Volume 44,Issue 12,2015 Table of Contents
2015, 44(12):2960-2964.
Abstract:
Ni-SiC composite coating was electrodeposited from the modified bath containing SiC particles. The system consisting of NiSO4·6H2O (35 g/100 mL), NiCl2·6H2O (4 g/100 mL), H3BO3 (3.5 g/100 mL), sodium dodecyl sulfate (SDS) (0.5 g/100 mL) and SiC (0.4~1.0 g/100 mL) was used at pH=4 and 35~50 ℃ to obtain a Ni-based composite coating containing SiC particles. The effects of temperature, current density, content of SiC in the electrolyte and ultrasonic dispersion time on codeposited content of SiC particles were investigated. The Ni-SiC composite coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicate that the codeposited content of SiC particles increases with increasing of temperature and then decreases at 35~50 °C. When current density is between 0.026~ 0.06 A/cm2, SiC content increases with the increase of current density and then decreases. When the concentration of SiC is between 0.4~1.0 g/100 mL in the plating solution, it increases with the increase of concentration of SiC. When the content of SiC exceeds a certain value (0.6 g/100 mL), the rate increase becomes low. When the ultrasonic dispersion time is between 10~50 min, the codeposited content of SiC particles first increases and then decreases with increasing of time. Uniform distribution of SiC particles in the coating is beneficial to refine the grain size of deposit
Ni-SiC composite coating was electrodeposited from the modified bath containing SiC particles. The system consisting of NiSO4·6H2O (35 g/100 mL), NiCl2·6H2O (4 g/100 mL), H3BO3 (3.5 g/100 mL), sodium dodecyl sulfate (SDS) (0.5 g/100 mL) and SiC (0.4~1.0 g/100 mL) was used at pH=4 and 35~50 ℃ to obtain a Ni-based composite coating containing SiC particles. The effects of temperature, current density, content of SiC in the electrolyte and ultrasonic dispersion time on codeposited content of SiC particles were investigated. The Ni-SiC composite coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicate that the codeposited content of SiC particles increases with increasing of temperature and then decreases at 35~50 °C. When current density is between 0.026~ 0.06 A/cm2, SiC content increases with the increase of current density and then decreases. When the concentration of SiC is between 0.4~1.0 g/100 mL in the plating solution, it increases with the increase of concentration of SiC. When the content of SiC exceeds a certain value (0.6 g/100 mL), the rate increase becomes low. When the ultrasonic dispersion time is between 10~50 min, the codeposited content of SiC particles first increases and then decreases with increasing of time. Uniform distribution of SiC particles in the coating is beneficial to refine the grain size of deposit
2015, 44(12):2970-2975.
Abstract:
To obtain better microstructures, a new aluminum grain refiner, Al-Ti-B-RE master alloy, was synthesized by the mix-molten method. Analyzed by thermodynamics and kinetics, the synthesis reactions of Al-Ti-B-RE master alloy would be possible, existent and to the right spontaneously. The second phase particles of the Al-Ti-B-RE master alloy mainly contained A13Ti, TiB2 and Ti2A120RE, etc. Under appropriate conditions, the second phase particles could be distributed homogeneously in the matrix. The morphology and the distribution of second phases of Al-Ti-B-RE master alloy, refining effects and mechanical properties were studied by XRD, SEM，OM and the electron all-purpose test machine (CSS-44100). The refinement experiment indicates that the self-made Al-5Ti-1B-1RE master alloy can refine the commercial pure aluminum into the level of the average grain size less than 150 μm, which belongs to the fine grain category. The tensile testing results show that after the addition of 0.2% self-made Al-5Ti-1B-1RE master alloy grain refiner into the commercial pure aluminum, the mechanical properties are improved significantly. Under the same condition, compared with the commercial pure aluminum without refinement, tensile strength σb and elongation δ are increased by 28.39 MPa and 29.97%, respectively. It is evident that the self-made Al-5Ti-1B-1RE master alloy grain refiner is superior to some domestic Al-5Ti-1B grain refiner
To obtain better microstructures, a new aluminum grain refiner, Al-Ti-B-RE master alloy, was synthesized by the mix-molten method. Analyzed by thermodynamics and kinetics, the synthesis reactions of Al-Ti-B-RE master alloy would be possible, existent and to the right spontaneously. The second phase particles of the Al-Ti-B-RE master alloy mainly contained A13Ti, TiB2 and Ti2A120RE, etc. Under appropriate conditions, the second phase particles could be distributed homogeneously in the matrix. The morphology and the distribution of second phases of Al-Ti-B-RE master alloy, refining effects and mechanical properties were studied by XRD, SEM，OM and the electron all-purpose test machine (CSS-44100). The refinement experiment indicates that the self-made Al-5Ti-1B-1RE master alloy can refine the commercial pure aluminum into the level of the average grain size less than 150 μm, which belongs to the fine grain category. The tensile testing results show that after the addition of 0.2% self-made Al-5Ti-1B-1RE master alloy grain refiner into the commercial pure aluminum, the mechanical properties are improved significantly. Under the same condition, compared with the commercial pure aluminum without refinement, tensile strength σb and elongation δ are increased by 28.39 MPa and 29.97%, respectively. It is evident that the self-made Al-5Ti-1B-1RE master alloy grain refiner is superior to some domestic Al-5Ti-1B grain refiner
2015, 44(12):2976-2981.
Abstract:
To enhance the wear resistance of CoCrMo alloy used as hip joints for longer service time, the W-DLC (W doped-diamond like carbon) films and Ti-DLC (Ti doped-diamond like carbon) films were prepared by a DC magnetron sputtering method combined with ion source technique. The thickness of the as-prepared films was 1.89 μm. Results show that the coated CoCrMo alloy exhibits higher wear resistance in comparison with uncoated CoCrMo one, and the friction properties of W-DLC coated CoCrMo alloy are better than those of Ti-DLC coated CoCrMo alloy. The wear rates of uncoated CoCrMo, Ti-DLC coated CoCrMo and W-DLC coated CoCrMo are 15.25×10-6, 0.76×10-6, and 0.19×10-6 mm3·m-1·N-1, respectively. Raman spectrum analysis shows that the excellent wear resistance of coated CoCrMo alloys is attributed to the graphitization of the top layer of DLC films during rubbing
To enhance the wear resistance of CoCrMo alloy used as hip joints for longer service time, the W-DLC (W doped-diamond like carbon) films and Ti-DLC (Ti doped-diamond like carbon) films were prepared by a DC magnetron sputtering method combined with ion source technique. The thickness of the as-prepared films was 1.89 μm. Results show that the coated CoCrMo alloy exhibits higher wear resistance in comparison with uncoated CoCrMo one, and the friction properties of W-DLC coated CoCrMo alloy are better than those of Ti-DLC coated CoCrMo alloy. The wear rates of uncoated CoCrMo, Ti-DLC coated CoCrMo and W-DLC coated CoCrMo are 15.25×10-6, 0.76×10-6, and 0.19×10-6 mm3·m-1·N-1, respectively. Raman spectrum analysis shows that the excellent wear resistance of coated CoCrMo alloys is attributed to the graphitization of the top layer of DLC films during rubbing
2015, 44(12):2987-2991.
Abstract:
TiB2/TiC nanocomposite powder was synthesized by ball milling the industrial grade Ti powder and B4C powder. The results show that the milling atmosphere plays a crucial role in the synthesis of TiB2/TiC. After 5 h milling under an appropriate argon protection, a solid state reaction between Ti and B4C occurs resulting in the formation of TiB2/TiC phases. With increasing of the milling time, the crystal size of synthesized TiC is decreased to about 10 nm while the crystal size of TiB2 is slightly larger. When the air is introduced in the milling process, a large amount of TiN and TiO will occur in the milled product.
