The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability,high strength,cost-effectiveness,and recyclability.In the present work,the Cu...The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability,high strength,cost-effectiveness,and recyclability.In the present work,the Cu-12Fe alloy strip with the thickness of 2.4 mm was successfully produced by twin-roll strip casting.The microstructure and properties of the Cu-12Fe alloy were tailored by cold rolling and aging treatment.The tensile strength of the as-cast strip is approximately 328 MPa and its elongation is 25%.The Fe phase randomly dispersed in the matrix,and the average size of Fe-rich phase is 2μm.Besides,enrichment of Fe phase is observed in the central layer of the strip,results in the formation of the“sandwich structure”.Moreover,the as-cast strip of Cu-12Fe was directly cold-rolled from 2.4 to 0.12 mm.The directly cold-rolled sample after aging at 450℃for 16 h(ProcessⅠ)shows excellent electrical conductivity of 69.5%IACS,the tensile strength and elongation are 513 MPa and 3.8%,the saturation magnetic flux density is 20.1 emu·g^(-1),and the coercive force is 25.2 Oe.In ProcessⅡ,the as-cast strip firstly cold-rolled to 1.2 mm,then aged at 500℃for 1.5 h,followed by cold rolling to 0.12 mm,finally aged at 450℃for 16 h.The sample after ProcessⅡshows the electrical conductivity of 66.3%IACS,the tensile strength of 533 MPa,an elongation of 3.5%,saturation magnetic flux density of 21.4 emu·g^(-1),and the coercive force of 22.3 Oe.展开更多
The aim of this study is to investigate microscopic structure and characterize cancellous bone of avascular necrosis of the femoral head （ANFH）. The rabbit model of the ANFH is established. The histopathologic featu...The aim of this study is to investigate microscopic structure and characterize cancellous bone of avascular necrosis of the femoral head （ANFH）. The rabbit model of the ANFH is established. The histopathologic features are studied successfully. The differences between the steroidinjection group （S.G.） and the controlled group （C.G.） are examined, including the weight of rabbits, the hematological examination and the three-dimensional stnactures. It is found that the plasma levels of cholesterol （CHO）, high-density lipoprotein （HDL） and low-density lipoprotein （LDL） in S.G. are lower than those in C.G. when the triglyceride （TG） increased in the S.G.; but the bone mineral content （BMC） and the structural model index （SMI） of the organ and tissue decreased significantly in S.G. Three-dimensional structures of the femoral head are obtained using micro-computed tomography （CT） scanning and the mechanical model is established to analyze the influences of these structural changes on the mechanical properties of the cancellous bone.展开更多
93W-4.9Ni-2.1Fe alloys strengthened by nanoscale ZrC particles were prepared by spark-plasma-sintering(SPS)and hot rotary swaging,separately.Results show that the addition of a small number of ZrC nanoparticles can re...93W-4.9Ni-2.1Fe alloys strengthened by nanoscale ZrC particles were prepared by spark-plasma-sintering(SPS)and hot rotary swaging,separately.Results show that the addition of a small number of ZrC nanoparticles can refine grains and increase the hardness of the WNiFe alloys,but hinder the formation of theγ-(Ni,Fe)phase during SPS.SPSed WNiFe and WNiFe-ZrC alloys are brittle at room temperature,while the swaged WNiFe and WNiFe-0.5ZrC(wt%)alloys are ductile.At 400°C,the swaged WNiFe-0.5ZrC alloy exhibits both higher tensile strength and better ductility than the swaged WNiFe.The nanoscale particles distributed in the W grains andγ-(Ni,Fe)phase provide a good pinning effect,which enhances the strength.The thermal conductivity of swaged WNiFe-0.5ZrC is only 71 W·m^(-1)·K^(-1)at room temperature,but it increases to about 100 W·m^(-1)·K^(-1)at 800°C,which is close to that of pure W(121 W·m^(-1)·K^(-1)).These results show the potential of WNiFe alloys as plasma-facing materials in fusion reactor.展开更多
In this study,Al-xSi-0.3Mn-0.3Mg-0.14Fe alloys(x=6.5,7.5,8.5,wt.%)were prepared by super-slow-speed die-casting,and the effects of Si content on the microstructure,mechanical,and thermal/electrical conductivities in a...In this study,Al-xSi-0.3Mn-0.3Mg-0.14Fe alloys(x=6.5,7.5,8.5,wt.%)were prepared by super-slow-speed die-casting,and the effects of Si content on the microstructure,mechanical,and thermal/electrical conductivities in as-cast,T5,and T6 states(DIN EN 1706:2020)were investigated.It is found that the increase of Si content in the alloy enhances the formation of eutectic segregation band in the casting surface microstructure.Within the Si content range of 6.5%-8.5%,as a comprehensive evaluation criterion of mechanical properties,the quality index(QI)of 376.1 MPa can be obtained in the as-cast state of the alloy with about 7.5%Si content,373.4 MPa in T5 state of the alloy with 6.5%Si content,and 432.2 MPa in T6 state of the alloy containing 8.5%Si.The heat treatment state significantly affects the thermal conductivity and electrical conductivity of the alloys.The eutectic silicon in the alloy is segemented and further spheroidizaed during the solution process,and the solute atoms of Mg and Si are more adequately precipitated during the aging process.Both of these greatly reduce the probability of electron scattering.Thus,T6 treatment significantly improves the electrical and thermal conductivities.With the increase of Si content,both thermal conductivity and electrical conductivity decrease slightly,demonstrating a strong correlation with the Si content in the alloy.展开更多
