In order to predict and control the properties of Cu-Cr-Sn-Zn alloy,a model of aging processes via an artificial neural network(ANN) method to map the non-linear relationship between parameters of aging process and th...In order to predict and control the properties of Cu-Cr-Sn-Zn alloy,a model of aging processes via an artificial neural network(ANN) method to map the non-linear relationship between parameters of aging process and the hardness and electrical conductivity properties of the Cu-Cr-Sn-Zn alloy was set up.The results show that the ANN model is a very useful and accurate tool for the property analysis and prediction of aging Cu-Cr-Sn-Zn alloy.Aged at 470-510 ℃ for 4-1 h,the optimal combinations of hardness 110-117(HV) and electrical conductivity 40.6-37.7 S/m are available respectively.展开更多
The effect of deformation and aging treatment on the electrical conductivity of Cu-Cr alloy was studied. The results show that deformation can reduce the electrical conductivity of Cu-Cr alloy, but deformation followe...The effect of deformation and aging treatment on the electrical conductivity of Cu-Cr alloy was studied. The results show that deformation can reduce the electrical conductivity of Cu-Cr alloy, but deformation followed by optimum aging treatment can effectively improve the electrical conductivity of Cu-Cr alloy, under the condition of 0~70% deformation, and the electrical conductivity of Cu-Cr alloy by aging treatment increases and the aging time of obtaining much better electrical conductivity of Cu-Cr alloy decreases with increase in deformation quantity of Cu-Cr alloy. The best electrical conductivity of Cu-Cr alloy after deformation can be obtained by aging treatment at 500 ℃. And also the reasons for the variations of alloy's electrical conductivity and the function of adding RE were analyzed.展开更多
Creep aging behavior of retrogression and re-aged(RRAed)7150 aluminum alloy(AA7150)was systematically investigated using the creep aging experiments,mechanical properties tests,electrical conductivity tests and transm...Creep aging behavior of retrogression and re-aged(RRAed)7150 aluminum alloy(AA7150)was systematically investigated using the creep aging experiments,mechanical properties tests,electrical conductivity tests and transmission electron microscope(TEM)observations.Creep aging results show that the steady-state creep mechanism of RRAed alloys is mainly dislocation climb(stress exponent≈5.8),which is insensitive to the grain interior and boundary precipitates.However,the total creep deformation increases over the re-aging time.In addition,the yield strength and tensile strength of the four RRAed samples are essentially the same after creep aging at 140℃ for 16 h,but the elongation decreases slightly with the re-aging time.What’s more,the retrogression and re-aging treatment are beneficial to increase the hardness and electrical conductivity of the creep-aged 7150 aluminum alloy.It can be concluded that the retrogression and re-aging treatment before creep aging forming process can improve the microstructure within grain and at grain boundary,forming efficiency and comprehensive performance of mechanical properties and electrical conductivity of 7150 aluminum alloy.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
Cu-Cr-Sn-Zn alloys are one of the most popular lead frame alloys due to their high thermal and electrical conductivity as well as high strength. The effects of microstructure and aging processes on hardness and electr...Cu-Cr-Sn-Zn alloys are one of the most popular lead frame alloys due to their high thermal and electrical conductivity as well as high strength. The effects of microstructure and aging processes on hardness and electrical conductivity of Cu-Cr-Sn-Zn alloy were studied. At 450 ℃ aging for 1 h the fine and ordered precipitates Cr are found and are coherent with Cu matrix. Small and fine Cr precipitates make the Cu-Cr-Sn-Zn lead frame alloy possesses higher hardness and conductivity. At 450 ℃ for 3~6 h,the hardness and electrical conductivity can reach 122~106 HV and 68% IACS -70% IACS,respectively. Hardness 113~109 HV and conductivity 66% IACS -69% IACS are available at 500 ℃ aging for 2~3 h.展开更多
