The microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-2Cu alloys microalloyed with Ti,Sc and Sc+Zr were studied by optical microscopy(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD),h...The microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-2Cu alloys microalloyed with Ti,Sc and Sc+Zr were studied by optical microscopy(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD),hardness testing,and tensile testing.The swirled equilibrium enthalpy device(SEED)process was introduced to prepare the semisolid slurry.Results show that the addition of Ti,Sc,and Sc+Zr refines the grain size and improves the uniformity of the semisolid slurry and then suppresses the growth of theα-Al grain during solution heat treatment.The microstructure of the four alloys in as-cast state mainly consists of sphericalα-Al and the Mg(Al,Cu,Zn)_(2)(η)eutectic phase.Moreover,primary Al_(3)Sc,Al_(3)(Sc,Zr)and Al_(3)Zr are also found in the micro-alloying alloys.After solution and aging heat treatment,most of the Mg(Al,Cu,Zn)_(2) phases dissolve into theα-Al matrix,while part of Mg(Al,Cu,Zn)_(2) phases transform to Al_(2)CuMg(S)phases.However,the coarse primary Al_(3)Sc and Al_(3)(Sc,Zr)still remain in the matrix,and promote crack initiation and propagation.With the tensile strength of 553 MPa,yield strength of 463 MPa and elongation of 13.4%at T6 state,trace Ti addition generates more attractive mechanical properties than the other three alloys.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°C for 1 h, cold drawing to 96% deformation, followed by aging at 400°C for 3 h. TEM analysis re-vealed two kinds of finely dispersed precipitates of Cr and Cu4Zr. 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 elevated temperature performances of 2D70 Al alloy hot extrusion rods after two-stage homogenization and intensive deformation were studied by measuring the elevated temperature enduring strength and the creep ult...The elevated temperature performances of 2D70 Al alloy hot extrusion rods after two-stage homogenization and intensive deformation were studied by measuring the elevated temperature enduring strength and the creep ultimate strength. The fracture morphology of some selected samples after testing at different elevated temperatures was observed by scanning electron microscopy (SEM). The results indicate that, as the test temperature increases, the elevated temperature enduring strength of 2D70 Al alloy decreases gradually. In a comparison between 150 C and 240 C, the notch enduring strength drops from 375 to 185 MPa and the smooth enduring strength drops from 337 to 130 MPa. Enduring strength is not sensitive to the notch. The notch sensitivity ratio (NSR) coefficient is in the range of 1.119 to 1.423 from 150 C to 240 C. The creep test results show that, as the test temperature increases from 150 C to 240 C, the creep ultimate strength of 2D70 Al alloy rods drops gradually from 312 to 117 MPa.展开更多
We have performed first-principles density functional theory calculations to investigate the retention and migration of hydrogen in Be_(22) W, a stable low-W intermetallic compound. The solution energy of interstitial...We have performed first-principles density functional theory calculations to investigate the retention and migration of hydrogen in Be_(22) W, a stable low-W intermetallic compound. The solution energy of interstitial H in Be_(22) W is found to be 0.49 eV lower, while the diffusion barrier, on the other hand, is higher by 0.13 eV compared to those in pure hcp-Be. The higher solubility and lower diffusivity for H atoms make Be_(22) W a potential beneficial secondary phase in hcp-Be to impede the accumulation of H atoms, and hence better resist H blistering. We also find that in Be_(22) W, the attraction between an interstitial H and a beryllium vacancy ranges from 0.34 eV to 1.08 eV, which indicates a weaker trapping for hydrogen than in pure Be. Our calculated results suggest that small size Be_(22) W particles in hcp-Be might serve as the hydrogen trapping centers, hinder hydrogen bubble growth, and improve the resistance to irradiation void swelling, just as dispersed oxide particles in steel do.展开更多
The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (...The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The results indicate that the microstructure of the as-cast 7A55 aluminum alloy mainly consists of the dendritic network of aluminum solid solution, Al/AlZnMgCu eutectic phases, and intermetallic compounds MgZn2, Al2CuMg, Al7Cu2Fe, and Al23CuFe4. After homogenization at 470°C for 48 h, Al/AlZnMgCu eutectic phases are dissolved into the matrix, and a small amount of high melting-point secondary phases were formed, which results in an increasing of the starting melting temperature of 7A55 aluminum alloy. The high melting-point secondary phases were eliminated mostly when the homogenization time achieved to 72 h. Therefore, the reasonable homogenization heat treatment process for 7A55 aluminum alloy ingots was chosen as 470°C/72 h.展开更多
The effects of interrupted multi-step aging on the microstructure and properties of Al-Cu-Mg-Ag-Zr alloy were studied by tensile,hardness,electrical conductivity tests and transmission electron microscopy(TEM).Interru...The effects of interrupted multi-step aging on the microstructure and properties of Al-Cu-Mg-Ag-Zr alloy were studied by tensile,hardness,electrical conductivity tests and transmission electron microscopy(TEM).Interrupted multi-step aging delayed the peak aging time compared to one-step aging and kept the same levels of hardness,electrical conductivity,ultimate tensile strength(UTS),yield strength(YS) and elongation as those of the T6 temper alloy while increased the fracture toughness notably.Ω phase and a little θ' phase precipitated and grew simultaneously in the process of one-step aging at 160℃.During the second-step aging at 65℃ of interrupted multi-step aging,no TEM characteristic of Ω precipitates could be found.During the third step of interrupted multi-step aging,Ω began to dominate the microstructure like what happened in the process of one-step aging.The difference of properties between the T6 temper and the interrupted multi-step aged alloys might be related to the different precipitation sequences in the process of the two heat treatment technologies.展开更多
