Volume 45,Issue 5,2016 Table of Contents
2016, 45(5):1093-1099.
Abstract:
Microwave irradiation has advantages of being simple, quick and provides uniform heat. Such method was used for supporting metal oxides on ordered mesoporous carbon (OMC), which was named as NiO/C. Microwave assisted heating process involved Ni2 being reduced by glycol under alkaline surroundings. This greatly shortened supporting time and provided quantificational support when comparing with conventional impregnation method. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, inductively coupled plasma (ICP) and cyclic voltammetry (CV) were employed to characterize the samples. Slightly reduce of pore size showed that nanoparticles were embedded on the pore wall of OMC. However, retaining ordered mesostructure and large surface area with appropriate NiO content were confirmed by XRD, TEM and nitrogen sorption. The data of ICP showed high supporting efficiency in microwave-assisted method. A great specific capacitance over 400 F?g-1 and high electrochemical stability implied favorable application prospect for this supporting method.
Microwave irradiation has advantages of being simple, quick and provides uniform heat. Such method was used for supporting metal oxides on ordered mesoporous carbon (OMC), which was named as NiO/C. Microwave assisted heating process involved Ni2 being reduced by glycol under alkaline surroundings. This greatly shortened supporting time and provided quantificational support when comparing with conventional impregnation method. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption, inductively coupled plasma (ICP) and cyclic voltammetry (CV) were employed to characterize the samples. Slightly reduce of pore size showed that nanoparticles were embedded on the pore wall of OMC. However, retaining ordered mesostructure and large surface area with appropriate NiO content were confirmed by XRD, TEM and nitrogen sorption. The data of ICP showed high supporting efficiency in microwave-assisted method. A great specific capacitance over 400 F?g-1 and high electrochemical stability implied favorable application prospect for this supporting method.
2016, 45(5):1100-1105.
Abstract:
The cold roll bonding process of an Al-Ni layer composite sheet which is applied as a brazing solder for the welding of Nickel and Aluminum structures in the Lithium-ion battery packaging is investigated. The effects of roll bonding and annealing treatment on the application properties and the interface compounds of Al-Ni composite sheet are also studied. The results show that the appropriate rolling reduction to bond and produce Al-Ni layer composite sheet is about 50% to 60% deformation degree. During the annealing process, the first formed Al3Ni phase in the interface of Al and Ni is benefit to the bonding of such two metals but the sequent formed Al3Ni2 phase results in the cracks and separation of the Al-Ni layers. The roll bonding Al-Ni layer composite sheet acquires good bending endurance, stable weldability and suitable electrical resistivity with annealing from 698K to 748K for 1 hour.
The cold roll bonding process of an Al-Ni layer composite sheet which is applied as a brazing solder for the welding of Nickel and Aluminum structures in the Lithium-ion battery packaging is investigated. The effects of roll bonding and annealing treatment on the application properties and the interface compounds of Al-Ni composite sheet are also studied. The results show that the appropriate rolling reduction to bond and produce Al-Ni layer composite sheet is about 50% to 60% deformation degree. During the annealing process, the first formed Al3Ni phase in the interface of Al and Ni is benefit to the bonding of such two metals but the sequent formed Al3Ni2 phase results in the cracks and separation of the Al-Ni layers. The roll bonding Al-Ni layer composite sheet acquires good bending endurance, stable weldability and suitable electrical resistivity with annealing from 698K to 748K for 1 hour.
2016, 45(5):1106-1110.
Abstract:
The Ostwald ripening behavior of Al8CeCu4 phase in the Al-14Cu-7Ce alloy annealing at elevated temperatures was investigated using hardness testing, scanning electron microscopy, image analyses and physical modeling. The average radius of Al8CeCu4 particles increases while the hardness of the alloy decreases with increasing annealing temperature and time. The ripening process of Al8CeCu4 phase is mainly controlled by the volume diffusion of Ce. The ripening kinetic of Al8CeCu4 particles satisfies well the modified Lifshits-Slyozov-Wagner theory, taking into account the effect of the volume fraction of Al8CeCu4 particles. The volume diffusion coefficient of Ce and the interfacial energy between the matrix and Al8CeCu4 phase are also calculated based on the general rate equation.
The Ostwald ripening behavior of Al8CeCu4 phase in the Al-14Cu-7Ce alloy annealing at elevated temperatures was investigated using hardness testing, scanning electron microscopy, image analyses and physical modeling. The average radius of Al8CeCu4 particles increases while the hardness of the alloy decreases with increasing annealing temperature and time. The ripening process of Al8CeCu4 phase is mainly controlled by the volume diffusion of Ce. The ripening kinetic of Al8CeCu4 particles satisfies well the modified Lifshits-Slyozov-Wagner theory, taking into account the effect of the volume fraction of Al8CeCu4 particles. The volume diffusion coefficient of Ce and the interfacial energy between the matrix and Al8CeCu4 phase are also calculated based on the general rate equation.
2016, 45(5):1111-1116.
Abstract:
The microstructural evolution and mechanical properties of Mg-6Zn-1Mn-4Sn-0.5Y wrought alloy extruded at 360 and 420℃ were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron back scattered diffraction (EBSD) and tensile test. The results shown that the phase compositions of as-cast and extruded alloys were α-Mg, Mn, Mg7Zn3, Mg2Sn, and MgSnY phases. As the extrusion temperature increased from 360 to 420℃, dynamic recrystallization completed and grain growth occurred. The yield strength, ultimate tensile strength and elongation decreased from 259MPa, 350MPa and 18.3% to 239MPa, 332MPa and 12.5%, respectively. The theoretical values combined with the experimental values revealed that grain size strengthening and solid solution strengthening played the dominating role in the enhancement of yield strength.
The microstructural evolution and mechanical properties of Mg-6Zn-1Mn-4Sn-0.5Y wrought alloy extruded at 360 and 420℃ were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron back scattered diffraction (EBSD) and tensile test. The results shown that the phase compositions of as-cast and extruded alloys were α-Mg, Mn, Mg7Zn3, Mg2Sn, and MgSnY phases. As the extrusion temperature increased from 360 to 420℃, dynamic recrystallization completed and grain growth occurred. The yield strength, ultimate tensile strength and elongation decreased from 259MPa, 350MPa and 18.3% to 239MPa, 332MPa and 12.5%, respectively. The theoretical values combined with the experimental values revealed that grain size strengthening and solid solution strengthening played the dominating role in the enhancement of yield strength.
2016, 45(5):1117-1121.
Abstract:
This study presents the preparation and application of nano γ-Fe2O3/TiO2 nanotube magnetic heterojunction photocatalysts (MHPs) for photodegradation of methylene blue under visible light irradiation. The morphology, microstructure, magnetic properties, and photocatalytic activity of γ-Fe2O3/TiO2 (NT) MHPs were studied. The results showed that the MHPs were provided with highly ordered TiO2 (titania) nanotube arrays (55 nm diameter and 10 nm wall thickness) and nano γ-Fe2O3 (maghemite) particle (approximately 15 nm) co-deposition. The MHPs exhibited a superparamagnetic behavior of γ-Fe2O3/TiO2 (NT) MHPs resulting from the small size of γ-Fe2O3 particles. The photocatalytic activity of γ-Fe2O3/TiO2 (NT) MHPs was greater than that of Fe3O4/TiO2 (NT) MHPs or pure TiO2 (NT) under visible light irradiation. The interaction between γ-Fe2O3 and TiO2 improved charge separation and extended TiO2 response into the visible region. Moreover, the formed heterojunction between γ-Fe2O3 and TiO2 could further prevent the recombination between photoelectrons and holes.
This study presents the preparation and application of nano γ-Fe2O3/TiO2 nanotube magnetic heterojunction photocatalysts (MHPs) for photodegradation of methylene blue under visible light irradiation. The morphology, microstructure, magnetic properties, and photocatalytic activity of γ-Fe2O3/TiO2 (NT) MHPs were studied. The results showed that the MHPs were provided with highly ordered TiO2 (titania) nanotube arrays (55 nm diameter and 10 nm wall thickness) and nano γ-Fe2O3 (maghemite) particle (approximately 15 nm) co-deposition. The MHPs exhibited a superparamagnetic behavior of γ-Fe2O3/TiO2 (NT) MHPs resulting from the small size of γ-Fe2O3 particles. The photocatalytic activity of γ-Fe2O3/TiO2 (NT) MHPs was greater than that of Fe3O4/TiO2 (NT) MHPs or pure TiO2 (NT) under visible light irradiation. The interaction between γ-Fe2O3 and TiO2 improved charge separation and extended TiO2 response into the visible region. Moreover, the formed heterojunction between γ-Fe2O3 and TiO2 could further prevent the recombination between photoelectrons and holes.
2016, 45(5):1122-1127.
Abstract:
The layer of oxide film was prepared on the surface of 7475 aluminum alloy by anodic oxidation, and the friction and wear performance under different loads were investigated with the friction and wear test. The atomic binding energy spectrum, wear morphologies, surface hardness and residual stress were analyzed with XPS, SEM, hard meter and XRD stress tester, respectively. The results show that the oxide film on the surface is relatively dense after anodic oxidation, existing in the form of Al2O3, and the form of the diffusion type in the interface is contained. The average friction coefficient is decreased after anodic oxidation, indicating the friction performance improving. The wear mechanism of primitive sample is adhesive wear and tear, accompanying with abrasive wear, and the wear mechanism of the sample after the anodic oxidation is abrasive wear, where high surface hardness is the main factor of the wear resistance.
The layer of oxide film was prepared on the surface of 7475 aluminum alloy by anodic oxidation, and the friction and wear performance under different loads were investigated with the friction and wear test. The atomic binding energy spectrum, wear morphologies, surface hardness and residual stress were analyzed with XPS, SEM, hard meter and XRD stress tester, respectively. The results show that the oxide film on the surface is relatively dense after anodic oxidation, existing in the form of Al2O3, and the form of the diffusion type in the interface is contained. The average friction coefficient is decreased after anodic oxidation, indicating the friction performance improving. The wear mechanism of primitive sample is adhesive wear and tear, accompanying with abrasive wear, and the wear mechanism of the sample after the anodic oxidation is abrasive wear, where high surface hardness is the main factor of the wear resistance.
2016, 45(5):1128-1131.