TiB2/TiC nanocomposite powder was synthesized by ball milling the industrial grade Ti powder and B4C powder. The results show that the milling atmosphere plays a crucial role in the synthesis of TiB2/TiC. After 5 h milling under an appropriate argon protection, a solid state reaction between Ti and B4C occurs resulting in the formation of TiB2/TiC phases. With increasing of the milling time, the crystal size of synthesized TiC is decreased to about 10 nm while the crystal size of TiB2 is slightly larger. When the air is introduced in the milling process, a large amount of TiN and TiO will occur in the milled product.
2015, 44(12):2992-2995.
Abstract:
The leakage current density-voltage properties of HfO2 high-k dielectrics annealed at different temperatures and the current conduction mechanisms under gate injection were studied in details. It is found that the leakage currents are mostly associated with the high trap density at the interface of Au/HfO2 under gate injection, and the dominant conduction mechanisms of Au/HfO2/p-Si structure are the Schottky emission and Poole-Frenkel mechanism in the region of high electric fields. To study the reliability of the gate dielectric film, the capacitors were stressed at constant voltages under gate injection. Time dependent dielectric breakdown (TDDB) can be observed due to the formation of a percolation cluster under constant voltage stress.
The leakage current density-voltage properties of HfO2 high-k dielectrics annealed at different temperatures and the current conduction mechanisms under gate injection were studied in details. It is found that the leakage currents are mostly associated with the high trap density at the interface of Au/HfO2 under gate injection, and the dominant conduction mechanisms of Au/HfO2/p-Si structure are the Schottky emission and Poole-Frenkel mechanism in the region of high electric fields. To study the reliability of the gate dielectric film, the capacitors were stressed at constant voltages under gate injection. Time dependent dielectric breakdown (TDDB) can be observed due to the formation of a percolation cluster under constant voltage stress.
2015, 44(12):3000-3004.
Abstract:
A TiCN coating was deposited on Cr12MoV cold worked die steel by cathodic arc ion plating (CAIP). The plane distributions of chemical elements and the line scans of chemical elements at the coating interface were analyzed by SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy). The interface bonding mechanism was discussed, and the interface bonding of the coating was characterized and analyzed with scratch tester. The results show that the TiCN coating is composed of TiN, TiC and C atom, of which the TiC and TiN increase the coating hardness, and the C atom improves the friction lubrication properties of the coating. The number of N atoms in the coating is higher than that of C atoms, and the mutual diffusions occur at the bonding interface between the coating and the substrate. The C atoms diffuse to the substrate more than other atoms of elements in the coating, so Si atoms in the substrate, and a metallurgical bonding is formed between the coating and the substrate, its bonding with strength of 79.6 N
A TiCN coating was deposited on Cr12MoV cold worked die steel by cathodic arc ion plating (CAIP). The plane distributions of chemical elements and the line scans of chemical elements at the coating interface were analyzed by SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy). The interface bonding mechanism was discussed, and the interface bonding of the coating was characterized and analyzed with scratch tester. The results show that the TiCN coating is composed of TiN, TiC and C atom, of which the TiC and TiN increase the coating hardness, and the C atom improves the friction lubrication properties of the coating. The number of N atoms in the coating is higher than that of C atoms, and the mutual diffusions occur at the bonding interface between the coating and the substrate. The C atoms diffuse to the substrate more than other atoms of elements in the coating, so Si atoms in the substrate, and a metallurgical bonding is formed between the coating and the substrate, its bonding with strength of 79.6 N
2015, 44(12):3005-3008.
Abstract:
W-15Cu composite samples were prepared by electroless plating (for composite powder) and powder metallurgy (for sintering samples). Starting W powder was activated by a chemical pretreatment first, and then the pretreated W powder was electroless plating to get Cu-cladded W powder, which was pressed into green compacts at different pressing pressures. Afterward, the composite was sintered into W-15Cu composite samples, and Cu-cladded W powder was characterized. The relative density, hardness, compressive strength and electrical conductivity of the composite samples were tested. The morphologies of the Cu-cladded W powder and the samples were investigated. Results show that the prepared powder has good compaction behavior with high purity, uniform particle size and a dense Cu cladding layer. W particles still remain sole ones and no obvious grain coarsening appears in the sintering samples, while 3D Cu network is all over the structure of the samples. The electrical conductivity and the compressive strength of the sample change with pressing pressure and sintering temperature
W-15Cu composite samples were prepared by electroless plating (for composite powder) and powder metallurgy (for sintering samples). Starting W powder was activated by a chemical pretreatment first, and then the pretreated W powder was electroless plating to get Cu-cladded W powder, which was pressed into green compacts at different pressing pressures. Afterward, the composite was sintered into W-15Cu composite samples, and Cu-cladded W powder was characterized. The relative density, hardness, compressive strength and electrical conductivity of the composite samples were tested. The morphologies of the Cu-cladded W powder and the samples were investigated. Results show that the prepared powder has good compaction behavior with high purity, uniform particle size and a dense Cu cladding layer. W particles still remain sole ones and no obvious grain coarsening appears in the sintering samples, while 3D Cu network is all over the structure of the samples. The electrical conductivity and the compressive strength of the sample change with pressing pressure and sintering temperature
2015, 44(12):3014-3018.
Abstract:
We conducted a theoretical study on magneto-optical (MO) properties of cylindrical metallic nanowires. The MO conductivity was calculated using the Kubo formula. Results show that in contrast to parabolically confined quantum wires realized from low-dimensional semiconductor systems, the features of MO absorption and the retard effect of the MO response by cylindrical metallic nanowires depend sensitively on the polarization of the radiation field due to corresponding selection rules. The frequencies of resonant absorption induced by inter-subband MO transition channels are within the terahertz (THz) bandwidth and can be tuned effectively by adjusting the radius of the nanowire and/or varying the strength of the magnetic field. This study is pertinent to the potential application of metallic nanowires as frequency-tunable THz optoelectronic devices
We conducted a theoretical study on magneto-optical (MO) properties of cylindrical metallic nanowires. The MO conductivity was calculated using the Kubo formula. Results show that in contrast to parabolically confined quantum wires realized from low-dimensional semiconductor systems, the features of MO absorption and the retard effect of the MO response by cylindrical metallic nanowires depend sensitively on the polarization of the radiation field due to corresponding selection rules. The frequencies of resonant absorption induced by inter-subband MO transition channels are within the terahertz (THz) bandwidth and can be tuned effectively by adjusting the radius of the nanowire and/or varying the strength of the magnetic field. This study is pertinent to the potential application of metallic nanowires as frequency-tunable THz optoelectronic devices
2015, 44(12):3019-3022.
Abstract:
We conducted a detailed theoretical study on quantized acoustic-phone modes in metallic nanowile structures. Cylindrical metallic nanowire (NW) structures realized from the state-of-the-art nanotechnology, were used to demonstrate Ni NW embedded in Al2O3 template. The phonon modes were examined by solving the wave equations with corresponding boundary conditions. We find that the quantized phonon energy and the energy spacing between different phonon states increase with decreasing of NW radius. The allowed phonon modes lie below the straight line of qzVAl2O3 in the dispersion relation, and such a feature does not vary significantly with altering of NW radius. This study will be pertinent to the applications of metallic NW systems as high-frequency ultrasonic devices
We conducted a detailed theoretical study on quantized acoustic-phone modes in metallic nanowile structures. Cylindrical metallic nanowire (NW) structures realized from the state-of-the-art nanotechnology, were used to demonstrate Ni NW embedded in Al2O3 template. The phonon modes were examined by solving the wave equations with corresponding boundary conditions. We find that the quantized phonon energy and the energy spacing between different phonon states increase with decreasing of NW radius. The allowed phonon modes lie below the straight line of qzVAl2O3 in the dispersion relation, and such a feature does not vary significantly with altering of NW radius. This study will be pertinent to the applications of metallic NW systems as high-frequency ultrasonic devices
10 Correlations of Photoluminescence and Size Evolution of Si Quantum Dots in Amorphous Silicon Carbide
2015, 44(12):3023-3026.
