The inherent trade-off between ductility and strength in Mg alloys remains a significant challenge,primarily governed by microstructural distribution and texture characteristics.Friction stir processing(FSP),a severe ...The inherent trade-off between ductility and strength in Mg alloys remains a significant challenge,primarily governed by microstructural distribution and texture characteristics.Friction stir processing(FSP),a severe plastic deformation(SPD)technique,refines microstructures by generating fine grains,uniformly dispersed fragmented particles,and a high fraction of high-angle grain boundaries(HAGBs),thereby facilitating superplastic forming at high strain rates and low temperatures.In the present work,a dual eccentric-pin tool(DEPT)FSP was employed to incorporate ZrO_(2) particles into a 6 mm thick AZ91D Mg alloy,leading to the formation of high volume{10-12}twins,dislocations,and β-Mg_(17)Al_(12) precipitates within the stirred zone.The microstructural evolution and mechanical behaviour of the stir zone under various process parameters were analysed using scanning electron microscopy(SEM),X-ray diffraction(XRD),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).The DEPT enhanced plastic shearing and dynamic recrystallization,significantly reducing the grain size from 15.6μm to 2.35μm while promoting uniform dislocation distribution within the stir zone(SZ).Grain orientation analysis revealed a transition from basal to prismatic texture dominance(29.3% volume fraction)due to intensified radial-tangential coupling shear deformation,facilitating the activation of non-basal slip systems.The DEPT evidently improved the hardness of the SZ from 58 to 92 HV and increased tensile strength from 234 MPa to 325 MPa while maintaining an elongation of 23.8%,achieving an optimal strengthductility balance.This work presents a one-step approach for tailoring microstructural heterogeneity and enhancing mechanical properties in AZ91D/ZrO_(2) composites using the DEPT FSP technique.The method provides an effective strategy for mitigating the strength-ductility trade-off commonly observed in Mg alloys.展开更多
Progresses in thermoelectric(TE)materials will contribute to solving the world's demands for energy and global climate protection.It also calls for higher ZT to achieve ideal commercial conversion efficiency.As an...Progresses in thermoelectric(TE)materials will contribute to solving the world's demands for energy and global climate protection.It also calls for higher ZT to achieve ideal commercial conversion efficiency.As an effective way,nanostructuring can reduce the thermal conductivity by the selective scattering of phonons or enhance Seebeck coefficient via modification of the density of the states,resulting in good ZT value.Meanwhile,TE properties of nanostructured materials should depend on the size and morphology of the microstructure features.This review emphasizes the developments in the TE bulk materials at the nanoscale in the past several years and summarizes the understanding in this active field.展开更多
Microalloyed steels are extensively utilized in the automotive industry for their superior strength–toughness synergy.Structural components,such as cranks,wheels,and front axles,are subjected to fluctuating or repeti...Microalloyed steels are extensively utilized in the automotive industry for their superior strength–toughness synergy.Structural components,such as cranks,wheels,and front axles,are subjected to fluctuating or repetitive stresses during service,which cause fatigue damage or failure.Therefore,improving the fatigue properties of microalloyed steels is crucial to broaden their applications.An overview of the factors affecting the fatigue properties of microalloyed steels is provided,beginning with a concise description of microalloyed steels,followed by a discussion of key factors,such as microstructure,precipitation,and non-metallic inclusions,that influence fatigue performance.Strategies for enhancing fatigue properties are also explored,including non-metallic inclusion modification,surface treatment,and microstructure tailoring.Modification treatment of non-metallic inclusions can alter their morphology,size,quantity,distribution,etc.,thereby reducing the adverse effect on fatigue performance.The surface treatment enhances resistance to crack initiation by introducing compressive residual stress or refining the surface microstructure.Microstructure tailoring involves various heat treatment processes that can slow fatigue crack growth.Ultimately,the latest developments and future prospects of fatigue properties in microalloyed steels,based on academic research and industrial practices,are also summarized.展开更多
B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites...B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites show better macroscopic plastic deformability and obvious work-hardening behavior compared to the conventional amorphous alloy matrix composites reinforced with ductile phases.However,the in-situ metastable B2-CuZr phase tends to undergo eutectoid decomposition during solidification,and the volume fraction,size,and distribution of B2-CuZr phase are difficult to control,which limits the development and application of these materials.To date,much efforts have been made to solve the above problems through composition optimization,casting parameter tailoring,and post-processing technique.In this study,a review was given based on relevant studies,focusing on the predictive approach,reinforcing mechanism,and microstructure tailoring methods of B2-CuZr phase reinforced amorphous alloy matrix composites.The research focus and future prospects were also given for the future development of the present composite system.展开更多