Abstract:
NiTi alloy was subjected to one-step hydrothermal treatment in the concentrated CaHPO4 and Ca(H2PO4)2 solutions for bioactive surface modification. The treated samples are covered by films composed of fine grains (~70 nm) and large particles (100-250 nm). XPS analysis shows that Ti at the surface presents as TiO2, Ni is not detectable, and Ca and P are in the form of calcium phosphate. X-ray diffraction peaks of anatase TiO2 and hydroxyapatite are present for the treated samples. Potentiodynamic polarization test in a Ca-free Hank’s balanced solution reveals that the treated sample has markedly improved corrosion resistance compared with the polished sample. The present work would provide a one-step bioactive surface modification method that is easily-operated, low-temperatured, less corrosive, and potentially suitable for biomedical porous NiTi alloy.
NiTi alloy was subjected to one-step hydrothermal treatment in the concentrated CaHPO4 and Ca(H2PO4)2 solutions for bioactive surface modification. The treated samples are covered by films composed of fine grains (~70 nm) and large particles (100-250 nm). XPS analysis shows that Ti at the surface presents as TiO2, Ni is not detectable, and Ca and P are in the form of calcium phosphate. X-ray diffraction peaks of anatase TiO2 and hydroxyapatite are present for the treated samples. Potentiodynamic polarization test in a Ca-free Hank’s balanced solution reveals that the treated sample has markedly improved corrosion resistance compared with the polished sample. The present work would provide a one-step bioactive surface modification method that is easily-operated, low-temperatured, less corrosive, and potentially suitable for biomedical porous NiTi alloy.
2016, 45(5):1132-1137.
Abstract:
Fatigue fracture is a common failure mode for dissimilar materials friction welding components. To reduce the major accidents caused by sudden fracture of friction welding parts, the paper discussed the feasibility of the combined usage of electric resistance (ER), infrared thermograph (IRT) and acoustic emission (AE) to monitor the critical fatigue damage from the perspectives of energy dissipation and micro defects evolution. The study found that three kinds of signal could be acquired synchronously. They are non-interfering and mutual support. After entering the critical fracture stage, there is a good mapping relationship between ER and the AE ampjavascript:EditorCenter();litude and energy for the specimens of abnormal and normal fracture. They all can be regarded as the parameters of monitoring critical failure. Although IRT is usually used to predict the fatigue limit of materials, but the rapid temperature rising stage may not always be obvious near the fracture. Compared with the single signal monitoring, multi- information fusion has the higher credibility, which is beneficial to increase the service safety and reliability of friction welding parts.
Fatigue fracture is a common failure mode for dissimilar materials friction welding components. To reduce the major accidents caused by sudden fracture of friction welding parts, the paper discussed the feasibility of the combined usage of electric resistance (ER), infrared thermograph (IRT) and acoustic emission (AE) to monitor the critical fatigue damage from the perspectives of energy dissipation and micro defects evolution. The study found that three kinds of signal could be acquired synchronously. They are non-interfering and mutual support. After entering the critical fracture stage, there is a good mapping relationship between ER and the AE ampjavascript:EditorCenter();litude and energy for the specimens of abnormal and normal fracture. They all can be regarded as the parameters of monitoring critical failure. Although IRT is usually used to predict the fatigue limit of materials, but the rapid temperature rising stage may not always be obvious near the fracture. Compared with the single signal monitoring, multi- information fusion has the higher credibility, which is beneficial to increase the service safety and reliability of friction welding parts.
2016, 45(5):1138-1141.
Abstract:
Ti-5Al-5Mo-5V-1Fe-1Cr Ti alloy is fabricated via consumable vacuum arc-remelting furnace in this work, and then is subjected to thermo-mechanical processing and heat treatment. The microstructural characteristics and tensile properties of the heat-treated material are investigated. Primary α dispersing in β phase shows as spheroidization, near equiaxed, plate-shaped and rod-shaped after heat treatment. This is associated with boundary segregation of α grain. The material has a good combination of strength and plasticity during tensile test. However, the value of σy /σb of the material reaches 0.95. It is suggested that the grain boundary absorb dislocations during tensile test. Therefore, the dislocation strengthening increases very slowly. This is the primary reason for the material to obtain high value of σy /σb.
Ti-5Al-5Mo-5V-1Fe-1Cr Ti alloy is fabricated via consumable vacuum arc-remelting furnace in this work, and then is subjected to thermo-mechanical processing and heat treatment. The microstructural characteristics and tensile properties of the heat-treated material are investigated. Primary α dispersing in β phase shows as spheroidization, near equiaxed, plate-shaped and rod-shaped after heat treatment. This is associated with boundary segregation of α grain. The material has a good combination of strength and plasticity during tensile test. However, the value of σy /σb of the material reaches 0.95. It is suggested that the grain boundary absorb dislocations during tensile test. Therefore, the dislocation strengthening increases very slowly. This is the primary reason for the material to obtain high value of σy /σb.
2016, 45(5):1142-1146.
Abstract:
During the manufacturing of Al-based thin films for electronic applications, a post-deposition annealing is required in order to achieve a lower resistivity. However, the electrical transportation behavior of the magnetron sputtering Al film has been rarely investigated. To address this objective, we have explored the microstructure of the film before and after annealing with emphasis on the structural features related to diffusion and interface using TEM observation. Hall-effect measurement was employed to determine the variation of carrier density and mobility brought by the evolution originating at the interface. The results demonstrate that during annealing an intimate contact was formed between the film and substrate via diffusion, leading to a combination of high mobility and high density. Furthermore, a model was proposed from the aspect of energy bands in order to explain the positive effect of the interface phenomenon upon electron conductivity.
During the manufacturing of Al-based thin films for electronic applications, a post-deposition annealing is required in order to achieve a lower resistivity. However, the electrical transportation behavior of the magnetron sputtering Al film has been rarely investigated. To address this objective, we have explored the microstructure of the film before and after annealing with emphasis on the structural features related to diffusion and interface using TEM observation. Hall-effect measurement was employed to determine the variation of carrier density and mobility brought by the evolution originating at the interface. The results demonstrate that during annealing an intimate contact was formed between the film and substrate via diffusion, leading to a combination of high mobility and high density. Furthermore, a model was proposed from the aspect of energy bands in order to explain the positive effect of the interface phenomenon upon electron conductivity.
2016, 45(5):1147-1151.
Abstract:
This paper investigates the directional migration behavior of the element in the rafting process of the single crystal superalloy DD6 with [001] orientation under 300 MPa at 1000 °C. The microstructure of the single crystal superalloy DD6 is acquired by SEM. The results indicate that the rafting direction of γ′ phase is nearly perpendicular to stress axis. The matrix channel running parallel to the stress axis gets wider, but it will tend to fade away in vertical. Statistical analysis of the alloy components by TEM shows the directional migrations of the elements Al, Re and W in the single crystal superalloy DD6. The element Al spreads to the matrix channel which is parallel to the stress axis, while Re and W diffuse to the matrix channel which is perpendicular to the stress axis.
This paper investigates the directional migration behavior of the element in the rafting process of the single crystal superalloy DD6 with [001] orientation under 300 MPa at 1000 °C. The microstructure of the single crystal superalloy DD6 is acquired by SEM. The results indicate that the rafting direction of γ′ phase is nearly perpendicular to stress axis. The matrix channel running parallel to the stress axis gets wider, but it will tend to fade away in vertical. Statistical analysis of the alloy components by TEM shows the directional migrations of the elements Al, Re and W in the single crystal superalloy DD6. The element Al spreads to the matrix channel which is parallel to the stress axis, while Re and W diffuse to the matrix channel which is perpendicular to the stress axis.
2016, 45(5):1152-1156.
Abstract:
In this paper, the laser brazing of diamond abrasives using Ni-based solders in an Ar atmosphere was investigated. The microstructure and phase composition of interfaces between diamond abrasives and Ni-based solders were analyzed using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Meanwhile, the formation mechanism of carbides at interfaces between solders and diamond abrasives was discussed. The results indicate that during laser brazing, the Cr-enriched layer around the diamond surface reacts with the C in the diamond surface and consequently forms Cr3C2. Based on reaction thermodynamics and kinetics analysis, it is revealed that the interface reaction products can be formed via replacement reactions, which realizes the tight combination between diamond abrasives and solders.
In this paper, the laser brazing of diamond abrasives using Ni-based solders in an Ar atmosphere was investigated. The microstructure and phase composition of interfaces between diamond abrasives and Ni-based solders were analyzed using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Meanwhile, the formation mechanism of carbides at interfaces between solders and diamond abrasives was discussed. The results indicate that during laser brazing, the Cr-enriched layer around the diamond surface reacts with the C in the diamond surface and consequently forms Cr3C2. Based on reaction thermodynamics and kinetics analysis, it is revealed that the interface reaction products can be formed via replacement reactions, which realizes the tight combination between diamond abrasives and solders.
2016, 45(5):1157-1161.
Abstract:
Ball milling process has an important effect on the microstructure of final powder products and the corresponding as-sintered samples. In this study, Ti-Al-0.2B wt.% mixed powders were ball-milled by low-energy and high-energy types of ball mills, and then the milled powders were sintered by hot- pressing. On this basis, morphology evolution of the powders was analyzed, and the microstructure of the reinforcements in the as-sintered composites was investigated. In the low-energy ball milling process, mechanical alloying was occurred between the powder particles. TiB whiskers formed in sintering process were long and thin without coarse bars or clusters. For the high-energy type, the particle size was refined remarkably to 1um, and Ti (Al) supersaturated solid solution or even amorphous structure was formed during the milling process. In the following sintering process, nano-scale TiB whiskers were synthesized and they were uniformly distributed in the matrix.
Ball milling process has an important effect on the microstructure of final powder products and the corresponding as-sintered samples. In this study, Ti-Al-0.2B wt.% mixed powders were ball-milled by low-energy and high-energy types of ball mills, and then the milled powders were sintered by hot- pressing. On this basis, morphology evolution of the powders was analyzed, and the microstructure of the reinforcements in the as-sintered composites was investigated. In the low-energy ball milling process, mechanical alloying was occurred between the powder particles. TiB whiskers formed in sintering process were long and thin without coarse bars or clusters. For the high-energy type, the particle size was refined remarkably to 1um, and Ti (Al) supersaturated solid solution or even amorphous structure was formed during the milling process. In the following sintering process, nano-scale TiB whiskers were synthesized and they were uniformly distributed in the matrix.