The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength,uniform elongation,and electrical conductivity.Herein,we successfully fabricated a pure alum...The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength,uniform elongation,and electrical conductivity.Herein,we successfully fabricated a pure aluminum(Al)clad aluminum alloy(AA)rod with hierarchical compositions and microstructures.The proposed pure Al clad AA rod showcases an optimized combination of yield strength,uniform elongation,and electrical conductivity,i.e.,easing the restriction on improving yield strength,uniform elongation,and electrical conductivity.Compared to existing experiments,uniform elongation improved fourfold,while yield strength increased by 13%and electrical conductivity improved by 2%in terms of the international annealed copper standard(IACS).Microstructural characterizations and theoretical analyses revealed that the optimal performance of the Al clad AA arose from low-density low-angle grain boundaries(LAGBs)in the outer Al and high-density LAGBs with nanoscale precipitations in the inner AA.Our findings offer a compelling strategy for fabricating high-performance aluminum conductors,thereby laying a solid technical foundation for their wide application in power delivery systems.展开更多
In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,en...In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,environmental scanning electron microscopy(ESEM)and nuclear magnetic resonance(NMR)analyses were conducted to gain microstructural insights into loess behavior at the laboratory scale.The results indicate that the maximum saturated hydraulic conductivity is observed at the lowest compaction water content,particularly in the early stage of permeability tests.In particular,for loess compacted at water contents below the optimum(as determined by the modified Proctor compaction test),the hydraulic conductivity decreases throughout the permeability tests.Conversely,when the water content exceeds the optimum level,the hydraulic conductivity shows an increasing trend.In terms of compression behavior,when the as-compacted samples are loaded in oedometer conditions,an increase in material compressibility is observed with increasing compaction water content.Again,a different phenomenological behavior was observed when the compaction water content exceeded the optimum,i.e.an abrupt increase in loess compressibility.ESEM tests provide microstructural confirmation of this evidence,as the surface morphology of the compacted loess changes significantly with increasing compaction water content.The microstructural evolution was also quantified in terms of area ratio using image processing software.Finally,NMR was used to quantify the intra-and inter-aggregate water at different compaction water contents,once again highlighting a threshold for the presence or absence of inter-aggregate water similar to the optimum water content.展开更多
Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electric...Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously,the rare earth La was introduced to modify the Al-Mg-Si alloy.The effect of La addition on the microstructure,tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically.Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys.When the addition of La is 0.2wt.%,theα-Al grains are refined apparently,Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg_(2)Si phase;the distribution of Al_(11)La_(3)phases is uniform,and the morphology of AlFeSi phase transforms from continuous state to discontinuous state.The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity,with an ultimate tensile strength of 170 MPa,a yield strength of 88 MPa,an elongation of 18.9%,and an electrical conductivity of 44.0%IACS.These values represent improvements of 9.0%,15.8%,70.3%,and 17.3%,respectively,compared to the Al-Mg-Si alloy without La addition.However,excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.展开更多
The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production,due to t...The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production,due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.展开更多
The thermophysical properties of the SiC /Al composites mixed with diamond（SiC-Dia/Al） were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of ...The thermophysical properties of the SiC /Al composites mixed with diamond（SiC-Dia/Al） were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of the SiC-Dia/Al were calculated by differential effective medium（DEM） theoretical model and extended Turner model, respectively. The microstructure of the SiC-Dia/Al shows that the combination between SiC particles and Al is close, while that between diamond particles and Al is not close. The experimental results of the thermophysical properties of the SiC-Dia/Al are consistent with the calculated ones. The calculation results show that when the volume ratio of the diamond particles to the SiC particles is 3：7, the thermal conductivity and the thermal expansion coefficient can be improved by 39% and 30% compared to SiC/Al composites, respectively. In other words, by adding a small amount of diamond particles, the thermophysical properties of the composites can be improved effectively, while the cost increases little.展开更多
Microstructures and element distributions of the as-cast, hot-rolled and cold-rolled Cu-Mg-Te-Y alloys were studied. Effects of rolling process and annealing temperature on the properties of the Cu-Mg-Te-Y alloys were...Microstructures and element distributions of the as-cast, hot-rolled and cold-rolled Cu-Mg-Te-Y alloys were studied. Effects of rolling process and annealing temperature on the properties of the Cu-Mg-Te-Y alloys were correspondingly investigated. The results indicate that the Mg element is homogeneously distributed in the matrix and the fragmentized Cu2Te phase is dispersed in the matrix after hot rolling. Then, the Cu2Te phase is further stretched to strip shape after the cold rolling process. The microstructures of the cold-rolled alloy keep unchanged for the sample annealed below 390 ℃ for 1 h. However, after annealing at 550 ℃ for 1 h, the copper alloy with fibrous microstructures formed during the cold rolling process recrystallizes, leading to an obvious drop of hardening effect and an increase of electrical conductivity. The Cu-Mg-Te-Y alloy with better comprehensive properties is obtained by annealing at 360-390 ℃.展开更多
Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the mo...Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the modification treatment,the room-temperature tensile strength of the alloy remains nearly unchanged,the elongation at break slightly increases from 1.82%to 3.34%,and the electrical conductivity significantly increases from 40.1%international annealed copper standard(IACS)to 42.0%IACS.After the modification,the alloy was subjected to solid solution treatment at 515℃for 8 h,followed by aging treatment at 180,200,220 and 240℃for 6 h.With increasing aging temperature,the electrical conductivity increases monotonously from 41.4%IACS to 45.5%IACS,while the room-temperature tensile strength initially increases and then decreases.At 200℃,the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength:the electrical conductivity is 42.5%IACS,and the room-temperature tensile strength is 282.9 MPa.When the aging temperature continues to rise,the alloy undergoes overaging.Although the conductivity continues to increase,the room-temperature tensile strength drops sharply,and it is only 177.1 MPa at 240℃.展开更多
A Ni-P coating was deposited on Cu substrate by electroless plating and the Al/Cu bimetal was produced by solid？liquid compound casting technology. The microstructure, mechanical properties and conductivity of Al/Cu ...A Ni-P coating was deposited on Cu substrate by electroless plating and the Al/Cu bimetal was produced by solid？liquid compound casting technology. The microstructure, mechanical properties and conductivity of Al/Cu joints with different process parameters （bonding temperature and preheating time） were investigated. The results showed that intermetallics formed at the interface and the thickness and variety increased with the increase of bonding temperature and preheating time. The Ni？P interlayer functioned as a diffusion barrier and protective film which effectively reduced the formation of intermetallics. The shear strength and conductivity of Al/Cu bimetal were reduced by increasing the thickness of intermetallics. In particular, the detrimental effect of Al2Cu phase was more obvious compared with the others. The sample preheated at 780 ℃ for 150 s exhibited the maximum shear strength and conductivity of 49.8 MPa and 5.29×10^5 S/cm, respectively.展开更多
The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that ...The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that the initial T1 ageing contributes a major increase of the tensile strength, and the 0.2% proof stress value reaches 482 MPa after ageing for 7 h at 115℃. Behavioral differences in the tensile properties of the alloy after the two-step ageing treatment were less with the first-step ageing at 115~C for different time periods （7, 14, and 21 h）. The effects of the second ageing parameters on the properties and microstructure of the 7B04 alloy were remarkable. TEM analysis of the samples aged at Temper I （7 h at 115℃ ＋ 12 h at 160℃） and Temper II （7 h at 115℃ ＋ 16 h at 165℃） indicates that two kinds of phases, i.e. 11＇ and 11 phases, precipitate from the matrix and efficiently improve the tensile strength of the alloy, and the grain boundary precipitates are coarse and discrete. There are obvious precipitate free zones （PFZs） along the grain boundary in the microstructure of the alloy after the two-step ageing treatment.展开更多
The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solut...The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920℃ for 1 h, cold drawing to 96% deformation, followed by aging at 400℃ for 3 h. TEM analysis revealed two kinds of finely dispersed precipitates of Cr and CuaZr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.展开更多
Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. Th...Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopies, and by mea- suring thermal properties, including thermal conductivity and coefficient of thermal expansion （CTE）. The results show that the milled fibers are preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composites. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer. This carbide layer establishes a good metallurgical interracial bonding in the composites, which can improve the thermal properties effectively. When the fiber content ranges from 35 vol% to 50 vol%, the in-plane thermal conductivities of the composites increase from 383 to 407 W.（m.K）-~, and the in-plane CTEs decrease from 9.5 x 10-6 to 6.3 10-6 K-1.展开更多
The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper.The effects of the particle v...The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper.The effects of the particle volume fraction,the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were studied.The DEM theoretical calculation results show that,for the diamond hybrid SiC/Cu composite,when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12,the thermal conductivity of the composite can reach 500 W·m-1·K-1.The thermal conduc-tivity of the composite has little change when the particle size is above 200μm.The experimental results show that Ti can improve the wettability of the SiC and Cu.The thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/Cu.It is feasible to predict the thermal conductivity of the composite by DEM theoretical model.展开更多
The effects of Ni addition and aging treatments on the microstructure and properties of a Cu–3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning ...The effects of Ni addition and aging treatments on the microstructure and properties of a Cu–3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; the hardness, electrical conductivity, and elastic modulus of the resulting alloys were also tested. The results show that Ni addition increases the electrical conductivity and elastic modulus, but decreases the hardness of the aged Cu–3Ti alloy. Within the range of the experimentally investigated parameters, the optimal two-stage aging treatment for the Cu–3Ti–1Ni and Cu–3Ti–5Ni alloy was 300℃ for 2 h and 450℃ for 7 h. The hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–1Ni alloy were HV 205, 18.2% IACS, and 146 GPa, respectively, whereas the hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–5Ni alloy were HV 187, 31.32% IACS, and 147 GPa, respectively. Microstructural analyses revealed that β′-Ni3 Ti and β′-Cu4 Ti precipitate from the Cu matrix during aging of the Cu–3Ti–5Ni alloy and that some residual Ni Ti phase remains. The increased electrical conductivity is ascribed to the formation of Ni Ti, β′-Ni3 Ti, and β′-Cu4 Ti phases.展开更多
