The magnetic properties and microstructure of diffusion annealed [Ta/Nd/NdFeB/Nd/Ta]thin films have been investigated. The films were deposited on Si substrate with various thickness ratio of Nd/NdFeB layer (R=0～3.3)...The magnetic properties and microstructure of diffusion annealed [Ta/Nd/NdFeB/Nd/Ta]thin films have been investigated. The films were deposited on Si substrate with various thickness ratio of Nd/NdFeB layer (R=0～3.3), then diffused and crystallized by annealing at 650℃ for 10 min. The film without Nd layer showed soft magnetic behavior and high content of a-Fe phase. The films with R > =1 showed good hard magnetic properties with the high coercivity of about 20 kOe.展开更多
AZ31/Mg3Y composites with a layer thickness of 100-200μm were fabricated by accumulated rolling bonding(ARB),which was followed by diffusion annealing at 300℃ for 0-32 h.An interface layer,containing numerous Al-Y p...AZ31/Mg3Y composites with a layer thickness of 100-200μm were fabricated by accumulated rolling bonding(ARB),which was followed by diffusion annealing at 300℃ for 0-32 h.An interface layer,containing numerous Al-Y precipitates,is formed in the Mg3Y layer that is adjacent to the interface as a result of Al diffusing from the AZ31 layers into the Mg3Y layers.The thickness of the interface layer gets increased and more precipitates are formed in the interface layer with the extension of the annealing time.The microhardness of the AZ31 and Mg3Y layer decreases firstly and then reaches a stable value,while the microhardness of the interface layer increases gradually with the extension of the annealing time.The AZ31/Mg3Y composites exhibit equivalent strength but increased ductility after diffusion annealing,in comparison to the as-rolled AZ31/Mg3Y composite.In addition,the AZ31/Mg3Y composites after annealing always present higher strength and ductility than AZ31/AZ31 composite,which was fabricated by the same process as that for the AZ31/Mg3Y composites.Hetero-deformation induced strengthening also plays an important role in the excellent strength and ductility of the annealed AZ31/Mg3Y composite.This study can provide a direction for improving the plasticity and strength of magnesium alloys synergistically.展开更多
Mn distribution and austenite morphology at the early stage of intercritical annealing of 5Mn steel were investigated. It was experimentally demonstrated that a newly formed 20 nm-thick austenite was formed without th...Mn distribution and austenite morphology at the early stage of intercritical annealing of 5Mn steel were investigated. It was experimentally demonstrated that a newly formed 20 nm-thick austenite was formed without the partitioning of Mn. The elemental analysis confirmed that the growth of austenite should be controlled by the diffusion of C prior to the diffusion of Mn at a low heating rate. The austenite growth started under negligible-partitioning local equilibrium mode and then switched to partitioning local equilibrium mode. Mn segregation at the γ/α interface suggested that the collector plate mechanism was the essential way of Mn partitioning at the early stage of austenite growth.展开更多
To investigate potential strengthening approaches,multi-layered zirconium–titanium(Zr-Ti)composites were fabricated by hot-rolling bonding and annealing.The microstructures of these composites were characterized usin...To investigate potential strengthening approaches,multi-layered zirconium–titanium(Zr-Ti)composites were fabricated by hot-rolling bonding and annealing.The microstructures of these composites were characterized using scanning electron microscopy with energy dispersive spectroscopy(SEM-EDS)and electron backscatter diffractometry(EBSD).Their mechanical properties were evaluated by uniaxial tension and compression measurements.It was found that the fabricated Zr–Ti composites are composed of alternating Zr/diffusion/Ti layers,and chemical compositions of Zr and Ti showed a gradient distribution in the diffusion layer.Compared with as-rolled samples,annealing can strengthen the layered gradient Zr–Ti composite,and this is mainly caused by solid-solution strengthening and microstructure refinement-induced strengthening.Compared with the raw materials,a synergistic improvement of strength and ductility is achieved in the Zr–Ti composite as a result of the layered gradient microstructure.Tension–compression asymmetry is observed in the Zr–Ti composites,which may be attributed to twinning and microvoids induced by unbalanced diffusion.展开更多
Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment was investigated.Fractographies and microstructures of heat treated samples were observed using a scanning elect...Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment was investigated.Fractographies and microstructures of heat treated samples were observed using a scanning electron microscope and mechanical properties were measured by a universal tensile test machine.The results indicated that during isothermal annealing at 750°C,the tensile strength of pearlitic ductile cast iron was increased to a peak value at 0.5h,and decreased gradually thereafter but the elongation was enhanced with the increase of annealing time.Moreover,the diffusion coefficient of carbon atoms could be approximately calculated as 0.56μm2/s that could be regarded as the shortrange diffusion.As the holding time was short（0.5h）,diffusion of carbon atoms was incomplete and mainly occurred around the graphites where the morphology of cementites changed from fragmentized shape to granular shape.In addition,the ductile cast iron with tensile strength of 740MPa and elongation of 7% could be achieved after graphitization annealing heat treatment for 0.5h.Two principal factors should be taken into account.First,the decomposition of a small amount of cementites was beneficial for increasing the ductility up to elongation of 7%.Second,the diffusion of carbon atoms from cementites to graphites could improve the binding force between graphites and matrix,enhancing the tensile strength to 740 MPa.展开更多
The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of...The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.展开更多
A new preparation method of near-net-shape 6.5 wt% Si high silicon steel sheets was proposed by combining composite electrodeposition(CED) and diffusion annealing under magnetic field. The obtained sheets were charact...A new preparation method of near-net-shape 6.5 wt% Si high silicon steel sheets was proposed by combining composite electrodeposition(CED) and diffusion annealing under magnetic field. The obtained sheets were characterized by scanning electron microscopy, energy dispersive spectrometry, analytical balance and a silicon steel material measurement system. The results show that the surface morphology,the elemental distribution, the cathode current efficiency and the silicon content of coatings were obviously influenced by the micro and macro magnetohydrodynamics(MHD) flows under magnetic field.With the effect of magnetic field, the silicon particles content of coatings showed an increasing trend and the diffusion process showed that an approximately uniform 6.5 wt% silicon steel sheet has been successfully obtained. The magnetism measurement showed that the high silicon steel sheet has the lower iron loss, and the iron loss further decreased under magnetic field. The new method proposed in this article,which is more environmentally friendly and low energy consumption, is feasible to prepare high silicon steel sheets.展开更多
The micro structure of 10Cr15MoVCo electroslag remelting(ESR)ingot was observed using an optical microscope and a scanning electron microscope.There are differences in the number,size,and distribution of primary carbi...The micro structure of 10Cr15MoVCo electroslag remelting(ESR)ingot was observed using an optical microscope and a scanning electron microscope.There are differences in the number,size,and distribution of primary carbides in different positions of ESR ingot.The results show that the two-dimensional morphology of primary carbides is blocky,fibrous,and spherulitic.The three-dimensional morphology of primary carbides is blocky,spherulitic,fibrous,and short rods.X-ray diffraction results show that primary carbides are M_(7)C_(3) carbides.Electron backscattered diffraction results indicate that large-sized primary carbides consist of blocky,fibrous,and spherulitic carbides with different orientations.High-tem-perature diffusion annealing experiments show that as the temperature increases,the continuity between primary carbides decreases,and the precipitated secondary carbides disappear.The area fraction of primary carbides is reduced,but the morphology of primary carbide is unchanged.The effect of high-temperature diffusion annealing on the dissolution of M_(7)C_(3) primary carbon compounds in ESR ingot was limited.展开更多
