The authors regret that the affiliation b and c are wrong.Affiliation b should be changed to“School of Civil and Environmental Engineering,Harbin Institute of Technology,Shenzhen,China;Department of Data Analysis and...The authors regret that the affiliation b and c are wrong.Affiliation b should be changed to“School of Civil and Environmental Engineering,Harbin Institute of Technology,Shenzhen,China;Department of Data Analysis and Mathematical Modelling,Ghent University,Belgium”.And affiliation c should be changed to“State Key Laboratory of Urban Water Resource and Environment(SKLUWRE),School of Environment,Harbin Institute of Technology,China”.展开更多
High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST s...High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST solution heat treatment can not only retain partial deformation dislocations,but inhibit the recrystallization behavior and increase the proportion of low-angle grain boundaries(LAGBs).In the subsequent NIA process,HTST solution heat treatment combined with NIA is instrumental in restraining the degradation of dislocations and promoting precipitation of nano-scale T'-Mg_(32)(Al,Zn,Ag)49 phase,which improves the strength of the alloy greatly.In addition,a higher fraction of LAGBs and the discontinuous distribution of grain boundary precipitates caused by this novel technology meliorate the corrosion resistance of Al−4.5Mg−2.0Zn−0.3Ag alloy.展开更多
The effect of cooling rate of the solidification process on the following solution heat treatment of A356 alloy was investigated,where the cooling rates of 96 K/s and 3 K/s were obtained by the step-like metal mold.Th...The effect of cooling rate of the solidification process on the following solution heat treatment of A356 alloy was investigated,where the cooling rates of 96 K/s and 3 K/s were obtained by the step-like metal mold.Then the eutectic silicon morphology evolution and tensile properties of the alloy samples were observed and analyzed after solution heat treatment at 540 °C for different time.The results show that the high cooling rate of the solidification process can not only reduce the solid solution heat treatment time to rapidly modify the eutectic silicon morphology,but also improve the alloy tensile properties.Specially,it is found that the disintegration,the spheroidization and coarsening of eutectic silicon of A356 alloy are completed during solution heat treatment through two stages,i.e.,at first,the disintegration and spheroidization of the eutectic silicon mainly takes place,then the eutectic silicon will coarsen.展开更多
For the compromise of mechanical properties and product cost, the end-chilled sand casting technique was applied to studying the microstructure evolution of A356 Al alloy with cooling rate and the effect of different ...For the compromise of mechanical properties and product cost, the end-chilled sand casting technique was applied to studying the microstructure evolution of A356 Al alloy with cooling rate and the effect of different as-cast microstructures on the subsequent solution-treatment process. The experimental results show that the secondary dendrite arm spacing (SDAS) of primaryα(Al), the size of eutectic Si and the volume fraction of Al?Si eutectic are reduced with increasing the cooling rate. Eutectic Si, subjected to solution treatment at 540 °C for 1 h followed by water quenching to room temperature, is completely spheroidized at cooling rate of 2.6 K/s; is partially spheroidized atcooling rate of 0.6 K/s; and is only edge-rounded at cooling rates of 0.22 and 0.12 K /s. Whilst the microhardness is also the maximum at cooling rate of 2.6 K/s. It consequently suggests that subjected to modification by high cooling rate, the eutectic Si is more readily modified, thus shortening the necessary solution time at given solution temperature, i.e., reducing the product cost.展开更多
As-received nickel-titanium （NiTi） shape memory alloy with a nominal composition of Ni50.9Ti49.1 （mole fraction,%） was subjected to solution treatment at 1123 K for 2 h and subsequent aging for 2 h at 573 K, 723 K...As-received nickel-titanium （NiTi） shape memory alloy with a nominal composition of Ni50.9Ti49.1 （mole fraction,%） was subjected to solution treatment at 1123 K for 2 h and subsequent aging for 2 h at 573 K, 723 K and 873 K, respectively. The influence of solution treatment and aging on microstructural evolution and mechanical behavior of NiTi alloy was systematically investigated by transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, scanning electron microscopy （SEM） and compression test. Solution treatment contributes to eliminating the Ti2Ni phase in the as-received NiTi sample, in which the TiC phase is unable to be removed. Solution treatment leads to ordered domain of atomic arrangement in NiTi alloy. In all the aged NiTi samples, the Ni4Ti3 precipitates, the R phase and the B2 austenite coexist in the NiTi matrix at room temperature, while the martensitic twins can be observed in the NiTi samples aged at 873 K. In the NiTi samples aged at 573 and 723 K, the fine and dense Ni4Ti3 precipitates distribute uniformly in the NiTi matrix, and thus they are coherent with the B2 matrix. However, in the NiTi sample aged at 873 K, the Ni4Ti3 precipitates exhibit the very inhomogeneous size, and they are coherent, semi-coherent and incoherent with the B2 matrix. In the case of aging at 723 K, the NiTi sample exhibits the maximum yield strength, where the fine and homogeneous Ni4Ti3 precipitates act as the effective obstacles against the dislocation motion, which results in the maximum critical resolved shear stress for dislocation slip.展开更多