2016, 45(5):1162-1167.
Abstract:
The effect of aging treatment on the microstructure and properties of Cu-3Ti-3Ni alloy was studied. The microstructure and precipitated phase were characterized by X-ray diffractometer, scanning electron microscope and transmission electron microscope, and the hardness, electrical conductivity and elastic modulus were measured as well. The results show that a number of Ni3Ti and β'-Cu4Ti phase precipitate from the Cu matrix after aging treatment. With increase of secondary aging time, the partial alloying elements dissolve into the Cu matrix and the metastable Cu4Ti phase transform into incoherent equilibrium Cu3Ti phase. The enhanced electrical conductivity is ascribed to the decrease of Ti solubility in the Cu matrix by the formation of the Ni3Ti and β'-Cu4Ti precipitates. After an appropriate aging treatment of Cu-3Ti-3Ni alloy, the Ni3Ti and coherent metastable β'-Cu4Ti phase precipitate completely, giving rise to the increase of hardness. Aging treatment has no obvious effect on the elastic modulus of Cu-3Ti-3Ni alloy. In the range of the experiments, the optimal two-step aging treatment for Cu-3Ti-3Ni alloy is at 300°C for 2 h and 450 °C for 7 h. The hardness, electrical conductivity and elastic modulus are 183 HV, 31.34 %IACS (International Annealed Copper Standard) and 148.62 GPa, respectively.
The effect of aging treatment on the microstructure and properties of Cu-3Ti-3Ni alloy was studied. The microstructure and precipitated phase were characterized by X-ray diffractometer, scanning electron microscope and transmission electron microscope, and the hardness, electrical conductivity and elastic modulus were measured as well. The results show that a number of Ni3Ti and β'-Cu4Ti phase precipitate from the Cu matrix after aging treatment. With increase of secondary aging time, the partial alloying elements dissolve into the Cu matrix and the metastable Cu4Ti phase transform into incoherent equilibrium Cu3Ti phase. The enhanced electrical conductivity is ascribed to the decrease of Ti solubility in the Cu matrix by the formation of the Ni3Ti and β'-Cu4Ti precipitates. After an appropriate aging treatment of Cu-3Ti-3Ni alloy, the Ni3Ti and coherent metastable β'-Cu4Ti phase precipitate completely, giving rise to the increase of hardness. Aging treatment has no obvious effect on the elastic modulus of Cu-3Ti-3Ni alloy. In the range of the experiments, the optimal two-step aging treatment for Cu-3Ti-3Ni alloy is at 300°C for 2 h and 450 °C for 7 h. The hardness, electrical conductivity and elastic modulus are 183 HV, 31.34 %IACS (International Annealed Copper Standard) and 148.62 GPa, respectively.
2016, 45(5):1168-1174.
Abstract:
The experiments of asymmetric and symmetric hot rolling were carried out to investigate the role of asymmetric hot rolling on microstructure and mechanical properties of titanium alloy by showing metallographic microstructure, mechanical property, fracture morphology and microscopic orientation. The results demonstrate that complex strain path is prior to monotonic strain path for refining grain and improving simultaneously the values of strength and ductility, and the grain size in asymmetric rolled specimen surface is smaller than that in specimen center. Asymmetric hot rolling could refine grain compared with symmetric hot rolling. The values of strength and ductility of asymmetric rolled specimen is higher than that of symmetric rolled specimen, and the values of strength and ductility increase with the development of roll speed ratio. The plastic deformation mechanism of asymmetric rolled specimen may be slip. While, the one of symmetric rolled specimen are twin and slip.
The experiments of asymmetric and symmetric hot rolling were carried out to investigate the role of asymmetric hot rolling on microstructure and mechanical properties of titanium alloy by showing metallographic microstructure, mechanical property, fracture morphology and microscopic orientation. The results demonstrate that complex strain path is prior to monotonic strain path for refining grain and improving simultaneously the values of strength and ductility, and the grain size in asymmetric rolled specimen surface is smaller than that in specimen center. Asymmetric hot rolling could refine grain compared with symmetric hot rolling. The values of strength and ductility of asymmetric rolled specimen is higher than that of symmetric rolled specimen, and the values of strength and ductility increase with the development of roll speed ratio. The plastic deformation mechanism of asymmetric rolled specimen may be slip. While, the one of symmetric rolled specimen are twin and slip.
16 Mathematical Model of Coupled Thermal-stress about AZ31B Magnesium Alloy Plate during Hot Rolling
2016, 45(5):1175-1181.
Abstract:
Under a wide range of deformation conditions, hot compression tests of AZ31B magnesium alloy cast cylinder were carried by Gleeble-1500D thermal simulator. According to the strain softening characteristics of magnesium alloy, a new thermal deformation constitutive model was established. Relying on Deform-3D, the coupled thermal-stress simulation of hot rolling process of magnesium plate was analyzed. Based on the rolling theoretical assumptions, macroscopic continuum mechanics and thermodynamics, strain and strain rate value distribution models, three-dimensional temperature field and stress field mathematical models in rolling deformation zone were established by mathematical analysis method. The results showed that the new thermal constitutive model was in a higher accuracy and the average relative error was 5.1%.Strain distribution model, strain rate value distribution model, mathematical model of temperature field and mathematical model of stress field were not only concise in form and easy to be controlled online, but also could accurately characterize thermal-mechanical coupled deformation mechanism of hot rolling of magnesium plate.
Under a wide range of deformation conditions, hot compression tests of AZ31B magnesium alloy cast cylinder were carried by Gleeble-1500D thermal simulator. According to the strain softening characteristics of magnesium alloy, a new thermal deformation constitutive model was established. Relying on Deform-3D, the coupled thermal-stress simulation of hot rolling process of magnesium plate was analyzed. Based on the rolling theoretical assumptions, macroscopic continuum mechanics and thermodynamics, strain and strain rate value distribution models, three-dimensional temperature field and stress field mathematical models in rolling deformation zone were established by mathematical analysis method. The results showed that the new thermal constitutive model was in a higher accuracy and the average relative error was 5.1%.Strain distribution model, strain rate value distribution model, mathematical model of temperature field and mathematical model of stress field were not only concise in form and easy to be controlled online, but also could accurately characterize thermal-mechanical coupled deformation mechanism of hot rolling of magnesium plate.
2016, 45(5):1182-1188.
Abstract:
Possible geometrical structure, relative stabilities of Mg3N2Hm(m=1-4) and (Mg3N2)nHm(n=2-4,m=1-2) clusters are studied by using the density functional theory (B3LYP) with 6-311G* basis sets. For the most stable isomers of Mg3N2Hm(m=1-4) and (Mg3N2)nHm (n=2-4,m=1-2) clusters, the electronic structure,bonding characteristics, charge distribution, vibrational properties and relative stabilities are analyzed. When the number of the adsorbed H atoms less than that of N atoms, it mainly forms -NH group. And then some H atoms are adsorbed by the -NH groups and it forms -NH2 groups while some other H atoms are adsorbed by Mg forming MgH when all the N atoms bond as -NH. H atom is easialy adsorped on N atom which is projecting and contains the lone pair electrons. Due to the repulsion between the lone pair electrons, the adsorption positions of H atoms were away from each other. The N-H in cluster showed covalent interaction, where the Mg-H showed ionic bond interaction. The properties of-NH and -NH2 group are consistent with that of crystals, so the cluster can describe the behavior of the hydrogen storage in crystals.
Possible geometrical structure, relative stabilities of Mg3N2Hm(m=1-4) and (Mg3N2)nHm(n=2-4,m=1-2) clusters are studied by using the density functional theory (B3LYP) with 6-311G* basis sets. For the most stable isomers of Mg3N2Hm(m=1-4) and (Mg3N2)nHm (n=2-4,m=1-2) clusters, the electronic structure,bonding characteristics, charge distribution, vibrational properties and relative stabilities are analyzed. When the number of the adsorbed H atoms less than that of N atoms, it mainly forms -NH group. And then some H atoms are adsorbed by the -NH groups and it forms -NH2 groups while some other H atoms are adsorbed by Mg forming MgH when all the N atoms bond as -NH. H atom is easialy adsorped on N atom which is projecting and contains the lone pair electrons. Due to the repulsion between the lone pair electrons, the adsorption positions of H atoms were away from each other. The N-H in cluster showed covalent interaction, where the Mg-H showed ionic bond interaction. The properties of-NH and -NH2 group are consistent with that of crystals, so the cluster can describe the behavior of the hydrogen storage in crystals.
2016, 45(5):1189-1195.
Abstract:
The perforated parts of damage tolerant titanium alloy TC21 in rear fuselage frame were easy to prematurely suffer fatigue crack in the service process. With the purpose of resolving the problem mentioned above, different expansion degrees were applied to the hole of plate specimens of TC21 in the split sleeve cold expansion experiment。The effect of expansion degree to fatigue life was achieved in the fatigue tests. By the method of 3D finite element simulation, the distribution regularity of residual stress was obtained around the hole after cold expansion. The surface feature of fatigue fracture has been observed and analyzed from macroscopic aspect and microscopic aspect with different expansion degree. The examination of fractured sections show that cold expansion can change fatigue crack initiation position around the hole surface, and extend the fatigue crack propagation life under cyclic loading. It was further show that fatigue life increase as expansion degree, furthermore, the fatigue life is increased more than 50%.
The perforated parts of damage tolerant titanium alloy TC21 in rear fuselage frame were easy to prematurely suffer fatigue crack in the service process. With the purpose of resolving the problem mentioned above, different expansion degrees were applied to the hole of plate specimens of TC21 in the split sleeve cold expansion experiment。The effect of expansion degree to fatigue life was achieved in the fatigue tests. By the method of 3D finite element simulation, the distribution regularity of residual stress was obtained around the hole after cold expansion. The surface feature of fatigue fracture has been observed and analyzed from macroscopic aspect and microscopic aspect with different expansion degree. The examination of fractured sections show that cold expansion can change fatigue crack initiation position around the hole surface, and extend the fatigue crack propagation life under cyclic loading. It was further show that fatigue life increase as expansion degree, furthermore, the fatigue life is increased more than 50%.
2016, 45(5):1196-1203.