To investigate the dynamic recrystallization behavior of 7xxx aluminum alloys,the isothermal compression tests were carried on the 7056 aluminum alloy in the temperatures range of 320-440℃and in the strain rates rang...To investigate the dynamic recrystallization behavior of 7xxx aluminum alloys,the isothermal compression tests were carried on the 7056 aluminum alloy in the temperatures range of 320-440℃and in the strain rates range of 0.001-1 s^(-1).In addition,the microstructure of samples were observed via electron back scanning diffraction microscope.According to the results,true stress and true strain curves were established and an Arrhenius-type equation was established,showing the flow stress increases with the temperature decreasing and the strain rate increasing.The critical strain(ε_(c))and the critical stress(σ_(c))of the onset of dynamic recrystallization were identified via the strain hardening rate and constructed relationship between deformation parameters as follows:ε_(c)=6.71×10^(-4)Z^(0.1373) and σ_(p)=1.202σ_(c)+12.691.The DRX is incomplete in this alloy,whose volume fraction is only 20%even if the strain reaches 0.9.Through this study,the flow stress behavior and DRX behavior of 7056 aluminum alloys are deeply understood,which gives benefit to control the hot working process.展开更多
Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under ...Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under friction coefficient ranging from 0 to 0.22.The lubricants selected for the tests were mechanical oil,butter and dry film lubricant,and the friction coefficient of these lubricants were 0.05,0.10 and 0.15,respectively.Microstructural evolution of 6 A16 aluminum alloy plate during drawing forming was investigated by OM,SEM and EBSD.The results showed that,with the increase of friction coefficient,the stress,strain and deformation degree in deformation zone increased,while the grain size in deformation zone decreased.Thus,the hardness of the cup-typed component increased with the increase of friction coefficient.Butter-lubricated cups had the highest tensile strength and yield strength after paint-bake cycle.The combination of simulation results and microstructure analysis of 6A16 aluminum alloy plate after drawing forming indicates that the appropriate lubricant is butter.展开更多
Precipitation reactions in the differential scanning calorimetry (DSC) of an Al-Cu-Mg-Ag alloy were identified by analyzing the results from hardness test,electrical conductivity test,and transmission electron microsc...Precipitation reactions in the differential scanning calorimetry (DSC) of an Al-Cu-Mg-Ag alloy were identified by analyzing the results from hardness test,electrical conductivity test,and transmission electron microscope (TEM) examination.It is discovered that thermal effects can be identified through selected area electron diffraction and bright-field images.The reaction peaks around 171,231,and 276℃ can be attributed to a structural rearrangement of coherent zones,to the precipitation of Ω phases,and to the precipitation of Ω and θ' and possible combination with the transition of θ'→θ,respectively.In addition,the hardness and electrical conductivity of the alloy change proportionately with the progression of reactions during the heating process.This phenomenon can be attributed to the evolution of the micro-structure.展开更多
In the present work,the precipitate compositions and precipitate amounts of these elements(including the size distribution,volume fraction,and inter-precipitate distance) on the Cu-containing 7000 series aluminum allo...In the present work,the precipitate compositions and precipitate amounts of these elements(including the size distribution,volume fraction,and inter-precipitate distance) on the Cu-containing 7000 series aluminum alloys(7150 and 7085 Al alloys),are investigated by anomalous small-angle x-ray scattering(ASAXS) at various energies.The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side,while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge.Similar results are observed in the 7085 alloy in an aging process(120℃) by employing in-situ ASAXS measurements,indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min.In the aging process,the precipitate particles with an initial average size of ~ 8 ?A increase with aging time at an energy of 9.60 ke V,while the increase with a slower rate is observed at an energy of 9.65 ke V as near the Zn absorption edge.展开更多
<div style="text-align:justify;"> The residual stress distribution for two strategies of asymmetric quenching in Al-Zn-Mg-Cu aluminum alloy plates has been simulated using the finite element method. Th...<div style="text-align:justify;"> The residual stress distribution for two strategies of asymmetric quenching in Al-Zn-Mg-Cu aluminum alloy plates has been simulated using the finite element method. The results show that for asymmetric quenching between the upper and lower surfaces, the through-thickness asymmetric quenching residual stress distribution lies between the two distributions corre-sponding to the heat transfer coefficients on the upper and lower surfaces respectively. The surface and central stress magnitudes are equal to the average of the stress magnitudes corresponding to the two heat transfer coefficients. For asymmetric quenching of a single surface, the surface stress distribution is the same as the heat transfer coefficient distribution and the stress magnitude is equal to the stress magnitude corresponding to the average value of the heat transfer coefficients at each location. However, the center quench residual stress distribution is approximately uniform and the stress magnitude is equal to the average of the stress magnitudes corresponding to the maximum and minimum heat transfer coefficients. </div>展开更多