This article delivers a robust overview of potential electrode materials for use in symmetrical solid oxide fuel cells(S-SOFCs),a relatively new SOFC technology.To this end,this article provides a comprehensive review...This article delivers a robust overview of potential electrode materials for use in symmetrical solid oxide fuel cells(S-SOFCs),a relatively new SOFC technology.To this end,this article provides a comprehensive review of recent advances and progress in electrode materials for S-SOFC,discussing both the selection of materials and the challenges that come with making that choice.This article discussed the relevant factors involved in developing electrodes with nano/microstructure.Nanocomposites,e.g.,non-cobalt and lithiated materials,are only a few of the electrode types now being researched.Furthermore,the phase structure and microstructure of the produced materials are heavily influenced by the synthesis procedure.Insights into the possibilities and difficulties of the material are discussed.To achieve the desired microstructural features,this article focuses on a synthesis technique that is either the most recent or a better iteration of an existing process.The portion of this analysis that addresses the risks associated with manufacturing and the challenges posed by materials when fabricating S-SOFCs is the most critical.This article also provides important and useful recommendations for the strategic design of electrode materials researchers.展开更多
Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron micro...Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron microscopy.Theα＋βannealing treatments with different solid solution temperatures and cooling rates were conducted in order to tailor microstructure with differentαphase features in the Ti-6242 alloy,and fatigue crack growth mechanism was discussed after detailed microstructure characterization.The results showed that fatigue crack growth rate of Ti-6242 alloy decreased with the decrease in volume fraction of the primaryαphase（αp）.Samples with a large-sizedαgrain microstructure treated at high solid solution temperature and slow cooling rate have lower fatigue crack growth rate.The appearance of secondaryαphase（αs）with the increase of solid solution temperature led to crack deflection.Moreover,a fatigue crack growth transition phenomenon was observed in the Paris regime of Ti-6242 alloy with 29.8% αp（typical bi-modal microstructure）and large-sizedαgrain microstructure,owing to the change of fatigue crack growth mechanism.展开更多
Poor flowability of printable powders and long preparation cycles are the main challenges in the selective laser sintering(SLS)of chopped carbon fiber(C_(f))reinforced silicon carbide(SiC)composites with complex struc...Poor flowability of printable powders and long preparation cycles are the main challenges in the selective laser sintering(SLS)of chopped carbon fiber(C_(f))reinforced silicon carbide(SiC)composites with complex structures.In this study,we develop an efficient and novel processing route in the fabrication of lightweight SiC composites via the SLS of phenolic resin(PR)and Cr powders with the addition of a-SiC particles combined with the one-step reactive melt infiltration(RMI).The effects of a-SiC addition on the microstructural evolution of the C_(f)/SiC/PR printed bodies,C_(f)/SiC/C green bodies,and derived SiC composites were investigated.The results indicate that the added a-SiC particles play an important role in enhancing the flowability of raw powders,reducing the porosity.increasing the reliability of the C/SiC/C green bodies,and contributing to improving the microstructure homogeneity and mechanical properties of the SiC composites.The maximum density,flexural strength,and fracture toughness(Kic)of the SiC composites are 2.749±0.006 g·cm^(3),266±5 MPa,and 3.30±0.06 MPa-m,respectively.The coefficient of thermal expansion(CTE,a)of the SiC composites is approximately 4.29×10^(-6)K^(-1)from room temperature(RT)to 900℃,and the thermal conductivity(x)is in the range of 80.15-92.48 W·m^(-1)·K^(-1)at RT.The high-temperature strength of the SiC composites increase to 287±18 MPa up to 1200℃.This study provides a novel as well as feasible tactic for the preparation of high-quality printable powders as well as lightweight,high-strength,and high-x SiC composites with complex structures by the SLS and RMI.展开更多
基金the financial support from the Shandong Provincial Science Foundation for Outstanding Young Scholars(Grant No ZR2024YQ020)the National Natural Science Foundation of China(Grant Nos.52275349 and 52035005)+3 种基金the National Key Research and Development Program of China(Grant No 2022YFB4600902)the Excellent Young Team Project of Central Universities(No.2023QNTD002)Key Research and Development Program of Shandong Province(Grant No 2021ZLGX01)sponsored by the China/Shandong University International Postdoctoral Exchange Program.
