An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method （TE/QP）. The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents ...An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method （TE/QP）. The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results have shown that TiCp/Al composite with 40～70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy （TEM）. The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as （220）Al//（022）TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength （σ） and modulus （E） are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.展开更多
In the framework of finite volume method(FVM),two modified schemes of quadratic upstream interpolation for convective kinematics(QUICK),namely quasi-QUICK(Q-QUICK) and normal quasi-QUICK(NQ-QUICK),for improving the pr...In the framework of finite volume method(FVM),two modified schemes of quadratic upstream interpolation for convective kinematics(QUICK),namely quasi-QUICK(Q-QUICK) and normal quasi-QUICK(NQ-QUICK),for improving the precision of convective flux approximation are verified in 3D unsteady advectiondiffusion equation of pollutants on unstructured grids.The constructed auxiliary nodes for Q-QUICK or NQQUICK are composed of two neighboring nodes plus the next upwind node;the later node is generated from intersection of the line of current neighboring nodes and their corresponding interfaces.The numerical results show that Q-QUICK and NQ-QUICK overwhelm central differencing scheme(CDS) in computational accuracy and behave similar numerical stability to upwind difference scheme(UDS),hybrid differencing scheme(HDS) and power difference scheme(PDS) after applying the deferred correction method.Their corresponding CPU time is approximately equivalent to that of traditional difference schemes.In addition,their abilities for adapting high grid deformation are robust.It is so promising to apply the suggested schemes to simulate pollutant transportation on arbitrary 3D natural boundary in the hydraulic or environmental engineering.展开更多
文摘An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method （TE/QP）. The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results have shown that TiCp/Al composite with 40～70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy （TEM）. The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as （220）Al//（022）TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength （σ） and modulus （E） are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.
基金the National Public Research Institutes for Basic Research and Development Operating Expenses Special Project (Nos.CKSF2010014/SL,YWF0905,CKSF2010011 and CKSF2012008/SL)the National Basic Research Program (973) of China(No.2007CB714106)
文摘In the framework of finite volume method(FVM),two modified schemes of quadratic upstream interpolation for convective kinematics(QUICK),namely quasi-QUICK(Q-QUICK) and normal quasi-QUICK(NQ-QUICK),for improving the precision of convective flux approximation are verified in 3D unsteady advectiondiffusion equation of pollutants on unstructured grids.The constructed auxiliary nodes for Q-QUICK or NQQUICK are composed of two neighboring nodes plus the next upwind node;the later node is generated from intersection of the line of current neighboring nodes and their corresponding interfaces.The numerical results show that Q-QUICK and NQ-QUICK overwhelm central differencing scheme(CDS) in computational accuracy and behave similar numerical stability to upwind difference scheme(UDS),hybrid differencing scheme(HDS) and power difference scheme(PDS) after applying the deferred correction method.Their corresponding CPU time is approximately equivalent to that of traditional difference schemes.In addition,their abilities for adapting high grid deformation are robust.It is so promising to apply the suggested schemes to simulate pollutant transportation on arbitrary 3D natural boundary in the hydraulic or environmental engineering.