For Cu-Ni-Si alloys,cold rolling is usually performed after solution treatment to enhance physical properties such as strength and electrical conductivity during the aging process.This paper reports the variation in m...For Cu-Ni-Si alloys,cold rolling is usually performed after solution treatment to enhance physical properties such as strength and electrical conductivity during the aging process.This paper reports the variation in microstructure and physical properties during the aging process of Cu-2.3Ni-0.5Si alloy cold-rolled at room temperature(RT) and cryogenic temperature(CT).When aged at 450℃ for 2 h,RT-rolled samples exhibited a maximum hardness of HV5234 with an electric conductivity of 39.9% IACS.For CTrolled samples,the peak hardness was achieved when the samples were aged at 450% for 1 h.展开更多
The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM)...The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM),transmission electron microscopy(TEM)and tensile tests.The results show that the microstructure of solution-treated alloy comprises NiTi matrix,Ti_(2)Ni and(Nb,Ti)ss phases.After aging treatment at 700℃for 6 and100 h,the distribution of Ti_(2)Ni and(Nb,Ti)ss precipitates increases in uniformity.No new type of precipitate is observed in the specimen aged at 700℃.After aging at800℃for 100 h,numerous nanosized Ni_(2)TiAl phases are precipitated within the grains.Solution and aging treatments improve the tensile properties at room temperature.Tensile strength and ductility are improved after solution treatment at 1100℃plus aging treatment at 800℃for 6 h or 700℃for 100 h.With aging time prolonging to 100 h at 800℃,the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation.展开更多
Solution and quenching heat treatments are generally carried out in a roller hearth furnace for large-scale thick aluminum alloy plates.However,the asymmetric or uneven spray water flow rate is inevitable under indust...Solution and quenching heat treatments are generally carried out in a roller hearth furnace for large-scale thick aluminum alloy plates.However,the asymmetric or uneven spray water flow rate is inevitable under industrial production conditions,which leads to an asymmetric residual stress distribution.The spray quenching treatment was conducted on self-designed spray equipment,and the residual stress along the thickness direction was measured by a layer removal method based on deflections.Under the asymmetric spray quenching condition,the subsurface stress of the high-flow rate surface was lower than that of the low-flow rate surface,and the difference between the two subsurface stresses increased with the increase in the difference in water flow rates.The subsurface stress underneath the surface with a water flow rate of 0.60 m^(3)/h was 15.38 MPa less than that of 0.15 m^(3)/h.The simulated residual stress by finite element(FE)method of the high heat transfer coefficient(HTC)surface was less than that of the low HTC surface,which is consistent with the experimental results.The FE model can be used to analyze the strain and stress evolution and predict the quenched stress magnitude and distribution.展开更多
As the next generation of commercial automotive power batteries begins replacing liquid lithium batteries,many look towards all-solid-state batteries to pioneer the future.All-so lid-state batteries have attracted the...As the next generation of commercial automotive power batteries begins replacing liquid lithium batteries,many look towards all-solid-state batteries to pioneer the future.All-so lid-state batteries have attracted the attention of countless researchers around the world because of their high safety and high energy density.In recent times,halide solid-state electrolytes have become a research hotspot within solid-state electrolytes because of their potentially superior properties.In this paper,in the framework of DFT,we investigated the atomic mechanisms of improving the ionic conductivity and stability of Li_(3)YbCl_(6).Our calculations show that both trigonal and orthorhombic Li_(3)YbCl_(6) exhibit wide electrochemical windows and metastable properties(100 meV/atom>Ehull>0 meV/atom).However,the orthorhombic Li_(3)YbCl_(6) can be stabilized at high temperatures by taking the vibrational entropy into account,which is supported by the experimental results.Moreover,it is expected that because of the Yb/Li synergistic interactions that,due to their strong mutual coulomb repulsion,influence the Li^(+)transport behavior,the orthorhombic Li_(3)YbCl_(6) might have superior ionic conductivities with appropriate Li+migration paths determined by the Yb^(3+) distribution.Also,higher ionic conductivities can be obtained by regulating the random distribution of Li^(+) ions.Further Li^(+)-deficiency can also largely increase the ionic conductivity by invoking vacancies.This study helps gain a deeper understanding of the laws that govern ionic conductivities and stabilities and provides a certain theoretical reference for the experimental development and design of halide solid-state electrolytes.展开更多