LaFe_(11.8)Si_(1.2)/10 wt%Ce_(60)Co_(40) composites were prepared by spark plasma sintering and subsequent diffusion annealing.A novel core-shell structure is observed with the LaFe11.8Si1.2 particles as the core and ...LaFe_(11.8)Si_(1.2)/10 wt%Ce_(60)Co_(40) composites were prepared by spark plasma sintering and subsequent diffusion annealing.A novel core-shell structure is observed with the LaFe11.8Si1.2 particles as the core and the(La,Ce)_(2)(Fe,Co,Si)_(17)(2:17)phase as the shell.As diffusion annealing time(t_(a))increases,this core-shell structure is replaced by the formation of the(La,Ce)_(1)(Fe,Co,Si)_(13) phase.Annealing at 1323 K for 12 h results in samples with(-ΔSM)^(max) of 9.30 J/(kg·K)(Δμ0H=2 T),good mechanical properties((σbc)^(max)=402 MPa,ε=4.21%)and thermal conductivity of 8.7 W/(m·K).Thus,bulk composites with excellent comprehensive properties for magnetic refrigeration are obtained in this work.展开更多
The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that ...The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that an optimum applied pressure followed by an optimum diffusion annealing process can markedly reduce the degree of microsegregation and improve the mechanical properties to a degree that can approach the level of forged 2024 Al alloy.展开更多
South China can be divided into four metallogenic belts:The Middle-Lower Yangtze Metallogenic Belt(MLYB),Qinzhou-Hangzhou Metallogenic Belt(QHMB),Nanling Metallogenic Belt(NLMB),and Wuyi Metallogenic Belt(WYMB).The ma...South China can be divided into four metallogenic belts:The Middle-Lower Yangtze Metallogenic Belt(MLYB),Qinzhou-Hangzhou Metallogenic Belt(QHMB),Nanling Metallogenic Belt(NLMB),and Wuyi Metallogenic Belt(WYMB).The major mineralization in the four metallogenic belts is granite-related Cu–Au–Mo and porphyrite Fe-apatite,porphyry Cu(Au),and epithermal Pb–Zn–Ag,hydrothermal Cu–Au–Pb–Zn–Ag,and granite-related skarn-type and quartz-veins W–Sn,respectively.Low-temperature thermochronology,including fissiontrack and U-Th/He dating,has been widely used to constrain tectonic thermal evolution and ore deposits preservation.Understanding fission-track annealing and He diffusion kinetics in accessory minerals,such as zircon and apatite,is essential for dating and applications.In this study,previous zircon fission-track(ZFT)and apatite fission-track(AFT)ages in South China were collected.The result shows that the ZFT ages are mainly concentrated at140–90 Ma,and the AFT ages are mainly distributed at70–40 Ma.The age distribution and inversion temperature–time paths reveal heterogeneous exhumation histories in South China.The MLYB experienced Late CretaceousCenozoic extremely slow exhumation after rapid cooling in the Early Cretaceous.The northern QHMB(i.e.from southern Anhui province to the Hangzhou Bay)had a relatively faster rate of uplifting and denudation than the southern QHMB in the Cretaceous.Subsequently,the northern QHMB rapidly exhumed,while the continuously slow exhumation operated the southern QHMB in the Cenozoic.The southern NLMB had a more rapid cooling rate than the northern NLMB during the Cretaceous time,and the whole NLMB experienced rapid cooling in the Cenozoic,except that the southern Hunan province had the most rapid cooling rate.The WYMB possibly had experienced slow exhumation since the Late Cretaceous.The exhumation thickness of the four metallogenic belts since90 Ma is approximately calculated as follows:the MLYB≤3.5 km,the northern QHMB concentrated at3.5–5.5 km,and the southern QHMB usually less than3.5 km,the NLMB 4.5–6.5 km and the WYMB<3.5 km.The exhumation thickness of the NLMB is corresponding to the occurrence of the world-class W deposits,which were emplaced into a deeper depth of 1.5–8 km.As such,we infer that the uplifting and denudation processes of the four metallogenic belts have also played an important role in dominated ore deposits.展开更多
文摘The magnetic properties and microstructure of diffusion annealed [Ta/Nd/NdFeB/Nd/Ta]thin films have been investigated. The films were deposited on Si substrate with various thickness ratio of Nd/NdFeB layer (R=0～3.3), then diffused and crystallized by annealing at 650℃ for 10 min. The film without Nd layer showed soft magnetic behavior and high content of a-Fe phase. The films with R > =1 showed good hard magnetic properties with the high coercivity of about 20 kOe.