The aging precipitation behavior in solution treated Cu-Ni-Si-Cr alloy has been studied in terms of the analyses of the variations in electrical conductivity. On the basis of the linear relationship between the electr...The aging precipitation behavior in solution treated Cu-Ni-Si-Cr alloy has been studied in terms of the analyses of the variations in electrical conductivity. On the basis of the linear relationship between the electrical conductivity and the volume fraction of the precipitates, the phase transformation kinetics equation was deduced from the Avrami empiricai formula. On the basis of this equation, transformation kinetics curves corresponding to 5% and 50% transformation were established.展开更多
Cu-Ag-Zr-Ce alloy has an excellent combination of high mechanical strength and high electrical conductivity. By means of a vacuum induction melting, Cu-Ag-Zr-Ce alloy was produced. The effects of aging processes and r...Cu-Ag-Zr-Ce alloy has an excellent combination of high mechanical strength and high electrical conductivity. By means of a vacuum induction melting, Cu-Ag-Zr-Ce alloy was produced. The effects of aging processes and rare earths element cerium on microhardness and conductivity of Cu-Ag-Zr-Ce alloy were studied. By aging at 480 ℃ for 2 h, the alloy has an excellent combination of microhardness and conductivity, the microhardness and conductivity reach 132 HV and 80.24%IACS, respectively. The precipitates responsible for the age-hardening effect are f. c. c. Cu_5Zr, the fine and dispersed precipitates are fully coherent with the Cu matrix, and make the Cu-Ag-Zr-Ce alloy possesses higher hardness and conductivity. With the addition of trace rare earth element cerium, the strength is increased about 9~49 MPa, but the effect on conductivity is very little.展开更多
The aging properties of Cu-0.35Cr-0.038Zr-0.055Ce alloy are studied. The results show that can obtain higher electrical conductivity and microhardness after solutioned at 920°Cfor Ih, and aged at 500°C. The ...The aging properties of Cu-0.35Cr-0.038Zr-0.055Ce alloy are studied. The results show that can obtain higher electrical conductivity and microhardness after solutioned at 920°Cfor Ih, and aged at 500°C. The process of precipitation of the secondary phase can be accelerated with cold deformation before aging, so properties of the alloy are improved. Upon aging at 500°C for 30 minutes after 60% cold deformation, the values of electrical conductivity and microhardness are 69.0%IACS and 152HV respectively, but they are only 66.2%IACS and 136HV upon directly aging after solution. With the addition of a trace of rare earth element Ce, the value of microhardness of Cu-0.35Cr-0.038Zr alloy increases 18-25HV, while the value of electrical conductivity drops a little.展开更多
This paper presents the effects of aging processes on the properties and microstructure of Cu-0.3Cr-0.15Zr-0.05Mg lead frame alloy. Optimal conditions for good hardening and electrical conductivity can be obtained by ...This paper presents the effects of aging processes on the properties and microstructure of Cu-0.3Cr-0.15Zr-0.05Mg lead frame alloy. Optimal conditions for good hardening and electrical conductivity can be obtained by solution treating at 920 °C for Ih and aging at 470^0 for 4h and at 550^ for Ih. The hardness and electrical conductivity can reach 108HV, 73%IACS and 106HV, 76%IACS, respectively. Aging precipitation was dealt with by transmission electronic microscope (TEM). At 470 °C aging for 4h the fine precipitation of an ordered compound CrCu2(Zr,Mg) is found in matrix as well as fine Cr and Cu4Zr. Aging at 550’C for Ih some precipitates are still coherent with matrix. The CrCu2(Zr,Mg) completely dissolves into Cr and Cu4Zr.展开更多
The electrical conductivity of Cu-10Ag in situ filamentary composite was studied during the deformation and annealing processes. The dependence of electrical resistivity of the deformed composites on the true strain p...The electrical conductivity of Cu-10Ag in situ filamentary composite was studied during the deformation and annealing processes. The dependence of electrical resistivity of the deformed composites on the true strain presents a two-stage change with increase of the true strain. The intermediate heat treatment and the stabilized annealing treatment to the deformed composite promote the separation of Ag precipitate, and increase the electrical conductivity. The maximum conductivity of the composite experienced the stabilizing heat treatment can reach about 97% IACS with σb≥400 MPa at 550 ℃ annealing, and reach about 70% IACS with σb≥1 250 MPa at 300 ℃ annealing. The corresponded strength of the composite was reported. The microstructure reason for the changes of the conductivity was discussed.展开更多