The transformation and dissolution of Mg(Zn,Cu, Al)_2 phase during solution treatment of an Al-Zn-MgCu alloy containing high zinc were investigated by means of optical microscopy(OM), scanning electron microscopy(SEM)...The transformation and dissolution of Mg(Zn,Cu, Al)_2 phase during solution treatment of an Al-Zn-MgCu alloy containing high zinc were investigated by means of optical microscopy(OM), scanning electron microscopy(SEM), energy-dispersive X-ray spectrometry(EDX) and X-ray diffraction(XRD). The results show that solution temperature is the main factor influencing phase dissolution. With solution temperature increasing, the content of residual phases decreases. Phase transformation from Mg(Zn, Cu, Al)2 to S(Al_2 CuMg) occurs under solution temperature of 450,460 and 465 ℃. Mg(Zn,Cu,Al)_2 phase is directly dissolved into the matrix under solution temperature of 470 and 475 ℃,and no S(Al_2 CuMg) phase transformed from Mg(Zn, Cu, Al)_2 phase is observed. The formation of S(Al_2 CuMg) phase is mainly controlled by Zn elemental diffusion. The mechanism of transformation and dissolution of second phases was investigated. At low temperature, the dissolution of Zn is faster than that of Mg and Cu, resulting in an appropriate condition to form S(Al_2 CuMg) phase. At high temperature, the dissolution of main alloying elements has no significant barrier among them to form S(Al_2 CuMg) phase.展开更多
With the aid of scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD), differential scanning calorimetry(DSC)analysis and electron backscatter diffraction(EBSD), the microstruc...With the aid of scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD), differential scanning calorimetry(DSC)analysis and electron backscatter diffraction(EBSD), the microstructure of the alloy in as-extruded state and various solution-treated states was investigated. The results indicate that second phase of the as-extruded 7136 aluminum alloy mainly consists of Mg(Zn, Cu, Al)_2and Fe-rich phases. The Mg(Zn, Cu, Al)_2phase directly dissolves into the matrix during solution treatment with various solution temperatures. After solution treated at 475 °C for 1 h,Mg(Zn, Cu, Al)_2phases are dissolved into the matrix,while Fe-rich phases still exist. Fe-rich phases could not dissolve into the matrix by prolonging solution time. The mechanical property test and EBSD observation show that two-stage solution treatment makes no significant improvement in mechanical properties and recrystallization of the alloy. The optimized solution treatment parameter is chosen as 475 °C/1 h.展开更多
7055 aluminum alloy plates with the same size were rolled by two processes: small percentage reduction per pass(PRPP) and large percentage reduction per pass,respectively. Meanwhile, the effect of PRPP on the precipit...7055 aluminum alloy plates with the same size were rolled by two processes: small percentage reduction per pass(PRPP) and large percentage reduction per pass,respectively. Meanwhile, the effect of PRPP on the precipitates and corrosion resistance of 7055 aluminum alloy plate was investigated. The mechanisms were analyzed and discussed by optical microscopy(OM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM) and electron back-scattered diffraction(EBSD) technique. Large PRPP can improve the corrosion resistance. For the plate rolled by small PRPP, the main precipitate is guinier-preston(GP) zone and continuous grain boundary precipitates(GBPs), while,for the plate rolled by large PRPP, the main precipitates are the GP zone and η' precipitate, and the GBPs are discontinuous.展开更多
The effect of solution treatment on the microstructure and mechanical properties of a novel 7 A56 aluminum alloy plate was investigated by optical microscopy(OM),scanning electron microscopy(SEM),transmission electron...The effect of solution treatment on the microstructure and mechanical properties of a novel 7 A56 aluminum alloy plate was investigated by optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),conductivity,hardness and tensile tests.The results indicate that the coarse second phases in the hot-rolled plate mainly consist of AlZnMgCu quaternary phase and Al_(7) Cu_(2) Fe phase,and no Al_(2) CuMg phase is found.The amount of the second phases gradually reduces with the increase in temperature(450-480℃)and time(1-8 h)during the solution treatment,and the soluble particles are completely dissolved into the matrix after solution treatment at 470℃for 4 h,while the residual phases are mainly Fe-rich phase along the grain boundaries.The recrystallization fraction of the alloy gradually increases with the degree of solution treatment deepened.When the temperature exceeds480℃,over-burning takes place.The mechanical properties of samples treated at 470℃for various times were tested.After the solution treated at 470℃for 4 h,the quenching conductivity and peak-aged hardness of the alloy are 30.8%IACS and HV 204,respectively.The ultimate tensile strength and yield strength of the samples aged at 120℃for 24 h are 661 and 588 MPa,respectively.展开更多
Ti-62421 S(Ti-6 Al-2 Sn-4 Zr-2 Nb-1 Mo-0.2 Si)is a novel short-time using high-temperature titanium alloy.The effects of annealing on microstructure and tensile properties of Ti-62421 S alloy plate were studied throug...Ti-62421 S(Ti-6 Al-2 Sn-4 Zr-2 Nb-1 Mo-0.2 Si)is a novel short-time using high-temperature titanium alloy.The effects of annealing on microstructure and tensile properties of Ti-62421 S alloy plate were studied through optical microscopy(OM), electron probe microanalysis(EPMA), transmission electron microscopy(TEM), and tensile tests. The results show that, with annealing temperature increasing, the volume fraction of primary α(α_p)-phase decreases while that of transformed β(β_t)-structure and secondary α(α_s)-phase increases. The room-temperature strength and plasticity are insensitive to annealing temperature. However, with annealing temperature increasing, the tensile strength decreases at 550 ℃, while increases at 600 and 650 ℃ instead. It is suggested that, at550 ℃, the strengthening mechanism is mainly boundary strengthening and the biggest contributor is α_p-phase by providing α_p/β-boundary area. Above 600 ℃, the strengthening mechanism is grain strengthening, where α_sphase strengthens the β-phase.展开更多
基金financial support from the National Key R&D Program of China(No.2016YFB0301003).