Temperature variation and solution treatment of high strength aluminum alloy were investigated with temperature data acquisition system,microstructural observation,mechanical properties test,electrical conductivity me...Temperature variation and solution treatment of high strength aluminum alloy were investigated with temperature data acquisition system,microstructural observation,mechanical properties test,electrical conductivity measurement and differential scanning calorimetry（DSC） analysis.Specimens with two dimensions were employed in the experiment.The results indicate that the specimens with large size undergo low solution temperature and short time,giving rise to the reduction of hardening precipitates.The optimized solution treatments for specimens with dimensions of 25 mm×25 mm×2.5 mm and 70 mm×60 mm×20 mm are（480 ℃,30 min） and（480 ℃,90 min）,respectively.The densities of GP zones and η＇ phases of the small specimen are higher than those of the large specimen,which is consistent with the properties of the alloys.展开更多
The influence of solution treatment on the microstructure and properties of Mg2Si/AZ91D composites fabricated from Mg-SiO2 system via in-situ processing method was investigated.The results show that coarse Chinese scr...The influence of solution treatment on the microstructure and properties of Mg2Si/AZ91D composites fabricated from Mg-SiO2 system via in-situ processing method was investigated.The results show that coarse Chinese script shape Mg2Si phases can be formed by adding SiO2 into AZ91D magnesium alloy with Si content up to 1.5% of the alloy melt.During solution treatment,the morphology and distribution of the coarse Chinese script shape Mg2Si phases are modified.Meanwhile,the β-Mg17Al12 phase is dissolved into the magnesium matrix.With increasing holding time,the coarse Mg2Si phases tend to dissolve,break and spheroidize.After solution treatment at 420 ℃ for 16 h,Mg2Si phases become the finest and relatively well-distributed phase.The tensile strength and elongation are increased by 14.9% and 38.9%,respectively.It is believed that the Mg2Si phases continuously dissolve and break,and finally the spheroidized Mg2Si particles are obtained due to the interface tension of Mg2Si/Mg interface.展开更多
The microstructural evolution and kinetic characteristics were studied during solution treatment of AM60B Mg alloy prepared by thixoforming. The results indicate that the microstructural evolution includes two stages...The microstructural evolution and kinetic characteristics were studied during solution treatment of AM60B Mg alloy prepared by thixoforming. The results indicate that the microstructural evolution includes two stages： the first stage involves rapid dissolution of eutectic β （Mg 17 Al 12 ） phase, homogenization and coarsening, and the second stage is regarded as normal grain growth consisting of primary α-Mg particles （primary particles） and secondary α-Mg grains （secondary grains）. In the first stage, the dissolution completes in a quite short time because the fine β phase can quickly dissolve into the small-sized secondary grains. The homogenization of Al element needs relatively long time. Simultaneously, the microstructure morphology and average grain size obviously change. The first stage sustains approximately 1 h when it is solutionized at 395 ℃ Comparatively, the second stage needs very long time and the microstructure evolves quite slowly as a result of low Al content gradient and thus low diffusivity of Al element after the homogenization of the first stage. The growth model of primary particles obeys power function while that of the secondary grains follows the traditional growth equation in the first stage. In the second stage, both of the primary particles and secondary grains behave a same model controlled by diffusion along grain boundaries and through crystal lattice.展开更多
The effects of on-line solution, off-line solution and aging heat treatment on the microstructure and hardness of the die-cast AZ91D alloys were investigated. Brinell hardness of die-cast AZ91D alloy increases through...The effects of on-line solution, off-line solution and aging heat treatment on the microstructure and hardness of the die-cast AZ91D alloys were investigated. Brinell hardness of die-cast AZ91D alloy increases through on-line solution and off-line aging treatment but decreases after off-line solution treatment. By X-ray diffractometry, optical microscopy, differential thermal analysis, scanning electron microscopy and X-ray energy dispersive spectroscopy, it is found that the microstructures of the die-cast AZ91D magnesium alloy before and after on-line solution and off-line aging are similar, consisting of α-Mg and β-Al12Mg17. The precipitation of Al element is prevented by on-line solution so that the effect of solid solution strengthening is enhanced. The β-Al12Mg17 phases precipitate from supersaturated Mg solid solution after off-line aging treatment, and lead to microstructure refinement of AZ91D alloy, so the effect of precipitation hardening is enhanced. The β-Al12Mg17 phases dissolve in the substructure after off-line solution treatment, which leads to that the grain boundary strengthening phase is reduced significantly and the hardness of die cast AZ91D is reduced.展开更多
