HIP (Hot isostatic pressing) treatment can only decrease porosity to some extent, but cannot eliminate it completely. 展开更多
关键词 TiAl based alloy powder metallurgy DENSIFICATION hot pressing
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Microstructure evolution and phase transformation of the mushy zone in a quenchedβ-solidifying TiAl alloy
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作者 Fuqiang Zhang Xianfei Ding +5 位作者 Leming Xu Xin Feng Hai Nan Jianping He Yongfeng Liang junpin lin 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2024年第2期28-41,共14页
This study investigates the phase constitutions and transformations that occur in the mushy zone and in the adjacent phase fields of a directionally solidified Ti-44Al-8Nb-1Cr alloy via quenching technique.The results... This study investigates the phase constitutions and transformations that occur in the mushy zone and in the adjacent phase fields of a directionally solidified Ti-44Al-8Nb-1Cr alloy via quenching technique.The results indicate that the mushy zone consists of unmeltedβdendrites and interdendritic liquid,whose formation can be attributed to the difference in melting point aroused by local heterogeneity in solutecontent.Theβdendrite is composed of numerous subgrains with various orientations.During quenching,theβdendrite transforms into Widmanstättenαvia a precipitation reaction,owing to the decreasing cooling rate caused by heat transfer from the surrounding liquid.Additionally,after quenching,the interdendritic liquid is transformed intoγplates.Within the singleβphase field and the lower part of the mushy zone,a massive transformation ofβtoγoccurs.Conversely,in theβ+αphase field,bothβandαphases are retained to ambient temperature.During the heating process,the transformation ofα→βgives rise to the formation ofβvariants,which affects the orientation ofβdendrites in the mushy zone.The growth kinematics of theα→βtransformation was elucidated,revealing the preferential growth directions of111and112forβvariants.Furthermore,this study presents an illustration of the formation process of the mushy zone and the microstructural evolution during the heating and quenching process. 展开更多
关键词 Titanium aluminides Mushy zone Quenching Electron backscattering diffraction Phase transformation
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Simultaneous enhancement of strength and ductility in high Nb-TiAl by Si alloying
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作者 Jun Cao Tielong Sun +3 位作者 Zhichao Guo Hui Xue Yongfeng Liang junpin lin 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2024年第10期128-132,共5页
1.Introduction TiAl alloys are lightweight and high-temperature-resistant structural materials having applicability in automotive and aerospace applications owing to their low density and excellent high-temperature pr... 1.Introduction TiAl alloys are lightweight and high-temperature-resistant structural materials having applicability in automotive and aerospace applications owing to their low density and excellent high-temperature properties[1-3].High-Nb-containing TiAl(High Nb-TiAl)alloys are considered as a new generation of TiAl alloys for applications at higher service temperatures[4-6].Components of TiAl alloys that have achieved long-term stability in the industry are mainly manufactured by casting,which is the most economical method[7-9].However,the mechanical properties of these com-ponents are limited at room temperature(RT),significantly hinder-ing their broad applications[7,10-12]. 展开更多
关键词 ALLOYS ALLOYING DUCTILITY
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Excellent ductility and serration feature of metastable CoCrFeNi high-entropy alloy at extremely low temperatures 被引量:19
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作者 Junpeng Liu Xiaoxiang Guo +10 位作者 Qingyun lin Zhanbing He Xianghai An Laifeng Li Peter K. Liaw Xiaozhou Liao Liping Yu junpin lin Lu Xie Jingli Ren Yong Zhang 《Science China Materials》 SCIE EI CSCD 2019年第6期853-863,共11页
Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion.However, a face-centered-cubic(FCC) CoCrFeNi highentropy alloy(HEA... Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion.However, a face-centered-cubic(FCC) CoCrFeNi highentropy alloy(HEA) with great ductility is investigated under the cryogenic environment. The tensile strength of this alloy can reach a maximum at 1,251±10 MPa, and the strain to failure can stay at as large as 62% at the liquid helium temperature. We ascribe the high strength and ductility to the low stacking fault energy at extremely low temperatures,which facilitates the activation of deformation twinning.Moreover, the FCC→HCP(hexagonal close-packed) transition and serration lead to the sudden decline of ductility below 77 K. The dynamical modeling and analysis of serrations at 4.2 and 20 K verify the unstable state due to the FCC→HCP transition. The deformation twinning together with phase transformation at liquid helium temperature produces an adequate strain-hardening rate that sustains the stable plastic flow at high stresses, resulting in the serration feature. 展开更多
关键词 high-entropy alloy liquid-helium temperature TWINNING phase transition serration feature
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On the reversibility of the α_(2)/ω_(o) phase transformation in a high Nb containing TiAl alloy during high temperature deformation 被引量:1