The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,th...The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,the precipitation of Cr at nanometer scale provided further strengthening and brought substantial recovery of electrical conductivity.The aged nanostructured CuCrZr alloy exhibited a high tensile strength of 832MPa and a high electrical conductivity of 71.2%IACS.The details of precipitation tuned by nanotwin boundaries were demonstrated in this work.The combined strengthening of nanostructures and nanoprecipitates was discussed.展开更多
Developing heat-resistant conductors with high strength and high electrical conductivity is a key issue in the electrical conductor industries, as the ever-increasing power transmission poses higher requirement on the...Developing heat-resistant conductors with high strength and high electrical conductivity is a key issue in the electrical conductor industries, as the ever-increasing power transmission poses higher requirement on the thermal stability of electrical conductor wires. Dilute Al-Sc-Zr alloys are considered as promising candidates due to the excellent heat resistance and high electrical conductivity, but the low strength always limits their application on electrical wires. Yet, few efforts on process design have been made in dilute Al-Sc-Zr alloys to enhance the strength. Here, various kinds of processing paths via combination of cold drawing, ageing and/or annealing were conducted to improve the strength and electrical conductivity of a dilute Al-Sc-Zr alloy. Results show that enhanced strength and electrical conductivity were obtained after cold drawing + ageing or pre-ageing + cold drawing + annealing treatments processes.Optimal properties(194 MPa in ultimate tensile strength and 61% IACS in electrical conductivity) were obtained through cold drawing followed by ageing. Microstructure evolution which affects strength and electrical conductivity was systematically investigated using TEM and 3 DAP. The enhanced strength was mainly attributed to the suitable interactions between strain strengthening and precipitation strengthening. The enhancement in electrical conductivity was caused by precipitation of solute atoms and recovery of defects. These results provide foundations for the processing design of Al-Sc-Zr conducting wires with good properties and push forward their potential application in heat resistant conductor industries.展开更多
A new cast Mg-2Gd-2Nd-2Y-1Ho-1Er-0.5Zn-0.4Zr (wt%) alloy was prepared by direct-chill semicontinuous casting technology. The microstructure, mechanical properties and thermal conductivity of the alloy in as-cast, so...A new cast Mg-2Gd-2Nd-2Y-1Ho-1Er-0.5Zn-0.4Zr (wt%) alloy was prepared by direct-chill semicontinuous casting technology. The microstructure, mechanical properties and thermal conductivity of the alloy in as-cast, solid-solution treated and especially peak-aged conditions were investigated. The as-cast alloy mainly consists of α-Mg matrix, (Mg, Zn)3 RE phase and basal plane stacking faults. After proper solid-solution treatment, the microstructure becomes almost Mg-based single phase solid solution except just very few RE-riched particles. The as-cast and solid-solution treated alloys exhibit moderate tensile properties and thermal conductivity. It is noteworthy that the Mg alloy with 8 wt% multiple RE exhibits remarkable age-hardening response (AHV=35.7), which demonstrates that the multiple RE (RE = Gd, Nd, Y, Ho, Er) alloying instead of single Gd can effectively improve the age-hardening response. The peak-aged alloy has a relatively good combination of high strength/hardness (UTS (ultimate tensile strength) 〉 300 MPa; TYS (tensile yield strength)〉210 MPa; 115.3 HV), proper ductility (ε≈ 6%) and moderate thermal conductivity (52.5 W/(m K)). The relative mechanisms mainly involving aging precipitation of β″ and β" phases were discussed. The results provide a basis for development of high performance cast Mg alloys.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.展开更多