Abstract:
Silicon quantum dots (Si QDs) with dot density up to 9×1013 cm-2 in amorphous SixC (x>1) thin films were obtained by magnetron sputtering deposition and post-annealing process at 1100 oC. Photoluminescence measurement indicates a multi-band configuration in the range from ultraviolet to green (2.3~3.5 eV). The analysis of Stokes shift and HRTEM demonstrates that there exist two kinds of Si QDs embedded in silicon carbide dielectric matrix: α-Si QDs and c-Si QDs which show the multi-band characteristics. The photoluminescence is closely related with the microstructure size distribution of Si QDs from 1.0 to 4.0 nm. Moreover, the density and the size distribution of Si QDs can be improved further by optimizing the ratio of Si/C atoms as well as annealing parameters. This opens a route to fabricate all-Si tandem solar cell
Silicon quantum dots (Si QDs) with dot density up to 9×1013 cm-2 in amorphous SixC (x>1) thin films were obtained by magnetron sputtering deposition and post-annealing process at 1100 oC. Photoluminescence measurement indicates a multi-band configuration in the range from ultraviolet to green (2.3~3.5 eV). The analysis of Stokes shift and HRTEM demonstrates that there exist two kinds of Si QDs embedded in silicon carbide dielectric matrix: α-Si QDs and c-Si QDs which show the multi-band characteristics. The photoluminescence is closely related with the microstructure size distribution of Si QDs from 1.0 to 4.0 nm. Moreover, the density and the size distribution of Si QDs can be improved further by optimizing the ratio of Si/C atoms as well as annealing parameters. This opens a route to fabricate all-Si tandem solar cell
2015, 44(12):3037-3040.
Abstract:
We demonstrate a visible light frequencies metamaterials (MMs) composed of disordered dendritic cells, and a novel bottom-up approach to fabricate the MMs using chemical method. When the diameter of the cell is about 500 nm, the as-prepared gold dendritic nanostructural array exhibits passbands at wavelength of 470, 540 and 670 nm, respectively. The MMs also realize slab focusing effect at visible wavelength. It would be significant to accelerate the development of visible frequencies MMs
We demonstrate a visible light frequencies metamaterials (MMs) composed of disordered dendritic cells, and a novel bottom-up approach to fabricate the MMs using chemical method. When the diameter of the cell is about 500 nm, the as-prepared gold dendritic nanostructural array exhibits passbands at wavelength of 470, 540 and 670 nm, respectively. The MMs also realize slab focusing effect at visible wavelength. It would be significant to accelerate the development of visible frequencies MMs
2015, 44(12):3041-3044.
Abstract:
Bismuth telluride alloy thin films were prepared on quartz substrates by co-sputtering method and thermally annealed at 423~623 K, for 1 h. It is found that the Te/Bi ratio decreases upon thermal annealing, indicating the loss of Te as a result of evaporation. This leads to the transformation of Bi2Te3 thin films from n-type to p-type, and consequently the change of Seebeck coefficient from the negative value to the positive one. In addition, the grain growth occurs during thermal annealing, in particular, at higher temperature, as a result, both the electrical conductivity and the seebeck coefficient are increased
Bismuth telluride alloy thin films were prepared on quartz substrates by co-sputtering method and thermally annealed at 423~623 K, for 1 h. It is found that the Te/Bi ratio decreases upon thermal annealing, indicating the loss of Te as a result of evaporation. This leads to the transformation of Bi2Te3 thin films from n-type to p-type, and consequently the change of Seebeck coefficient from the negative value to the positive one. In addition, the grain growth occurs during thermal annealing, in particular, at higher temperature, as a result, both the electrical conductivity and the seebeck coefficient are increased
2015, 44(12):3045-3049.
Abstract:
The wear ability and the corrosion resistance of TAMZ alloy implanted by carbon ions were investigated in Hank’s body fluid. The results show that the uniformly modified layer formed by implanting carbon ion on TAMZ alloy surface is composed of TiC and Ti with carbon content of 1.07wt%. The thickness of the carbon ions implanted layer is 9 μm. Electrochemical test results indicate that the implanted alloy corrosion potentials and the charge transfer resistance are all increased, and the anodic polarization current density is decreased in Hank’s body fluid. This is because the disordered carbide film is formed, which blocks the dissolution of alloying elements. In Hank’s body fluid, the friction coefficient and the wear rate of the TAMZ alloy implanted by carbon ions are less than those of TAMZ matrix, but hardness is increased after implantation. In addition, the implanted alloy’s anodic polarization current density is decreased and the charge transfer resistance is increased after friction. It means that the modified layer formed by implanting carbon ions has the excellent wear resistance and the corrosion resistance in a simulated human body fluid
The wear ability and the corrosion resistance of TAMZ alloy implanted by carbon ions were investigated in Hank’s body fluid. The results show that the uniformly modified layer formed by implanting carbon ion on TAMZ alloy surface is composed of TiC and Ti with carbon content of 1.07wt%. The thickness of the carbon ions implanted layer is 9 μm. Electrochemical test results indicate that the implanted alloy corrosion potentials and the charge transfer resistance are all increased, and the anodic polarization current density is decreased in Hank’s body fluid. This is because the disordered carbide film is formed, which blocks the dissolution of alloying elements. In Hank’s body fluid, the friction coefficient and the wear rate of the TAMZ alloy implanted by carbon ions are less than those of TAMZ matrix, but hardness is increased after implantation. In addition, the implanted alloy’s anodic polarization current density is decreased and the charge transfer resistance is increased after friction. It means that the modified layer formed by implanting carbon ions has the excellent wear resistance and the corrosion resistance in a simulated human body fluid
2015, 44(12):3055-3059.
Abstract:
The acoustic band gap structures of Ni and Cu nanowire triangular arrays (NWAs) were investigated by the plane wave expansion method. The structures were proposed on the basis of metallic NWAs realized from the state-of-the-art nanotechnology. The band gaps with GHz frequency can be achieved. We find that, in XΓ direction, Ni arrays are more easily to obtain the wider z mode band gaps. In ΓM direction, Cu arrays are more easily to motivate xy mode band gaps and larger band gaps at high frequency area. In some filling fraction, the band gap frequencies with z mode and xy mode can be obtained. Structurally, the two dimensional square lattice NWAs are more advantageous to produce hypersonic band gaps
The acoustic band gap structures of Ni and Cu nanowire triangular arrays (NWAs) were investigated by the plane wave expansion method. The structures were proposed on the basis of metallic NWAs realized from the state-of-the-art nanotechnology. The band gaps with GHz frequency can be achieved. We find that, in XΓ direction, Ni arrays are more easily to obtain the wider z mode band gaps. In ΓM direction, Cu arrays are more easily to motivate xy mode band gaps and larger band gaps at high frequency area. In some filling fraction, the band gap frequencies with z mode and xy mode can be obtained. Structurally, the two dimensional square lattice NWAs are more advantageous to produce hypersonic band gaps
2015, 44(12):3073-3077.