文摘The microstructure and mechanical properties of rheo-diecasting Al-6Zn-2Mg-2Cu alloys microalloyed with Ti,Sc and Sc+Zr were studied by optical microscopy(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD),hardness testing,and tensile testing.The swirled equilibrium enthalpy device(SEED)process was introduced to prepare the semisolid slurry.Results show that the addition of Ti,Sc,and Sc+Zr refines the grain size and improves the uniformity of the semisolid slurry and then suppresses the growth of theα-Al grain during solution heat treatment.The microstructure of the four alloys in as-cast state mainly consists of sphericalα-Al and the Mg(Al,Cu,Zn)_(2)(η)eutectic phase.Moreover,primary Al_(3)Sc,Al_(3)(Sc,Zr)and Al_(3)Zr are also found in the micro-alloying alloys.After solution and aging heat treatment,most of the Mg(Al,Cu,Zn)_(2) phases dissolve into theα-Al matrix,while part of Mg(Al,Cu,Zn)_(2) phases transform to Al_(2)CuMg(S)phases.However,the coarse primary Al_(3)Sc and Al_(3)(Sc,Zr)still remain in the matrix,and promote crack initiation and propagation.With the tensile strength of 553 MPa,yield strength of 463 MPa and elongation of 13.4%at T6 state,trace Ti addition generates more attractive mechanical properties than the other three alloys.
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°C for 1 h, cold drawing to 96% deformation, followed by aging at 400°C for 3 h. TEM analysis re-vealed two kinds of finely dispersed precipitates of Cr and Cu4Zr. 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support from the National Key Technology Research and Development Program of China (No.2007BAE38B06)Heilongjiang Province Science Fund for Distinguished Young Scholars(No. JC201013)
文摘The elevated temperature performances of 2D70 Al alloy hot extrusion rods after two-stage homogenization and intensive deformation were studied by measuring the elevated temperature enduring strength and the creep ultimate strength. The fracture morphology of some selected samples after testing at different elevated temperatures was observed by scanning electron microscopy (SEM). The results indicate that, as the test temperature increases, the elevated temperature enduring strength of 2D70 Al alloy decreases gradually. In a comparison between 150 C and 240 C, the notch enduring strength drops from 375 to 185 MPa and the smooth enduring strength drops from 337 to 130 MPa. Enduring strength is not sensitive to the notch. The notch sensitivity ratio (NSR) coefficient is in the range of 1.119 to 1.423 from 150 C to 240 C. The creep test results show that, as the test temperature increases from 150 C to 240 C, the creep ultimate strength of 2D70 Al alloy rods drops gradually from 312 to 117 MPa.
基金Project supported by the National Magnetic Confinement Fusion Program of China(Grant Nos.2014GB104003 and 2015GB105001)the National Natural Science Foundation of China(Grant No.51504033)
文摘We have performed first-principles density functional theory calculations to investigate the retention and migration of hydrogen in Be_(22) W, a stable low-W intermetallic compound. The solution energy of interstitial H in Be_(22) W is found to be 0.49 eV lower, while the diffusion barrier, on the other hand, is higher by 0.13 eV compared to those in pure hcp-Be. The higher solubility and lower diffusivity for H atoms make Be_(22) W a potential beneficial secondary phase in hcp-Be to impede the accumulation of H atoms, and hence better resist H blistering. We also find that in Be_(22) W, the attraction between an interstitial H and a beryllium vacancy ranges from 0.34 eV to 1.08 eV, which indicates a weaker trapping for hydrogen than in pure Be. Our calculated results suggest that small size Be_(22) W particles in hcp-Be might serve as the hydrogen trapping centers, hinder hydrogen bubble growth, and improve the resistance to irradiation void swelling, just as dispersed oxide particles in steel do.
基金financially supported by the National Key Technologies R&D Program of China (No.2007BAE38B06)the National Natural Science Foundation of China (No.50904010)
文摘The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) analysis. The results indicate that the microstructure of the as-cast 7A55 aluminum alloy mainly consists of the dendritic network of aluminum solid solution, Al/AlZnMgCu eutectic phases, and intermetallic compounds MgZn2, Al2CuMg, Al7Cu2Fe, and Al23CuFe4. After homogenization at 470°C for 48 h, Al/AlZnMgCu eutectic phases are dissolved into the matrix, and a small amount of high melting-point secondary phases were formed, which results in an increasing of the starting melting temperature of 7A55 aluminum alloy. The high melting-point secondary phases were eliminated mostly when the homogenization time achieved to 72 h. Therefore, the reasonable homogenization heat treatment process for 7A55 aluminum alloy ingots was chosen as 470°C/72 h.
