Casing deformation affects the implementation of stimulation and development measures of oilfields directly;however, the reshaping forceand torque usually are determined by experience when the deformed casing is repai...Casing deformation affects the implementation of stimulation and development measures of oilfields directly;however, the reshaping forceand torque usually are determined by experience when the deformed casing is repaired with the spinning reshaping technology;if the repairingforce or torque is too large, it will result in the damage of casing and cement sheath as well as sticking accident. So, the collapse experimentswere performed on the YAW-200 pressure testing machine by using one production casing which is often used in the oilfield and then thereshaping test of deformed casing (C110) was performed in turn by using two spinning casing swages of which the diameter is 126 mm and129 mm respectively. The continuous rotator and thrust bearing were used to provide the torque and reshaping force respectively in the repairingprocess. The reshaping force and torque required to reshape the deformed casing, the deformation law and the springback value of deformedcasing were obtained. Test results show that the diameter differential between the two spinning casing swages is reasonable. Furthermore, inorder to ensure the safety and reliability of the implementation of post-production technologies, the mechanical properties of deformed casingbefore and after reshaping were tested. It was found that all the mechanical parameters of the deformed casing after reshaping reduced, whichresulted in the decrease of the strength of the reshaped casing. These research achievements would provide important experimental data inoptimizing the structure and construction parameters of spinning casing swages.展开更多
Combining the processing maps with FEA,the critical values of reduction of diameter(ΔR) for the appearance of as-cast microstructure,dynamic recrystallization grains and twins in the swaged magnesium were respectivel...Combining the processing maps with FEA,the critical values of reduction of diameter(ΔR) for the appearance of as-cast microstructure,dynamic recrystallization grains and twins in the swaged magnesium were respectively studied,by which the rational range ofΔR was obtained.To ensure that the as-cast microstructure wouldn't be retained in the rotary-swaged magnesium,ΔR should be larger than 0.25 mm.To avoid the appearance of twins in the microstructure of rotary-swaged magnesium,ΔR should be less than 1.0 mm.ΔR should be between 0.25 mm and 1.0 mm to ensure the appearance of recrystallized grains.The surface roughness of rotary-swaged magnesium increases with the increase ofΔR by quadratic function.The simulated results accord well with the experimental data.In the process control of rotary-swaging(RS),ΔR should be maximized between 0.25 mm and 1.0 mm on the precondition that the requests for surface roughness have been satisfied.展开更多
The microstructures of the cold-swaged and recrystallized Ti-23Nb-0.7Ta-2Zr-O(TNTZO)(mole fraction,%) alloy were investigated by electron backscatter diffraction(EBSD). The difference in microstructure,texture and rec...The microstructures of the cold-swaged and recrystallized Ti-23Nb-0.7Ta-2Zr-O(TNTZO)(mole fraction,%) alloy were investigated by electron backscatter diffraction(EBSD). The difference in microstructure,texture and recrystallization process was evaluated between the TNTZO alloy and traditional body centered cubic(bcc) metals. The results show that the cold-swaged TNTZO alloy presents a pronounced 〈110〉fiber texture in the axial direction. The recrystallization of the TNTZO alloy is achieved by the nucleation of new grains and the growth of these new grains at the expense of the deformed structure. The TNTZO alloy behaves a very similar way to traditional bcc metals in the features of the microstructure,texture and recrystallization.展开更多
Tungsten-based materials are one of the most important candidates for the plasma facing materials(PFMs)of future fusion reactors,and it is necessary to study the properties of tungsten-based materials under the servic...Tungsten-based materials are one of the most important candidates for the plasma facing materials(PFMs)of future fusion reactors,and it is necessary to study the properties of tungsten-based materials under the service conditions of fusion devices to ensure the long-term steady-state operation of future fusion reactors.In this paper,different tungsten-based materials made by the same rotary swaging process are selected to simulate the transient thermal loads on the PFMs of a fusion reactor using an electron beam,and thermal load experiments are carried out by changing the power density of a loading pulse and the pulse number.It is found that different tungsten-based materials made by the same process have large differences in thermal shock resistance,and the doped tungsten materials(W-K and W-La_(2)O_(3))are significantly better than the pure tungsten materials with the increase in thermal shock power density and the number of cycles,especially the W-K materials,which have excellent performance.展开更多