Effects of additions minor contents of 0.03%Sc and 0.12%Zr and solution treatment on microstructure and mechanical properties of Al-9.0Zn-2.8Mg-2.5Cu alloy were studied by metallographic microscopy, differential therm...Effects of additions minor contents of 0.03%Sc and 0.12%Zr and solution treatment on microstructure and mechanical properties of Al-9.0Zn-2.8Mg-2.5Cu alloy were studied by metallographic microscopy, differential thermal analysis （DSC） and transmission electron microscopy （TEM）, in order to obtain high-performance Al alloys. The minor additions of Sc （less than 0.1%） were carried out. The results show that with the additions of 0.03% Sc and 0.12% Zr, the petaloid Al3（Sc,Zr） precipitated phases occur in Al-9.0Zn-2.8Mg-2.5Cu alloy, and Al3（Sc,Zr） particles obviously hinder the recrystallization of Al-9.0Zn-2.8Mg-2.5Cu alloy during homogenizing and extruding processes due to their strong pinning effect on dislocation. Multi-stage solution is better than single solution, for it can avoid recrystallization of Al-9.0Zn-2.8Mg-2.5Cu alloy with the minor contents of Sc （less than 0.1%）. The proper solution treatment is （420 °C, 3 h）＋（465 °C, 2 h） under which Al-9.0Zn-2.8Mg-2.5Cu-0.12Zr-0.03Sc alloy obtains a tensile strength of 777.29 MPa and a elongation of 11.84%.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）...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 indi- cate that second phase of the as-extruded 7136 aluminum alloy mainly consists of Mg（Zn, Cu, Al）2 and Fe-rich phases. The Mg（Zn, Cu, Al）2 phase directly dissolves into the matrix during solution treatment with various solution temperatures. After solution treated at 475℃ for 1 h, Mg（Zn, Cu, Al）2 phases 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 ℃/1 h.展开更多
The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solu...The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.展开更多
The microstructure characteristics of AlSiCuMg cast alloys were studied withdifferent Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. Themelting point of alpha (Al) + Si decreases...The microstructure characteristics of AlSiCuMg cast alloys were studied withdifferent Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. Themelting point of alpha (Al) + Si decreases and polynary eutectic phases with low melting point formwith increase of Cu content. Gradual solution treatment includes two steps: solution treating nearthe melting point of polynary eutectic phase to take it dissolve first, and then increasing solutiontemperature to take the remainder copper intermetallics dissolved into alpha (Al). Grain boundariesmelting can be avoided by gradual solution treatment, even the maximum solution temperature isabove final solidification point, and the age hardening response increases correspondingly展开更多
The transformation and dissolution of Mg（Zn, Cu, Al）2 phase during solution treatment of an Al-Zn-Mg-Cu alloy containing high zinc were investigated by means of optical microscopy （OM）, scanning electron microsco...The transformation and dissolution of Mg（Zn, Cu, Al）2 phase during solution treatment of an Al-Zn-Mg-Cu 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（Al2CuMg） 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（Al2CuMg） phase transformed from Mg（Zn, Cu, Al）2 phase is observed. The formation of S（Al2CuMg） 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（Al2CuMg） phase. At high temperature, the dissolution of main alloying elements has no significant barrier among them to form S（Al2CuMg） phase.展开更多
In this study,the morphology,composition and evolution of intermetallics in Al-7Si-0.3Mg,Al-7Si-0.3Mg-0.47Hf,Al-7Si-0.3Mg-0.16 Zr and Al-7Si-0.3Mg-0.14Zr-0.44Hf alloys were characterized by optical microscope(OM),scan...In this study,the morphology,composition and evolution of intermetallics in Al-7Si-0.3Mg,Al-7Si-0.3Mg-0.47Hf,Al-7Si-0.3Mg-0.16 Zr and Al-7Si-0.3Mg-0.14Zr-0.44Hf alloys were characterized by optical microscope(OM),scanning electron microscope(SEM)with energy-dispersive spectrometer(EDS) and transmission electron microscope(TEM).The AlSiZr,AlSiHf and AlSiZrHf phases are formed with additions of Zr and/or Hf in base alloy during solidification,especially the AlZrHf primary particles.The three-dimensional morphology of the AlZrHf particle evolves from 10-polyhedron-like to compressed cube-like during solidification.The new AlZrHf phase experiences partial dissolution after solution treatment,while the others remain in the initial morphology.High Si contents lead to form thermally stable Zr/Hfrich precipitates in Zr/Hf-containing alloys during solution treatment,especially the nanobelt-like Si2Zr,Si2Hf and Si2(Zr,Hf) precipitates.Particular orientation relationships and the growth mechanism are identified.The finding of the work broadens the elevated temperature application of Al-Si-Mg in modern automotive aluminum engine.展开更多
The effects of solution treatment on the evolution of the second phases and mechanical properties of7075Al alloy werestudied with scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),differentia...The effects of solution treatment on the evolution of the second phases and mechanical properties of7075Al alloy werestudied with scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),differential scanning calorimetry(DSC),hardness and tensile tests.The results show that Mg(Zn,Cu,Al)2phases gradually dissolve into the matrix,yet the size andmorphology of Al7Cu2Fe phase exhibit no change with the increase of the solution treatment temperature and time due to its highmelting point.When the solution treatment temperature and time continue to increase,the formation of coarse black Mg2Si particlesoccurs.Compared to the as-cast alloy,the microhardness,tensile strength,and elongation of the sample under solution heat treatmentat460°C for5h are increased by55.1%,40.9%and109.1%,respectively.This is because the eutectic Mg(Zn,Cu,Al)2phases almostcompletely dissolve and basically no coarse black Mg2Si particles are formed.展开更多