基金This work was financially supported by the National Natural Science Foundation of China(Projects 52171102,51971041)the Fundamental Research Funds for the central universities(No.2023CDJXY-018).
文摘AZ31/Mg3Y composites with a layer thickness of 100-200μm were fabricated by accumulated rolling bonding(ARB),which was followed by diffusion annealing at 300℃ for 0-32 h.An interface layer,containing numerous Al-Y precipitates,is formed in the Mg3Y layer that is adjacent to the interface as a result of Al diffusing from the AZ31 layers into the Mg3Y layers.The thickness of the interface layer gets increased and more precipitates are formed in the interface layer with the extension of the annealing time.The microhardness of the AZ31 and Mg3Y layer decreases firstly and then reaches a stable value,while the microhardness of the interface layer increases gradually with the extension of the annealing time.The AZ31/Mg3Y composites exhibit equivalent strength but increased ductility after diffusion annealing,in comparison to the as-rolled AZ31/Mg3Y composite.In addition,the AZ31/Mg3Y composites after annealing always present higher strength and ductility than AZ31/AZ31 composite,which was fabricated by the same process as that for the AZ31/Mg3Y composites.Hetero-deformation induced strengthening also plays an important role in the excellent strength and ductility of the annealed AZ31/Mg3Y composite.This study can provide a direction for improving the plasticity and strength of magnesium alloys synergistically.
基金Item Sponsored by National Basic Research Program of China(2010CB630800,2015CB921700)National Natural Science Foundation of China(51001064,51471096)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education of China(20100002120047)Tsinghua University Initiative Scientific Research Program(20141081200)
文摘Mn distribution and austenite morphology at the early stage of intercritical annealing of 5Mn steel were investigated. It was experimentally demonstrated that a newly formed 20 nm-thick austenite was formed without the partitioning of Mn. The elemental analysis confirmed that the growth of austenite should be controlled by the diffusion of C prior to the diffusion of Mn at a low heating rate. The austenite growth started under negligible-partitioning local equilibrium mode and then switched to partitioning local equilibrium mode. Mn segregation at the γ/α interface suggested that the collector plate mechanism was the essential way of Mn partitioning at the early stage of austenite growth.
基金financially supported by the National Natural Science Foundation of China(No.51971041)the Natural Science Foundation of Chongqing,China(No.cstc2019jcyj-msxm X0234)。
文摘To investigate potential strengthening approaches,multi-layered zirconium–titanium(Zr-Ti)composites were fabricated by hot-rolling bonding and annealing.The microstructures of these composites were characterized using scanning electron microscopy with energy dispersive spectroscopy(SEM-EDS)and electron backscatter diffractometry(EBSD).Their mechanical properties were evaluated by uniaxial tension and compression measurements.It was found that the fabricated Zr–Ti composites are composed of alternating Zr/diffusion/Ti layers,and chemical compositions of Zr and Ti showed a gradient distribution in the diffusion layer.Compared with as-rolled samples,annealing can strengthen the layered gradient Zr–Ti composite,and this is mainly caused by solid-solution strengthening and microstructure refinement-induced strengthening.Compared with the raw materials,a synergistic improvement of strength and ductility is achieved in the Zr–Ti composite as a result of the layered gradient microstructure.Tension–compression asymmetry is observed in the Zr–Ti composites,which may be attributed to twinning and microvoids induced by unbalanced diffusion.