The Cu-Cr-Zr alloys were aged at different temperatures for different time with different current densities. The results show that both the electrical conductivity and hardness are greatly improved after being aged wi...The Cu-Cr-Zr alloys were aged at different temperatures for different time with different current densities. The results show that both the electrical conductivity and hardness are greatly improved after being aged with current at a proper temperature. The electrical conductivity increases approximately linearly with increasing current density while the hardness remains constant. The microstructure observation reveals that a much higher density of dislocations and nanosized Cr precipitates appear after the imposition of current, which contributes to the higher electrical conductivity and hardness. The mechanism is related with three factors: 1) Joule heating due to the current, 2) migration of mass electrons, 3) solute atoms, vacancies, and dislocations promoted by electron wind force.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
The in situ filamentary composites based on the Cu-10Ag and Cu-10Ag-Ce alloys were prepared. The microstructure and properties of the composites were studied. The effects of Ce addition on the microstructure as cast, ...The in situ filamentary composites based on the Cu-10Ag and Cu-10Ag-Ce alloys were prepared. The microstructure and properties of the composites were studied. The effects of Ce addition on the microstructure as cast, including refining Cu grains and the Ag filaments, increasing the proportion of (Cu+Ag) eutectic and decreasing the proportion of the Ag precipitate, were researched. The average size of the Ag filaments in the composites could be approached by a formula: d=C·exp(-0.228η), here C is a coefficient related to the size of the original grains and 1500 nm for Cu-10Ag and 800 nm for Cu-10Ag-Ce. A two-stage strain strengthening effect was found for the deformed composites, that is the dislocation strengthening at low strain stage and the ultra-fine Ag filaments or interface strengthening at the high strain stage. The intermediate heat treatment at lower temperature further refined the Ag filaments and therefore improved the properties. The high strengthening rate of Ce addition on Cu-10Ag alloy attributed the refining effect to Cu grains and Ag filaments. The typical properties of the heavy deformed composites with 1 IHT reached to UTS=1500 MPa with conductivity 62% IACS for the Cu-10Ag alloy and UTS=1550 MPa with conductivity 65% IACS for the Cu-10Ag-Ce alloy, respectively.展开更多
基金Project(2006AA03Z528) supported by the National High-Tech Research and Development Program of ChinaProject(102102210174) supported by the Science and Technology Research Project of Henan Province,ChinaProject(2008ZDYY005) supported by Special Fund for Important Forepart Research in Henan University of Science and Technology
文摘In order to predict and control the properties of Cu-Cr-Sn-Zn alloy,a model of aging processes via an artificial neural network(ANN) method to map the non-linear relationship between parameters of aging process and the hardness and electrical conductivity properties of the Cu-Cr-Sn-Zn alloy was set up.The results show that the ANN model is a very useful and accurate tool for the property analysis and prediction of aging Cu-Cr-Sn-Zn alloy.Aged at 470-510 ℃ for 4-1 h,the optimal combinations of hardness 110-117(HV) and electrical conductivity 40.6-37.7 S/m are available respectively.
文摘The effect of deformation and aging treatment on the electrical conductivity of Cu-Cr alloy was studied. The results show that deformation can reduce the electrical conductivity of Cu-Cr alloy, but deformation followed by optimum aging treatment can effectively improve the electrical conductivity of Cu-Cr alloy, under the condition of 0~70% deformation, and the electrical conductivity of Cu-Cr alloy by aging treatment increases and the aging time of obtaining much better electrical conductivity of Cu-Cr alloy decreases with increase in deformation quantity of Cu-Cr alloy. The best electrical conductivity of Cu-Cr alloy after deformation can be obtained by aging treatment at 500 ℃. And also the reasons for the variations of alloy's electrical conductivity and the function of adding RE were analyzed.