The effect of Ce/La misch metal addition on the microstructural evolution of as-cast and as-soluted Mg-5.3Zn-0.5Ca（wt.%） alloys was systematically investigated. It was found that Ce/La could effectively refine the a...The effect of Ce/La misch metal addition on the microstructural evolution of as-cast and as-soluted Mg-5.3Zn-0.5Ca（wt.%） alloys was systematically investigated. It was found that Ce/La could effectively refine the as-cast alloy and restrain grain growth during solution treatment, which was derived from the constitutional supercooling during solidification process and the formation of stable intermetallic compounds Ce Mg12 and Mg17La2. Furthermore, Ce/La microalloying and solution treatment resulted in an evolution from the original lamellar Ca2Mg6Zn3/α-Mg to the divorced eutectic structure. The thermal stability of Mg-Zn-Ca alloy could be effectively improved by Ce/La addition, because the low-melting-point binary Mg-Zn phase was transformed to Mg x Zn y-Ca-（Ce/La） phase with higher thermal stability and the amount of Ca2Mg6Zn3/α-Mg eutectic structure was reduced.展开更多
The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy.It was found that as-cast microstructures of unmodif...The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy.It was found that as-cast microstructures of unmodified and Sr-modified Al-Si alloys consisted of a coarse acicular plate of eutectic Si,Cu_3NiAl_6 and Mg_2Si phases in theα-Al matrix but different in size and morphology.Both size and inter-particle spacing of Si particles were significantly changed by increasing the solution treatment time.After a short solution treatment,the coarse acicular plate of the eutectic Si appears to be fragmented.Fully modified microstructure of Sr-modified alloy can reduce the solution treatment time compared to unmodified alloy.The maximum of a peak hardness value is found in the very short solution treatment of both Al-Si piston alloys.Compared to 10 h solution treatment,the solution treatment of 2-4 h is sufficient to achieve appropriate microstructures and hardness. The short solution treatment is very useful to increase the productivity and to reduce the manufacturing cost of the Al-Si piston alloys.展开更多
In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the stand...In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the standard artificial aging treatment for Al-Cu alloy followed heat treatments of solution treatment at 510-530 ℃ for 2 h,quenching in water at 60 ℃ and then artificial aging at 160-190 ℃ for 2-8 h.The effects of solution treatment and artificial aging on the microstructure and mechanical properties of Al-Cu alloy were studied by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,transmission electron microscopy（TEM） and tensile test.The results of solution treatment indicate that the mechanical properties of Al-Cu alloy increase and then decrease with the increase of solution temperature.This is because the residual phases dissolve gradually into the matrix,and the fraction of the precipitation and the size of the re-crystallized grain increased.Compared to the solution temperature,the solution holding time has less effect on the microstructure and the mechanical properties of Al-Cu alloy.The artificial aging treatments were conducted at 160-180 ℃ for 2-8 h.The results show that the ultimate tensile strength can be obtained at 180 ℃ for 8 h.Ultimate tensile strength increased with increasing time or temperature.Yield strength was found as the same as the ultimate tensile strength result.展开更多
Solution treatment is a useful way to improve the degradation resistance of Mg alloys.In this work,effects of solution treatment temperature on mechanical and biodegradable properties of an extruded Mg-2Zn-1Gd-0.5Zr a...Solution treatment is a useful way to improve the degradation resistance of Mg alloys.In this work,effects of solution treatment temperature on mechanical and biodegradable properties of an extruded Mg-2Zn-1Gd-0.5Zr alloy were studied.Microstructure analysis,tensile test,three-point bending test,immersion test and electrochemical test were performed.The results showed that increasing solution temperature decreases the mechanical properties of the alloy.However,three-point bending test revealed that the solution-treated alloy at 510℃could maintain 95%of its maximum bending force(F_(max))during the 28-day immersion period.After treatment at 510℃for 5 h,all the second phases were dissolved into the alloy,the galvanic corrosion was inhibited,and the alloy exhibited good corrosion resistance with a corrosion rate of 0.35 mm·year-1 in Hank’s solution.展开更多
文摘The authors regret that the affiliation b and c are wrong.Affiliation b should be changed to“School of Civil and Environmental Engineering,Harbin Institute of Technology,Shenzhen,China;Department of Data Analysis and Mathematical Modelling,Ghent University,Belgium”.And affiliation c should be changed to“State Key Laboratory of Urban Water Resource and Environment(SKLUWRE),School of Environment,Harbin Institute of Technology,China”.