A study of the effect of rotary swaging(RS)at 350℃ on mechanical properties,corrosion resistance and biocompatibility in vitro and in vivo of biodegradable Mg-1%Zn-0.6%Ca alloy was conducted.It is shown that the form...A study of the effect of rotary swaging(RS)at 350℃ on mechanical properties,corrosion resistance and biocompatibility in vitro and in vivo of biodegradable Mg-1%Zn-0.6%Ca alloy was conducted.It is shown that the formation of a recrystallized microstructure after RS with a grain size of 3.2±0.2μm leads to an increase in the strength of the alloy without reduction of level of ductility and corrosion resistance.At the same time,aging of the quenched alloy at 100℃ for 8 h leads to a slight increase in strength,but significantly reduces its ductility and corrosion resistance.The study of the degradation process of the alloy in the quenched state and after RS,both under in vitro and in vivo conditions,did not reveal a significant difference between these two microstructural states.However,an increase in the duration of incubation of the alloy in a complete growth medium from 4 h to 24 days leads to a decrease in the degradation rate(DR)by 4times(from~2 to~0.5 mm/year)due to the formation of a dense layer of degradation products.The study of biocompatibility in vitro did not reveal a significant effect of RS on the hemolytic and cytotoxic activity of the alloy.No signs of systemic toxicity were observed after subcutaneous implantation of alloy samples into mice before and after RS.However,it was found that RS promotes uniform degradation of the alloy over the entire contact surface.In summary,RS at 350℃ allows to increase the strength of Mg-1%Zn-0.6%Ca alloy up to348±5 MPa at a ductility level of 17.3±2.8%and a DRin vivoequal to 0.56±0.12 mm/year without impairing its biocompatibility in vitro and in vivo.展开更多
The paper deals with the FEM(Finite Element Method)simulation of rotary swaging of Dievar alloy produced by additive manufacturing technology Selective Laser Melting and conventional process.Swaging was performed at a...The paper deals with the FEM(Finite Element Method)simulation of rotary swaging of Dievar alloy produced by additive manufacturing technology Selective Laser Melting and conventional process.Swaging was performed at a temperature of 900℃.True flow stress-strain curves were determined for 600℃–900℃and used to construct a Hensel-Spittel model for FEM simulation.The process parameters,i.e.,stress,temperature,imposed strain,and force,were investigation during the rotary swaging process.Firstly,the stresses induced during rotary swaging and the resistance of the material to deformation were investigated.The amount and distribution of imposed strain in the cross-section can serve as a valuable indicator of the reduction in porosity and the texture evolution of the material.The simulation revealed the force required to swag the Dievar alloy.It also showed the evolution of temperature,which is important for phase transformation during solidification.Furthermore,microstructure evolutionwas observed before and then after rotary swaging.Dievar alloy is a critical material in the manufacture of dies for high-pressure die casting,forging tools,and other equipment subjected to high temperatures and mechanical loads.Understanding its viscoelastoplastic behavior under rotary swaging conditions is essential to optimize its performance in these demanding industrial applications.展开更多
The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materia...The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materials.A lamellar-structured Mg-4Li-3Al-0.4Ca alloy with high performance was prepared by hot extrusion and rotary swaging.The as-swaged alloy exhibits excellent mechanical properties with tensile strength,yield strength,elongation to failure,and specific strength of 391 MPa,312 MPa,14.2%,and 238.4 kN m kg^(-1),respectively.The average grain size of the as-swaged alloy is 160±23 nm,and the microstructure is mainly composed of lamellar structures,twins,ultrafine grains,and nano-grains.The abundant lamellar structures and twins promote the storage of dislocations and SFs,leading to the formation of twin-twin interactions and enhancing strain hardening.The formation of UFG and NG by dynamic recrystallization further improves the yield strength.Shearable second phases play a critical role in enhancing the yield strength and ductility.More importantly,extensive planar dislocation glide and(c+a)dislocations efficiently relax the local stress concentrations,and thus improve the ductility.展开更多
A Mg−3.2Bi−0.8Ca(BX31,wt.%)ternary alloy with a yield strength of~358.1 MPa was fabricated by hot extrusion,room-temperature(RT)rotary swaging and subsequent aging treatment.A fine grain structure(~2μm)and a few seco...A Mg−3.2Bi−0.8Ca(BX31,wt.%)ternary alloy with a yield strength of~358.1 MPa was fabricated by hot extrusion,room-temperature(RT)rotary swaging and subsequent aging treatment.A fine grain structure(~2μm)and a few secondary phases were observed in the as-extruded alloy,accompanied by a weak non-basal texture.After RT rotary swaging,the average grain size was reduced to~1μm via continuous dynamic recrystallization(CDRX).In addition,a large number of residual dislocations piled up within the grain interior,along with the dynamic precipitation of nano-phases.Peak aging occurred rapidly at 448 K for 35 min.After aging,the grain size hardly changed,the density of residual dislocations slightly decreased,and a large number of nano-precipitates were introduced at the dislocation pile-up sites.The grain boundary strengthening,dislocation strengthening and precipitation strengthening co-dominated the strength of the as-aged alloy.展开更多
