Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing T...
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Effects of Al2O3 and Ni as the additives on the sinterability, microstructure and mechanical properties were systematic studied. The experimental results show that only a relative density about 96.2% of hot-pressing TiB2-30%Al2O3 can be attained due to the plate-like TiB2 particle and its random orientation and excessive Al2O3 grain growth. When sintering temperature is higher than 1 700 ℃, TiB2 grain growth can be found, which obvious improves flexural strength of TiB2 matrix but decreases toughness. It seems that mechanical properties of TiB2-Al2O3 composites are mainly depended on relative density besides grain growth. otherwise, they will be determined by relative density and TiB2 matrix strength together. Anyway, Al2O3 addition can weaken the grain boundary and thus improve the toughness of the materials. A flexural strength of 529 MPa, Vickers hardness of 24.8 GPa and indentation toughness of 4.56 MPa·m1/2 can be achieved inTiB2-30vol% Al2O3.
Multi-walled carbon nanotube （MWCNT）/TiO2/C60 composite catalysts were prepared by hydrothermal method. TiO2 was deposited on the MWCNT surface. Their photocatalytic activities for degradation of Rhodamine B dye wer...
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Multi-walled carbon nanotube （MWCNT）/TiO2/C60 composite catalysts were prepared by hydrothermal method. TiO2 was deposited on the MWCNT surface. Their photocatalytic activities for degradation of Rhodamine B dye were studied. X-ray diffraction, field emission transmission electron microscopy, ultraviolet-visible light absorption spectrum and photoluminescence spectrum were carried out to characterize the composite catalysts. The results indicated that MWCNTs and C60 could greatly enhance the photocatalytic activity of TiO2.
The thermal expansions of the rare earth zirconate (Ln2Zr 2O7, Ln = La, Nd, Sm, and Gd) pyrochlore were studied by the Debye and quasi harmonic approximation combined with the first principles calculations. The differ...
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The development of Functionally Graded materials (FGM) for energy-absorbing applications requires understanding of stress wave propagation in these structures in order to optimize their resistance to failure. One-dime...
The development of Functionally Graded materials (FGM) for energy-absorbing applications requires understanding of stress wave propagation in these structures in order to optimize their resistance to failure. One-dimensional stress wave in FGM composites under elastic and plastic wave loading have been investigated. The stress distributions through the thickness and stress status have been analyzed and some comparisons have been done with the materials of sharp interfaces (two-layered material). The results demonstrate that the gradient structure design greatly decreases the severity of the stress concentrations at the interfaces and there are no clear differences in stress distribution in FGM composites under elastic and plastic wave loading.
The stress increments depend not only on the plastic strain but also on the gradient of plastic strain, when the characteristic length scale associated with non-uniform plastic deformation is on the order of microns. ...
The stress increments depend not only on the plastic strain but also on the gradient of plastic strain, when the characteristic length scale associated with non-uniform plastic deformation is on the order of microns. In the present research, the Taylor-based nonlocal theory of plasticity (TNT plasticity), with considering both geometrically necessary dislocations and statistically stored dislocations, is applied to investigated the effect of particle shapes on the strain gradient and mechanical properties of SiC particle reinforced aluminum composites (SiC/Al composites). Based on this theory, a two-dimensional axial symmetry cell model is built in the ABAQUS finite element code through its USER-ELEMENT (UEL) interface. Some comparisons with the classical plastic theory demonstrate that the effective stress predicted by TNT plasticity is obviously higher than that predicted by classical plastic theory. The results also demonstrate that the irregular particles cause higher effective gradient strain which is attributed to the fact that angular shape particles give more geometrically.
Strain gradient theories have been considered to be an effective means for capturing the size effects on ceramic particle-reinforced metal-matrix composites (MMCp), but the results predicted by them are significantly ...
Strain gradient theories have been considered to be an effective means for capturing the size effects on ceramic particle-reinforced metal-matrix composites (MMCp), but the results predicted by them are significantly lower than the corresponding experimental data. One reason might be, that the thermal residual stresses caused by thermal contraction mismatch between the metal matrix and the ceramic particle were neglected in the numerical models. By incorporating the Taylor-based nonlocal theory (TNT) of plasticity, the finite element method (FEM) is applied in the present research, to investigate the effect of thermal residual stresses on the yield stress and average axial stresses of the aluminium matrix reinforced by silicon carbide particles (SiCp/Al). The elements of the matrix have been implemented in the ABAQUS finite element code through its USER-ELEMENT (UEL) interface for TNT plasticity. Some comparisons with the associated literature demonstrate that the numerical model with the thermal residual stresses is more in agreement with the experimental results.
Based on microstructure evolution of Mg-20Al-0.8Zn magnesium alloys realized by semisolid isothermal heat-treatment(SSIT),we obtained the non-dendrite or spherical grains microstructure under the suitable technologica...
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Based on microstructure evolution of Mg-20Al-0.8Zn magnesium alloys realized by semisolid isothermal heat-treatment(SSIT),we obtained the non-dendrite or spherical grains microstructure under the suitable technological parameters that isothermal temperature is 495 and holding time is 120 min.℃ With the help of special experimental equipment,the semisolid die-casting process has been studied and the specimens have been *** effects of different parameters as injection speed and pressure on tensile strength,elongation rate,hardness,etc have been *** results indicate that tensile strength was improved along with increasing injection speed and ***,excessive speed will involve gas,which formed defects and reduced the mechanical *** the injection pressure is 40MPa and injection speed is 4m/s,the tensile strength and elongation rate can reach maximal 220MPa and 5.63% *** fracture mechanism was intercrystalline cracking.
Tin bronze wires were produced by dieless drawing. The effects of heating power, the distance between cooler and heater as well as feeding speed on the diameter, the temperature field, and the deformation region profi...
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Tin bronze wires were produced by dieless drawing. The effects of heating power, the distance between cooler and heater as well as feeding speed on the diameter, the temperature field, and the deformation region profile of the wires were investigated. The results indi-cated that each processing parameter exhibited both lower and upper limits of stable deformation based on the criterion of stable deformation with the diameter fluctuation of ±0.05 mm. Both the temperature and its gradient of the deformation region increased with increasing heating power under stable deformation, but decreased with an increase in feeding speed. As the distance between cooler and heater increased, the temperature of the deformation region increased and the slope of the deformation region profile decreased. The processing limit map of sta-ble deformation exhibited a closed curve and the unstable deformation consisted of wire breakage and diameter fluctuations.
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