Abstract:
ZnO-TiO2 core-shell nanowires were prepared by a thermal reduction method and an atomic layer deposition (ALD) technique. The effects of deposition thickness, deposition temperature and annealing on crystallization and structure of ZnO-TiO2 core-shell nanowires were studied. ZnO-TiO2 core-shell nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that TiO2 shell is transformed from amorphous to crystallization with the increasing of the deposition thickness and deposition temperature. After 500 oC annealing, the crystallinity of TiO2 shell is improved, but wavy deformation is observed in the fine core-shell nanowires (the diameter of ZnO nanowires < 80 nm). As for amorphous TiO2 shell deposited at 150 oC after 500 oC annealing, convex grains are formed on the TiO2 shell and the loss of ZnO appears at the ZnO-TiO2 interface
ZnO-TiO2 core-shell nanowires were prepared by a thermal reduction method and an atomic layer deposition (ALD) technique. The effects of deposition thickness, deposition temperature and annealing on crystallization and structure of ZnO-TiO2 core-shell nanowires were studied. ZnO-TiO2 core-shell nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that TiO2 shell is transformed from amorphous to crystallization with the increasing of the deposition thickness and deposition temperature. After 500 oC annealing, the crystallinity of TiO2 shell is improved, but wavy deformation is observed in the fine core-shell nanowires (the diameter of ZnO nanowires < 80 nm). As for amorphous TiO2 shell deposited at 150 oC after 500 oC annealing, convex grains are formed on the TiO2 shell and the loss of ZnO appears at the ZnO-TiO2 interface
2015, 44(12):3094-3099.
Abstract:
Microstructure and texture of new Al-Zn-Mg-Cu high-strength aluminum alloy during hot planar compression deformation and annealing processes were studied by thermo-mechanical modeling planar compression experiments and Electron Back Scattering Diffraction (EBSD). The results show that the softening mechanism during deformation processes at the temperature of 350 °C and the strain rate of 0.1 s-1 is dominated by dynamic recovery and large strain geometric dynamic recrystallization (GDRX). The Rotated Cube {001} < > and the Brass {111} <110> aligned to α and β fibers, respectively, appear in the deformed alloy. After the annealing process, the Rotated Cube texture decreases and the Brass texture increases; meanwhile the Rotated Cube texture transforms to Brass texture along the α-fiber. When hot planar compression is up to 80% high reduction at 420 °C and the strain rate of 0.1 s-1, refined grains with high angle grain boundaries locate at the triangle grain boundaries formed by migration and rotation of subgrain boundaries. The Rotated Cube {110} < > and Brass {011} <211> are presented. After the annealing process, the Rotated Cube texture is enhanced, while the Brass texture transforms to Goss texture
Microstructure and texture of new Al-Zn-Mg-Cu high-strength aluminum alloy during hot planar compression deformation and annealing processes were studied by thermo-mechanical modeling planar compression experiments and Electron Back Scattering Diffraction (EBSD). The results show that the softening mechanism during deformation processes at the temperature of 350 °C and the strain rate of 0.1 s-1 is dominated by dynamic recovery and large strain geometric dynamic recrystallization (GDRX). The Rotated Cube {001} < > and the Brass {111} <110> aligned to α and β fibers, respectively, appear in the deformed alloy. After the annealing process, the Rotated Cube texture decreases and the Brass texture increases; meanwhile the Rotated Cube texture transforms to Brass texture along the α-fiber. When hot planar compression is up to 80% high reduction at 420 °C and the strain rate of 0.1 s-1, refined grains with high angle grain boundaries locate at the triangle grain boundaries formed by migration and rotation of subgrain boundaries. The Rotated Cube {110} < > and Brass {011} <211> are presented. After the annealing process, the Rotated Cube texture is enhanced, while the Brass texture transforms to Goss texture
17 Effect of Overheating Treatment Time on Mechanical Properties of Zr-Cu-Based Bulk Metallic Glasses
2015, 44(12):3109-3112.
Abstract:
Zr48Cu36Ag8Al8 bulk metallic glasses with 3 mm diameter were prepared with suction-casting into a water-cooling-copper mold for different casting treatment time from the same overheating temperature. The effect of treatment time in metallic liquid on the mechanical properties of Zr-Cu-based bulk metallic glasses were studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC), compression tests and scanning electron microscope (SEM). The results show that in a certain range of treatment time, longer treatment time of overheating treatment time would increase the density of the free volume and the deformation ability, thus decreasing the local deformation degree and increasing the fracture strength as well as the plasticity of the Zr48Cu36Ag8Al8 bulk metallic glasses
Zr48Cu36Ag8Al8 bulk metallic glasses with 3 mm diameter were prepared with suction-casting into a water-cooling-copper mold for different casting treatment time from the same overheating temperature. The effect of treatment time in metallic liquid on the mechanical properties of Zr-Cu-based bulk metallic glasses were studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC), compression tests and scanning electron microscope (SEM). The results show that in a certain range of treatment time, longer treatment time of overheating treatment time would increase the density of the free volume and the deformation ability, thus decreasing the local deformation degree and increasing the fracture strength as well as the plasticity of the Zr48Cu36Ag8Al8 bulk metallic glasses
2015, 44(12):3124-3129.
Abstract:
NiSe2 thermoelectric materials were prepared by the combination of mechanical alloying (MA) and spark plasma sintering (SPS). The effects of MA time and SPS temperature on the phase structure, microstructure, thermoelectric and optical properties were investigated. The results show that NiSe2 nanopowders with the grain sizes of 45 nm are synthesized by applying MA at 425 r/min for 40 h. It is proved that NiSe2 powder material is a direct band gap semiconductor with an optical band gap of about 2.653 eV and the NiSe2 bulk possesses a n-type semiconductive characteristic. The NiSe2 bulk prepared by applying SPS at 773 K attains a maximum power factor of 101 μW·m-1·K-2 along with a thermal conductivity 7.5 W·m-1·K-1 and the largest ZT value 0.0045
NiSe2 thermoelectric materials were prepared by the combination of mechanical alloying (MA) and spark plasma sintering (SPS). The effects of MA time and SPS temperature on the phase structure, microstructure, thermoelectric and optical properties were investigated. The results show that NiSe2 nanopowders with the grain sizes of 45 nm are synthesized by applying MA at 425 r/min for 40 h. It is proved that NiSe2 powder material is a direct band gap semiconductor with an optical band gap of about 2.653 eV and the NiSe2 bulk possesses a n-type semiconductive characteristic. The NiSe2 bulk prepared by applying SPS at 773 K attains a maximum power factor of 101 μW·m-1·K-2 along with a thermal conductivity 7.5 W·m-1·K-1 and the largest ZT value 0.0045
2015, 44(12):3130-3135.
Abstract:
The oxidation behavior of Silicon Carbide Particles (SiCp) was investigated, and oxidized-SiCp reinforced 5052Al matrix composites with SiC volume fraction beyond 55% were prepared by pressureless infiltration. Moreover, the microstructure and interface morphologies of the composites were examined, and its influence on thermal conductivity of the composites was discussed as well. The results show that the oxidation increment of SiCp and the thickness of SiO2 layer increase with the increasing of pre-oxidation time at 1100 °C; when the oxidized time exceeds 6 h at 1100 °C, the rate of the oxidation increment will decline. After oxidation, the sharp edge is obviously passivated for the SiCp; meanwhile, the distribution of the oxidized SiCp in Al alloy matrix is uniform and almost no holes can be found in the composites. Besides, the reaction and combination at the interface are different with the duration time for the oxidation, short-rod-like Al4C3 can be found on the surface of the particles before oxidation, but octahedron MgAl2O4 appears after the oxidation for 4h, and there is still residual SiO2 after the oxidation for 6 h. In addition, the thermal conductivity and interface heat transfer coefficient of the composites both increase at first and then decrease with the increasing of pre-oxidation time, which is closely related with the actual interface status due to different oxidation degrees
The oxidation behavior of Silicon Carbide Particles (SiCp) was investigated, and oxidized-SiCp reinforced 5052Al matrix composites with SiC volume fraction beyond 55% were prepared by pressureless infiltration. Moreover, the microstructure and interface morphologies of the composites were examined, and its influence on thermal conductivity of the composites was discussed as well. The results show that the oxidation increment of SiCp and the thickness of SiO2 layer increase with the increasing of pre-oxidation time at 1100 °C; when the oxidized time exceeds 6 h at 1100 °C, the rate of the oxidation increment will decline. After oxidation, the sharp edge is obviously passivated for the SiCp; meanwhile, the distribution of the oxidized SiCp in Al alloy matrix is uniform and almost no holes can be found in the composites. Besides, the reaction and combination at the interface are different with the duration time for the oxidation, short-rod-like Al4C3 can be found on the surface of the particles before oxidation, but octahedron MgAl2O4 appears after the oxidation for 4h, and there is still residual SiO2 after the oxidation for 6 h. In addition, the thermal conductivity and interface heat transfer coefficient of the composites both increase at first and then decrease with the increasing of pre-oxidation time, which is closely related with the actual interface status due to different oxidation degrees
2015, 44(12):3136-3140.