Nanocrystalline(NC)metals and alloys are prone to mechanical and thermal instability under force and thermal fields due to their high Gibbs free energy,which limits their industrial applications.In this work,by employ...Nanocrystalline(NC)metals and alloys are prone to mechanical and thermal instability under force and thermal fields due to their high Gibbs free energy,which limits their industrial applications.In this work,by employing rotary swaging(RS),bulk NC Cu–15 at.%Al alloys with both high strength and high thermal stability were prepared.Quasi-static tensile test results show that the yield strength is 1016 MPa.Moreover,the grain growth temperature was retarded up to 0.4 Tm,higher than the literature values.Microstructural characterizations revealed that after RS deformation,coarse-grained Cu–Al was refined into fibrous NC grains with a diameter of 45 nm and a length of 190 nm,and the contents of high-angle grain boundaries(GBs),low-angle GBs,and twin boundaries are 17%,45%,and 38%,respectively.Moreover,there is a significant multiscale chemical fluctuation within the grains,at the GBs,and between the grains through extreme defect accumulation.The atomistic simulation suggests that the segregation behavior of Al solute is essentially driven by the atomic size and local stress state.Besides,Al segregation greatly reduces the grain boundary energy,which further improves the thermal stability of the material.The main strengthening mechanism is Hall–Petch strengthening and the strengthening brought by the chemical fluctuations.Our work provides ideas for designing strong and thermally stable bulk NC alloys.展开更多
The thermoelectric transport of n-type Bi_(2)Te_(3) heavily depends on grain alignment,causing perfor-mance limitations that severely restrict the demand for low-grade waste heat recovery.Here,the n-type Bi_(2)Te_(2.7...The thermoelectric transport of n-type Bi_(2)Te_(3) heavily depends on grain alignment,causing perfor-mance limitations that severely restrict the demand for low-grade waste heat recovery.Here,the n-type Bi_(2)Te_(2.7)Se_(0.3) material with a certain textured structure is prepared by an innovative rotary swag-ing method.It is found that various defects including Te vacancies,dislocations,and grain boundaries significantly strengthen the phonon scattering.With an obviously suppressed thermal conductivity and well-maintained carrier mobility,the obtained rods extending up to several tens of centimeters achieve a peak ZT of 1.2 at 450 K and an average ZT of 1.0(300-550 K),with Vickers hardness and compressive strength increased to 0.42 GPa and 52.6 MPa,respectively.Moreover,the assembled 17-pair thermoelec-tric module achieves a competitive conversion efficiency of up to 6.3% and a high output power of 0.93 W at a temperature difference of 250 K.This study develops an effective strategy for synergistically en-hancing the thermoelectric and mechanical properties of n-type Bi_(2)(Te,Se)_(3).展开更多
The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on ...The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on microstructures and mechanical properties were investigated using the SEM, TEM, OM and the universal material testing machine. Results show that the alloy can be easily hot forged and cold swaged due to the fine-grained microstructure. Only after cold swaging by 85%, the alloy shows the typical ＂marble-like＂ structure. And thecold deformation is accompanied by stress-induced a＂ phase transformations. Moreover, both the strength and the ductility of the alloy are significantly improved by hot and cold working.展开更多
文摘Casing deformation affects the implementation of stimulation and development measures of oilfields directly;however, the reshaping forceand torque usually are determined by experience when the deformed casing is repaired with the spinning reshaping technology;if the repairingforce or torque is too large, it will result in the damage of casing and cement sheath as well as sticking accident. So, the collapse experimentswere performed on the YAW-200 pressure testing machine by using one production casing which is often used in the oilfield and then thereshaping test of deformed casing (C110) was performed in turn by using two spinning casing swages of which the diameter is 126 mm and129 mm respectively. The continuous rotator and thrust bearing were used to provide the torque and reshaping force respectively in the repairingprocess. The reshaping force and torque required to reshape the deformed casing, the deformation law and the springback value of deformedcasing were obtained. Test results show that the diameter differential between the two spinning casing swages is reasonable. Furthermore, inorder to ensure the safety and reliability of the implementation of post-production technologies, the mechanical properties of deformed casingbefore and after reshaping were tested. It was found that all the mechanical parameters of the deformed casing after reshaping reduced, whichresulted in the decrease of the strength of the reshaped casing. These research achievements would provide important experimental data inoptimizing the structure and construction parameters of spinning casing swages.