基金National Natural Science Foundation of China(Nos.52204400,52204401)Natural Science Foundation of Hebei Province,China(No.E2022203033)。
文摘High-temperature and short-time(HTST)solution heat treatment combined with non-isothermal aging(NIA)was employed to regulate the microstructure and properties of Al−4.5Mg−2.0Zn−0.3Ag alloy.Results indicate that HTST solution heat treatment can not only retain partial deformation dislocations,but inhibit the recrystallization behavior and increase the proportion of low-angle grain boundaries(LAGBs).In the subsequent NIA process,HTST solution heat treatment combined with NIA is instrumental in restraining the degradation of dislocations and promoting precipitation of nano-scale T'-Mg_(32)(Al,Zn,Ag)49 phase,which improves the strength of the alloy greatly.In addition,a higher fraction of LAGBs and the discontinuous distribution of grain boundary precipitates caused by this novel technology meliorate the corrosion resistance of Al−4.5Mg−2.0Zn−0.3Ag alloy.
基金Project(3102014KYJD002)supported by the Fundamental Research Funds for the Central Universities of ChinaProjects(50901059,51431008,51134011)supported by the National Natural Science Foundation of China+2 种基金Project(2011CB610403)supported by the National Basic Research Program of ChinaProject(51125002)supported by the China National Funds for Distinguished Young ScientistsProject(JC20120223)supported by the Fundamental Research Fund of Northwestern Polytechnical University,China
文摘The effect of cooling rate of the solidification process on the following solution heat treatment of A356 alloy was investigated,where the cooling rates of 96 K/s and 3 K/s were obtained by the step-like metal mold.Then the eutectic silicon morphology evolution and tensile properties of the alloy samples were observed and analyzed after solution heat treatment at 540 °C for different time.The results show that the high cooling rate of the solidification process can not only reduce the solid solution heat treatment time to rapidly modify the eutectic silicon morphology,but also improve the alloy tensile properties.Specially,it is found that the disintegration,the spheroidization and coarsening of eutectic silicon of A356 alloy are completed during solution heat treatment through two stages,i.e.,at first,the disintegration and spheroidization of the eutectic silicon mainly takes place,then the eutectic silicon will coarsen.
基金Project(2011CB610403)support by the National Basic Research Program of ChinaProjects(51134011,51431008)supported by the National Natural Science Foundation of China+1 种基金Project(JC20120223)supported by the Fundamental Research Fund of Northwestern Polytechnical University,ChinaProject(51125002)supported by the National Funds for Distinguished Young Scientists of China
文摘For the compromise of mechanical properties and product cost, the end-chilled sand casting technique was applied to studying the microstructure evolution of A356 Al alloy with cooling rate and the effect of different as-cast microstructures on the subsequent solution-treatment process. The experimental results show that the secondary dendrite arm spacing (SDAS) of primaryα(Al), the size of eutectic Si and the volume fraction of Al?Si eutectic are reduced with increasing the cooling rate. Eutectic Si, subjected to solution treatment at 540 °C for 1 h followed by water quenching to room temperature, is completely spheroidized at cooling rate of 2.6 K/s; is partially spheroidized atcooling rate of 0.6 K/s; and is only edge-rounded at cooling rates of 0.22 and 0.12 K /s. Whilst the microhardness is also the maximum at cooling rate of 2.6 K/s. It consequently suggests that subjected to modification by high cooling rate, the eutectic Si is more readily modified, thus shortening the necessary solution time at given solution temperature, i.e., reducing the product cost.
基金Project (51071056) supported by the National Natural Science Foundation of ChinaProjects (HEUCF121712,HEUCF201317002) supported by the Fundamental Research Funds for the Central Universities of China
文摘As-received nickel-titanium （NiTi） shape memory alloy with a nominal composition of Ni50.9Ti49.1 （mole fraction,%） was subjected to solution treatment at 1123 K for 2 h and subsequent aging for 2 h at 573 K, 723 K and 873 K, respectively. The influence of solution treatment and aging on microstructural evolution and mechanical behavior of NiTi alloy was systematically investigated by transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, scanning electron microscopy （SEM） and compression test. Solution treatment contributes to eliminating the Ti2Ni phase in the as-received NiTi sample, in which the TiC phase is unable to be removed. Solution treatment leads to ordered domain of atomic arrangement in NiTi alloy. In all the aged NiTi samples, the Ni4Ti3 precipitates, the R phase and the B2 austenite coexist in the NiTi matrix at room temperature, while the martensitic twins can be observed in the NiTi samples aged at 873 K. In the NiTi samples aged at 573 and 723 K, the fine and dense Ni4Ti3 precipitates distribute uniformly in the NiTi matrix, and thus they are coherent with the B2 matrix. However, in the NiTi sample aged at 873 K, the Ni4Ti3 precipitates exhibit the very inhomogeneous size, and they are coherent, semi-coherent and incoherent with the B2 matrix. In the case of aging at 723 K, the NiTi sample exhibits the maximum yield strength, where the fine and homogeneous Ni4Ti3 precipitates act as the effective obstacles against the dislocation motion, which results in the maximum critical resolved shear stress for dislocation slip.