Abstract:
TiO2 nanotube arrays were fabricated on Si substrate in HF solution with the low concentration of 0.05 wt%. The diameter and the morphology of the TiO2 nanotubes were observed by scanning electronic microscope (SEM). The effects of oxidation voltage and the applying way of voltage on the nanotubes morphology were investigated. The results show that the diameter and the morphology of the TiO2 nanotubes are obviously influenced by the parameters of the oxidation condition. The TiO2 nanotubes with diameters of 120 nm are obtained by applying a voltage of 0.5 V for 28 min in HF solution with the low concentration of 0.05 wt%. The diameter of the nanotubes could be enlarged to a larger range by optimizing the oxidation time. The dense TiO2 nanotubes with diameters ranging from about 100 to 270 nm are fabricated by the two-step anodic oxidation method, which are much better than the TiO2 nanotubes with diameters from about 70 to 100 nm obtained in the organic electrolyte
TiO2 nanotube arrays were fabricated on Si substrate in HF solution with the low concentration of 0.05 wt%. The diameter and the morphology of the TiO2 nanotubes were observed by scanning electronic microscope (SEM). The effects of oxidation voltage and the applying way of voltage on the nanotubes morphology were investigated. The results show that the diameter and the morphology of the TiO2 nanotubes are obviously influenced by the parameters of the oxidation condition. The TiO2 nanotubes with diameters of 120 nm are obtained by applying a voltage of 0.5 V for 28 min in HF solution with the low concentration of 0.05 wt%. The diameter of the nanotubes could be enlarged to a larger range by optimizing the oxidation time. The dense TiO2 nanotubes with diameters ranging from about 100 to 270 nm are fabricated by the two-step anodic oxidation method, which are much better than the TiO2 nanotubes with diameters from about 70 to 100 nm obtained in the organic electrolyte
2015, 44(12):3141-3146.
Abstract:
The influencing mechanism of different vibration frequencies on the filling and solidification mode and casting-mold gap was investigated in the filling and solidification process of AZ91 magnesium alloy. And the effect of mechanical vibration on heat transfer efficiency of the casting-mold interface was studied through independently designed heat transfer device. The results show that the mechanical vibration enhances the Reynolds number and reduces the thickness of laminar boundary layer during the filling process. It also destroys the initially solidified thin layer on the cavity wall, changes the solidification mode of magnesium alloy, refines the grains and changes the phase morphology and distribution. Finally, the vibration makes the casting-mold gap in a dynamic changing process after solidification and thus influences the heart-transfer of the casting-mold interface. Under vibration frequency of 0, 20 and 50 Hz, the mould’s highest temperature is 365.3, 372.1 and 377.1 °C, respectively, while the required time of mould reaching the maximum temperature is 111 s, 100 s and 91 s, respectively. With the vibration frequency changing from 0 Hz to 50 Hz, the mould’s maximum temperature increases gradually while the required time reduces
The influencing mechanism of different vibration frequencies on the filling and solidification mode and casting-mold gap was investigated in the filling and solidification process of AZ91 magnesium alloy. And the effect of mechanical vibration on heat transfer efficiency of the casting-mold interface was studied through independently designed heat transfer device. The results show that the mechanical vibration enhances the Reynolds number and reduces the thickness of laminar boundary layer during the filling process. It also destroys the initially solidified thin layer on the cavity wall, changes the solidification mode of magnesium alloy, refines the grains and changes the phase morphology and distribution. Finally, the vibration makes the casting-mold gap in a dynamic changing process after solidification and thus influences the heart-transfer of the casting-mold interface. Under vibration frequency of 0, 20 and 50 Hz, the mould’s highest temperature is 365.3, 372.1 and 377.1 °C, respectively, while the required time of mould reaching the maximum temperature is 111 s, 100 s and 91 s, respectively. With the vibration frequency changing from 0 Hz to 50 Hz, the mould’s maximum temperature increases gradually while the required time reduces
2015, 44(12):3151-3155.
Abstract:
Al-substituted nickel hydroxides with the Al3+/Ni2+ molar ratio of 0%, 5%, 10%, 15% and 20% were prepared by a chemical co-precipitation method. Tap density tests demonstrate that the tap-density of samples increases obviously with the increasing of the Al content when the Al content is less than 10%; the sample presents the highest tap-density when the Al content is 10%; however, further increasing of Al content leads to the decrease of tap density. X-ray diffraction (XRD) analysis reveals that the sample shows β phase when the Al content is less than 5%, and α/β mixed phase when the Al content is between 5% and 10%, but when the Al content is higher than 10% the samples show α phase. The results of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge tests indicate that Al-substituted nickel hydroxide has higher electrochemical activity and smaller electrochemical reaction resistance than the pure nickel hydroxide. In particular, the Al-substituted nickel hydroxide with Al3+/Ni2+ molar ratio of 15% exhibits the best electrochemical performance. For example, the stable specific discharge capacity is up to 324 mAh/g (516 mAh/cm3) at the charge-discharge current density of 100 mA/g. Meanwhile, the samples also possess excellent cycling performance
Al-substituted nickel hydroxides with the Al3+/Ni2+ molar ratio of 0%, 5%, 10%, 15% and 20% were prepared by a chemical co-precipitation method. Tap density tests demonstrate that the tap-density of samples increases obviously with the increasing of the Al content when the Al content is less than 10%; the sample presents the highest tap-density when the Al content is 10%; however, further increasing of Al content leads to the decrease of tap density. X-ray diffraction (XRD) analysis reveals that the sample shows β phase when the Al content is less than 5%, and α/β mixed phase when the Al content is between 5% and 10%, but when the Al content is higher than 10% the samples show α phase. The results of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge-discharge tests indicate that Al-substituted nickel hydroxide has higher electrochemical activity and smaller electrochemical reaction resistance than the pure nickel hydroxide. In particular, the Al-substituted nickel hydroxide with Al3+/Ni2+ molar ratio of 15% exhibits the best electrochemical performance. For example, the stable specific discharge capacity is up to 324 mAh/g (516 mAh/cm3) at the charge-discharge current density of 100 mA/g. Meanwhile, the samples also possess excellent cycling performance
2015, 44(12):3156-3160.