基金Project(2007CB613706)supported by the National Basic Research Program of ChinaProject(52009999200702)supported by theInitiating Fund of Doctors'Research of Beijing University of Technology.China
文摘Combining the processing maps with FEA,the critical values of reduction of diameter(ΔR) for the appearance of as-cast microstructure,dynamic recrystallization grains and twins in the swaged magnesium were respectively studied,by which the rational range ofΔR was obtained.To ensure that the as-cast microstructure wouldn't be retained in the rotary-swaged magnesium,ΔR should be larger than 0.25 mm.To avoid the appearance of twins in the microstructure of rotary-swaged magnesium,ΔR should be less than 1.0 mm.ΔR should be between 0.25 mm and 1.0 mm to ensure the appearance of recrystallized grains.The surface roughness of rotary-swaged magnesium increases with the increase ofΔR by quadratic function.The simulated results accord well with the experimental data.In the process control of rotary-swaging(RS),ΔR should be maximized between 0.25 mm and 1.0 mm on the precondition that the requests for surface roughness have been satisfied.
基金Project(50571063) supported by the National Natural Science Foundation of ChinaProject (04JC14054) supported by the Science and Technology Committee of Shanghai Municipal.
文摘The microstructures of the cold-swaged and recrystallized Ti-23Nb-0.7Ta-2Zr-O(TNTZO)(mole fraction,%) alloy were investigated by electron backscatter diffraction(EBSD). The difference in microstructure,texture and recrystallization process was evaluated between the TNTZO alloy and traditional body centered cubic(bcc) metals. The results show that the cold-swaged TNTZO alloy presents a pronounced 〈110〉fiber texture in the axial direction. The recrystallization of the TNTZO alloy is achieved by the nucleation of new grains and the growth of these new grains at the expense of the deformed structure. The TNTZO alloy behaves a very similar way to traditional bcc metals in the features of the microstructure,texture and recrystallization.
基金supported by the Natural Science Foundation of Sichuan Province(2022NSFSC0329)the National Natural Science Foundation of China(Grant Nos.11975092,12205086,12192283,and 12075114)。
文摘Tungsten-based materials are one of the most important candidates for the plasma facing materials(PFMs)of future fusion reactors,and it is necessary to study the properties of tungsten-based materials under the service conditions of fusion devices to ensure the long-term steady-state operation of future fusion reactors.In this paper,different tungsten-based materials made by the same rotary swaging process are selected to simulate the transient thermal loads on the PFMs of a fusion reactor using an electron beam,and thermal load experiments are carried out by changing the power density of a loading pulse and the pulse number.It is found that different tungsten-based materials made by the same process have large differences in thermal shock resistance,and the doped tungsten materials(W-K and W-La_(2)O_(3))are significantly better than the pure tungsten materials with the increase in thermal shock power density and the number of cycles,especially the W-K materials,which have excellent performance.
基金Funding support of this work was carried out within the governmental task#075-00319-25-00.
文摘A study of the effect of rotary swaging(RS)at 350℃ on mechanical properties,corrosion resistance and biocompatibility in vitro and in vivo of biodegradable Mg-1%Zn-0.6%Ca alloy was conducted.It is shown that the formation of a recrystallized microstructure after RS with a grain size of 3.2±0.2μm leads to an increase in the strength of the alloy without reduction of level of ductility and corrosion resistance.At the same time,aging of the quenched alloy at 100℃ for 8 h leads to a slight increase in strength,but significantly reduces its ductility and corrosion resistance.The study of the degradation process of the alloy in the quenched state and after RS,both under in vitro and in vivo conditions,did not reveal a significant difference between these two microstructural states.However,an increase in the duration of incubation of the alloy in a complete growth medium from 4 h to 24 days leads to a decrease in the degradation rate(DR)by 4times(from~2 to~0.5 mm/year)due to the formation of a dense layer of degradation products.The study of biocompatibility in vitro did not reveal a significant effect of RS on the hemolytic and cytotoxic activity of the alloy.No signs of systemic toxicity were observed after subcutaneous implantation of alloy samples into mice before and after RS.However,it was found that RS promotes uniform degradation of the alloy over the entire contact surface.In summary,RS at 350℃ allows to increase the strength of Mg-1%Zn-0.6%Ca alloy up to348±5 MPa at a ductility level of 17.3±2.8%and a DRin vivoequal to 0.56±0.12 mm/year without impairing its biocompatibility in vitro and in vivo.
