SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tens...SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tensile and hardness tests. The experimental results showed that SiC particles distributed uniformly in the matrix and were in good combination with matrix. The tensile strength and hardness were improved significantly after heat treatment. With the increase of solid solution temperature, the alloy phases dissolved in the matrix gradually. When the solid solution temperature arrived at 505 ℃, the alloy phases dissolved thoroughly, and the composite exhibited the highest tensile strength and hardness（σb=360 MPa, HBS=104）. The main strengthening phase was Al2Cu, which was granular and distributed dispersively in the matrix. Effect of T6 was better than that of T4 at the same solid solution temperature.展开更多
In this study,a mathematical model was developed to optimize the heat treatment process for maximum tensile strength and ductility of aluminum(8011) silicon carbide particulate composites.The process parameters are so...In this study,a mathematical model was developed to optimize the heat treatment process for maximum tensile strength and ductility of aluminum(8011) silicon carbide particulate composites.The process parameters are solutionizing time,aging temperature,and aging time.The experiments were performed on an universal testing machine according to centre rotatable design matrix.A mathematical model was developed with the main and interactive effects of the parameters considered.The analysis of variance technique was used to check the adequacy of the developed model.The optimum parameters were obtained for maximum tensile strength.Fractographic examination shows the cracks and dimples on the fractured surfaces of heat-treated specimen.展开更多
The effect of the solid matrix and porosity of the porous medium are first introduced to the study of power-law nanofluids, and the Marangoni boundary layer flow with heat generation is investigated. Two cases of soli...The effect of the solid matrix and porosity of the porous medium are first introduced to the study of power-law nanofluids, and the Marangoni boundary layer flow with heat generation is investigated. Two cases of solid matrix of porous medium including glass balls and aluminum foam are considered. The governing partial differential equations are simplified by dimensionless variables and similarity transformations, and are solved numerically by using a shooting method with the fourth-fifth-order Runge-Kutta integration technique. It is indicated that the increase of the porosity leads to the enhancement of heat transfer in the surface of the Marangoni boundary layer flow.展开更多
The effects of solid solution and aging processing on the microstructures and mechanical properties of the multi-layer spray co-deposited 7090Al/SiCp composite were investigated. The experimented results show that fin...The effects of solid solution and aging processing on the microstructures and mechanical properties of the multi-layer spray co-deposited 7090Al/SiCp composite were investigated. The experimented results show that fine grains and homogeneous microstructures can be obtained,the average grain size of the as-solid solution treated and as-aged composites after extrusion is under 3.0 μm. A large amount of the Cu-rich phase particles form in the as-extruded samples,and solve into the matrix after solid solution treatment. After aging,the size of the precipitate phases,mainly MgZn2 and CuAl2 is less than 1.0 μm,which homogeneously distribute inside the grains and at the grain boundaries. The ultimate tensile strength of the composite treated at T6 state,i.e. solid solution treated at 475 ℃ for 1 h then aged at 120 ℃ for 24 h,is up to 765 MPa.展开更多
微波加热具有加热速度快、均匀性好以及体加热等优点,已广泛应用于食品、材料、化工以及医药等领域。在实际应用中,一般采用比例-积分-微分控制(Proportional Integral Derivative control,PID)算法来控制加热过程的温度,以达到较好的...微波加热具有加热速度快、均匀性好以及体加热等优点,已广泛应用于食品、材料、化工以及医药等领域。在实际应用中,一般采用比例-积分-微分控制(Proportional Integral Derivative control,PID)算法来控制加热过程的温度,以达到较好的加热效果。然而,基于PID算法的微波加热温控系统存在控制速度较慢、超调量较高以及稳态误差较大的问题。为此,本文提出了采用动态矩阵控制(Dynamic Matrix Control,DMC)算法,实现对微波加热过程的快速稳定控制。本文首先介绍了DMC算法的基本原理。然后以土豆为例,搭建了基于固态源的微波加热系统,并测量了系统的模型参数,讨论了优化时域、校正系数、控制系数和控制时域等参数对控制系统性能的影响。最后与PID控制算法的实际控制结果进行了比较。结果表明,与PID算法相比,本文提出的基于DMC算法的微波加热的温度控制,其超调量减小了69.8%,上升时间减小了22.2%,调整时间减小了64.9%,最大稳态误差减小了22.9%。展开更多
基金Funded by the National Natural Science Foundation of China(51371077)
文摘SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tensile and hardness tests. The experimental results showed that SiC particles distributed uniformly in the matrix and were in good combination with matrix. The tensile strength and hardness were improved significantly after heat treatment. With the increase of solid solution temperature, the alloy phases dissolved in the matrix gradually. When the solid solution temperature arrived at 505 ℃, the alloy phases dissolved thoroughly, and the composite exhibited the highest tensile strength and hardness（σb=360 MPa, HBS=104）. The main strengthening phase was Al2Cu, which was granular and distributed dispersively in the matrix. Effect of T6 was better than that of T4 at the same solid solution temperature.
文摘In this study,a mathematical model was developed to optimize the heat treatment process for maximum tensile strength and ductility of aluminum(8011) silicon carbide particulate composites.The process parameters are solutionizing time,aging temperature,and aging time.The experiments were performed on an universal testing machine according to centre rotatable design matrix.A mathematical model was developed with the main and interactive effects of the parameters considered.The analysis of variance technique was used to check the adequacy of the developed model.The optimum parameters were obtained for maximum tensile strength.Fractographic examination shows the cracks and dimples on the fractured surfaces of heat-treated specimen.
基金Supported by the National Natural Science Foundation of China under Grant No 51305080
文摘The effect of the solid matrix and porosity of the porous medium are first introduced to the study of power-law nanofluids, and the Marangoni boundary layer flow with heat generation is investigated. Two cases of solid matrix of porous medium including glass balls and aluminum foam are considered. The governing partial differential equations are simplified by dimensionless variables and similarity transformations, and are solved numerically by using a shooting method with the fourth-fifth-order Runge-Kutta integration technique. It is indicated that the increase of the porosity leads to the enhancement of heat transfer in the surface of the Marangoni boundary layer flow.
基金Project(06FJ3041) supported by the Science and Technology Bureau of Hunan Province, China
文摘The effects of solid solution and aging processing on the microstructures and mechanical properties of the multi-layer spray co-deposited 7090Al/SiCp composite were investigated. The experimented results show that fine grains and homogeneous microstructures can be obtained,the average grain size of the as-solid solution treated and as-aged composites after extrusion is under 3.0 μm. A large amount of the Cu-rich phase particles form in the as-extruded samples,and solve into the matrix after solid solution treatment. After aging,the size of the precipitate phases,mainly MgZn2 and CuAl2 is less than 1.0 μm,which homogeneously distribute inside the grains and at the grain boundaries. The ultimate tensile strength of the composite treated at T6 state,i.e. solid solution treated at 475 ℃ for 1 h then aged at 120 ℃ for 24 h,is up to 765 MPa.