Abstract:
In situ NbC reinforced CoCrCuFeNiMn(NbC)x (x=0, 0.05, 0.1, 0.2, 0.3, 0.4) high entropy alloys were prepared by plasma cladding on the Q235 steel. The phase constitution, microstructure and microhardness of the cladding layer were investigated. The results show that C and Nb addition doesn’t cause complex phase and the diffraction peaks are composed of fcc1, fcc2 and NbC phase. Most of the NbC is deposited in the interdendrite and a few of them is dendrite. The shape of NbC is related to its content. When x is small, NbC is granular. When x is large, NbC is granular, strip and cross dendritic. Compared with that of the matrix, the hardness of in situ high entropy alloy matrix composite is significantly improved. The hardness of the cladding layer is increased with more NbC in a certain range (x=0~0.4)
In situ NbC reinforced CoCrCuFeNiMn(NbC)x (x=0, 0.05, 0.1, 0.2, 0.3, 0.4) high entropy alloys were prepared by plasma cladding on the Q235 steel. The phase constitution, microstructure and microhardness of the cladding layer were investigated. The results show that C and Nb addition doesn’t cause complex phase and the diffraction peaks are composed of fcc1, fcc2 and NbC phase. Most of the NbC is deposited in the interdendrite and a few of them is dendrite. The shape of NbC is related to its content. When x is small, NbC is granular. When x is large, NbC is granular, strip and cross dendritic. Compared with that of the matrix, the hardness of in situ high entropy alloy matrix composite is significantly improved. The hardness of the cladding layer is increased with more NbC in a certain range (x=0~0.4)
2015, 44(12):3161-3165.
Abstract:
Because the strength and stiffness of titanium alloy pipe are very high, it is difficult to be straightened. Considering the strengthening of material, the formula of bending moment in the process of pipe straightening was deduced. With the basic principle of straightening, the theoretical calculation model of straightening precision was deduced. With the help of the straightening precision calculation model, the amount of bending combination was optimized. The segmentation curvature straightening roller shape for titanium alloy tubes have been designed using the optimized combination of inflection. The reasonable value scope is presented after comprehensive analysis. It can provide reference for roll gap adjustment in practical production
Because the strength and stiffness of titanium alloy pipe are very high, it is difficult to be straightened. Considering the strengthening of material, the formula of bending moment in the process of pipe straightening was deduced. With the basic principle of straightening, the theoretical calculation model of straightening precision was deduced. With the help of the straightening precision calculation model, the amount of bending combination was optimized. The segmentation curvature straightening roller shape for titanium alloy tubes have been designed using the optimized combination of inflection. The reasonable value scope is presented after comprehensive analysis. It can provide reference for roll gap adjustment in practical production
2015, 44(12):3166-3172.
Abstract:
Effects of no treatment, pulsed magnetic field (PMF) treatment, mechanical vibration treatment and compound treatment of pulsed magnetic field and mechanical vibration on the solidified structure and mechanical properties of superalloy K4169 were studied comparatively. Morphologies of primary phase of the alloy with different pulse voltages, pulse frequencies and pouring temperatures under the conditions of compound treatment were investigated. The results show that average grain size of the alloy is refined from 4.5 mm to 0.98 mm, and the fraction of equiaxed grains of the alloy is increased from 36% to 96% by compound treatment. Refinement effect of solidified structure by compound treatment is more efficient than that of pulsed magnetic field treatment or mechanical vibration treatment. Meanwhile, tensile strength and elongation of the alloy with compound treatment compared with the alloy in traditional condition increase by up to 49.2% and 37.3%, respectively. With the increase of the pulse voltage or frequency, primary phase of the alloy degrades gradually from well-developed dendrites into fine equiaxed grains or rosette crystals. When the pouring temperature is 1380~1530 °C, the increase of pouring temperature enhances the refinement effect of compound treatment
Effects of no treatment, pulsed magnetic field (PMF) treatment, mechanical vibration treatment and compound treatment of pulsed magnetic field and mechanical vibration on the solidified structure and mechanical properties of superalloy K4169 were studied comparatively. Morphologies of primary phase of the alloy with different pulse voltages, pulse frequencies and pouring temperatures under the conditions of compound treatment were investigated. The results show that average grain size of the alloy is refined from 4.5 mm to 0.98 mm, and the fraction of equiaxed grains of the alloy is increased from 36% to 96% by compound treatment. Refinement effect of solidified structure by compound treatment is more efficient than that of pulsed magnetic field treatment or mechanical vibration treatment. Meanwhile, tensile strength and elongation of the alloy with compound treatment compared with the alloy in traditional condition increase by up to 49.2% and 37.3%, respectively. With the increase of the pulse voltage or frequency, primary phase of the alloy degrades gradually from well-developed dendrites into fine equiaxed grains or rosette crystals. When the pouring temperature is 1380~1530 °C, the increase of pouring temperature enhances the refinement effect of compound treatment
2015, 44(12):3173-3177.
Abstract:
Nearly spherical composite powders of high nitrogen nickel-saving stainless steel were synthesized by a high energy milling technique, and the MIM (metal injection molding) feedstock was prepared by mixing these metal powders with paraffin based multi-component binder. The rheological properties of MIM feedstock including feedstock viscosity and its sensitivity to the shear rate and the temperature were also investigated. The results show that the high energy milling can remarkably improve technological characteristics of the powders, and it is found that the powders milled for 60 h have fine particle size, good sphericity and high tap density, suitable for making high-quality MIM feedstock. The feedstock with powder loading of 58% presents the minimum shear rate sensitivity factor, the lowest viscous flow activation energy, and the largest general rheological index, which are n=0.45, E=28.70 kJ/mol and αSTV=2.96, respectively, exhibiting the best rheological properties and meeting process requirements for subsequent injection procedure very well
Nearly spherical composite powders of high nitrogen nickel-saving stainless steel were synthesized by a high energy milling technique, and the MIM (metal injection molding) feedstock was prepared by mixing these metal powders with paraffin based multi-component binder. The rheological properties of MIM feedstock including feedstock viscosity and its sensitivity to the shear rate and the temperature were also investigated. The results show that the high energy milling can remarkably improve technological characteristics of the powders, and it is found that the powders milled for 60 h have fine particle size, good sphericity and high tap density, suitable for making high-quality MIM feedstock. The feedstock with powder loading of 58% presents the minimum shear rate sensitivity factor, the lowest viscous flow activation energy, and the largest general rheological index, which are n=0.45, E=28.70 kJ/mol and αSTV=2.96, respectively, exhibiting the best rheological properties and meeting process requirements for subsequent injection procedure very well
2015, 44(12):3188-3191.
Abstract:
Nanocrystalline layer of a certain thickness has been prepared on the surface of tungsten copper alloy by a supersonic fine particles bombarding (SFPB) method. The micro-hardness and electrical properties were measured and then their phases as well as microstructure were analyzed by XRD and SEM, respectively. The results show that the continuous bombardment on the surface of tungsten copper alloy leading by high kinetic energy of particles during SFPB makes the W particles and copper phase broken and refined. Finally a nano layer has been prepared on the surface of CuW70, whose grain size is about 80 nm and the thickness is about a dozen microns. And the optimum effect is in the subsurface. Micro-hardnesses of the sample’s nano layer significantly increase by about 40%~60% while the conductivity decreases slightly. The formation of the arc can be inhibited and extinguished rapidly for achieving the arc erosion resistance
Nanocrystalline layer of a certain thickness has been prepared on the surface of tungsten copper alloy by a supersonic fine particles bombarding (SFPB) method. The micro-hardness and electrical properties were measured and then their phases as well as microstructure were analyzed by XRD and SEM, respectively. The results show that the continuous bombardment on the surface of tungsten copper alloy leading by high kinetic energy of particles during SFPB makes the W particles and copper phase broken and refined. Finally a nano layer has been prepared on the surface of CuW70, whose grain size is about 80 nm and the thickness is about a dozen microns. And the optimum effect is in the subsurface. Micro-hardnesses of the sample’s nano layer significantly increase by about 40%~60% while the conductivity decreases slightly. The formation of the arc can be inhibited and extinguished rapidly for achieving the arc erosion resistance
2015, 44(12):3192-3196.