Abstract:
The mechanical anisotropy and inhomogeneity through thickness of 2297-T87 aluminum alloy thick plate of 85 mm were investigated by tensile test, optical microscopy, X ray diffractometry, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that the mechanical properties in L orientation is inhomogeneous in different layers along the thickness direction, that the strength increases from the surface to the center. The difference of LT orientation is not significant, however. Meanwhile the texture distributes nonuniformly through thickness. The centre of the plate is mainly β fiber texture and Goss texture, while besides deformation texture, the recrystallization texture is observed near the surface. In the T/8 layer, the fraction of the shear texture is maximum. The T/4 layer seems to serve as a transition layer, presenting a small amount of the recrystallization texture, shear texture and β fiber texture at the same time. At the same thickness, the anisotropy of mechanical properties is obvious. There is reasonable concordance between changes of the strength and plasticity: L>LT>ST. The anisotropy is associated with the grain structure and the second phase particles.
The mechanical anisotropy and inhomogeneity through thickness of 2297-T87 aluminum alloy thick plate of 85 mm were investigated by tensile test, optical microscopy, X ray diffractometry, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that the mechanical properties in L orientation is inhomogeneous in different layers along the thickness direction, that the strength increases from the surface to the center. The difference of LT orientation is not significant, however. Meanwhile the texture distributes nonuniformly through thickness. The centre of the plate is mainly β fiber texture and Goss texture, while besides deformation texture, the recrystallization texture is observed near the surface. In the T/8 layer, the fraction of the shear texture is maximum. The T/4 layer seems to serve as a transition layer, presenting a small amount of the recrystallization texture, shear texture and β fiber texture at the same time. At the same thickness, the anisotropy of mechanical properties is obvious. There is reasonable concordance between changes of the strength and plasticity: L>LT>ST. The anisotropy is associated with the grain structure and the second phase particles.
2016, 45(5):1203-1208.
Abstract:
The typical characteristics of S-N curve and the fracture surface in very high cycle fatigue regime were analyzed in this paper. The fatigue lifetime prediction models based on crack growth and dislocation theory were introduced. On the basis of the numerical data of previous researches on very high cycle fatigue, the prediction errors of the two modes were analyzed. The results indicate that the model based on dislocation theory has better prediction ability. The prediction accuracy decreases with the increment of fatigue lifetime. That is to say, the fatigue crack initiation consumes the main fraction of total life. Finally, some possible and prospective topics of future researches on fatigue lifetime prediction in very high cycle fatigue regime are proposed: the competing failure mechanism of surface/internal fatigue fracture modes, the lifetime prediction in very high cycle fatigue regime based on statistical methods by establishing large samples data.
The typical characteristics of S-N curve and the fracture surface in very high cycle fatigue regime were analyzed in this paper. The fatigue lifetime prediction models based on crack growth and dislocation theory were introduced. On the basis of the numerical data of previous researches on very high cycle fatigue, the prediction errors of the two modes were analyzed. The results indicate that the model based on dislocation theory has better prediction ability. The prediction accuracy decreases with the increment of fatigue lifetime. That is to say, the fatigue crack initiation consumes the main fraction of total life. Finally, some possible and prospective topics of future researches on fatigue lifetime prediction in very high cycle fatigue regime are proposed: the competing failure mechanism of surface/internal fatigue fracture modes, the lifetime prediction in very high cycle fatigue regime based on statistical methods by establishing large samples data.
2016, 45(5):1209-1214.
Abstract:
(Ti,Al)N thin films were prepared under different Ti/Al mosaic target(30%Al、50%Al、70%Al) by multi-arc ion plating technology which is in hollow cathode electron beam assisted deposition situation.The quality and properties were detected by XRD、CLSM and universal nano/micro material tester.The effects of Ti/Al target on phase composition 、surface roughness、friction coefficient、hardness and oxidation resistance were analyzed.The results show that coatings produced by 50%Al target give priority to Ti1-xAlxN phase composition and show minimum surface roughness(0.3188), friction coefficient(0.6074), maximum hardness (34.19GPa).The coating show no obvious change on phase composition when heating temperature lower than 800℃. At 900℃ substrate is oxidized due to the coating cracks. "hybrid interface" can form when hollow cathode electron beam assisted deposition,and “surface roughness” can also be reduced under this condition.
(Ti,Al)N thin films were prepared under different Ti/Al mosaic target(30%Al、50%Al、70%Al) by multi-arc ion plating technology which is in hollow cathode electron beam assisted deposition situation.The quality and properties were detected by XRD、CLSM and universal nano/micro material tester.The effects of Ti/Al target on phase composition 、surface roughness、friction coefficient、hardness and oxidation resistance were analyzed.The results show that coatings produced by 50%Al target give priority to Ti1-xAlxN phase composition and show minimum surface roughness(0.3188), friction coefficient(0.6074), maximum hardness (34.19GPa).The coating show no obvious change on phase composition when heating temperature lower than 800℃. At 900℃ substrate is oxidized due to the coating cracks. "hybrid interface" can form when hollow cathode electron beam assisted deposition,and “surface roughness” can also be reduced under this condition.
2016, 45(5):1215-1219.
Abstract:
A sample of K465 nickel-base superalloy was prepared by laser solid forming (LSF) technology. The microstructure evolution of grains, γ′ phase and carbides was investigated. It is found that the central region of the sample consists of coarse grains, while the top edge of the sample consists of fine grains. Dendrites in the sample present apparent epitaxial growth along the deposition direction, but the vergens dendrites appear occasionally at the top of several cladding layers near the bottom of the sample due to the inadequate remelting depth. The γ′ particles at the junction of adjacent cladding layers are larger than that inside the layers, and the interdendritic γ′ phase is larger than that at the core of dendrites. MC carbides present variable morphology in the sample, that is, flowerlike at the bottom, short rod-like in the middle and octahedral at the top.
A sample of K465 nickel-base superalloy was prepared by laser solid forming (LSF) technology. The microstructure evolution of grains, γ′ phase and carbides was investigated. It is found that the central region of the sample consists of coarse grains, while the top edge of the sample consists of fine grains. Dendrites in the sample present apparent epitaxial growth along the deposition direction, but the vergens dendrites appear occasionally at the top of several cladding layers near the bottom of the sample due to the inadequate remelting depth. The γ′ particles at the junction of adjacent cladding layers are larger than that inside the layers, and the interdendritic γ′ phase is larger than that at the core of dendrites. MC carbides present variable morphology in the sample, that is, flowerlike at the bottom, short rod-like in the middle and octahedral at the top.
2016, 45(5):1220-1224.
Abstract:
The microscopic phase-field method was employed to study the antisite defect in Al-9.0at%Li alloys with aged time and tempture. At the same aged tempture, the antistie defect AlLi and LiAl in Al3Li phase which is L12 structure gradually reduced as the aged time wore on. Under Al-rich condition, the concentration of AlLi antisite defect was higher than the the concentration of LiAl antisite defect. In Al3Li phase, the antistie defect was mainly about AlLi, and with a few of LiAl. Then the aging temperature changed, after Al3Li phase nucleation stable, with the tempture higher, the concentration of AlLi and LiAl antistie defect were higher. Also had the characteristics before the nucleation stable, but the regularity was not remarkable.
The microscopic phase-field method was employed to study the antisite defect in Al-9.0at%Li alloys with aged time and tempture. At the same aged tempture, the antistie defect AlLi and LiAl in Al3Li phase which is L12 structure gradually reduced as the aged time wore on. Under Al-rich condition, the concentration of AlLi antisite defect was higher than the the concentration of LiAl antisite defect. In Al3Li phase, the antistie defect was mainly about AlLi, and with a few of LiAl. Then the aging temperature changed, after Al3Li phase nucleation stable, with the tempture higher, the concentration of AlLi and LiAl antistie defect were higher. Also had the characteristics before the nucleation stable, but the regularity was not remarkable.
2016, 45(5):1225-1229.
Abstract:
The recrystallization of powder metallurgy superalloy FGH96 undergoes three characteristic periods, viz., incubation, nucleation and growth period. The recrystallization behavior is sensitive to annealing temperature. When the temperature is 1050℃, there is lots of nucleation at the previous particle boundaries. The nucleation grow up and the fine equiaxed grains are obtained when the temperature is 1080℃. However, the equiaxed grains would be significantly getting coarse when the temperature is1110℃. Recrystallization usually takes place at previous particle boundaries during hot deformation process. When the deformation is not enough, a typically incomplete recrystallization microstructure, named the necklace microstructure, will be obtained. The necklace microstructure has fine equiaxed grains inlayed in non-equiaxed coarse grains surronding. Meanwhile, it is also the intermediate microstructure during the refinement processing of the PM materials. Both the severe total deformation and multiple deformation direction are favorable for grain refinement.
The recrystallization of powder metallurgy superalloy FGH96 undergoes three characteristic periods, viz., incubation, nucleation and growth period. The recrystallization behavior is sensitive to annealing temperature. When the temperature is 1050℃, there is lots of nucleation at the previous particle boundaries. The nucleation grow up and the fine equiaxed grains are obtained when the temperature is 1080℃. However, the equiaxed grains would be significantly getting coarse when the temperature is1110℃. Recrystallization usually takes place at previous particle boundaries during hot deformation process. When the deformation is not enough, a typically incomplete recrystallization microstructure, named the necklace microstructure, will be obtained. The necklace microstructure has fine equiaxed grains inlayed in non-equiaxed coarse grains surronding. Meanwhile, it is also the intermediate microstructure during the refinement processing of the PM materials. Both the severe total deformation and multiple deformation direction are favorable for grain refinement.
2016, 45(5):1230-1234.
Abstract:
Effects of laser peening and shot peening on fatigue performance of the powder metallurgy nickel-based FGH97 superalloy were investigated. Compressive residual stresses in the surface layer were analyzed by the X-ray diffraction stress analyse tester. The rotating bending fatigue test at 650℃ was used to compare the surface enhancement effects between laser peening and shot peening. Moveover, the fatigue fracture characteristics were analyzed by scanning electron microscope. The results showed that both laser peening and shot peening can improve the fatigue property of FGH97, but laser peening had much better surface enhance effect than shot peening due to deeper compressive residual stress layer and good surface roughness, and the compressive residual stresses induced by laser peening were more stable than ones by shot peening under fatigue process at high temperature. Furthermore, the fatigue crack sources of both laser peened and shot peened speciemens initiated subsurface, while untreated at the surface.