文摘The effects of interrupted multi-step aging on the microstructure and properties of Al-Cu-Mg-Ag-Zr alloy were studied by tensile,hardness,electrical conductivity tests and transmission electron microscopy(TEM).Interrupted multi-step aging delayed the peak aging time compared to one-step aging and kept the same levels of hardness,electrical conductivity,ultimate tensile strength(UTS),yield strength(YS) and elongation as those of the T6 temper alloy while increased the fracture toughness notably.Ω phase and a little θ' phase precipitated and grew simultaneously in the process of one-step aging at 160℃.During the second-step aging at 65℃ of interrupted multi-step aging,no TEM characteristic of Ω precipitates could be found.During the third step of interrupted multi-step aging,Ω began to dominate the microstructure like what happened in the process of one-step aging.The difference of properties between the T6 temper and the interrupted multi-step aged alloys might be related to the different precipitation sequences in the process of the two heat treatment technologies.
基金Funded by the National Key R&D Program of China(Nos.2016YFB0300803,2016YFB0300903)the National Program of China(No.2012CB619504)
文摘To investigate the dynamic recrystallization behavior of 7xxx aluminum alloys,the isothermal compression tests were carried on the 7056 aluminum alloy in the temperatures range of 320-440℃and in the strain rates range of 0.001-1 s^(-1).In addition,the microstructure of samples were observed via electron back scanning diffraction microscope.According to the results,true stress and true strain curves were established and an Arrhenius-type equation was established,showing the flow stress increases with the temperature decreasing and the strain rate increasing.The critical strain(ε_(c))and the critical stress(σ_(c))of the onset of dynamic recrystallization were identified via the strain hardening rate and constructed relationship between deformation parameters as follows:ε_(c)=6.71×10^(-4)Z^(0.1373) and σ_(p)=1.202σ_(c)+12.691.The DRX is incomplete in this alloy,whose volume fraction is only 20%even if the strain reaches 0.9.Through this study,the flow stress behavior and DRX behavior of 7056 aluminum alloys are deeply understood,which gives benefit to control the hot working process.
基金Funded by the National Key Research and Development Program of China(No.2016YFB0300805).
文摘Based on the ABAQUS/Explicit finite element method,the forming force changing trend of deep drawing test for 6A16 aluminum alloy plate after pre-aging and storage at room temperature for one month was simulated under friction coefficient ranging from 0 to 0.22.The lubricants selected for the tests were mechanical oil,butter and dry film lubricant,and the friction coefficient of these lubricants were 0.05,0.10 and 0.15,respectively.Microstructural evolution of 6 A16 aluminum alloy plate during drawing forming was investigated by OM,SEM and EBSD.The results showed that,with the increase of friction coefficient,the stress,strain and deformation degree in deformation zone increased,while the grain size in deformation zone decreased.Thus,the hardness of the cup-typed component increased with the increase of friction coefficient.Butter-lubricated cups had the highest tensile strength and yield strength after paint-bake cycle.The combination of simulation results and microstructure analysis of 6A16 aluminum alloy plate after drawing forming indicates that the appropriate lubricant is butter.
文摘Precipitation reactions in the differential scanning calorimetry (DSC) of an Al-Cu-Mg-Ag alloy were identified by analyzing the results from hardness test,electrical conductivity test,and transmission electron microscope (TEM) examination.It is discovered that thermal effects can be identified through selected area electron diffraction and bright-field images.The reaction peaks around 171,231,and 276℃ can be attributed to a structural rearrangement of coherent zones,to the precipitation of Ω phases,and to the precipitation of Ω and θ' and possible combination with the transition of θ'→θ,respectively.In addition,the hardness and electrical conductivity of the alloy change proportionately with the progression of reactions during the heating process.This phenomenon can be attributed to the evolution of the micro-structure.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11005143,11405259,and 51274046)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China(Grant No.[2014]1685)
文摘In the present work,the precipitate compositions and precipitate amounts of these elements(including the size distribution,volume fraction,and inter-precipitate distance) on the Cu-containing 7000 series aluminum alloys(7150 and 7085 Al alloys),are investigated by anomalous small-angle x-ray scattering(ASAXS) at various energies.The scattering intensity of 7150 alloy with T6 aging treatment decreases as the incident x-ray energy approaches the Zn absorption edge from the lower energy side,while scattering intensity does not show a noticeable energy dependence near the Cu absorption edge.Similar results are observed in the 7085 alloy in an aging process(120℃) by employing in-situ ASAXS measurements,indicating that the precipitate compositions should include Zn element and should not be strongly related to Cu element at the early stage after 10 min.In the aging process,the precipitate particles with an initial average size of ~ 8 ?A increase with aging time at an energy of 9.60 ke V,while the increase with a slower rate is observed at an energy of 9.65 ke V as near the Zn absorption edge.