Abstract:
IrO2+ZrO2 binary oxide coatings deposited on Ti substrate were prepared by thermal decomposition. The influence of the annealing temperature on the structure, surface morphology, surface composition, and capacitive performance was tested by XRD, SEM, EDX, XPS, CV, etc. The nonlinear equation q*(v)=A1exp(-v/t1)+A2exp(-v/t2)+y0 was used to calculate the active sites located inside and outside of the coatings. The results show that the critical crystallization temperature of IrO2-ZrO2 is between 340~360 °C. The phase of the coating annealed at 340 °C still remains amorphous. While annealing at 360 °C, the coatings contain both crystalline and amorphous structures. They have typical crack-like morphology and Ir3+, Ir4+, as well as higher valence Ir atoms. The specific capacitance increases with the increasing of temperature up to 360 °C, and then decreases with further increasing temperature. The electrodes annealed at 360 °C have the highest specific capacitance probably due to the optimal structures of "amorphous/crystalline mixture" which favor both electron and proton conductivity. The proton transfer has a greater influence on the capacitance than electronic conductivity. The effect of the CV scanning speed on proton migration is greater than that on electronic conductivity
IrO2+ZrO2 binary oxide coatings deposited on Ti substrate were prepared by thermal decomposition. The influence of the annealing temperature on the structure, surface morphology, surface composition, and capacitive performance was tested by XRD, SEM, EDX, XPS, CV, etc. The nonlinear equation q*(v)=A1exp(-v/t1)+A2exp(-v/t2)+y0 was used to calculate the active sites located inside and outside of the coatings. The results show that the critical crystallization temperature of IrO2-ZrO2 is between 340~360 °C. The phase of the coating annealed at 340 °C still remains amorphous. While annealing at 360 °C, the coatings contain both crystalline and amorphous structures. They have typical crack-like morphology and Ir3+, Ir4+, as well as higher valence Ir atoms. The specific capacitance increases with the increasing of temperature up to 360 °C, and then decreases with further increasing temperature. The electrodes annealed at 360 °C have the highest specific capacitance probably due to the optimal structures of "amorphous/crystalline mixture" which favor both electron and proton conductivity. The proton transfer has a greater influence on the capacitance than electronic conductivity. The effect of the CV scanning speed on proton migration is greater than that on electronic conductivity
2015, 44(12):3197-3201.
Abstract:
The oxidation kinetics of austenitic Fe24Mn4Al5Cr alloy oxidized at 800 °C for 160 h and 950 °C for 10 h in air, and the surface morphology, composition and the microstructure of the oxide scales were investigated in order to improve the corrosion resistance. An oxidation-induced Mn depletion layer between the alloy matrix and the oxide scales formed at the two oxidation temperatures by the selective oxidation of Mn. The results show that after oxidation at 800 °C for 160 h, the continueous and smooth ferrite layer about 9 μm thick near the scale-metal interface has an enrichment of Fe content of 83 at%~72 at% and Cr content of 8 at%, and a depletion Mn of 6 at%~19 at%. However, at 950 °C for 10 h, the ferrite layer about 6 μm thick is in curved shape with the enrichment in Fe of 85at% and the depletion in Mn of 5at%. The anodic polarization curves of the Mn depletion layer at 800 °C for 160 h in 1 mol·L-1 Na2SO4 solution has a self-passivation, with the higher corrosion potential of 57 mV(SCE) and the lower passive current density of 0.7 μA/cm2, compared with –710 mV(SCE) and 3.3 μA/cm2 for Fe24Mn4Al5Cr austenitic alloy. Therefore, the corrosion resistance of the oxidation-induced Mn depletion layer on Fe24Mn4Al5Cr alloy increases
The oxidation kinetics of austenitic Fe24Mn4Al5Cr alloy oxidized at 800 °C for 160 h and 950 °C for 10 h in air, and the surface morphology, composition and the microstructure of the oxide scales were investigated in order to improve the corrosion resistance. An oxidation-induced Mn depletion layer between the alloy matrix and the oxide scales formed at the two oxidation temperatures by the selective oxidation of Mn. The results show that after oxidation at 800 °C for 160 h, the continueous and smooth ferrite layer about 9 μm thick near the scale-metal interface has an enrichment of Fe content of 83 at%~72 at% and Cr content of 8 at%, and a depletion Mn of 6 at%~19 at%. However, at 950 °C for 10 h, the ferrite layer about 6 μm thick is in curved shape with the enrichment in Fe of 85at% and the depletion in Mn of 5at%. The anodic polarization curves of the Mn depletion layer at 800 °C for 160 h in 1 mol·L-1 Na2SO4 solution has a self-passivation, with the higher corrosion potential of 57 mV(SCE) and the lower passive current density of 0.7 μA/cm2, compared with –710 mV(SCE) and 3.3 μA/cm2 for Fe24Mn4Al5Cr austenitic alloy. Therefore, the corrosion resistance of the oxidation-induced Mn depletion layer on Fe24Mn4Al5Cr alloy increases
2015, 44(12):3208-3214.
Abstract:
Ti-22Nb-6Zr (at%) shape memory alloys with various amount of boron (B) addition (0.02 wt%~1.5 wt%) were fabricated using a powder sintering method. Optical microscope, XRD and SEM were used to investigate the microstructure and phase constituents of the sintered alloys. It is shown that boron addition induces the precipitation of α phase and TiB phase in β matrix, which facilitates distinct refinement of microstructure. The addition of boron exerts only little influence on the Young’s modulus (around 30 GPa) and superelasticity (over 3%), but affects strongly the compression strength and yield strength of sintered Ti-22Nb-6Zr-B alloys. In order to acquire a relatively high yield strength and compression strength, the amount of boron addition into Ti-22Nb-6Zr shape memory alloys should be around 0.02 wt%~0.1 wt% and 1 wt%. Polarization curves analysis shows that the corrosion resistance of these Ti-22Nb-6Zr-B alloys is very good when boron content is about 0.02 wt%~1 wt%. Taking into account microstructure, mechanical properties and corrosion resistance, the appropriate amount of B addition for Ti-22Nb-6Zr shape memory alloys is 0.02 wt%~0.1 wt% and 1 wt%
Ti-22Nb-6Zr (at%) shape memory alloys with various amount of boron (B) addition (0.02 wt%~1.5 wt%) were fabricated using a powder sintering method. Optical microscope, XRD and SEM were used to investigate the microstructure and phase constituents of the sintered alloys. It is shown that boron addition induces the precipitation of α phase and TiB phase in β matrix, which facilitates distinct refinement of microstructure. The addition of boron exerts only little influence on the Young’s modulus (around 30 GPa) and superelasticity (over 3%), but affects strongly the compression strength and yield strength of sintered Ti-22Nb-6Zr-B alloys. In order to acquire a relatively high yield strength and compression strength, the amount of boron addition into Ti-22Nb-6Zr shape memory alloys should be around 0.02 wt%~0.1 wt% and 1 wt%. Polarization curves analysis shows that the corrosion resistance of these Ti-22Nb-6Zr-B alloys is very good when boron content is about 0.02 wt%~1 wt%. Taking into account microstructure, mechanical properties and corrosion resistance, the appropriate amount of B addition for Ti-22Nb-6Zr shape memory alloys is 0.02 wt%~0.1 wt% and 1 wt%
2015, 44(12):3215-3218.