基金supported by the Program for Innovative Research Team in University of Liaoning Province(Grant No.LT2015020)National Natural Science Foundation of China(Grant No.51274142)
文摘Cementites decomposition of a pearlitic ductile cast iron during graphitization annealing heat treatment was investigated.Fractographies and microstructures of heat treated samples were observed using a scanning electron microscope and mechanical properties were measured by a universal tensile test machine.The results indicated that during isothermal annealing at 750°C,the tensile strength of pearlitic ductile cast iron was increased to a peak value at 0.5h,and decreased gradually thereafter but the elongation was enhanced with the increase of annealing time.Moreover,the diffusion coefficient of carbon atoms could be approximately calculated as 0.56μm2/s that could be regarded as the shortrange diffusion.As the holding time was short（0.5h）,diffusion of carbon atoms was incomplete and mainly occurred around the graphites where the morphology of cementites changed from fragmentized shape to granular shape.In addition,the ductile cast iron with tensile strength of 740MPa and elongation of 7% could be achieved after graphitization annealing heat treatment for 0.5h.Two principal factors should be taken into account.First,the decomposition of a small amount of cementites was beneficial for increasing the ductility up to elongation of 7%.Second,the diffusion of carbon atoms from cementites to graphites could improve the binding force between graphites and matrix,enhancing the tensile strength to 740 MPa.
基金the National Natural Science Foundation of China (No. 50375019).
文摘The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.
基金financial support of the National Key Research and Development Program of China(No.2016YFB0300401)the Science and Technology Commission of Shanghai Municipality(Key Project No.13JC1402500,15520711000)the Independent Research and Development Project of State Key of Advanced Special Steel,Shanghai University(Nos.SKLASS2015-Z021 and SELF-2014-02)
文摘A new preparation method of near-net-shape 6.5 wt% Si high silicon steel sheets was proposed by combining composite electrodeposition(CED) and diffusion annealing under magnetic field. The obtained sheets were characterized by scanning electron microscopy, energy dispersive spectrometry, analytical balance and a silicon steel material measurement system. The results show that the surface morphology,the elemental distribution, the cathode current efficiency and the silicon content of coatings were obviously influenced by the micro and macro magnetohydrodynamics(MHD) flows under magnetic field.With the effect of magnetic field, the silicon particles content of coatings showed an increasing trend and the diffusion process showed that an approximately uniform 6.5 wt% silicon steel sheet has been successfully obtained. The magnetism measurement showed that the high silicon steel sheet has the lower iron loss, and the iron loss further decreased under magnetic field. The new method proposed in this article,which is more environmentally friendly and low energy consumption, is feasible to prepare high silicon steel sheets.
基金This work was supported by the Guangdong YangFan Innovative&Entrepreneurial Research Team Program(No.2016YT03C071)the Guangdong Science and Technology Special Fund Project(No.SDZX202005)the National Natural Science Foundation of China(Nos.51874030 and 51904022).
文摘The micro structure of 10Cr15MoVCo electroslag remelting(ESR)ingot was observed using an optical microscope and a scanning electron microscope.There are differences in the number,size,and distribution of primary carbides in different positions of ESR ingot.The results show that the two-dimensional morphology of primary carbides is blocky,fibrous,and spherulitic.The three-dimensional morphology of primary carbides is blocky,spherulitic,fibrous,and short rods.X-ray diffraction results show that primary carbides are M_(7)C_(3) carbides.Electron backscattered diffraction results indicate that large-sized primary carbides consist of blocky,fibrous,and spherulitic carbides with different orientations.High-tem-perature diffusion annealing experiments show that as the temperature increases,the continuity between primary carbides decreases,and the precipitated secondary carbides disappear.The area fraction of primary carbides is reduced,but the morphology of primary carbide is unchanged.The effect of high-temperature diffusion annealing on the dissolution of M_(7)C_(3) primary carbon compounds in ESR ingot was limited.