The multi-component A1CrCuFeMnTi high entropy alloy was prepared using a vacuum arc melting process. Serial annealing processes were subsequently performed at 590 ℃, 750 ℃, 955 ℃ and 1 100 ℃ respectively with a ho...The multi-component A1CrCuFeMnTi high entropy alloy was prepared using a vacuum arc melting process. Serial annealing processes were subsequently performed at 590 ℃, 750 ℃, 955 ℃ and 1 100 ℃ respectively with a holding time of 4 h at each temperature. The effects of annealing on microstructure, mechanical and electrical properties of as-cast alloy were investigated by using differential thermal analysis （DTA）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that two C14 hexagonal structures remain unchanged after annealing the as-cast A1CrCuFeMnTi alloy specimens being heated to 1 100℃. Both annealed and as-cast microstructures show typical cast-dendrite morphology and similar elemental segregation. The hardness of alloys declines as the annealing temperature increases while the strength of as-cast alloy improves obviously by the annealing treatment. The electrical conductivities of annealed and as-cast alloys are influenced by the distribution of interdendrite re^ions which is rich in Cu element.展开更多
The effects of Ni addition and aging treatment on the microstructure and properties of Cu?3Ti alloy were investigated. Themicrostructure and phase constituents were characterized by optical microscopy, scanning electr...The effects of Ni addition and aging treatment on the microstructure and properties of Cu?3Ti alloy were investigated. Themicrostructure and phase constituents were characterized by optical microscopy, scanning electron microscopy, X-ray diffractometerand high-resolution transmission electron microscopy, and the hardness and electrical conductivity were measured as well. Theresults show that NiTi phase forms with addition of Ni into as-cast Cu-3Ti alloy during solidification, and the as-cast microstructureevolves from dentrite to equiaxial structure. After aging treatment, coherent metastable β′-Cu4Ti precipitates from the Cu matrix.However, β′-Cu4Ti precipitation phase transforms into equilibrium, incoherent and lamellar Cu3Ti phase after overaging. Meanwhile,aging treatment results in appearance of annealing twins in the residual NiTi phase, and dislocation lines exist in the Cu matrix. Niaddition enhances the electrical conductivity, but decreases the hardness of Cu?3Ti alloy. In the range of experiments, the optimumaging treatment for Cu?3Ti?1Ni alloy is 300 °C for 2 h and 450 °C for 7 h. The hardness and electrical conductivity were HV 205and 18.2%IACS (international annealed copper standard), respectively.展开更多
To identify the microstructural features of the lattice structures of Al alloys built via the selective laser melting(SLM)process,AlSil OMg alloy with a body-centered cubic(BCC)-type lattice structure was prepared.Cha...To identify the microstructural features of the lattice structures of Al alloys built via the selective laser melting(SLM)process,AlSil OMg alloy with a body-centered cubic(BCC)-type lattice structure was prepared.Characteristic microstructures comprising melt pools with several columnarα-Al phases with<001>orientations along the elongation direction and surrounded by eutectic Si particles were observed at all portions of the built lattice structure.In the node portions of the lattice structure,a gradient microstructure(continuous change in microstructure)was observed.The columnarα-Al phases were observed near the top surface of the node portion,whereas they became coarser and more equiaxed near the bottom surface,resulting in softening localized near the bottom surface.In the strut portions of the lattice structure,the columnarα-Al phases were elongated along the inclined direction of struts.This trend was more prevalent near the bottom surface.Theα-Al phases became coarser and more equiaxed near the bottom surface as well.The aforementioned results were the basis of a discussion of the development of the gradient microstructure in lattice-structured Al alloys during the SLM process in terms of thermal conductivities at the boundaries between the manufactured(locally melted and rapidly solidified)portions and adjacent(unmelted)alloy powder.展开更多
基金financially supported by the Natural Science Foundation of Liaoning Province of China(2022-MS-109)the Key Research and Development Program of Liaoning Province(2023JH2/101800045)the Ministry of Science and Technology of the Peoples Republic of China(ZZ2021006).
文摘The Cu-12Fe alloy has attracted significant attention due to its excellent electrical conductivity and electromagnetic shielding capability,high strength,cost-effectiveness,and recyclability.In the present work,the Cu-12Fe alloy strip with the thickness of 2.4 mm was successfully produced by twin-roll strip casting.The microstructure and properties of the Cu-12Fe alloy were tailored by cold rolling and aging treatment.The tensile strength of the as-cast strip is approximately 328 MPa and its elongation is 25%.The Fe phase randomly dispersed in the matrix,and the average size of Fe-rich phase is 2μm.Besides,enrichment of Fe phase is observed in the central layer of the strip,results in the formation of the“sandwich structure”.Moreover,the as-cast strip of Cu-12Fe was directly cold-rolled from 2.4 to 0.12 mm.The directly cold-rolled sample after aging at 450℃for 16 h(ProcessⅠ)shows excellent electrical conductivity of 69.5%IACS,the tensile strength and elongation are 513 MPa and 3.8%,the saturation magnetic flux density is 20.1 emu·g^(-1),and the coercive force is 25.2 Oe.In ProcessⅡ,the as-cast strip firstly cold-rolled to 1.2 mm,then aged at 500℃for 1.5 h,followed by cold rolling to 0.12 mm,finally aged at 450℃for 16 h.The sample after ProcessⅡshows the electrical conductivity of 66.3%IACS,the tensile strength of 533 MPa,an elongation of 3.5%,saturation magnetic flux density of 21.4 emu·g^(-1),and the coercive force of 22.3 Oe.