基金Project(2017YFB0306300)supported by the National Key Research and Development Program of ChinaProject(2017ZX04005001)supported by the National Science and Technology Major Project,China+2 种基金Project(JCKY2014203A001)supported by National Defense Program of ChinaProjects(51905551,51675538,51601060)supported by the National Natural Science Foundation of ChinaProjects(Kfkt2018-03,zzYJKT2019-11)supported by State Key Laboratory of High-Performance Complex Manufacturing,China。
文摘Creep aging behavior of retrogression and re-aged(RRAed)7150 aluminum alloy(AA7150)was systematically investigated using the creep aging experiments,mechanical properties tests,electrical conductivity tests and transmission electron microscope(TEM)observations.Creep aging results show that the steady-state creep mechanism of RRAed alloys is mainly dislocation climb(stress exponent≈5.8),which is insensitive to the grain interior and boundary precipitates.However,the total creep deformation increases over the re-aging time.In addition,the yield strength and tensile strength of the four RRAed samples are essentially the same after creep aging at 140℃ for 16 h,but the elongation decreases slightly with the re-aging time.What’s more,the retrogression and re-aging treatment are beneficial to increase the hardness and electrical conductivity of the creep-aged 7150 aluminum alloy.It can be concluded that the retrogression and re-aging treatment before creep aging forming process can improve the microstructure within grain and at grain boundary,forming efficiency and comprehensive performance of mechanical properties and electrical conductivity of 7150 aluminum alloy.
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.
文摘Cu-Cr-Sn-Zn alloys are one of the most popular lead frame alloys due to their high thermal and electrical conductivity as well as high strength. The effects of microstructure and aging processes on hardness and electrical conductivity of Cu-Cr-Sn-Zn alloy were studied. At 450 ℃ aging for 1 h the fine and ordered precipitates Cr are found and are coherent with Cu matrix. Small and fine Cr precipitates make the Cu-Cr-Sn-Zn lead frame alloy possesses higher hardness and conductivity. At 450 ℃ for 3~6 h,the hardness and electrical conductivity can reach 122~106 HV and 68% IACS -70% IACS,respectively. Hardness 113~109 HV and conductivity 66% IACS -69% IACS are available at 500 ℃ aging for 2~3 h.
基金This work was supported by the National High Technology Research Project“863"under Grant No.2002AA331112by the Major Science&Technology Project of Henan Province,China,under Grant No.0122021300.
文摘The aging precipitation behavior in solution treated Cu-Ni-Si-Cr alloy has been studied in terms of the analyses of the variations in electrical conductivity. On the basis of the linear relationship between the electrical conductivity and the volume fraction of the precipitates, the phase transformation kinetics equation was deduced from the Avrami empiricai formula. On the basis of this equation, transformation kinetics curves corresponding to 5% and 50% transformation were established.
文摘Cu-Ag-Zr-Ce alloy has an excellent combination of high mechanical strength and high electrical conductivity. By means of a vacuum induction melting, Cu-Ag-Zr-Ce alloy was produced. The effects of aging processes and rare earths element cerium on microhardness and conductivity of Cu-Ag-Zr-Ce alloy were studied. By aging at 480 ℃ for 2 h, the alloy has an excellent combination of microhardness and conductivity, the microhardness and conductivity reach 132 HV and 80.24%IACS, respectively. The precipitates responsible for the age-hardening effect are f. c. c. Cu_5Zr, the fine and dispersed precipitates are fully coherent with the Cu matrix, and make the Cu-Ag-Zr-Ce alloy possesses higher hardness and conductivity. With the addition of trace rare earth element cerium, the strength is increased about 9~49 MPa, but the effect on conductivity is very little.
基金supported by the National 863 Plan Items of China(No.2002AA331112)
文摘The aging properties of Cu-0.35Cr-0.038Zr-0.055Ce alloy are studied. The results show that can obtain higher electrical conductivity and microhardness after solutioned at 920°Cfor Ih, and aged at 500°C. The process of precipitation of the secondary phase can be accelerated with cold deformation before aging, so properties of the alloy are improved. Upon aging at 500°C for 30 minutes after 60% cold deformation, the values of electrical conductivity and microhardness are 69.0%IACS and 152HV respectively, but they are only 66.2%IACS and 136HV upon directly aging after solution. With the addition of a trace of rare earth element Ce, the value of microhardness of Cu-0.35Cr-0.038Zr alloy increases 18-25HV, while the value of electrical conductivity drops a little.