基金funded by the project SP2024/089 of the Specific Research of the VŠB-Technical University of Ostrava and realized within the framework of the Johannes Amos Comenius Program,Materials and Technologies for Sustainable Development-MATUR,No.CZ.02.01.01/00/22_008/0004631Brno University of Technology project No.FSI-S-23-8231“Investigation of Dynamic Deformation Behavior ofMetallicMaterials Prepared via Alternative Production Methods”.
文摘The paper deals with the FEM(Finite Element Method)simulation of rotary swaging of Dievar alloy produced by additive manufacturing technology Selective Laser Melting and conventional process.Swaging was performed at a temperature of 900℃.True flow stress-strain curves were determined for 600℃–900℃and used to construct a Hensel-Spittel model for FEM simulation.The process parameters,i.e.,stress,temperature,imposed strain,and force,were investigation during the rotary swaging process.Firstly,the stresses induced during rotary swaging and the resistance of the material to deformation were investigated.The amount and distribution of imposed strain in the cross-section can serve as a valuable indicator of the reduction in porosity and the texture evolution of the material.The simulation revealed the force required to swag the Dievar alloy.It also showed the evolution of temperature,which is important for phase transformation during solidification.Furthermore,microstructure evolutionwas observed before and then after rotary swaging.Dievar alloy is a critical material in the manufacture of dies for high-pressure die casting,forging tools,and other equipment subjected to high temperatures and mechanical loads.Understanding its viscoelastoplastic behavior under rotary swaging conditions is essential to optimize its performance in these demanding industrial applications.
基金supported by the National Natural Science Foundation of China(Nos.52371093 and 52171104)the National Key Research and Development Program of China(No.2021YFB3701100)the Chongqing Research Program of Basic Research and Frontier Technology,China(Nos.CSTB2023NSCQ-BSX0036 and cstc2021ycjh-bgzxm0086).
文摘The low strength of Mg-Li alloys sets a limit to lightweight applications.Introducing crystal defects(twins,dislocations,and SFs)is a distinctive strategy for maintaining good mechanical properties of metallic materials.A lamellar-structured Mg-4Li-3Al-0.4Ca alloy with high performance was prepared by hot extrusion and rotary swaging.The as-swaged alloy exhibits excellent mechanical properties with tensile strength,yield strength,elongation to failure,and specific strength of 391 MPa,312 MPa,14.2%,and 238.4 kN m kg^(-1),respectively.The average grain size of the as-swaged alloy is 160±23 nm,and the microstructure is mainly composed of lamellar structures,twins,ultrafine grains,and nano-grains.The abundant lamellar structures and twins promote the storage of dislocations and SFs,leading to the formation of twin-twin interactions and enhancing strain hardening.The formation of UFG and NG by dynamic recrystallization further improves the yield strength.Shearable second phases play a critical role in enhancing the yield strength and ductility.More importantly,extensive planar dislocation glide and(c+a)dislocations efficiently relax the local stress concentrations,and thus improve the ductility.
基金supported by the financial supports from the National Key Research and Development Program of China(No.2021YFB3701100)the National Natural Science Foundation of China(Nos.51901204,52161023,52204407)+3 种基金Key Research and Development Plan of Shanxi Province,China(No.202102050201005)Science and Technology Project of Yunnan Precious Metal Laboratory,China(No.YPML-2023050208)Yunnan Science and Technology Planning Project,China(Nos.202201AU070010,202301AT070276,202302AB080008,202303AA080001)the Second Professional Practice Innovation Project of Yunnan University,China(No.ZC-22221620).
文摘A Mg−3.2Bi−0.8Ca(BX31,wt.%)ternary alloy with a yield strength of~358.1 MPa was fabricated by hot extrusion,room-temperature(RT)rotary swaging and subsequent aging treatment.A fine grain structure(~2μm)and a few secondary phases were observed in the as-extruded alloy,accompanied by a weak non-basal texture.After RT rotary swaging,the average grain size was reduced to~1μm via continuous dynamic recrystallization(CDRX).In addition,a large number of residual dislocations piled up within the grain interior,along with the dynamic precipitation of nano-phases.Peak aging occurred rapidly at 448 K for 35 min.After aging,the grain size hardly changed,the density of residual dislocations slightly decreased,and a large number of nano-precipitates were introduced at the dislocation pile-up sites.The grain boundary strengthening,dislocation strengthening and precipitation strengthening co-dominated the strength of the as-aged alloy.