基金supported by the National Natural Science Foundation of China(30470430 and 30400514)
文摘The aim of this study is to investigate microscopic structure and characterize cancellous bone of avascular necrosis of the femoral head （ANFH）. The rabbit model of the ANFH is established. The histopathologic features are studied successfully. The differences between the steroidinjection group （S.G.） and the controlled group （C.G.） are examined, including the weight of rabbits, the hematological examination and the three-dimensional stnactures. It is found that the plasma levels of cholesterol （CHO）, high-density lipoprotein （HDL） and low-density lipoprotein （LDL） in S.G. are lower than those in C.G. when the triglyceride （TG） increased in the S.G.; but the bone mineral content （BMC） and the structural model index （SMI） of the organ and tissue decreased significantly in S.G. Three-dimensional structures of the femoral head are obtained using micro-computed tomography （CT） scanning and the mechanical model is established to analyze the influences of these structural changes on the mechanical properties of the cancellous bone.
基金National Key Research and Development Program of China(2022YFE03140002,2019YFE03110200)National Natural Science Foundation of China(52273320,52173303,52325103,52171084)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0470000)Anhui Provincial Natural Science Foundation(2308085J07)HFIPS Director's Fund(YZJJ202102,YZJJQY202306,YZJJKX202202)。
文摘93W-4.9Ni-2.1Fe alloys strengthened by nanoscale ZrC particles were prepared by spark-plasma-sintering(SPS)and hot rotary swaging,separately.Results show that the addition of a small number of ZrC nanoparticles can refine grains and increase the hardness of the WNiFe alloys,but hinder the formation of theγ-(Ni,Fe)phase during SPS.SPSed WNiFe and WNiFe-ZrC alloys are brittle at room temperature,while the swaged WNiFe and WNiFe-0.5ZrC(wt%)alloys are ductile.At 400°C,the swaged WNiFe-0.5ZrC alloy exhibits both higher tensile strength and better ductility than the swaged WNiFe.The nanoscale particles distributed in the W grains andγ-(Ni,Fe)phase provide a good pinning effect,which enhances the strength.The thermal conductivity of swaged WNiFe-0.5ZrC is only 71 W·m^(-1)·K^(-1)at room temperature,but it increases to about 100 W·m^(-1)·K^(-1)at 800°C,which is close to that of pure W(121 W·m^(-1)·K^(-1)).These results show the potential of WNiFe alloys as plasma-facing materials in fusion reactor.
基金financially supported by the Nanjing Chervon Auto Precision Technology Co.,Ltd.(Grant No.322040)。
文摘In this study,Al-xSi-0.3Mn-0.3Mg-0.14Fe alloys(x=6.5,7.5,8.5,wt.%)were prepared by super-slow-speed die-casting,and the effects of Si content on the microstructure,mechanical,and thermal/electrical conductivities in as-cast,T5,and T6 states(DIN EN 1706:2020)were investigated.It is found that the increase of Si content in the alloy enhances the formation of eutectic segregation band in the casting surface microstructure.Within the Si content range of 6.5%-8.5%,as a comprehensive evaluation criterion of mechanical properties,the quality index(QI)of 376.1 MPa can be obtained in the as-cast state of the alloy with about 7.5%Si content,373.4 MPa in T5 state of the alloy with 6.5%Si content,and 432.2 MPa in T6 state of the alloy containing 8.5%Si.The heat treatment state significantly affects the thermal conductivity and electrical conductivity of the alloys.The eutectic silicon in the alloy is segemented and further spheroidizaed during the solution process,and the solute atoms of Mg and Si are more adequately precipitated during the aging process.Both of these greatly reduce the probability of electron scattering.Thus,T6 treatment significantly improves the electrical and thermal conductivities.With the increase of Si content,both thermal conductivity and electrical conductivity decrease slightly,demonstrating a strong correlation with the Si content in the alloy.
基金supported by the National Natural Science Foundation of China(Nos.12072327,12302497)the National Outstanding Youth Science Fund Project(No.12125206)+2 种基金Major International Joint Research Project(No.W2411003)Fund raised by China Electric Power Research Institute(No.GC80-21-002)CAS Project for Young Scientists in Basic Research(YSBR-096).
文摘The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength,uniform elongation,and electrical conductivity.Herein,we successfully fabricated a pure aluminum(Al)clad aluminum alloy(AA)rod with hierarchical compositions and microstructures.The proposed pure Al clad AA rod showcases an optimized combination of yield strength,uniform elongation,and electrical conductivity,i.e.,easing the restriction on improving yield strength,uniform elongation,and electrical conductivity.Compared to existing experiments,uniform elongation improved fourfold,while yield strength increased by 13%and electrical conductivity improved by 2%in terms of the international annealed copper standard(IACS).Microstructural characterizations and theoretical analyses revealed that the optimal performance of the Al clad AA arose from low-density low-angle grain boundaries(LAGBs)in the outer Al and high-density LAGBs with nanoscale precipitations in the inner AA.Our findings offer a compelling strategy for fabricating high-performance aluminum conductors,thereby laying a solid technical foundation for their wide application in power delivery systems.
基金the China Postdoctoral Science Foundation(Grant No.2024MD753992)Shaanxi Geotechnical Mechanics and Engineering Young Talent Support Program Project(Grant No.YESS2024005)the National Natural Science Foundation of China(Grant No.41931285).