基金Project supported by the Guangdong Basic and Applied Basic Research Foundation(2022A1515012578,2019A1515010970)the Guangzhou Municipal Science and Technology Project(201904010030)+2 种基金the National Natural Science Foundation of China(51874143,52066001)the Special Project of Foshan Scientific and Technological Innovation Team(2030032000171,2120001010823)partially supported by the National Research Foundation,Prime Minister’s Office,Singapore under its Campus of ResearchExcellence and Technological Enterprise(CREATE)programme。
文摘LaFe_(11.8)Si_(1.2)/10 wt%Ce_(60)Co_(40) composites were prepared by spark plasma sintering and subsequent diffusion annealing.A novel core-shell structure is observed with the LaFe11.8Si1.2 particles as the core and the(La,Ce)_(2)(Fe,Co,Si)_(17)(2:17)phase as the shell.As diffusion annealing time(t_(a))increases,this core-shell structure is replaced by the formation of the(La,Ce)_(1)(Fe,Co,Si)_(13) phase.Annealing at 1323 K for 12 h results in samples with(-ΔSM)^(max) of 9.30 J/(kg·K)(Δμ0H=2 T),good mechanical properties((σbc)^(max)=402 MPa,ε=4.21%)and thermal conductivity of 8.7 W/(m·K).Thus,bulk composites with excellent comprehensive properties for magnetic refrigeration are obtained in this work.
文摘The squeeze casting of a 2024 Al alloy was carried out to investigate the effect on microsegregation in the alloy of the application of pressure followed by diffusion annealing. The experimental results indicate that an optimum applied pressure followed by an optimum diffusion annealing process can markedly reduce the degree of microsegregation and improve the mechanical properties to a degree that can approach the level of forged 2024 Al alloy.
基金the National Science Fund for Distinguished Young Scholars(42025301)Natural Science Foundation of China(41673057)。
文摘South China can be divided into four metallogenic belts:The Middle-Lower Yangtze Metallogenic Belt(MLYB),Qinzhou-Hangzhou Metallogenic Belt(QHMB),Nanling Metallogenic Belt(NLMB),and Wuyi Metallogenic Belt(WYMB).The major mineralization in the four metallogenic belts is granite-related Cu–Au–Mo and porphyrite Fe-apatite,porphyry Cu(Au),and epithermal Pb–Zn–Ag,hydrothermal Cu–Au–Pb–Zn–Ag,and granite-related skarn-type and quartz-veins W–Sn,respectively.Low-temperature thermochronology,including fissiontrack and U-Th/He dating,has been widely used to constrain tectonic thermal evolution and ore deposits preservation.Understanding fission-track annealing and He diffusion kinetics in accessory minerals,such as zircon and apatite,is essential for dating and applications.In this study,previous zircon fission-track(ZFT)and apatite fission-track(AFT)ages in South China were collected.The result shows that the ZFT ages are mainly concentrated at140–90 Ma,and the AFT ages are mainly distributed at70–40 Ma.The age distribution and inversion temperature–time paths reveal heterogeneous exhumation histories in South China.The MLYB experienced Late CretaceousCenozoic extremely slow exhumation after rapid cooling in the Early Cretaceous.The northern QHMB(i.e.from southern Anhui province to the Hangzhou Bay)had a relatively faster rate of uplifting and denudation than the southern QHMB in the Cretaceous.Subsequently,the northern QHMB rapidly exhumed,while the continuously slow exhumation operated the southern QHMB in the Cenozoic.The southern NLMB had a more rapid cooling rate than the northern NLMB during the Cretaceous time,and the whole NLMB experienced rapid cooling in the Cenozoic,except that the southern Hunan province had the most rapid cooling rate.The WYMB possibly had experienced slow exhumation since the Late Cretaceous.The exhumation thickness of the four metallogenic belts since90 Ma is approximately calculated as follows:the MLYB≤3.5 km,the northern QHMB concentrated at3.5–5.5 km,and the southern QHMB usually less than3.5 km,the NLMB 4.5–6.5 km and the WYMB<3.5 km.The exhumation thickness of the NLMB is corresponding to the occurrence of the world-class W deposits,which were emplaced into a deeper depth of 1.5–8 km.As such,we infer that the uplifting and denudation processes of the four metallogenic belts have also played an important role in dominated ore deposits.