基金Project(2010DFB50340) supported by the International Technical Cooperation ProjectProject(50904010) supported by the National Natural Science Foundation of China
文摘Temperature variation and solution treatment of high strength aluminum alloy were investigated with temperature data acquisition system,microstructural observation,mechanical properties test,electrical conductivity measurement and differential scanning calorimetry（DSC） analysis.Specimens with two dimensions were employed in the experiment.The results indicate that the specimens with large size undergo low solution temperature and short time,giving rise to the reduction of hardening precipitates.The optimized solution treatments for specimens with dimensions of 25 mm×25 mm×2.5 mm and 70 mm×60 mm×20 mm are（480 ℃,30 min） and（480 ℃,90 min）,respectively.The densities of GP zones and η＇ phases of the small specimen are higher than those of the large specimen,which is consistent with the properties of the alloys.
基金Project (BG2007030) supported by High-tech Research Program of Jiangsu Province, ChinaProject (07KJA43008) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject (20070299004) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The influence of solution treatment on the microstructure and properties of Mg2Si/AZ91D composites fabricated from Mg-SiO2 system via in-situ processing method was investigated.The results show that coarse Chinese script shape Mg2Si phases can be formed by adding SiO2 into AZ91D magnesium alloy with Si content up to 1.5% of the alloy melt.During solution treatment,the morphology and distribution of the coarse Chinese script shape Mg2Si phases are modified.Meanwhile,the β-Mg17Al12 phase is dissolved into the magnesium matrix.With increasing holding time,the coarse Mg2Si phases tend to dissolve,break and spheroidize.After solution treatment at 420 ℃ for 16 h,Mg2Si phases become the finest and relatively well-distributed phase.The tensile strength and elongation are increased by 14.9% and 38.9%,respectively.It is believed that the Mg2Si phases continuously dissolve and break,and finally the spheroidized Mg2Si particles are obtained due to the interface tension of Mg2Si/Mg interface.
基金Project(G2007CB613706)supported by the National Basic Research Program of ChinaProject supported by the Development Program for Outstanding Young Teachers in Lanzhou University of Technology, ChinaProject(SKL03004)supported by the Opening Foundation of State Key Laboratory of Advanced Nonferrous Materials, China
文摘The microstructural evolution and kinetic characteristics were studied during solution treatment of AM60B Mg alloy prepared by thixoforming. The results indicate that the microstructural evolution includes two stages： the first stage involves rapid dissolution of eutectic β （Mg 17 Al 12 ） phase, homogenization and coarsening, and the second stage is regarded as normal grain growth consisting of primary α-Mg particles （primary particles） and secondary α-Mg grains （secondary grains）. In the first stage, the dissolution completes in a quite short time because the fine β phase can quickly dissolve into the small-sized secondary grains. The homogenization of Al element needs relatively long time. Simultaneously, the microstructure morphology and average grain size obviously change. The first stage sustains approximately 1 h when it is solutionized at 395 ℃ Comparatively, the second stage needs very long time and the microstructure evolves quite slowly as a result of low Al content gradient and thus low diffusivity of Al element after the homogenization of the first stage. The growth model of primary particles obeys power function while that of the secondary grains follows the traditional growth equation in the first stage. In the second stage, both of the primary particles and secondary grains behave a same model controlled by diffusion along grain boundaries and through crystal lattice.
基金Projects (2011BAE22B01, 2011BAE22B06) supported by the National Key Technologies R&D Program During the 12th Five-Year Plan Period of ChinaProject (2010NC018) supported by the Innovation Fund of Inner Mongolia University of Science and Technology, China
文摘The effects of on-line solution, off-line solution and aging heat treatment on the microstructure and hardness of the die-cast AZ91D alloys were investigated. Brinell hardness of die-cast AZ91D alloy increases through on-line solution and off-line aging treatment but decreases after off-line solution treatment. By X-ray diffractometry, optical microscopy, differential thermal analysis, scanning electron microscopy and X-ray energy dispersive spectroscopy, it is found that the microstructures of the die-cast AZ91D magnesium alloy before and after on-line solution and off-line aging are similar, consisting of α-Mg and β-Al12Mg17. The precipitation of Al element is prevented by on-line solution so that the effect of solid solution strengthening is enhanced. The β-Al12Mg17 phases precipitate from supersaturated Mg solid solution after off-line aging treatment, and lead to microstructure refinement of AZ91D alloy, so the effect of precipitation hardening is enhanced. The β-Al12Mg17 phases dissolve in the substructure after off-line solution treatment, which leads to that the grain boundary strengthening phase is reduced significantly and the hardness of die cast AZ91D is reduced.