文摘<div style="text-align:justify;"> The residual stress distribution for two strategies of asymmetric quenching in Al-Zn-Mg-Cu aluminum alloy plates has been simulated using the finite element method. The results show that for asymmetric quenching between the upper and lower surfaces, the through-thickness asymmetric quenching residual stress distribution lies between the two distributions corre-sponding to the heat transfer coefficients on the upper and lower surfaces respectively. The surface and central stress magnitudes are equal to the average of the stress magnitudes corresponding to the two heat transfer coefficients. For asymmetric quenching of a single surface, the surface stress distribution is the same as the heat transfer coefficient distribution and the stress magnitude is equal to the stress magnitude corresponding to the average value of the heat transfer coefficients at each location. However, the center quench residual stress distribution is approximately uniform and the stress magnitude is equal to the average of the stress magnitudes corresponding to the maximum and minimum heat transfer coefficients. </div>
基金financially supported by the Science & Technology Innovation 2025 of the Ningbo Major Special Project (No.2019B10087)the National Key R&D Program of China (No.2016YFB0301300)。
文摘For Cu-Ni-Si alloys,cold rolling is usually performed after solution treatment to enhance physical properties such as strength and electrical conductivity during the aging process.This paper reports the variation in microstructure and physical properties during the aging process of Cu-2.3Ni-0.5Si alloy cold-rolled at room temperature(RT) and cryogenic temperature(CT).When aged at 450℃ for 2 h,RT-rolled samples exhibited a maximum hardness of HV5234 with an electric conductivity of 39.9% IACS.For CTrolled samples,the peak hardness was achieved when the samples were aged at 450% for 1 h.
基金financially supported by the National Natural Science Foundation of China(Nos.51571036 and 51201016)。
文摘The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM),transmission electron microscopy(TEM)and tensile tests.The results show that the microstructure of solution-treated alloy comprises NiTi matrix,Ti_(2)Ni and(Nb,Ti)ss phases.After aging treatment at 700℃for 6 and100 h,the distribution of Ti_(2)Ni and(Nb,Ti)ss precipitates increases in uniformity.No new type of precipitate is observed in the specimen aged at 700℃.After aging at800℃for 100 h,numerous nanosized Ni_(2)TiAl phases are precipitated within the grains.Solution and aging treatments improve the tensile properties at room temperature.Tensile strength and ductility are improved after solution treatment at 1100℃plus aging treatment at 800℃for 6 h or 700℃for 100 h.With aging time prolonging to 100 h at 800℃,the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation.
基金financially supported by the National Key Research and Development Program of China(No.2020YFF0218200)。
文摘Solution and quenching heat treatments are generally carried out in a roller hearth furnace for large-scale thick aluminum alloy plates.However,the asymmetric or uneven spray water flow rate is inevitable under industrial production conditions,which leads to an asymmetric residual stress distribution.The spray quenching treatment was conducted on self-designed spray equipment,and the residual stress along the thickness direction was measured by a layer removal method based on deflections.Under the asymmetric spray quenching condition,the subsurface stress of the high-flow rate surface was lower than that of the low-flow rate surface,and the difference between the two subsurface stresses increased with the increase in the difference in water flow rates.The subsurface stress underneath the surface with a water flow rate of 0.60 m^(3)/h was 15.38 MPa less than that of 0.15 m^(3)/h.The simulated residual stress by finite element(FE)method of the high heat transfer coefficient(HTC)surface was less than that of the low HTC surface,which is consistent with the experimental results.The FE model can be used to analyze the strain and stress evolution and predict the quenched stress magnitude and distribution.
基金Project supported by the GRINM Innovation Fund Project(2020TS0301)Jilin Province Science and Technology Major Project(20210301021GX)National Natural Science Foundation of China(U21A2080)。
文摘As the next generation of commercial automotive power batteries begins replacing liquid lithium batteries,many look towards all-solid-state batteries to pioneer the future.All-so lid-state batteries have attracted the attention of countless researchers around the world because of their high safety and high energy density.In recent times,halide solid-state electrolytes have become a research hotspot within solid-state electrolytes because of their potentially superior properties.In this paper,in the framework of DFT,we investigated the atomic mechanisms of improving the ionic conductivity and stability of Li_(3)YbCl_(6).Our calculations show that both trigonal and orthorhombic Li_(3)YbCl_(6) exhibit wide electrochemical windows and metastable properties(100 meV/atom>Ehull>0 meV/atom).However,the orthorhombic Li_(3)YbCl_(6) can be stabilized at high temperatures by taking the vibrational entropy into account,which is supported by the experimental results.Moreover,it is expected that because of the Yb/Li synergistic interactions that,due to their strong mutual coulomb repulsion,influence the Li^(+)transport behavior,the orthorhombic Li_(3)YbCl_(6) might have superior ionic conductivities with appropriate Li+migration paths determined by the Yb^(3+) distribution.Also,higher ionic conductivities can be obtained by regulating the random distribution of Li^(+) ions.Further Li^(+)-deficiency can also largely increase the ionic conductivity by invoking vacancies.This study helps gain a deeper understanding of the laws that govern ionic conductivities and stabilities and provides a certain theoretical reference for the experimental development and design of halide solid-state electrolytes.
基金financially supported by the National Program on Key Basic Research Project of China (No. 2012CB619504)National Natural Science Foundation of China (No. 51274046)
文摘The transformation and dissolution of Mg(Zn,Cu, Al)_2 phase during solution treatment of an Al-Zn-MgCu alloy containing high zinc were investigated by means of optical microscopy(OM), scanning electron microscopy(SEM), energy-dispersive X-ray spectrometry(EDX) and X-ray diffraction(XRD). The results show that solution temperature is the main factor influencing phase dissolution. With solution temperature increasing, the content of residual phases decreases. Phase transformation from Mg(Zn, Cu, Al)2 to S(Al_2 CuMg) occurs under solution temperature of 450,460 and 465 ℃. Mg(Zn,Cu,Al)_2 phase is directly dissolved into the matrix under solution temperature of 470 and 475 ℃,and no S(Al_2 CuMg) phase transformed from Mg(Zn, Cu, Al)_2 phase is observed. The formation of S(Al_2 CuMg) phase is mainly controlled by Zn elemental diffusion. The mechanism of transformation and dissolution of second phases was investigated. At low temperature, the dissolution of Zn is faster than that of Mg and Cu, resulting in an appropriate condition to form S(Al_2 CuMg) phase. At high temperature, the dissolution of main alloying elements has no significant barrier among them to form S(Al_2 CuMg) phase.