Effects of laser peening and shot peening on fatigue performance of the powder metallurgy nickel-based FGH97 superalloy were investigated. Compressive residual stresses in the surface layer were analyzed by the X-ray diffraction stress analyse tester. The rotating bending fatigue test at 650℃ was used to compare the surface enhancement effects between laser peening and shot peening. Moveover, the fatigue fracture characteristics were analyzed by scanning electron microscope. The results showed that both laser peening and shot peening can improve the fatigue property of FGH97, but laser peening had much better surface enhance effect than shot peening due to deeper compressive residual stress layer and good surface roughness, and the compressive residual stresses induced by laser peening were more stable than ones by shot peening under fatigue process at high temperature. Furthermore, the fatigue crack sources of both laser peened and shot peened speciemens initiated subsurface, while untreated at the surface.
26 Research on defomation and fracture of Ni-Ti shape memory alloys under the penetration of pojectiles
2016, 45(5):1235-1239.
Abstract:
Damage and fracture of Ni-Ti plate during high velocity impact have been investigated in this paper.The deformation microstructures have been studied by optical microscope.The results indicate that stress induced martensitic phase transformation (SIM) in Ni-Ti plate matrix for Austenite phase in the process of penetration.Defomation and fracture of Ni-Ti plate due to shearing band and micro-crack nucleated in interface with fracture mechanisms of microvoid nucleation, growth and coalescence.
Damage and fracture of Ni-Ti plate during high velocity impact have been investigated in this paper.The deformation microstructures have been studied by optical microscope.The results indicate that stress induced martensitic phase transformation (SIM) in Ni-Ti plate matrix for Austenite phase in the process of penetration.Defomation and fracture of Ni-Ti plate due to shearing band and micro-crack nucleated in interface with fracture mechanisms of microvoid nucleation, growth and coalescence.
2016, 45(5):1240-1244.
Abstract:
The isothermal section of the Zr-Cr-Cu ternary system at 700 ℃ was investigated by using X-ray diffraction, scanning electron microscope and energy dispersive analysis. It was composed of 10 single-phase regions, 18 two-phase regions and 9 three-phase regions. The τ phase was observed to occur as a stable ternary phase at 700 ℃ when Cr was introduced. No ternary compound was observed in the Zr-rich corner and Cu-rich corner. The alloys in Zr-rich corner was consists of ZrCr2, (α-Zr) and CuZr2, while those in the Cu-rich corner was consists of (Cr), (Cu) and Cu5Zr.
The isothermal section of the Zr-Cr-Cu ternary system at 700 ℃ was investigated by using X-ray diffraction, scanning electron microscope and energy dispersive analysis. It was composed of 10 single-phase regions, 18 two-phase regions and 9 three-phase regions. The τ phase was observed to occur as a stable ternary phase at 700 ℃ when Cr was introduced. No ternary compound was observed in the Zr-rich corner and Cu-rich corner. The alloys in Zr-rich corner was consists of ZrCr2, (α-Zr) and CuZr2, while those in the Cu-rich corner was consists of (Cr), (Cu) and Cu5Zr.
2016, 45(5):1245-1248.
Abstract:
The microstructure of as-cast Mg97Zn1Y2 with or without solid solution treatment was analysised by OM and SEM.Meanwhile, phase analysis was carried out by EDS and XRD. After solid solution treatment, LPSO phase grow up,turning into continuous distribution in Mg97Zn1Y2.Through damping testing, it was found that the damping capacity of Mg97Zn1Y2 was declined after solid solution treatment.The damping-temperture specturm of the as-cast Mg97Zn1Y2 with or without solid solution treatment was also analysised. There are two internal friction peaks:damping peak P1 located between 150 ℃ and 250 ℃ and the peak is very wide, which is caused by the dislocation mechanism.Meanwhile, the damping peak P2 is near the 350-500 ℃, which is preliminary considered as grain boundary internal friction peak.
The microstructure of as-cast Mg97Zn1Y2 with or without solid solution treatment was analysised by OM and SEM.Meanwhile, phase analysis was carried out by EDS and XRD. After solid solution treatment, LPSO phase grow up,turning into continuous distribution in Mg97Zn1Y2.Through damping testing, it was found that the damping capacity of Mg97Zn1Y2 was declined after solid solution treatment.The damping-temperture specturm of the as-cast Mg97Zn1Y2 with or without solid solution treatment was also analysised. There are two internal friction peaks:damping peak P1 located between 150 ℃ and 250 ℃ and the peak is very wide, which is caused by the dislocation mechanism.Meanwhile, the damping peak P2 is near the 350-500 ℃, which is preliminary considered as grain boundary internal friction peak.
2016, 45(5):1249-1252.
Abstract:
Multiferroic ceramics 0.7BiFeO3-0.2PbTiO3-0.1BaTiO3 (abbreviated as BF-BT-PT) was prepared by high temperature solid state method. The dielectric, piezoelectric properties and the aging behaviors were investigated. The results suggested that BF-PT-BT ceramics was a high potential lead-reduced high-temperature piezoceramics with excellent properties including the dielectric constant =390, =0.015, the piezoelectric coefficient of d33 ~100pC/N, the Curie temperature of Tc~600oC, good stability with the thermal depoling temperature of Td ~500oC. The primary thermal depoling mechanism was the decrease of remnant polarization, associated with the pinching effect on domain walls of low density oxygen vacancy defects.
Multiferroic ceramics 0.7BiFeO3-0.2PbTiO3-0.1BaTiO3 (abbreviated as BF-BT-PT) was prepared by high temperature solid state method. The dielectric, piezoelectric properties and the aging behaviors were investigated. The results suggested that BF-PT-BT ceramics was a high potential lead-reduced high-temperature piezoceramics with excellent properties including the dielectric constant =390, =0.015, the piezoelectric coefficient of d33 ~100pC/N, the Curie temperature of Tc~600oC, good stability with the thermal depoling temperature of Td ~500oC. The primary thermal depoling mechanism was the decrease of remnant polarization, associated with the pinching effect on domain walls of low density oxygen vacancy defects.
2016, 45(5):1253-1256.
Abstract:
The distribution of P and its effects on the mechanical properties of DD6 alloy were studied in the paper. When P contents were exceed 0.1%, Cr, Nb and Mo were segregated together while Al was rare in the region of P segregation. The region without gamma prime was formed around the region of P segregation. When the content of P was 0.01%, they were segregated in the ruptured interface although O, P and S were the rare elements. The segregatation of P greatlyll degenerated the interfacial strength. The stress-rupture properties and tensile properties were pronounced degenerated with the increments of P.
The distribution of P and its effects on the mechanical properties of DD6 alloy were studied in the paper. When P contents were exceed 0.1%, Cr, Nb and Mo were segregated together while Al was rare in the region of P segregation. The region without gamma prime was formed around the region of P segregation. When the content of P was 0.01%, they were segregated in the ruptured interface although O, P and S were the rare elements. The segregatation of P greatlyll degenerated the interfacial strength. The stress-rupture properties and tensile properties were pronounced degenerated with the increments of P.
2016, 45(5):1320-1324.
Abstract:
The (Ti, Al, Zr) N/(Ti, Al, Zr, Cr) N and CrN/(Ti, Al, Zr, Cr) N four-component bilayer nitride films were deposited on cemented carbide (WC-8 %CO) substrates by multi-arc ion plating technique using the combined Ti-Al-Zr alloy and pure Cr targets. The morphology, composition and crystalline structure of two bilayer films were analyzed by scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Scratch test and Vickers microindentation were used to compare the mechanical properties of two bilayer films. It is shown that the two prepared bilayer films are still the TiN (B1-NaCl) face-centered cubic structure. The cross-sectional morphologies reveal the typical columnar crystal structures. As the bias voltages vary from -50 to -200V, the mechanical properties of two bilayer films are better than those of the (Ti, Al, Zr, Cr) N monolayer films and almost close to those of the Ti-Al-Zr-Cr-N gradient films. The microhardness of the (Ti, Al, Zr) N/(Ti, Al, Zr, Cr) N bilayer film is more excellent than that of the CrN/(Ti, Al, Zr, Cr) N film (max. Hv0.01 4100). However, the adhesive strength of the CrN/(Ti, Al, Zr, Cr) N bilayer film is superior to that of the (Ti, Al, Zr) N/(Ti, Al, Zr, Cr) N film (all > 200 N).
The (Ti, Al, Zr) N/(Ti, Al, Zr, Cr) N and CrN/(Ti, Al, Zr, Cr) N four-component bilayer nitride films were deposited on cemented carbide (WC-8 %CO) substrates by multi-arc ion plating technique using the combined Ti-Al-Zr alloy and pure Cr targets. The morphology, composition and crystalline structure of two bilayer films were analyzed by scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Scratch test and Vickers microindentation were used to compare the mechanical properties of two bilayer films. It is shown that the two prepared bilayer films are still the TiN (B1-NaCl) face-centered cubic structure. The cross-sectional morphologies reveal the typical columnar crystal structures. As the bias voltages vary from -50 to -200V, the mechanical properties of two bilayer films are better than those of the (Ti, Al, Zr, Cr) N monolayer films and almost close to those of the Ti-Al-Zr-Cr-N gradient films. The microhardness of the (Ti, Al, Zr) N/(Ti, Al, Zr, Cr) N bilayer film is more excellent than that of the CrN/(Ti, Al, Zr, Cr) N film (max. Hv0.01 4100). However, the adhesive strength of the CrN/(Ti, Al, Zr, Cr) N bilayer film is superior to that of the (Ti, Al, Zr) N/(Ti, Al, Zr, Cr) N film (all > 200 N).
2016, 45(5):1257-1263.
Abstract:
Thick gold material was fabricated in cyanide-free chloroauric acid solution by bipolar pulse reverse technique, influence of forward and reverse current density and duty cycle on the morphology and microstructure of gold deposits were studied and discussed. Results showed that when forward current density increased from 2.25 A/dm2 to 3.75A/ dm2, grain sizes became smaller and gold particles stacked more compact, but overhigh forward current density lead to surface fluctuation and decreasing of gold deposits flatness; While when reverse current density increased from 6 A/ dm2 to 12A/ dm2, grains became larger and structure loosen. Cathodic overpotential would increase when forward duty cycle increased from 20% to 60%, thus refining the gold deposits，grain sizes became smaller, but cracks would appear if forward duty cycle increased too much; While pores appear and deposits grew thinner and became crisp gradually when reverse duty cycle increased from 10% to 40%. By calculating the texture coefficient, gold deposits showed a preferred orientation along (111) and (222) plain under higher cathodic overpotential; while（200）plain was preferred under lower cathodic overpotential.