基金Project(51004036)supported by the National Natural Science Foundation of ChinaProject(N120309002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Effects of additions minor contents of 0.03%Sc and 0.12%Zr and solution treatment on microstructure and mechanical properties of Al-9.0Zn-2.8Mg-2.5Cu alloy were studied by metallographic microscopy, differential thermal analysis （DSC） and transmission electron microscopy （TEM）, in order to obtain high-performance Al alloys. The minor additions of Sc （less than 0.1%） were carried out. The results show that with the additions of 0.03% Sc and 0.12% Zr, the petaloid Al3（Sc,Zr） precipitated phases occur in Al-9.0Zn-2.8Mg-2.5Cu alloy, and Al3（Sc,Zr） particles obviously hinder the recrystallization of Al-9.0Zn-2.8Mg-2.5Cu alloy during homogenizing and extruding processes due to their strong pinning effect on dislocation. Multi-stage solution is better than single solution, for it can avoid recrystallization of Al-9.0Zn-2.8Mg-2.5Cu alloy with the minor contents of Sc （less than 0.1%）. The proper solution treatment is （420 °C, 3 h）＋（465 °C, 2 h） under which Al-9.0Zn-2.8Mg-2.5Cu-0.12Zr-0.03Sc alloy obtains a tensile strength of 777.29 MPa and a elongation of 11.84%.
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 indi- cate that second phase of the as-extruded 7136 aluminum alloy mainly consists of Mg（Zn, Cu, Al）2 and Fe-rich phases. The Mg（Zn, Cu, Al）2 phase directly dissolves into the matrix during solution treatment with various solution temperatures. After solution treated at 475℃ for 1 h, Mg（Zn, Cu, Al）2 phases 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 ℃/1 h.
基金supported by the Aviation Industry Corporation of China (No. 201110026-01)
文摘The morphological evolution of the γ' phase in nickel-based superalloy жc6y during various solution heat treatments was investigated. The significant changes of the γ' precipitates were observed in the solution-treated samples. The coarsening and dissolution of γ' phase simulta-neously occurred at intermediate temperatures. In some areas, the primary precipitates became blunt and the adjacent ones were intercon-nected with each other via a diffuse neck, indicating a coarsening process of the primary γ' population. The coarsening was dominated by the precipitate agglomeration mechanism (PAM) rather than by the well-known Ostwald ripening mechanism. In other areas, the partial dissolu-tion of the γ' precipitates began to occur, spreading gradually from dendrite cores to interdendritic regions. In addition, a flower-like γ' struc-ture was developed during the subsolvus solution treatments. The observable long filaments composed of erraticly shaped precipitates were caused by the heterogeneous nucleation of the cooling precipitates during water quenching.
基金This work is financially supported by the National Natural Science Foundation of China(No.50071028)the Shandong Natural Science Foundation of China (No.Z2001F02)
文摘The microstructure characteristics of AlSiCuMg cast alloys were studied withdifferent Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. Themelting point of alpha (Al) + Si decreases and polynary eutectic phases with low melting point formwith increase of Cu content. Gradual solution treatment includes two steps: solution treating nearthe melting point of polynary eutectic phase to take it dissolve first, and then increasing solutiontemperature to take the remainder copper intermetallics dissolved into alpha (Al). Grain boundariesmelting can be avoided by gradual solution treatment, even the maximum solution temperature isabove final solidification point, and the age hardening response increases correspondingly
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-Mg-Cu 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（Al2CuMg） 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（Al2CuMg） phase transformed from Mg（Zn, Cu, Al）2 phase is observed. The formation of S（Al2CuMg） 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（Al2CuMg） phase. At high temperature, the dissolution of main alloying elements has no significant barrier among them to form S（Al2CuMg） phase.
基金financially supported by the National Natural Science Foundation of China(No.51271209)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51421001)
文摘In this study,the morphology,composition and evolution of intermetallics in Al-7Si-0.3Mg,Al-7Si-0.3Mg-0.47Hf,Al-7Si-0.3Mg-0.16 Zr and Al-7Si-0.3Mg-0.14Zr-0.44Hf alloys were characterized by optical microscope(OM),scanning electron microscope(SEM)with energy-dispersive spectrometer(EDS) and transmission electron microscope(TEM).The AlSiZr,AlSiHf and AlSiZrHf phases are formed with additions of Zr and/or Hf in base alloy during solidification,especially the AlZrHf primary particles.The three-dimensional morphology of the AlZrHf particle evolves from 10-polyhedron-like to compressed cube-like during solidification.The new AlZrHf phase experiences partial dissolution after solution treatment,while the others remain in the initial morphology.High Si contents lead to form thermally stable Zr/Hfrich precipitates in Zr/Hf-containing alloys during solution treatment,especially the nanobelt-like Si2Zr,Si2Hf and Si2(Zr,Hf) precipitates.Particular orientation relationships and the growth mechanism are identified.The finding of the work broadens the elevated temperature application of Al-Si-Mg in modern automotive aluminum engine.