基金supported by the National Key Research and Development Program of China (No. 2016YFB0300903)the National Program on Key Basic Research Project of China (No. 2012CB619504)the National Natural Science Foundation of China (No. 51274046)
文摘With the aid of scanning electron microscopy(SEM), energy-dispersive spectroscopy(EDS), X-ray diffraction(XRD), differential scanning calorimetry(DSC)analysis and electron backscatter diffraction(EBSD), the microstructure of the alloy in as-extruded state and various solution-treated states was investigated. The results indicate that second phase of the as-extruded 7136 aluminum alloy mainly consists of Mg(Zn, Cu, Al)_2and Fe-rich phases. The Mg(Zn, Cu, Al)_2phase directly dissolves into the matrix during solution treatment with various solution temperatures. After solution treated at 475 °C for 1 h,Mg(Zn, Cu, Al)_2phases are dissolved into the matrix,while Fe-rich phases still exist. Fe-rich phases could not dissolve into the matrix by prolonging solution time. The mechanical property test and EBSD observation show that two-stage solution treatment makes no significant improvement in mechanical properties and recrystallization of the alloy. The optimized solution treatment parameter is chosen as 475 °C/1 h.
基金financially supported by the Higher School Science Foundation of Inner Mongolia (No. NJZZ16082)National Natural Science Foundation of China (Nos. 51764043, 51461017 and 51364027)Science Program for Returned Chinese Scholars supported by Inner Mongolia and the Scientific and Technological Program of Innovation and Guidance of Inner Mongolia
文摘7055 aluminum alloy plates with the same size were rolled by two processes: small percentage reduction per pass(PRPP) and large percentage reduction per pass,respectively. Meanwhile, the effect of PRPP on the precipitates and corrosion resistance of 7055 aluminum alloy plate was investigated. The mechanisms were analyzed and discussed by optical microscopy(OM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM) and electron back-scattered diffraction(EBSD) technique. Large PRPP can improve the corrosion resistance. For the plate rolled by small PRPP, the main precipitate is guinier-preston(GP) zone and continuous grain boundary precipitates(GBPs), while,for the plate rolled by large PRPP, the main precipitates are the GP zone and η' precipitate, and the GBPs are discontinuous.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0300803)the National Natural Science Foundation of China(No.51274046)the National Key Basic Research Program(No.2012CB619504)。
文摘The effect of solution treatment on the microstructure and mechanical properties of a novel 7 A56 aluminum alloy plate was investigated by optical microscopy(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),conductivity,hardness and tensile tests.The results indicate that the coarse second phases in the hot-rolled plate mainly consist of AlZnMgCu quaternary phase and Al_(7) Cu_(2) Fe phase,and no Al_(2) CuMg phase is found.The amount of the second phases gradually reduces with the increase in temperature(450-480℃)and time(1-8 h)during the solution treatment,and the soluble particles are completely dissolved into the matrix after solution treatment at 470℃for 4 h,while the residual phases are mainly Fe-rich phase along the grain boundaries.The recrystallization fraction of the alloy gradually increases with the degree of solution treatment deepened.When the temperature exceeds480℃,over-burning takes place.The mechanical properties of samples treated at 470℃for various times were tested.After the solution treated at 470℃for 4 h,the quenching conductivity and peak-aged hardness of the alloy are 30.8%IACS and HV 204,respectively.The ultimate tensile strength and yield strength of the samples aged at 120℃for 24 h are 661 and 588 MPa,respectively.
基金financially supported by the National Natural Science Foundation of China (No. 51201016)
文摘Ti-62421 S(Ti-6 Al-2 Sn-4 Zr-2 Nb-1 Mo-0.2 Si)is a novel short-time using high-temperature titanium alloy.The effects of annealing on microstructure and tensile properties of Ti-62421 S alloy plate were studied through optical microscopy(OM), electron probe microanalysis(EPMA), transmission electron microscopy(TEM), and tensile tests. The results show that, with annealing temperature increasing, the volume fraction of primary α(α_p)-phase decreases while that of transformed β(β_t)-structure and secondary α(α_s)-phase increases. The room-temperature strength and plasticity are insensitive to annealing temperature. However, with annealing temperature increasing, the tensile strength decreases at 550 ℃, while increases at 600 and 650 ℃ instead. It is suggested that, at550 ℃, the strengthening mechanism is mainly boundary strengthening and the biggest contributor is α_p-phase by providing α_p/β-boundary area. Above 600 ℃, the strengthening mechanism is grain strengthening, where α_sphase strengthens the β-phase.