Thick gold material was fabricated in cyanide-free chloroauric acid solution by bipolar pulse reverse technique, influence of forward and reverse current density and duty cycle on the morphology and microstructure of gold deposits were studied and discussed. Results showed that when forward current density increased from 2.25 A/dm2 to 3.75A/ dm2, grain sizes became smaller and gold particles stacked more compact, but overhigh forward current density lead to surface fluctuation and decreasing of gold deposits flatness; While when reverse current density increased from 6 A/ dm2 to 12A/ dm2, grains became larger and structure loosen. Cathodic overpotential would increase when forward duty cycle increased from 20% to 60%, thus refining the gold deposits，grain sizes became smaller, but cracks would appear if forward duty cycle increased too much; While pores appear and deposits grew thinner and became crisp gradually when reverse duty cycle increased from 10% to 40%. By calculating the texture coefficient, gold deposits showed a preferred orientation along (111) and (222) plain under higher cathodic overpotential; while（200）plain was preferred under lower cathodic overpotential.
2016, 45(5):1264-1270.
Abstract:
The influence of directionally solidified process on porosity in cross-section transitions of dummy blade nickel-based superalloy DZ417G was investigated. It was found that the content of porosity at transition platform near the central runner was an order of magnitude higher than it is near the heater. In a certain casting temperature range (1480~1580 ℃)，with the increase of casting temperature，the content of porosity at transition platform near the central runner increased at first then decreased，the temperature with maximum content of porosity was 1550℃，however，in this casting temperature range，with the increase of casting temperature，the content of porosity at transition platform near the heater decrease a little bit. In a certain withdrawal rate (1~10mm/min)，with the increase of withdrawal rate，porosity at transition platform near the central runner increases gradually，however porosity at the opposite side part decreases. Based on these results，the relationship between casting temperature withdrawal rate and the content of porosity in transition platform dummy blade has been proposed. Besides，the influence of directional solidification process on the formation of porosity on the cross-section of the platform is mainly caused by the variation of temperature gradient of the solid-liquid interface.
The influence of directionally solidified process on porosity in cross-section transitions of dummy blade nickel-based superalloy DZ417G was investigated. It was found that the content of porosity at transition platform near the central runner was an order of magnitude higher than it is near the heater. In a certain casting temperature range (1480~1580 ℃)，with the increase of casting temperature，the content of porosity at transition platform near the central runner increased at first then decreased，the temperature with maximum content of porosity was 1550℃，however，in this casting temperature range，with the increase of casting temperature，the content of porosity at transition platform near the heater decrease a little bit. In a certain withdrawal rate (1~10mm/min)，with the increase of withdrawal rate，porosity at transition platform near the central runner increases gradually，however porosity at the opposite side part decreases. Based on these results，the relationship between casting temperature withdrawal rate and the content of porosity in transition platform dummy blade has been proposed. Besides，the influence of directional solidification process on the formation of porosity on the cross-section of the platform is mainly caused by the variation of temperature gradient of the solid-liquid interface.
2016, 45(5):1271-1277.
Abstract:
The effects of anionic surfactant (sodium dodecyl sulfate, SDS) and cationic surfactant (cetyl trimethyl ammonium bromide, CTAB) on the coelectrodeposition of Ti-coated diamond-Ni composite plating are studied in this paper. The electrolytic deposition behaviour of nickel is investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the diamond coated with Ti exhibits better infiltration when contact with Ni plating in contrast with that without Ti coating. The SDS with a concentration of 0.05 g/L inhibits the electrolytic deposition of Ni. While the CTAB with a concentration of 0.05 g/L promotes the transfer of Ni2 ions and accelerates the electrolytic deposition of Ni. The addition of SDS and CTAB refines the Ni coating and favours the evolution of hydrogen in the course of electrolytic deposition. Moreover,SDS and CTAB both decreases the numbers of pinhole and pitting in the coating.
The effects of anionic surfactant (sodium dodecyl sulfate, SDS) and cationic surfactant (cetyl trimethyl ammonium bromide, CTAB) on the coelectrodeposition of Ti-coated diamond-Ni composite plating are studied in this paper. The electrolytic deposition behaviour of nickel is investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the diamond coated with Ti exhibits better infiltration when contact with Ni plating in contrast with that without Ti coating. The SDS with a concentration of 0.05 g/L inhibits the electrolytic deposition of Ni. While the CTAB with a concentration of 0.05 g/L promotes the transfer of Ni2 ions and accelerates the electrolytic deposition of Ni. The addition of SDS and CTAB refines the Ni coating and favours the evolution of hydrogen in the course of electrolytic deposition. Moreover,SDS and CTAB both decreases the numbers of pinhole and pitting in the coating.
2016, 45(5):1278-1283.
Abstract:
Focused on in-situ utilization of lunar resources, we studied the preparation of aluminum alloy by aluminothermic reduction of ilmenite in molten cryolite media. The standard Gibbs free energy change of aluminothermic reduction of ilmenite are negative at temperature range 0-1500℃. The effects of reductant amount and reaction time on the aluminothermic reduction of ilmenite in 47.14mass%NaF-42.86mass%AlF3-10mass%?TiO3 at 960℃ were studied. The results obtained by XRF, XRD, SEM and EDS analysis show that the products mainly contain Al, Ti, Fe, and little Si, and the main phase of the product is Al3Ti. With the increase of reductant amount, the content of Ti in alloy products decreases, while the content of Fe in alloy products increases. In addition, the content of Al3Ti increases with the increase of reaction time. The highest content of Ti in the alloy obtained by aluminothermic reaction for 2h at 960℃ using three times reductant amount of theoretical amount is up to 18.82 mass%. Fe and Ti can be separated when FeTiO3 aluminothermic reduction was carried using lower reductant amount and higher reduction time. The FeTiO3 aluminothermic reduction reaction takes place between the dissolved Al atom and dissolved FeTiO3 in the Cryolite melt.
Focused on in-situ utilization of lunar resources, we studied the preparation of aluminum alloy by aluminothermic reduction of ilmenite in molten cryolite media. The standard Gibbs free energy change of aluminothermic reduction of ilmenite are negative at temperature range 0-1500℃. The effects of reductant amount and reaction time on the aluminothermic reduction of ilmenite in 47.14mass%NaF-42.86mass%AlF3-10mass%?TiO3 at 960℃ were studied. The results obtained by XRF, XRD, SEM and EDS analysis show that the products mainly contain Al, Ti, Fe, and little Si, and the main phase of the product is Al3Ti. With the increase of reductant amount, the content of Ti in alloy products decreases, while the content of Fe in alloy products increases. In addition, the content of Al3Ti increases with the increase of reaction time. The highest content of Ti in the alloy obtained by aluminothermic reaction for 2h at 960℃ using three times reductant amount of theoretical amount is up to 18.82 mass%. Fe and Ti can be separated when FeTiO3 aluminothermic reduction was carried using lower reductant amount and higher reduction time. The FeTiO3 aluminothermic reduction reaction takes place between the dissolved Al atom and dissolved FeTiO3 in the Cryolite melt.
2016, 45(5):1284-1289.
Abstract:
Based on finite element simulation, temperature field, temperature gradient and the evolution of solidification interface of the large hollow turbine blade in the process of directional solidification had been simulated.The experimental results demonstrated that defects were observed at the expanding cross section of casting in directionally solidified nickel-based superalloys. Numerical results indicated that the phenomenon should be attributed to the lower thermal gradient in this zone. Based on these results, one type of the new baffle was proposed.Calculated results reveal that the reasonable design of the new baffle could improve the thermal gradient in the local area. Therefore, the new baffle could more effectively affect the freckle formation and enhanced the mechanical performances of casting.
Based on finite element simulation, temperature field, temperature gradient and the evolution of solidification interface of the large hollow turbine blade in the process of directional solidification had been simulated.The experimental results demonstrated that defects were observed at the expanding cross section of casting in directionally solidified nickel-based superalloys. Numerical results indicated that the phenomenon should be attributed to the lower thermal gradient in this zone. Based on these results, one type of the new baffle was proposed.Calculated results reveal that the reasonable design of the new baffle could improve the thermal gradient in the local area. Therefore, the new baffle could more effectively affect the freckle formation and enhanced the mechanical performances of casting.
2016, 45(5):1290-1295.
Abstract:
The effects of process parameters, microstructure, mechanical properties of the joints, which were frabricated by friction stir welding (FSW) using 3mm 2A14 aluminium alloy and TC4 titanium alloy with a 0.05mm Zn and Ni ribbon as intermediate layer, were studied. The results indicate that the joint maximum tensile strength exceed to 237.3 MPa when the welding velocity, rotation speed are 75mm/min, 375 r/min, respectively, nearly 56.7% of the alluminum alloy. The joint maximum tensile strength reached 285.3 MPa at the same process parameters with add Zn as intermediate layer, nearly 68% of the alluminum alloy when add Ni as intermediate layer what can inhibit brittle phase TiAl3 , which the fracture mode is brittle/ductile fracture.
The effects of process parameters, microstructure, mechanical properties of the joints, which were frabricated by friction stir welding (FSW) using 3mm 2A14 aluminium alloy and TC4 titanium alloy with a 0.05mm Zn and Ni ribbon as intermediate layer, were studied. The results indicate that the joint maximum tensile strength exceed to 237.3 MPa when the welding velocity, rotation speed are 75mm/min, 375 r/min, respectively, nearly 56.7% of the alluminum alloy. The joint maximum tensile strength reached 285.3 MPa at the same process parameters with add Zn as intermediate layer, nearly 68% of the alluminum alloy when add Ni as intermediate layer what can inhibit brittle phase TiAl3 , which the fracture mode is brittle/ductile fracture.
2016, 45(5):1296-1301.
Abstract:
To improve the inhomogeneity and rolling forming ability of as-cast AZ91 magnesium, the effect of homogenizing annealing treatment on microstructure and mechanical properties of AZ91 magnesium alloy before and after rolling deformation was studied. The results showed that the distribution of second phase in the alloy tissue was improved effectively after homogenization annealing treatment. After multi-pass rolling at 400℃, the thin strip Mg17Al12 phase which originally distributed along the grain boundaries reduces significantly, with some of them fragmented, and some distributed near the grain boundaries or inside the grains as small particles. Compared with the strength of as-cast rolling structure, the strength of rolling structure after homogenization increases slightly; while the elongation increases by 50%.The tensile fracture morphology after rolling also shows that the ductility of alloy improves significantly. This lays a foundation for further study on the rolling forming of AZ91 magnesium alloy under different technological parameters.