文摘This paper presents the effects of aging processes on the properties and microstructure of Cu-0.3Cr-0.15Zr-0.05Mg lead frame alloy. Optimal conditions for good hardening and electrical conductivity can be obtained by solution treating at 920 °C for Ih and aging at 470^0 for 4h and at 550^ for Ih. The hardness and electrical conductivity can reach 108HV, 73%IACS and 106HV, 76%IACS, respectively. Aging precipitation was dealt with by transmission electronic microscope (TEM). At 470 °C aging for 4h the fine precipitation of an ordered compound CrCu2(Zr,Mg) is found in matrix as well as fine Cr and Cu4Zr. Aging at 550’C for Ih some precipitates are still coherent with matrix. The CrCu2(Zr,Mg) completely dissolves into Cr and Cu4Zr.
基金Project(50371031) supported by the National Natural Science Foundation of China
文摘The electrical conductivity of Cu-10Ag in situ filamentary composite was studied during the deformation and annealing processes. The dependence of electrical resistivity of the deformed composites on the true strain presents a two-stage change with increase of the true strain. The intermediate heat treatment and the stabilized annealing treatment to the deformed composite promote the separation of Ag precipitate, and increase the electrical conductivity. The maximum conductivity of the composite experienced the stabilizing heat treatment can reach about 97% IACS with σb≥400 MPa at 550 ℃ annealing, and reach about 70% IACS with σb≥1 250 MPa at 300 ℃ annealing. The corresponded strength of the composite was reported. The microstructure reason for the changes of the conductivity was discussed.
基金supported by the Ministry of Science&Technology of China(No.2017YFA0204401)the Chinese Academy of Sciences(No.zdyz201701)+3 种基金the Liaoning Revitalization Talents Program(No.XLYC1808008)the National Natural Science Foundation of China(Nos.51501192 and 51771196)the Fundamental Research Funds for the Central Universities(No.3072019CF1017)the Key Research Program of Frontier Science,Chinese Academy of Sciences.
文摘The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,the precipitation of Cr at nanometer scale provided further strengthening and brought substantial recovery of electrical conductivity.The aged nanostructured CuCrZr alloy exhibited a high tensile strength of 832MPa and a high electrical conductivity of 71.2%IACS.The details of precipitation tuned by nanotwin boundaries were demonstrated in this work.The combined strengthening of nanostructures and nanoprecipitates was discussed.
基金financially supported by Defense Industrial Technology Development Program and Natural Science Foundation of China (Grant No. 51474195 and No. U1737206)
文摘Developing heat-resistant conductors with high strength and high electrical conductivity is a key issue in the electrical conductor industries, as the ever-increasing power transmission poses higher requirement on the thermal stability of electrical conductor wires. Dilute Al-Sc-Zr alloys are considered as promising candidates due to the excellent heat resistance and high electrical conductivity, but the low strength always limits their application on electrical wires. Yet, few efforts on process design have been made in dilute Al-Sc-Zr alloys to enhance the strength. Here, various kinds of processing paths via combination of cold drawing, ageing and/or annealing were conducted to improve the strength and electrical conductivity of a dilute Al-Sc-Zr alloy. Results show that enhanced strength and electrical conductivity were obtained after cold drawing + ageing or pre-ageing + cold drawing + annealing treatments processes.Optimal properties(194 MPa in ultimate tensile strength and 61% IACS in electrical conductivity) were obtained through cold drawing followed by ageing. Microstructure evolution which affects strength and electrical conductivity was systematically investigated using TEM and 3 DAP. The enhanced strength was mainly attributed to the suitable interactions between strain strengthening and precipitation strengthening. The enhancement in electrical conductivity was caused by precipitation of solute atoms and recovery of defects. These results provide foundations for the processing design of Al-Sc-Zr conducting wires with good properties and push forward their potential application in heat resistant conductor industries.