基金Project(51364035)supported by the National Natural Science Foundation of ChinaProject(CX2015055)supported by the Innovation Special Funds of Nanchang University for Graduate Student,China
文摘The effects of solution treatment on the evolution of the second phases and mechanical properties of7075Al alloy werestudied with scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),differential scanning calorimetry(DSC),hardness and tensile tests.The results show that Mg(Zn,Cu,Al)2phases gradually dissolve into the matrix,yet the size andmorphology of Al7Cu2Fe phase exhibit no change with the increase of the solution treatment temperature and time due to its highmelting point.When the solution treatment temperature and time continue to increase,the formation of coarse black Mg2Si particlesoccurs.Compared to the as-cast alloy,the microhardness,tensile strength,and elongation of the sample under solution heat treatmentat460°C for5h are increased by55.1%,40.9%and109.1%,respectively.This is because the eutectic Mg(Zn,Cu,Al)2phases almostcompletely dissolve and basically no coarse black Mg2Si particles are formed.
基金supported by the National Natural Science Foundation of China(51401200)Natural Science Foundation of Jilin Province(20140520099JH)+4 种基金National Science & Technology Pillar Program(2012BAE01B04)Chinese Academy of Sciences of Western Action Plan Project(KZCX2-XB3-06)the National Natural Science Foundation of China Major Project(91122030)National High Technology Research and Development Program of China(2011AA03A407)National Natural Science Foundation for Creative Research Group(20921002)
文摘The effect of Ce/La misch metal addition on the microstructural evolution of as-cast and as-soluted Mg-5.3Zn-0.5Ca（wt.%） alloys was systematically investigated. It was found that Ce/La could effectively refine the as-cast alloy and restrain grain growth during solution treatment, which was derived from the constitutional supercooling during solidification process and the formation of stable intermetallic compounds Ce Mg12 and Mg17La2. Furthermore, Ce/La microalloying and solution treatment resulted in an evolution from the original lamellar Ca2Mg6Zn3/α-Mg to the divorced eutectic structure. The thermal stability of Mg-Zn-Ca alloy could be effectively improved by Ce/La addition, because the low-melting-point binary Mg-Zn phase was transformed to Mg x Zn y-Ca-（Ce/La） phase with higher thermal stability and the amount of Ca2Mg6Zn3/α-Mg eutectic structure was reduced.
文摘The purpose of this paper was to investigate the effects of solution treatment time and Sr-modification on the microstructure and property of the Al-Si piston alloy.It was found that as-cast microstructures of unmodified and Sr-modified Al-Si alloys consisted of a coarse acicular plate of eutectic Si,Cu_3NiAl_6 and Mg_2Si phases in theα-Al matrix but different in size and morphology.Both size and inter-particle spacing of Si particles were significantly changed by increasing the solution treatment time.After a short solution treatment,the coarse acicular plate of the eutectic Si appears to be fragmented.Fully modified microstructure of Sr-modified alloy can reduce the solution treatment time compared to unmodified alloy.The maximum of a peak hardness value is found in the very short solution treatment of both Al-Si piston alloys.Compared to 10 h solution treatment,the solution treatment of 2-4 h is sufficient to achieve appropriate microstructures and hardness. The short solution treatment is very useful to increase the productivity and to reduce the manufacturing cost of the Al-Si piston alloys.
文摘In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the standard artificial aging treatment for Al-Cu alloy followed heat treatments of solution treatment at 510-530 ℃ for 2 h,quenching in water at 60 ℃ and then artificial aging at 160-190 ℃ for 2-8 h.The effects of solution treatment and artificial aging on the microstructure and mechanical properties of Al-Cu alloy were studied by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,transmission electron microscopy（TEM） and tensile test.The results of solution treatment indicate that the mechanical properties of Al-Cu alloy increase and then decrease with the increase of solution temperature.This is because the residual phases dissolve gradually into the matrix,and the fraction of the precipitation and the size of the re-crystallized grain increased.Compared to the solution temperature,the solution holding time has less effect on the microstructure and the mechanical properties of Al-Cu alloy.The artificial aging treatments were conducted at 160-180 ℃ for 2-8 h.The results show that the ultimate tensile strength can be obtained at 180 ℃ for 8 h.Ultimate tensile strength increased with increasing time or temperature.Yield strength was found as the same as the ultimate tensile strength result.
基金financially supported by the Key Program of China on Biomedical Materials Research and Tissue and Organ Replacement(Nos.2016YFC1101804 and 2016YFC1100604)the Shenyang Key Research&Development and Technology Transfer Program(No.Z18-0-027)
文摘Solution treatment is a useful way to improve the degradation resistance of Mg alloys.In this work,effects of solution treatment temperature on mechanical and biodegradable properties of an extruded Mg-2Zn-1Gd-0.5Zr alloy were studied.Microstructure analysis,tensile test,three-point bending test,immersion test and electrochemical test were performed.The results showed that increasing solution temperature decreases the mechanical properties of the alloy.However,three-point bending test revealed that the solution-treated alloy at 510℃could maintain 95%of its maximum bending force(F_(max))during the 28-day immersion period.After treatment at 510℃for 5 h,all the second phases were dissolved into the alloy,the galvanic corrosion was inhibited,and the alloy exhibited good corrosion resistance with a corrosion rate of 0.35 mm·year-1 in Hank’s solution.