文摘The inherent trade-off between ductility and strength in Mg alloys remains a significant challenge,primarily governed by microstructural distribution and texture characteristics.Friction stir processing(FSP),a severe plastic deformation(SPD)technique,refines microstructures by generating fine grains,uniformly dispersed fragmented particles,and a high fraction of high-angle grain boundaries(HAGBs),thereby facilitating superplastic forming at high strain rates and low temperatures.In the present work,a dual eccentric-pin tool(DEPT)FSP was employed to incorporate ZrO_(2) particles into a 6 mm thick AZ91D Mg alloy,leading to the formation of high volume{10-12}twins,dislocations,and β-Mg_(17)Al_(12) precipitates within the stirred zone.The microstructural evolution and mechanical behaviour of the stir zone under various process parameters were analysed using scanning electron microscopy(SEM),X-ray diffraction(XRD),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).The DEPT enhanced plastic shearing and dynamic recrystallization,significantly reducing the grain size from 15.6μm to 2.35μm while promoting uniform dislocation distribution within the stir zone(SZ).Grain orientation analysis revealed a transition from basal to prismatic texture dominance(29.3% volume fraction)due to intensified radial-tangential coupling shear deformation,facilitating the activation of non-basal slip systems.The DEPT evidently improved the hardness of the SZ from 58 to 92 HV and increased tensile strength from 234 MPa to 325 MPa while maintaining an elongation of 23.8%,achieving an optimal strengthductility balance.This work presents a one-step approach for tailoring microstructural heterogeneity and enhancing mechanical properties in AZ91D/ZrO_(2) composites using the DEPT FSP technique.The method provides an effective strategy for mitigating the strength-ductility trade-off commonly observed in Mg alloys.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51272080,51572098 and 51472043)the National Basic Research Program of China(Grant No.2013CB632500)+1 种基金the Natural Science Foundation of Hubei province(Grant No.2015CFB432)the Open Fund of State Key Laboratory of Advanced Technology for Materials Synthesis and Processing,Wuhan University of Technology(Grant No.2013-KF-3).
文摘Progresses in thermoelectric(TE)materials will contribute to solving the world's demands for energy and global climate protection.It also calls for higher ZT to achieve ideal commercial conversion efficiency.As an effective way,nanostructuring can reduce the thermal conductivity by the selective scattering of phonons or enhance Seebeck coefficient via modification of the density of the states,resulting in good ZT value.Meanwhile,TE properties of nanostructured materials should depend on the size and morphology of the microstructure features.This review emphasizes the developments in the TE bulk materials at the nanoscale in the past several years and summarizes the understanding in this active field.
基金financially supported by the National Key R&D Program of China(No.2021YFB3702403)financial support from the National Natural Science Foundation of China(Nos.52122408 and 52071023)。
文摘Microalloyed steels are extensively utilized in the automotive industry for their superior strength–toughness synergy.Structural components,such as cranks,wheels,and front axles,are subjected to fluctuating or repetitive stresses during service,which cause fatigue damage or failure.Therefore,improving the fatigue properties of microalloyed steels is crucial to broaden their applications.An overview of the factors affecting the fatigue properties of microalloyed steels is provided,beginning with a concise description of microalloyed steels,followed by a discussion of key factors,such as microstructure,precipitation,and non-metallic inclusions,that influence fatigue performance.Strategies for enhancing fatigue properties are also explored,including non-metallic inclusion modification,surface treatment,and microstructure tailoring.Modification treatment of non-metallic inclusions can alter their morphology,size,quantity,distribution,etc.,thereby reducing the adverse effect on fatigue performance.The surface treatment enhances resistance to crack initiation by introducing compressive residual stress or refining the surface microstructure.Microstructure tailoring involves various heat treatment processes that can slow fatigue crack growth.Ultimately,the latest developments and future prospects of fatigue properties in microalloyed steels,based on academic research and industrial practices,are also summarized.
基金supported by the National Natural Science Foundation of China(No.52101138,No.52201075)the Natural Science Foundation of Hubei Province(No.2023AFB798,No.2022CFB614)+3 种基金the Shenzhen Science and Technology Program(No.JCYJ20220530160813032)the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202309,No.SKLSP202308)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011227)the State Key Laboratory of Powder Metallurgy of Central South University(No.SklpmKF-05)。
文摘B2-CuZr phase reinforced amorphous alloy matrix composites has become one of the research hotspots in the field of materials science due to the“transformation-induced plasticity”phenomenon,which makes the composites show better macroscopic plastic deformability and obvious work-hardening behavior compared to the conventional amorphous alloy matrix composites reinforced with ductile phases.However,the in-situ metastable B2-CuZr phase tends to undergo eutectoid decomposition during solidification,and the volume fraction,size,and distribution of B2-CuZr phase are difficult to control,which limits the development and application of these materials.To date,much efforts have been made to solve the above problems through composition optimization,casting parameter tailoring,and post-processing technique.In this study,a review was given based on relevant studies,focusing on the predictive approach,reinforcing mechanism,and microstructure tailoring methods of B2-CuZr phase reinforced amorphous alloy matrix composites.The research focus and future prospects were also given for the future development of the present composite system.