基金financial supports from National Key R&D Program of China(No.2021YFA1200203)National Natural Science Foundation of China(Nos.51971112,51225102,and 52171119)+3 种基金Jiangsu Province Leading Edge Technology Basic Research Major Project(No.BK20222014)Fundamental Research Funds for the Central Universities(No.2023201001)Jiangsu Funding Program for Excellent Postdoctoral Talent(No.2023ZB091)China Postdoctoral Science Foundation(No.2023M741699)。
文摘Nanocrystalline(NC)metals and alloys are prone to mechanical and thermal instability under force and thermal fields due to their high Gibbs free energy,which limits their industrial applications.In this work,by employing rotary swaging(RS),bulk NC Cu–15 at.%Al alloys with both high strength and high thermal stability were prepared.Quasi-static tensile test results show that the yield strength is 1016 MPa.Moreover,the grain growth temperature was retarded up to 0.4 Tm,higher than the literature values.Microstructural characterizations revealed that after RS deformation,coarse-grained Cu–Al was refined into fibrous NC grains with a diameter of 45 nm and a length of 190 nm,and the contents of high-angle grain boundaries(GBs),low-angle GBs,and twin boundaries are 17%,45%,and 38%,respectively.Moreover,there is a significant multiscale chemical fluctuation within the grains,at the GBs,and between the grains through extreme defect accumulation.The atomistic simulation suggests that the segregation behavior of Al solute is essentially driven by the atomic size and local stress state.Besides,Al segregation greatly reduces the grain boundary energy,which further improves the thermal stability of the material.The main strengthening mechanism is Hall–Petch strengthening and the strengthening brought by the chemical fluctuations.Our work provides ideas for designing strong and thermally stable bulk NC alloys.
基金supported by the National Natural Science Foundation of China(grant no.U21A2079)the China Post-doctoral Science Foundation(grant no.2024M753342)+3 种基金the Post-doctoral Fellowship Program of CPSF(grant no.GZB20230786)the Ningbo International Cooperation Project(grant no.2023H002)the Ningbo Science&Technology Project(grant no.2023A-160-B)the Ningbo Science&Technology Innovation 2025 Major Project(grant no.2022Z187).
文摘The thermoelectric transport of n-type Bi_(2)Te_(3) heavily depends on grain alignment,causing perfor-mance limitations that severely restrict the demand for low-grade waste heat recovery.Here,the n-type Bi_(2)Te_(2.7)Se_(0.3) material with a certain textured structure is prepared by an innovative rotary swag-ing method.It is found that various defects including Te vacancies,dislocations,and grain boundaries significantly strengthen the phonon scattering.With an obviously suppressed thermal conductivity and well-maintained carrier mobility,the obtained rods extending up to several tens of centimeters achieve a peak ZT of 1.2 at 450 K and an average ZT of 1.0(300-550 K),with Vickers hardness and compressive strength increased to 0.42 GPa and 52.6 MPa,respectively.Moreover,the assembled 17-pair thermoelec-tric module achieves a competitive conversion efficiency of up to 6.3% and a high output power of 0.93 W at a temperature difference of 250 K.This study develops an effective strategy for synergistically en-hancing the thermoelectric and mechanical properties of n-type Bi_(2)(Te,Se)_(3).
基金Project(2014CB644002)supported by the National Key Fundamental Research and Development Project of ChinaProject(51301203)supported by the National Natural Science Foundation of China+1 种基金Project(2015CX004)supported by the Innovation-driven Plan in Central South University,Chinasupported by the Outstanding Graduate Project of Advanced Non-ferrous Metal Structural Materials and Manufacturing Collaborative Innovation Center,China
文摘The Ti-36Nb-2Ta-3Zr-0.350 （mass fraction, %） （TNTZO） alloy was produced by cold isostatic pressing and sintering from elemental powders, followed by hot and cold deformation. The effects of deformation process on microstructures and mechanical properties were investigated using the SEM, TEM, OM and the universal material testing machine. Results show that the alloy can be easily hot forged and cold swaged due to the fine-grained microstructure. Only after cold swaging by 85%, the alloy shows the typical ＂marble-like＂ structure. And thecold deformation is accompanied by stress-induced a＂ phase transformations. Moreover, both the strength and the ductility of the alloy are significantly improved by hot and cold working.