To improve the inhomogeneity and rolling forming ability of as-cast AZ91 magnesium, the effect of homogenizing annealing treatment on microstructure and mechanical properties of AZ91 magnesium alloy before and after rolling deformation was studied. The results showed that the distribution of second phase in the alloy tissue was improved effectively after homogenization annealing treatment. After multi-pass rolling at 400℃, the thin strip Mg17Al12 phase which originally distributed along the grain boundaries reduces significantly, with some of them fragmented, and some distributed near the grain boundaries or inside the grains as small particles. Compared with the strength of as-cast rolling structure, the strength of rolling structure after homogenization increases slightly; while the elongation increases by 50%.The tensile fracture morphology after rolling also shows that the ductility of alloy improves significantly. This lays a foundation for further study on the rolling forming of AZ91 magnesium alloy under different technological parameters.
2016, 45(5):1302-1308.
Abstract:
The electronic beam welding (EBW )properties of low density niobium alloy(LDNb) with high strength niobium alloy、high temperature titanium alloy was investigated in this paper.For different alloys,deviate electrnic beam to higher melting alloy side,corresponding adjust the current、 welding speed and deflection distance,the results showed that the welded joint is smooth and has good tensile strength. Welding coefficients of welding itself 、joint of LDNb and Nb521 Alloy 、joint of LDNb and TC4 alloy all above 0.9 at room temperature,plastic are consistent with the base alloy.The ultimate strength of welding joint of LDNb and Nb521 alloy up to 75.3MPa at 1100℃.
The electronic beam welding (EBW )properties of low density niobium alloy(LDNb) with high strength niobium alloy、high temperature titanium alloy was investigated in this paper.For different alloys,deviate electrnic beam to higher melting alloy side,corresponding adjust the current、 welding speed and deflection distance,the results showed that the welded joint is smooth and has good tensile strength. Welding coefficients of welding itself 、joint of LDNb and Nb521 Alloy 、joint of LDNb and TC4 alloy all above 0.9 at room temperature,plastic are consistent with the base alloy.The ultimate strength of welding joint of LDNb and Nb521 alloy up to 75.3MPa at 1100℃.
40 AN EXPERIMENTAL STUDY ON PERFORATION BEHAVIOR OF WF/ZR-BASED BULK METALLIC GLASS MATRIX COMPOSITE
2016, 45(5):1308-1313.
Abstract:
An experimental study was conducted for W/ Zr38Ti17Cu10.5Co12Be22.5 composites which perforate 30CrMnMo steel plates at velocity between 1300 m/s and 1700m/s, and the results were analyzed as compared with the tungsten alloy. The results show that the penetration characteristics of composites are different from the tungsten alloy and the depleted uranium alloy, which are mainly presented as two characters. Firstly, under the high velocity penetration, the composites have the phenomena of the amorphous alloy gasification, the tungsten fiber outside of the penetrator buckling and fracture, the backflow of part of tungsten fiber during the penetration process, so the penetrator keeps self-sharping, and the penetration depth is higher than the tungsten alloy. Secondly, according to the analysis of the projectile and target destruction, because of the amorphous gasification, the tungsten fiber outside dynamic buckling and splitting, the stiffness of the penetrator reduction, and the penetration bifurcates, so the resistance of the plate is asymmetric, the ballistic bend and so on, which reduce the depth of the penetration. Meanwhile, the backflow of tungsten fiber gashes the sidewall of ballistic, then the high pressure gas from the amorphous gasification impacts the scratch, which will produce the perfoliate cracks, so it is beneficial to the second damage.
An experimental study was conducted for W/ Zr38Ti17Cu10.5Co12Be22.5 composites which perforate 30CrMnMo steel plates at velocity between 1300 m/s and 1700m/s, and the results were analyzed as compared with the tungsten alloy. The results show that the penetration characteristics of composites are different from the tungsten alloy and the depleted uranium alloy, which are mainly presented as two characters. Firstly, under the high velocity penetration, the composites have the phenomena of the amorphous alloy gasification, the tungsten fiber outside of the penetrator buckling and fracture, the backflow of part of tungsten fiber during the penetration process, so the penetrator keeps self-sharping, and the penetration depth is higher than the tungsten alloy. Secondly, according to the analysis of the projectile and target destruction, because of the amorphous gasification, the tungsten fiber outside dynamic buckling and splitting, the stiffness of the penetrator reduction, and the penetration bifurcates, so the resistance of the plate is asymmetric, the ballistic bend and so on, which reduce the depth of the penetration. Meanwhile, the backflow of tungsten fiber gashes the sidewall of ballistic, then the high pressure gas from the amorphous gasification impacts the scratch, which will produce the perfoliate cracks, so it is beneficial to the second damage.
2016, 45(5):1314-1319.
Abstract:
To fabricate tritium penetration barrier of aluminizing coating on Chinese low active martensite (CLAM) steel, electroplating of aluminum on CLAM steel from ambient temperature chloroaluminate ionic liquid AlCl3-MEIC（AlCl3-1-ethyl-3-methylimidazolium chloride） was carried out. The adhesion of substrates and aluminum coating at different pretreatment of the substrates was examined. The surface morphology,crystal size of aluminum coating at different current densities were examined by SEM and EDS. Comparing the surface morphology of aluminum plated by direct current process with which plated by pulse current process. The results show that the electroplating of aluminum on CLAM steel from AlCl3-MEIC is feasible. The current density of electrical pretreatment has influenced to the adhesion of substrates and aluminum coating. Increasing the current density can improve the adherence of substrates and aluminum coating. Using pulse current plating process can improve the compactness of surface morphology. Particle size of aluminum coating decreases with increasing current density. Spherical structure of aluminum coating increases with increasing current density. The deposited aluminum coating is whiter, smooth and uniform at preferable plating techniques. The preferable range of current density is 10～20 mA/cm2.The range of electroplating time is 45~95 min. The pulse current process is better.
To fabricate tritium penetration barrier of aluminizing coating on Chinese low active martensite (CLAM) steel, electroplating of aluminum on CLAM steel from ambient temperature chloroaluminate ionic liquid AlCl3-MEIC（AlCl3-1-ethyl-3-methylimidazolium chloride） was carried out. The adhesion of substrates and aluminum coating at different pretreatment of the substrates was examined. The surface morphology,crystal size of aluminum coating at different current densities were examined by SEM and EDS. Comparing the surface morphology of aluminum plated by direct current process with which plated by pulse current process. The results show that the electroplating of aluminum on CLAM steel from AlCl3-MEIC is feasible. The current density of electrical pretreatment has influenced to the adhesion of substrates and aluminum coating. Increasing the current density can improve the adherence of substrates and aluminum coating. Using pulse current plating process can improve the compactness of surface morphology. Particle size of aluminum coating decreases with increasing current density. Spherical structure of aluminum coating increases with increasing current density. The deposited aluminum coating is whiter, smooth and uniform at preferable plating techniques. The preferable range of current density is 10～20 mA/cm2.The range of electroplating time is 45~95 min. The pulse current process is better.
42 Study on the preparation of dense spherical molybdenum powders with high purity via induction plasma
2016, 45(5):1325-1329.
Abstract:
Using induction plasma, spheroidization, densification, refinement and purity of molybdenum powder were realized, Dense spherical powders with high purity were prepared. The effects of the plasma power and particle size of raw molybdenum powder on spheroidization efficiency of products were studied. The phase composition，morphologies and particle size distributions of the powder before and after spheroidization were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM) and laser micron sizer(LMS).The result show that the spherical molybdenum powder can be obtained from irregular powder after induction plasma spheroidization. The powder presents smooth surface and good disparity, and the spheroidization efficiency is almost 100%.After plasma treatment, the particle size become finer and its distribution is more concentrated. Under otherwise identical conditions, ,spheroidization efficiency increases firstly and then decreases with the increasing of plasma power. When the plasma power is 25kW,the effects of spheroidization is best. Smaller the particle size, higher the spheroidization efficiency is. With the increasing of spheriodization efficiency, the powder flow ability and apparent density have been significantly improved. The molybdenum powder flow ability is improved from 40s／50g to 11s／50g, and the apparent density from 2.3g／cm3 to 6.1g／cm3.
Using induction plasma, spheroidization, densification, refinement and purity of molybdenum powder were realized, Dense spherical powders with high purity were prepared. The effects of the plasma power and particle size of raw molybdenum powder on spheroidization efficiency of products were studied. The phase composition，morphologies and particle size distributions of the powder before and after spheroidization were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM) and laser micron sizer(LMS).The result show that the spherical molybdenum powder can be obtained from irregular powder after induction plasma spheroidization. The powder presents smooth surface and good disparity, and the spheroidization efficiency is almost 100%.After plasma treatment, the particle size become finer and its distribution is more concentrated. Under otherwise identical conditions, ,spheroidization efficiency increases firstly and then decreases with the increasing of plasma power. When the plasma power is 25kW,the effects of spheroidization is best. Smaller the particle size, higher the spheroidization efficiency is. With the increasing of spheriodization efficiency, the powder flow ability and apparent density have been significantly improved. The molybdenum powder flow ability is improved from 40s／50g to 11s／50g, and the apparent density from 2.3g／cm3 to 6.1g／cm3.
2016, 45(5):1330-1334.
Abstract:
Using ammonium metatungstate, soluble cobalt salt, and organic carbon source as the raw materials, the WC-Co composite powder was fabricated by spray conversion, calcinations and low temperature reduction-carbonization methods. The phase composition, grain size of WC, powder morphology, particle size distribution of precursor powder and composite powder were characterized. Results show that the composite powder was composed of WC and Co phases, The grain size of WC was about 60nm; the appearance of precursor powder was a kind of spherical shell structure, some of them are broken; powder morphology was not changed after calcinations; particle surface produces a large number of pore, the powder morphology was similar with precursor powder, genetic characteristics of morphology was fine; The mean grain size of composite powder was smaller than precursor powder and the particle size distribution was narrow; The mean particle size was increased with the increase of the slurry concentration, liquid feeding rate and with the decrease of centrifugal speed, but the particle size changes slightly with different inlet temperature.