基金supported by the Natural Science Foundation of Heilongjiang Province of China (No. E2017030)National Natural Science Foundation of China (No. 51301048)+2 种基金Foundation of State Key Laboratory of Rare Earth Resources Utilization (No. RERU2016025)Central University Foundation of Harbin Engineering University (No. GK2100260207)the Natural Science Foundation of Jiamusi University of China (No. JMSURCGG2016006)
文摘A new cast Mg-2Gd-2Nd-2Y-1Ho-1Er-0.5Zn-0.4Zr (wt%) alloy was prepared by direct-chill semicontinuous casting technology. The microstructure, mechanical properties and thermal conductivity of the alloy in as-cast, solid-solution treated and especially peak-aged conditions were investigated. The as-cast alloy mainly consists of α-Mg matrix, (Mg, Zn)3 RE phase and basal plane stacking faults. After proper solid-solution treatment, the microstructure becomes almost Mg-based single phase solid solution except just very few RE-riched particles. The as-cast and solid-solution treated alloys exhibit moderate tensile properties and thermal conductivity. It is noteworthy that the Mg alloy with 8 wt% multiple RE exhibits remarkable age-hardening response (AHV=35.7), which demonstrates that the multiple RE (RE = Gd, Nd, Y, Ho, Er) alloying instead of single Gd can effectively improve the age-hardening response. The peak-aged alloy has a relatively good combination of high strength/hardness (UTS (ultimate tensile strength) 〉 300 MPa; TYS (tensile yield strength)〉210 MPa; 115.3 HV), proper ductility (ε≈ 6%) and moderate thermal conductivity (52.5 W/(m K)). The relative mechanisms mainly involving aging precipitation of β″ and β" phases were discussed. The results provide a basis for development of high performance cast Mg alloys.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
基金Project (2009AA03Z109) supported by the National High-tech Research and Development Program of ChinaProject (09zz98) supported by Key Research and Innovation Program from Shanghai Municipal Education Commission, ChinaProjects (09dz1206401, 09dz1206402) supported by Key Project from Science and Technology Commission of Shanghai Municipality, China
文摘The Cu-Cr-Zr alloys were aged at different temperatures for different time with different current densities. The results show that both the electrical conductivity and hardness are greatly improved after being aged with current at a proper temperature. The electrical conductivity increases approximately linearly with increasing current density while the hardness remains constant. The microstructure observation reveals that a much higher density of dislocations and nanosized Cr precipitates appear after the imposition of current, which contributes to the higher electrical conductivity and hardness. The mechanism is related with three factors: 1) Joule heating due to the current, 2) migration of mass electrons, 3) solute atoms, vacancies, and dislocations promoted by electron wind force.
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.
文摘The in situ filamentary composites based on the Cu-10Ag and Cu-10Ag-Ce alloys were prepared. The microstructure and properties of the composites were studied. The effects of Ce addition on the microstructure as cast, including refining Cu grains and the Ag filaments, increasing the proportion of (Cu+Ag) eutectic and decreasing the proportion of the Ag precipitate, were researched. The average size of the Ag filaments in the composites could be approached by a formula: d=C·exp(-0.228η), here C is a coefficient related to the size of the original grains and 1500 nm for Cu-10Ag and 800 nm for Cu-10Ag-Ce. A two-stage strain strengthening effect was found for the deformed composites, that is the dislocation strengthening at low strain stage and the ultra-fine Ag filaments or interface strengthening at the high strain stage. The intermediate heat treatment at lower temperature further refined the Ag filaments and therefore improved the properties. The high strengthening rate of Ce addition on Cu-10Ag alloy attributed the refining effect to Cu grains and Ag filaments. The typical properties of the heavy deformed composites with 1 IHT reached to UTS=1500 MPa with conductivity 62% IACS for the Cu-10Ag alloy and UTS=1550 MPa with conductivity 65% IACS for the Cu-10Ag-Ce alloy, respectively.