文摘In this study,compacted loess samples with varying compaction water content but identical dry density were prepared to investigate the evolution of their hydraulic conductivity and compression behavior.Additionally,environmental scanning electron microscopy(ESEM)and nuclear magnetic resonance(NMR)analyses were conducted to gain microstructural insights into loess behavior at the laboratory scale.The results indicate that the maximum saturated hydraulic conductivity is observed at the lowest compaction water content,particularly in the early stage of permeability tests.In particular,for loess compacted at water contents below the optimum(as determined by the modified Proctor compaction test),the hydraulic conductivity decreases throughout the permeability tests.Conversely,when the water content exceeds the optimum level,the hydraulic conductivity shows an increasing trend.In terms of compression behavior,when the as-compacted samples are loaded in oedometer conditions,an increase in material compressibility is observed with increasing compaction water content.Again,a different phenomenological behavior was observed when the compaction water content exceeded the optimum,i.e.an abrupt increase in loess compressibility.ESEM tests provide microstructural confirmation of this evidence,as the surface morphology of the compacted loess changes significantly with increasing compaction water content.The microstructural evolution was also quantified in terms of area ratio using image processing software.Finally,NMR was used to quantify the intra-and inter-aggregate water at different compaction water contents,once again highlighting a threshold for the presence or absence of inter-aggregate water similar to the optimum water content.
基金supported by the National Natural Science Foundation of China(No.51704087)the Natural Science Foundation of Heilongjiang Province(No.LH2020E083).
文摘Lightweight aluminum alloy conductor materials(Al-Mg-Si alloys)require not only high electrical conductivity to reduce electrical loss,but also high strength to withstand extreme weather conditions.To improve electrical conductivity and mechanical properties of Al-Mg-Si alloy simultaneously,the rare earth La was introduced to modify the Al-Mg-Si alloy.The effect of La addition on the microstructure,tensile properties and electrical conductivity of cast Al-Mg-Si alloy was investigated systematically.Results indicate that the appropriate La content is helpful to improve the strength and electrical conductivity of Al-Mg-Si alloys.When the addition of La is 0.2wt.%,theα-Al grains are refined apparently,Mg and Si solute atoms in the Al matrix are reduced by the formation of Mg_(2)Si phase;the distribution of Al_(11)La_(3)phases is uniform,and the morphology of AlFeSi phase transforms from continuous state to discontinuous state.The Al-Mg-Si-0.2La alloy exhibits the optimal tensile properties and electrical conductivity,with an ultimate tensile strength of 170 MPa,a yield strength of 88 MPa,an elongation of 18.9%,and an electrical conductivity of 44.0%IACS.These values represent improvements of 9.0%,15.8%,70.3%,and 17.3%,respectively,compared to the Al-Mg-Si alloy without La addition.However,excessive La deteriorates the properties of Al-Mg-Si-xLa alloys.
基金the National Science and Technology Major Project of China(No.2012ZX04012-011)the National Natural Science Foundation of China(No.51675335)
文摘The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production,due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.
文摘The thermophysical properties of the SiC /Al composites mixed with diamond（SiC-Dia/Al） were studied through theoretical calculation and experiments. The thermal conductivity and the thermal expansion coefficient of the SiC-Dia/Al were calculated by differential effective medium（DEM） theoretical model and extended Turner model, respectively. The microstructure of the SiC-Dia/Al shows that the combination between SiC particles and Al is close, while that between diamond particles and Al is not close. The experimental results of the thermophysical properties of the SiC-Dia/Al are consistent with the calculated ones. The calculation results show that when the volume ratio of the diamond particles to the SiC particles is 3：7, the thermal conductivity and the thermal expansion coefficient can be improved by 39% and 30% compared to SiC/Al composites, respectively. In other words, by adding a small amount of diamond particles, the thermophysical properties of the composites can be improved effectively, while the cost increases little.
基金Project (50875031) supported by the National Natural Science Foundation of ChinaProject (DUT122D205) supported by the Fundamental Research Funds for the Central Universities,China
文摘Microstructures and element distributions of the as-cast, hot-rolled and cold-rolled Cu-Mg-Te-Y alloys were studied. Effects of rolling process and annealing temperature on the properties of the Cu-Mg-Te-Y alloys were correspondingly investigated. The results indicate that the Mg element is homogeneously distributed in the matrix and the fragmentized Cu2Te phase is dispersed in the matrix after hot rolling. Then, the Cu2Te phase is further stretched to strip shape after the cold rolling process. The microstructures of the cold-rolled alloy keep unchanged for the sample annealed below 390 ℃ for 1 h. However, after annealing at 550 ℃ for 1 h, the copper alloy with fibrous microstructures formed during the cold rolling process recrystallizes, leading to an obvious drop of hardening effect and an increase of electrical conductivity. The Cu-Mg-Te-Y alloy with better comprehensive properties is obtained by annealing at 360-390 ℃.