Using ammonium metatungstate, soluble cobalt salt, and organic carbon source as the raw materials, the WC-Co composite powder was fabricated by spray conversion, calcinations and low temperature reduction-carbonization methods. The phase composition, grain size of WC, powder morphology, particle size distribution of precursor powder and composite powder were characterized. Results show that the composite powder was composed of WC and Co phases, The grain size of WC was about 60nm; the appearance of precursor powder was a kind of spherical shell structure, some of them are broken; powder morphology was not changed after calcinations; particle surface produces a large number of pore, the powder morphology was similar with precursor powder, genetic characteristics of morphology was fine; The mean grain size of composite powder was smaller than precursor powder and the particle size distribution was narrow; The mean particle size was increased with the increase of the slurry concentration, liquid feeding rate and with the decrease of centrifugal speed, but the particle size changes slightly with different inlet temperature.
2016, 45(5):1335-1339.
Abstract:
In this study, the effect of alternating combined magnetic field composed (CMF) of downward travelling magnetic field (TMF) and alternating rotating magnetic field (RMF) to remove the inclusions from aluminum melt was investigated and primary silicon particles precipitating from the solidification of Al-Si hypereutectic alloy were regarded as inclusions need removing. Inclusions particles agglomerated into clusters and migrated to the top of the melt under alternating CMF. It was found alternating CMF had a better removing effect than oriented CMF composed of oriented RMF and downward TMF. The removing effect of alternating CMF increased when the current and frequency of alternating RMF consisting of alternating CMF increased. Alternating CMF had the best removing effect when the alternating time was at 10s.
In this study, the effect of alternating combined magnetic field composed (CMF) of downward travelling magnetic field (TMF) and alternating rotating magnetic field (RMF) to remove the inclusions from aluminum melt was investigated and primary silicon particles precipitating from the solidification of Al-Si hypereutectic alloy were regarded as inclusions need removing. Inclusions particles agglomerated into clusters and migrated to the top of the melt under alternating CMF. It was found alternating CMF had a better removing effect than oriented CMF composed of oriented RMF and downward TMF. The removing effect of alternating CMF increased when the current and frequency of alternating RMF consisting of alternating CMF increased. Alternating CMF had the best removing effect when the alternating time was at 10s.
2016, 45(5):1340-1344.
Abstract:
The microstructure, mechanical properties and annealing behaviors of Cu-Zn-Si alloy subjected to cryorolling was investigated by transmission electron microscope, tensile tests and microhardness measurement. It was found that cryorolling encouraged twinning and dislocation accumulation in Cu-Zn-Si alloy, leading to the distinct enhancement of tensile strength and microhardness. Furthermore, cryorolling could provide more nucleation sites for static recrystallization than cold rolling does. After annealing, cryorolled samples owned more excellent combination of strength and ductility than cold rolled ones, owing to the nanotwins generated by cryorolling and finer grains. A tensile strength of 787 MPa and an elongation to failure of 14.3% were obtained for Cu-Zn-Si alloy after cryorolling followed by annealing at 280 ℃ for 5 hours.
The microstructure, mechanical properties and annealing behaviors of Cu-Zn-Si alloy subjected to cryorolling was investigated by transmission electron microscope, tensile tests and microhardness measurement. It was found that cryorolling encouraged twinning and dislocation accumulation in Cu-Zn-Si alloy, leading to the distinct enhancement of tensile strength and microhardness. Furthermore, cryorolling could provide more nucleation sites for static recrystallization than cold rolling does. After annealing, cryorolled samples owned more excellent combination of strength and ductility than cold rolled ones, owing to the nanotwins generated by cryorolling and finer grains. A tensile strength of 787 MPa and an elongation to failure of 14.3% were obtained for Cu-Zn-Si alloy after cryorolling followed by annealing at 280 ℃ for 5 hours.
2016, 45(5):1345-1348.
Abstract:
Nickel power was synthesized using supercritical methanol with different nickel precursors (NiO, Ni(CH3COO)2, Ni(NO3)2). The impacts of temperature, pressure, reaction time, and kinds of precursors on the preparation of nickel, were investigated. XRD and SEM were applied to analyze the composition and morphology of the synthesized products. Results showed that the reducing capacity of supercritical methanol was enhanced obviously with the increasing of temperature and pressure. In the reaction system, methanol both played roles of reaction medium and reducing agent. In addition, it was known by studying the influence of precursor kinds on the process that the kind of precursor had a great effect on the preparation of ultrafine nickel. Pure ultrafine nickel could be obtained at the supercritical methanol of 250 ℃, 9 MPa using Ni(CH3COO)2 as precursor. While more higher temperature (280 ℃) and pressure (14.0 MPa) were needed for Ni(NO3)2. When NiO was used as precursor, the mixture of Ni and NiO was obtained even at the more drastic condition of 300 ℃ and 20 MPa.
Nickel power was synthesized using supercritical methanol with different nickel precursors (NiO, Ni(CH3COO)2, Ni(NO3)2). The impacts of temperature, pressure, reaction time, and kinds of precursors on the preparation of nickel, were investigated. XRD and SEM were applied to analyze the composition and morphology of the synthesized products. Results showed that the reducing capacity of supercritical methanol was enhanced obviously with the increasing of temperature and pressure. In the reaction system, methanol both played roles of reaction medium and reducing agent. In addition, it was known by studying the influence of precursor kinds on the process that the kind of precursor had a great effect on the preparation of ultrafine nickel. Pure ultrafine nickel could be obtained at the supercritical methanol of 250 ℃, 9 MPa using Ni(CH3COO)2 as precursor. While more higher temperature (280 ℃) and pressure (14.0 MPa) were needed for Ni(NO3)2. When NiO was used as precursor, the mixture of Ni and NiO was obtained even at the more drastic condition of 300 ℃ and 20 MPa.
2016, 45(5):1349-1352.
Abstract:
The mechanism of corrosion resistance for Cu-30Ni-xRE(x=0~0.213) alloy were investigated by employing electrochemical testing, x-ray diffraction, optical microscopy, scanning electrical microscopy and Energy Disperse Spectroscopy. The results showed that comparison with Cu-30Ni alloy without RE, Cu-30Ni-0.095RE alloy with right amount had decreasing composition segregation of Ni element. This resulted in the decease of corrosion driving force between centre of dendrite and interdendritic. As a result, for Cu-30Ni-0.095RE alloy the corrosion potential increased by 11.0%, and the corrosion current decreased by 37.3%.
The mechanism of corrosion resistance for Cu-30Ni-xRE(x=0~0.213) alloy were investigated by employing electrochemical testing, x-ray diffraction, optical microscopy, scanning electrical microscopy and Energy Disperse Spectroscopy. The results showed that comparison with Cu-30Ni alloy without RE, Cu-30Ni-0.095RE alloy with right amount had decreasing composition segregation of Ni element. This resulted in the decease of corrosion driving force between centre of dendrite and interdendritic. As a result, for Cu-30Ni-0.095RE alloy the corrosion potential increased by 11.0%, and the corrosion current decreased by 37.3%.
2016, 45(5):1353-1356.
Abstract:
2016, 45(5):1357-1363.
Abstract:
High Nb containing TiAl alloys possess high specific strength and excellent performance at evaluated temperature, which is the significant development of TiAl intermetallics for applying up to 800 ℃. The directionalloy solidified high Nb-TiAl alloys have huge potential on the blade materials in the next generation aviation engine with a high thrust-weight ratio. Based on the directional solidification (DS) of conventional TiAl alloys, the current status of DS high Nb-TiAl alloys was discussed in this paper. Firstly, the DS methods and mould materials for directionally solidifying high Nb-TiAl alloys were introduced. Then the macrosturcture, the interface morphology and the α2/γ lamella of directionally solidified high Nb-TiAl alloys were elaborated respectively. Further, the cold crucible directional solidification of high Nb-TiAl alloys was presented and the mechanical properties of TiAl alloys were analyzed. Last, the prospect of of DS high Nb-TiAl alloys was outlooked.
High Nb containing TiAl alloys possess high specific strength and excellent performance at evaluated temperature, which is the significant development of TiAl intermetallics for applying up to 800 ℃. The directionalloy solidified high Nb-TiAl alloys have huge potential on the blade materials in the next generation aviation engine with a high thrust-weight ratio. Based on the directional solidification (DS) of conventional TiAl alloys, the current status of DS high Nb-TiAl alloys was discussed in this paper. Firstly, the DS methods and mould materials for directionally solidifying high Nb-TiAl alloys were introduced. Then the macrosturcture, the interface morphology and the α2/γ lamella of directionally solidified high Nb-TiAl alloys were elaborated respectively. Further, the cold crucible directional solidification of high Nb-TiAl alloys was presented and the mechanical properties of TiAl alloys were analyzed. Last, the prospect of of DS high Nb-TiAl alloys was outlooked.
2016, 45(5):1364-1368.
Abstract:
There was a great biomedicine application value for TiNi shape memory alloys (SMAs) with nearly atomic ratio as implants, but its corrosion may produce some adverse effects and release of Ni can result in allergies, poisoning reactions of cells and tissues. So their biosecurity and surface modification technology have been researched by many researchers. The preparation and surface modification method of TiNi SMAs were stated synthetically in this paper, and the possibility of future development was put forward. Now the method including plasma immersion ion implantation and deposition combined treatment, oxidation treatment, hydroxyapatite coating technology and TiO2 nanotube surface modification can improve corrosion resistance and biocompatibility of TiNi SMAs. The combination of nanotechnology and biotechnology can create new materials with the value of science and application.
There was a great biomedicine application value for TiNi shape memory alloys (SMAs) with nearly atomic ratio as implants, but its corrosion may produce some adverse effects and release of Ni can result in allergies, poisoning reactions of cells and tissues. So their biosecurity and surface modification technology have been researched by many researchers. The preparation and surface modification method of TiNi SMAs were stated synthetically in this paper, and the possibility of future development was put forward. Now the method including plasma immersion ion implantation and deposition combined treatment, oxidation treatment, hydroxyapatite coating technology and TiO2 nanotube surface modification can improve corrosion resistance and biocompatibility of TiNi SMAs. The combination of nanotechnology and biotechnology can create new materials with the value of science and application.