Abstract:
Pre-alloyed Ti6Al4V powder was used to fabricate solid components by Electron Beam Selective Melting (EBSM). The characteristics of microstructures of the powder were investigated using OM, SEM, TEM and XRD. Results show that the EBSMed Ti6Al4V alloy contains fine-acicular martensite, basket-weave (α+β) as well as widmanstatten (α+β), and the martensite mainly concentrates at the last dozens of forming layers. With the increase of P/V, the height of martensite region rises from 7~8 forming layers to 22~25 forming layers. In addition, the mixed internal microstructure of basket-weave and widmanstatten is formed instead of lamellar widmanstatten microstructure. Meanwhile, the thickness of lamellar α phase increases from 1~2 μm to 2~4 μm
Pre-alloyed Ti6Al4V powder was used to fabricate solid components by Electron Beam Selective Melting (EBSM). The characteristics of microstructures of the powder were investigated using OM, SEM, TEM and XRD. Results show that the EBSMed Ti6Al4V alloy contains fine-acicular martensite, basket-weave (α+β) as well as widmanstatten (α+β), and the martensite mainly concentrates at the last dozens of forming layers. With the increase of P/V, the height of martensite region rises from 7~8 forming layers to 22~25 forming layers. In addition, the mixed internal microstructure of basket-weave and widmanstatten is formed instead of lamellar widmanstatten microstructure. Meanwhile, the thickness of lamellar α phase increases from 1~2 μm to 2~4 μm
2015, 44(12):3234-3237.
Abstract:
A quantitative experimental study with digital image correlation (DIC) algorithm on shear banding deformation behaviors of high purity, fully dense nanocrystalline Ni sheet subjected to quasi-static uniaxial tensile load was carried out. Based on that, onset and evolution of shear bands in nanocrystalline Ni were analyzed, and some critical points, such as shear band nucleation, broadening process and failure point were recognized quantitatively. Finally, the physical characteristics of shear bands, such as inclination and width, were discussed. Results show that the nanocrystalline Ni exhibits shear localization in the form of shear band, which is the main reason of the early failure during plastic deformation
A quantitative experimental study with digital image correlation (DIC) algorithm on shear banding deformation behaviors of high purity, fully dense nanocrystalline Ni sheet subjected to quasi-static uniaxial tensile load was carried out. Based on that, onset and evolution of shear bands in nanocrystalline Ni were analyzed, and some critical points, such as shear band nucleation, broadening process and failure point were recognized quantitatively. Finally, the physical characteristics of shear bands, such as inclination and width, were discussed. Results show that the nanocrystalline Ni exhibits shear localization in the form of shear band, which is the main reason of the early failure during plastic deformation
2015, 44(12):3243-3247.
Abstract:
Microstructure evolution of extruded Mg-2Zn-xY (x=0.5, 1, 2, at%) alloys in semi-solid isothermal heat treatment process was investigated. The results show that in these three kinds of Mg-2Zn-xY alloys, α-Mg grain size of extruded Mg-2Zn-1Y alloy is the minimum, and a large number of twins are found in extruded Mg-2Zn-2Y alloy. When the semi-solid isothermal time is 10 min, with increasing temperature, α-Mg solid phase grains in Mg-2Zn-xY alloy are gradually spheroidized, and separated by liquid phases. Otherwise, the liquid phase contents located both at the grain boundaries and in the grain interior significantly increase. With the increase of isothermal time (≤30 min) at 580 °C, Ostwald ripening mechanism acts a major role during microstructure evolution of semi-solid Mg-2Zn-0.5Y alloy. However, both Ostwald ripening mechanism and solid particle melting mechanism act major roles at the same time during microstructure evolution of semi-solid Mg-2Zn-1Y and Mg-2Zn-2Y alloys
Microstructure evolution of extruded Mg-2Zn-xY (x=0.5, 1, 2, at%) alloys in semi-solid isothermal heat treatment process was investigated. The results show that in these three kinds of Mg-2Zn-xY alloys, α-Mg grain size of extruded Mg-2Zn-1Y alloy is the minimum, and a large number of twins are found in extruded Mg-2Zn-2Y alloy. When the semi-solid isothermal time is 10 min, with increasing temperature, α-Mg solid phase grains in Mg-2Zn-xY alloy are gradually spheroidized, and separated by liquid phases. Otherwise, the liquid phase contents located both at the grain boundaries and in the grain interior significantly increase. With the increase of isothermal time (≤30 min) at 580 °C, Ostwald ripening mechanism acts a major role during microstructure evolution of semi-solid Mg-2Zn-0.5Y alloy. However, both Ostwald ripening mechanism and solid particle melting mechanism act major roles at the same time during microstructure evolution of semi-solid Mg-2Zn-1Y and Mg-2Zn-2Y alloys
2015, 44(12):3032-3036.
Abstract:
A novel alkali-activated magnesium slag-based cementitious nanocomposite (AMSCN) was synthesized by co-loaded NiO and CuO, and employed as a photocatalyst for the degradation of methyl orange dye. The FESEM images reveal that the AMSCN has a nanostructural morphology with average size of about 30 nm. The XRD patterns show that the AMSCN is principally composed of mineralogical phase of calcium silicate hydrate (C-S-H). NiO active species are uniformly dispersed in the form of amorphous phase and CuO emerged nanophase with mean size of 15 nm on the surface of AMSCN. The 10(NiO+CuO)/AMSCN nanocomposite exhibits the highest photocatalytic degradation rate (93%) due to the synergistic effect between the AMSCN matrix and active species of NiO and CuO. The kinetics analysis indicates that the photocatalytic degradation of methyl orange follows the first order reaction kinetics
A novel alkali-activated magnesium slag-based cementitious nanocomposite (AMSCN) was synthesized by co-loaded NiO and CuO, and employed as a photocatalyst for the degradation of methyl orange dye. The FESEM images reveal that the AMSCN has a nanostructural morphology with average size of about 30 nm. The XRD patterns show that the AMSCN is principally composed of mineralogical phase of calcium silicate hydrate (C-S-H). NiO active species are uniformly dispersed in the form of amorphous phase and CuO emerged nanophase with mean size of 15 nm on the surface of AMSCN. The 10(NiO+CuO)/AMSCN nanocomposite exhibits the highest photocatalytic degradation rate (93%) due to the synergistic effect between the AMSCN matrix and active species of NiO and CuO. The kinetics analysis indicates that the photocatalytic degradation of methyl orange follows the first order reaction kinetics
2015, 44(12):3089-3093.
Abstract:
A highly active LaNi5-xAlx alloy films was prepared by using pulse electrolysis. The depolarization of Ni cathode and the co-electrodepositing principle in the molten salt system was studied by thermodynamic calculation and cyclic voltammetry, microscopic structures of alloy films were observed and analyzed by scanning electron microscopy and X-ray diffractometry. The results show the electrodeposition and diffusion processes are effectively separated by pulse electrolysis. In fact, the precipitation of aluminium in Ni cathode is found to significantly decrease the activity of La2O3 from Na3AlF6114g, Al2O31.2g and La2O34.8g molten salts firstly, then the depolarization of Ni cathode makes it possible for the co-electrodepositing principle of La and Al. Finally, the LaNi5-xAlx alloy films with high surface area and uniform composition is prepared, where x values rang between 3.5-4.
A highly active LaNi5-xAlx alloy films was prepared by using pulse electrolysis. The depolarization of Ni cathode and the co-electrodepositing principle in the molten salt system was studied by thermodynamic calculation and cyclic voltammetry, microscopic structures of alloy films were observed and analyzed by scanning electron microscopy and X-ray diffractometry. The results show the electrodeposition and diffusion processes are effectively separated by pulse electrolysis. In fact, the precipitation of aluminium in Ni cathode is found to significantly decrease the activity of La2O3 from Na3AlF6114g, Al2O31.2g and La2O34.8g molten salts firstly, then the depolarization of Ni cathode makes it possible for the co-electrodepositing principle of La and Al. Finally, the LaNi5-xAlx alloy films with high surface area and uniform composition is prepared, where x values rang between 3.5-4.