基金Applied Basic Research Program of Liaoning Province(CN)(2022JH2/101300078)。
文摘Self-designed Al8Si0.4Mg0.4Fe aluminium alloy was modified with Sr,followed by solid solution and aging treatments to regulate its microstructure and mechanical/electrical properties.The results show that after the modification treatment,the room-temperature tensile strength of the alloy remains nearly unchanged,the elongation at break slightly increases from 1.82%to 3.34%,and the electrical conductivity significantly increases from 40.1%international annealed copper standard(IACS)to 42.0%IACS.After the modification,the alloy was subjected to solid solution treatment at 515℃for 8 h,followed by aging treatment at 180,200,220 and 240℃for 6 h.With increasing aging temperature,the electrical conductivity increases monotonously from 41.4%IACS to 45.5%IACS,while the room-temperature tensile strength initially increases and then decreases.At 200℃,the alloy achieves an optimal balance between electrical conductivity and room-temperature tensile strength:the electrical conductivity is 42.5%IACS,and the room-temperature tensile strength is 282.9 MPa.When the aging temperature continues to rise,the alloy undergoes overaging.Although the conductivity continues to increase,the room-temperature tensile strength drops sharply,and it is only 177.1 MPa at 240℃.
基金Project(51571080)supported by the National Natural Science Foundation of China
文摘A Ni-P coating was deposited on Cu substrate by electroless plating and the Al/Cu bimetal was produced by solid？liquid compound casting technology. The microstructure, mechanical properties and conductivity of Al/Cu joints with different process parameters （bonding temperature and preheating time） were investigated. The results showed that intermetallics formed at the interface and the thickness and variety increased with the increase of bonding temperature and preheating time. The Ni？P interlayer functioned as a diffusion barrier and protective film which effectively reduced the formation of intermetallics. The shear strength and conductivity of Al/Cu bimetal were reduced by increasing the thickness of intermetallics. In particular, the detrimental effect of Al2Cu phase was more obvious compared with the others. The sample preheated at 780 ℃ for 150 s exhibited the maximum shear strength and conductivity of 49.8 MPa and 5.29×10^5 S/cm, respectively.
基金the National High-Tech Research Development Program of China (No. 2003AA331100).
文摘The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that the initial T1 ageing contributes a major increase of the tensile strength, and the 0.2% proof stress value reaches 482 MPa after ageing for 7 h at 115℃. Behavioral differences in the tensile properties of the alloy after the two-step ageing treatment were less with the first-step ageing at 115~C for different time periods （7, 14, and 21 h）. The effects of the second ageing parameters on the properties and microstructure of the 7B04 alloy were remarkable. TEM analysis of the samples aged at Temper I （7 h at 115℃ ＋ 12 h at 160℃） and Temper II （7 h at 115℃ ＋ 16 h at 165℃） indicates that two kinds of phases, i.e. 11＇ and 11 phases, precipitate from the matrix and efficiently improve the tensile strength of the alloy, and the grain boundary precipitates are coarse and discrete. There are obvious precipitate free zones （PFZs） along the grain boundary in the microstructure of the alloy after the two-step ageing treatment.
基金financially supported by the National High-Tech Research and Development Program of China (No.2006AA03Z522)the National Natural Science Foundation of China (No.50704006)the Technology De-velopment Fund of CHALCO (No.CHINACO-2009-KJ-02)
文摘The effects of thermomechanical treatment on the properties and microstructure of Cu-Cr-Zr alloy and Cu-Cr-Zr-Ag alloy were investigated. Ag addition improves the mechanical properties of the alloy through solid solution strengthening and brings a little effect on the electrical conductivity of the alloy. A new Cu-Cr-Zr-Ag alloy was developed, which has an excellent combination of the tensile strength, elongation, and electrical conductivity reaching 476.09 MPa, 15.43% and 88.68% IACS respectively when subjected to the optimum thermomechanical treatment, i.e., solution-treating at 920℃ for 1 h, cold drawing to 96% deformation, followed by aging at 400℃ for 3 h. TEM analysis revealed two kinds of finely dispersed precipitates of Cr and CuaZr. It is very important to use the mechanisms of solid solution strengthening, work hardening effect as well as precipitate pinning effect of dislocations to improve tensile strength of the alloy without adversely affecting its electrical conductivity.
基金financially supported by the National Natural Science Foundation of China(No.51274040)the Fundamental Research Funds for the Central Universities(FRF-TP-10-003B)
文摘Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopies, and by mea- suring thermal properties, including thermal conductivity and coefficient of thermal expansion （CTE）. The results show that the milled fibers are preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composites. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer. This carbide layer establishes a good metallurgical interracial bonding in the composites, which can improve the thermal properties effectively. When the fiber content ranges from 35 vol% to 50 vol%, the in-plane thermal conductivities of the composites increase from 383 to 407 W.（m.K）-~, and the in-plane CTEs decrease from 9.5 x 10-6 to 6.3 10-6 K-1.
基金financially supported by High-Technology Research and Development Program of China (No.2008AA03Z505)
文摘The thermal conductivity of diamond hybrid SiC/Cu,diamond/Cu and SiC/Cu composite were calculated by using the extended differential effective medium (DEM) theoretical model in this paper.The effects of the particle volume fraction,the particle size and the volume ratio of the diamond particles to the total particles on the thermal conductivity of the composite were studied.The DEM theoretical calculation results show that,for the diamond hybrid SiC/Cu composite,when the particle volume fraction is above 46% and the volume ratio of the diamond particles to the SiC particles is above 13:12,the thermal conductivity of the composite can reach 500 W·m-1·K-1.The thermal conduc-tivity of the composite has little change when the particle size is above 200μm.The experimental results show that Ti can improve the wettability of the SiC and Cu.The thermal conductivity of the diamond hybrid SiCTi/Cu is almost two times better than that of the diamond hybrid SiC/Cu.It is feasible to predict the thermal conductivity of the composite by DEM theoretical model.