基金the Fundamental Research Grant Scheme (FRGS),grant No.FRGS/1/2021/TK0/UKM/01/5 funded by the Ministry of Higher Education (MOHE)。
文摘This article delivers a robust overview of potential electrode materials for use in symmetrical solid oxide fuel cells(S-SOFCs),a relatively new SOFC technology.To this end,this article provides a comprehensive review of recent advances and progress in electrode materials for S-SOFC,discussing both the selection of materials and the challenges that come with making that choice.This article discussed the relevant factors involved in developing electrodes with nano/microstructure.Nanocomposites,e.g.,non-cobalt and lithiated materials,are only a few of the electrode types now being researched.Furthermore,the phase structure and microstructure of the produced materials are heavily influenced by the synthesis procedure.Insights into the possibilities and difficulties of the material are discussed.To achieve the desired microstructural features,this article focuses on a synthesis technique that is either the most recent or a better iteration of an existing process.The portion of this analysis that addresses the risks associated with manufacturing and the challenges posed by materials when fabricating S-SOFCs is the most critical.This article also provides important and useful recommendations for the strategic design of electrode materials researchers.
基金support of National Natural Science Foundation of China under Grant No.51401175the Research Fund for the Doctoral Program of China(No.20130162110005)
文摘Fatigue crack growth as a function ofαphase volume fraction in Ti-6Al-2Sn-4Zr-2Mo（Ti-6242）alloy was investigated using fatigue testing,optical microscopy,scanning electron microscopy,and transmission electron microscopy.Theα＋βannealing treatments with different solid solution temperatures and cooling rates were conducted in order to tailor microstructure with differentαphase features in the Ti-6242 alloy,and fatigue crack growth mechanism was discussed after detailed microstructure characterization.The results showed that fatigue crack growth rate of Ti-6242 alloy decreased with the decrease in volume fraction of the primaryαphase（αp）.Samples with a large-sizedαgrain microstructure treated at high solid solution temperature and slow cooling rate have lower fatigue crack growth rate.The appearance of secondaryαphase（αs）with the increase of solid solution temperature led to crack deflection.Moreover,a fatigue crack growth transition phenomenon was observed in the Paris regime of Ti-6242 alloy with 29.8% αp（typical bi-modal microstructure）and large-sizedαgrain microstructure,owing to the change of fatigue crack growth mechanism.
基金supported by the National Natural Science Foundation of China(Nos.52073299,52172077,U22A20129,and 51902329)the National Key R&D Program of China(No.2022YFB3706303)the Youth Innovation Promotion Association CAS(No.2018289).
文摘Poor flowability of printable powders and long preparation cycles are the main challenges in the selective laser sintering(SLS)of chopped carbon fiber(C_(f))reinforced silicon carbide(SiC)composites with complex structures.In this study,we develop an efficient and novel processing route in the fabrication of lightweight SiC composites via the SLS of phenolic resin(PR)and Cr powders with the addition of a-SiC particles combined with the one-step reactive melt infiltration(RMI).The effects of a-SiC addition on the microstructural evolution of the C_(f)/SiC/PR printed bodies,C_(f)/SiC/C green bodies,and derived SiC composites were investigated.The results indicate that the added a-SiC particles play an important role in enhancing the flowability of raw powders,reducing the porosity.increasing the reliability of the C/SiC/C green bodies,and contributing to improving the microstructure homogeneity and mechanical properties of the SiC composites.The maximum density,flexural strength,and fracture toughness(Kic)of the SiC composites are 2.749±0.006 g·cm^(3),266±5 MPa,and 3.30±0.06 MPa-m,respectively.The coefficient of thermal expansion(CTE,a)of the SiC composites is approximately 4.29×10^(-6)K^(-1)from room temperature(RT)to 900℃,and the thermal conductivity(x)is in the range of 80.15-92.48 W·m^(-1)·K^(-1)at RT.The high-temperature strength of the SiC composites increase to 287±18 MPa up to 1200℃.This study provides a novel as well as feasible tactic for the preparation of high-quality printable powders as well as lightweight,high-strength,and high-x SiC composites with complex structures by the SLS and RMI.