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作者 lin Song Fritz Appel +6 位作者 Andreas Stark Uwe Lorenz Junyang He Zhanbing He junpin lin Tiebang Zhang Florian Pyczak 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第34期96-102,共7页
The transformations between the phasesα_(2)(Ti_(3)Al)andω_(o)were investigated in a lamellar multiphase titanium aluminide alloy based onγ(TiAl).The paper complements an earlier investigation performed on the same ... The transformations between the phasesα_(2)(Ti_(3)Al)andω_(o)were investigated in a lamellar multiphase titanium aluminide alloy based onγ(TiAl).The paper complements an earlier investigation performed on the same material in which the importance of deformation-induced twin structures for theα_(2)→ω_(o) transformation was demonstrated.The present study shows that the reverse transformationω_(o)→α_(2) can also occur during high-temperature deformation.The transformation is probably triggered by constraint stresses,which exist between the different constituents due to the crystalline mismatch.The combined operation of mechanical twinning of theα_(2) phase and the reversible transformation fully converts theα_(2) lamellae into a mixture ofα_(2) andω_(o).This conversion greatly reduces the mechanical anisotropy existing in formerα_(2) lamellae.Regarding the technical use of the alloy,the stability of the converted structure with respect to further annealing was also examined.The reported processes occur at the nano-meter and sub nano-meter scale,thus,advanced characterization techniques were applied,such as high-resolution transmission electron microscopy(HRTEM)and atom probe tomography(APT). 展开更多
关键词 TiAl alloys Phase transformation Electron microscopy MICROSTRUCTURE
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Deformation twinning in equiaxed-grained Fe-6.5 wt.%Si alloy after rotary swaging
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作者 Chaoyu Han Shibo Wen +5 位作者 Feng Ye Wenjia Wu Shaowei Xue Yongfeng Liang Binbin Liu junpin lin 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2020年第14期25-34,共10页
Tensile behavior of an equiaxed-grained Fe-6.5 wt.%Si alloy,which was deformed intoφ6 mm bar by hot rotary swaging,was investigated at various temperatures(300–400℃)and stretching rates(0.42–1 mm/min).The results ... Tensile behavior of an equiaxed-grained Fe-6.5 wt.%Si alloy,which was deformed intoφ6 mm bar by hot rotary swaging,was investigated at various temperatures(300–400℃)and stretching rates(0.42–1 mm/min).The results revealed an enhancement in the intermediate-temperature tensile ductility after heat treatments.Deformation twinning was found in the equiaxed-grained Fe-6.5 wt.%Si bars during the tensile test,and heat treatments can enhance the deformation twinning.More twins can be observed in the necking areas than other regions.The high Schmid factor values above 0.4 after heat treatments demonstrated that deformation twinning can easily occur in the equiaxed-grained Fe-6.5 wt.%Si alloy.Higher deformation temperatures,higher strain rates,and larger degree of order suppressed the formation of deformation twinning,while the grain sizes had little effect on the deformation twinning.The twinning stress of the Fe-6.5 wt.%Si alloy increased with the increasing grain size,which did not agree with the Hall–Petch type relationship.The deformation twinning resulted in the improved ductility of the Fe-6.5 wt.%Si alloy. 展开更多
关键词 Fe-6.5 wt.%Si alloy Hot rotary swaging Equiaxed microstructure Deformation twinning DUCTILITY
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Deformation and phase transformation behaviors of a high Nb-containing TiAl alloy compressed at intermediate temperatures
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作者 Xu Liu lin Song +5 位作者 Andreas Stark Uwe Lorenz Zhanbing He junpin lin Florian Pyczak Tiebang Zhang 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2022年第7期89-96,共8页
In modernβ-solidified TiAl alloys,the decomposition of α_(2) phase is frequently observed during heat treatment or high-temperature deformation of the alloys.In this study,high-temperature deformation and decomposit... In modernβ-solidified TiAl alloys,the decomposition of α_(2) phase is frequently observed during heat treatment or high-temperature deformation of the alloys.In this study,high-temperature deformation and decomposition mechanisms of α_(2) phase in a Ti-45Al-8.5Nb-0.2B-0.2W-0.02Y alloy are investigated.In a sample deformed at 800℃,the precipitation ofβ_(o)(ω_(o))phase is observed within the equiaxed α_(2) phase.The nucleation ofω_(o) particles within theβ_(o) matrix indicates the α_(2)→β_(o)→ω_(o) transformation.In addition,numerous y phase precipitates form within theβ_(o)(ω)areas.The α_(2) lamellae decompose into ultrafine( α_(2)+γ)lamellae and coarsened y lamellae via α_(2)→ α_(2)+γand α_(2)→γtransformation,re-spectively.Moreover,theω_(o) phase nucleates within the ultrafine lamellae via α_(2)→ω_(o) transformation.However,in a sample deformed at 1000℃,the nucleation ofβ_(o) particles is sluggish,which is caused by the efficient release of the internal stress via dynamic recrystallization(DRX).These results indicate that complex phase transformations can be introduced by the decomposition of α_(2) phase in TiAl alloys with a high amount ofβ-stabilizing elements. 展开更多
关键词 TiAl alloys Phase transformation Microstructure Electron microscopy
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