基金financially supported by the National Natural Science Foundation of China (Nos. 51201132 and 51274163)the Research Program of Shaanxi Provincial Key Laboratory (No. 13JS076)+1 种基金the China Scholarship Council, the Pivot Innovation Team of Shaanxi Electrical Materials and Infiltration Technique (No. 2012KCT-25)the Shaanxi Provincial Project of Special Foundation of Key Disciplines (No. 2011HBSZS009)
文摘The effects of Ni addition and aging treatments on the microstructure and properties of a Cu–3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; the hardness, electrical conductivity, and elastic modulus of the resulting alloys were also tested. The results show that Ni addition increases the electrical conductivity and elastic modulus, but decreases the hardness of the aged Cu–3Ti alloy. Within the range of the experimentally investigated parameters, the optimal two-stage aging treatment for the Cu–3Ti–1Ni and Cu–3Ti–5Ni alloy was 300℃ for 2 h and 450℃ for 7 h. The hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–1Ni alloy were HV 205, 18.2% IACS, and 146 GPa, respectively, whereas the hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–5Ni alloy were HV 187, 31.32% IACS, and 147 GPa, respectively. Microstructural analyses revealed that β′-Ni3 Ti and β′-Cu4 Ti precipitate from the Cu matrix during aging of the Cu–3Ti–5Ni alloy and that some residual Ni Ti phase remains. The increased electrical conductivity is ascribed to the formation of Ni Ti, β′-Ni3 Ti, and β′-Cu4 Ti phases.
基金Funded by the 2012 Opening Funding of National Key Laboratory on Advanced Composites in Special Environment
文摘The multi-component A1CrCuFeMnTi high entropy alloy was prepared using a vacuum arc melting process. Serial annealing processes were subsequently performed at 590 ℃, 750 ℃, 955 ℃ and 1 100 ℃ respectively with a holding time of 4 h at each temperature. The effects of annealing on microstructure, mechanical and electrical properties of as-cast alloy were investigated by using differential thermal analysis （DTA）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that two C14 hexagonal structures remain unchanged after annealing the as-cast A1CrCuFeMnTi alloy specimens being heated to 1 100℃. Both annealed and as-cast microstructures show typical cast-dendrite morphology and similar elemental segregation. The hardness of alloys declines as the annealing temperature increases while the strength of as-cast alloy improves obviously by the annealing treatment. The electrical conductivities of annealed and as-cast alloys are influenced by the distribution of interdendrite re^ions which is rich in Cu element.
基金Projects(51201132,51274163) supported by the National Natural Science Foundation of ChinaProject(13JS076) supported by Shaanxi Provincial Key Laboratory Research Program,ChinaProject(2011HBSZS009) supported by Shaanxi Provincial Project of Special Foundation of Key Disciplines,China
文摘The effects of Ni addition and aging treatment on the microstructure and properties of Cu?3Ti alloy were investigated. Themicrostructure and phase constituents were characterized by optical microscopy, scanning electron microscopy, X-ray diffractometerand high-resolution transmission electron microscopy, and the hardness and electrical conductivity were measured as well. Theresults show that NiTi phase forms with addition of Ni into as-cast Cu-3Ti alloy during solidification, and the as-cast microstructureevolves from dentrite to equiaxial structure. After aging treatment, coherent metastable β′-Cu4Ti precipitates from the Cu matrix.However, β′-Cu4Ti precipitation phase transforms into equilibrium, incoherent and lamellar Cu3Ti phase after overaging. Meanwhile,aging treatment results in appearance of annealing twins in the residual NiTi phase, and dislocation lines exist in the Cu matrix. Niaddition enhances the electrical conductivity, but decreases the hardness of Cu?3Ti alloy. In the range of experiments, the optimumaging treatment for Cu?3Ti?1Ni alloy is 300 °C for 2 h and 450 °C for 7 h. The hardness and electrical conductivity were HV 205and 18.2%IACS (international annealed copper standard), respectively.
基金support of the“Knowledge Hub Aichi”a Priority Research Project of Aichi Prefectural Government,Japan。
文摘To identify the microstructural features of the lattice structures of Al alloys built via the selective laser melting(SLM)process,AlSil OMg alloy with a body-centered cubic(BCC)-type lattice structure was prepared.Characteristic microstructures comprising melt pools with several columnarα-Al phases with<001>orientations along the elongation direction and surrounded by eutectic Si particles were observed at all portions of the built lattice structure.In the node portions of the lattice structure,a gradient microstructure(continuous change in microstructure)was observed.The columnarα-Al phases were observed near the top surface of the node portion,whereas they became coarser and more equiaxed near the bottom surface,resulting in softening localized near the bottom surface.In the strut portions of the lattice structure,the columnarα-Al phases were elongated along the inclined direction of struts.This trend was more prevalent near the bottom surface.Theα-Al phases became coarser and more equiaxed near the bottom surface as well.The aforementioned results were the basis of a discussion of the development of the gradient microstructure in lattice-structured Al alloys during the SLM process in terms of thermal conductivities at the boundaries between the manufactured(locally melted and rapidly solidified)portions and adjacent(unmelted)alloy powder.
