Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites wa...Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites was characterized by transmission electron microscopy （TEM） and high resolution transmission electron microscopy （HRTEM）. The selected area electron diffraction （SAED） for the interface was investigated. The elements at the interface were scanned by energy dispersive spectroscopy （EDS） and the EDS mapping was also obtained. X-ray diffraction （XRD） analysis was carried out for the composites fabricated by 1 pass, 2 passes and 4 passes ECAP-T. According to the XRD analysis, the influences of ECAP-T pass on the Bragg angle and interplanar spacing for AI crystalline planes were studied. The results show that after ECAP-T, the interface between A1 and SiC within the composites is a belt of amorphous SiO2 containing a trace of A1, Si and C which diffused from the matrix and the reinforcement. With the growing ECAP-T pass, the Bragg angle decreases and interplanar spacing increases for A1 crystalline planes, due to the accumulated lattice strain. The increasing lattice strain of A1 grains also boosts the density of the dislocation within A1 grains.展开更多
In order to improve the prediction capability of spring-back in aluminum sheet metal forming, the influence of the plastic deformation on elastic modulus is considered when the material undergoes a large plastic defor...In order to improve the prediction capability of spring-back in aluminum sheet metal forming, the influence of the plastic deformation on elastic modulus is considered when the material undergoes a large plastic deformation. The present work focused on establishing a new model to accurately describe the relation of elastic modulus and plastic deformation. The tensile tests were performed to investigate the influence of plastic deformation on elastic modulus at low strain rate. Two different aluminum sheets were used, AA2024-T3 and LY12-CZ, and the thickness of sheet metals was 1.3 mm and 2.0 mm, respectively. In order to overcome the drawback, which is directly measuring the slope of tension curve to obtain elastic modulus, an extrapolation method was adopted. The proposal macroscopic piecewise sinusoidal function can accurately model the elastic modulus variation.展开更多
For most strip-like plastic injection molded parts, whose cross section size is much smaller than their length, the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the war...For most strip-like plastic injection molded parts, whose cross section size is much smaller than their length, the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the warpage be- cause of their special shape. A new solution was suggested in this work. The strip-like plastic part was regarded as a little-curved beam macrnscopically, and was divided into a few one-dimensional elements. On the section of each elemental node location, two-dimensional thermal finite element analysis was made to obtain the non- uniform thermal stress caused by the time difference of the solidification of the plastic melt in the mold. The stress relaxation, or equivalently, strain creep was dealt with by using a special computing model. On the bases of in-mold elastic stress, the final bending moment to the beam was obtained and the warpage was predict- ed in good a^reement with practical cases.展开更多
Diffusion bonding is one of the most important techniques for composite materials, while bonding temperature, holding time,and rolling reduction are the key parameters that affect the bonding strength of sandwich plat...Diffusion bonding is one of the most important techniques for composite materials, while bonding temperature, holding time,and rolling reduction are the key parameters that affect the bonding strength of sandwich plates. To study the effect of plastic deformation on the bonding strength, laboratory experiments were carried on a Gleeble Thermal Simulator to imitate the diffusion-rolling bonding under different reductions for steel sandwich plates. The bonding strength and interlayer film thickness were measured, and the element diffusion was analyzed using line scanning. The relationship between the bonding strength and “diffused interlayer” thickness was investigated. It has been found that the bonding strength increases with reduction, whereas the interlayer film thickness decreases gradually as the reduction increases. The diffusion under plastic deformation is obviously enhanced in comparison with that of nil reduction. The mechanism of plastic deformation effect on the diffusion bonding and related models have been discussed.展开更多
Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies.The research activities are ...Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies.The research activities are funded primarily through four government-supported programs:the Key Technologies R&D Program of China,the National Basic Research Program of China,the National High-tech R&D Program of China,and the National Natural Science Foundation of China.The key R&D activities for the development of new wrought magnesium alloys in China are reviewed,and typical properties of some new alloys are summarized. More attentions are paid to high-strength wrought magnesium alloys and high-plasticity wrought magnesium alloys.Some novel plastic processing technologies,emerging in recent years,which aim to control deformation texture and to improve plasticity and formability especially at room temperature,are also introduced.展开更多
A new process of hydroforming with controllable radial pressure was proposed to overcome difficulties in the forming of low plastic materials and large height-to-diameter ratio workpieces. A typical 5A06 aluminum allo...A new process of hydroforming with controllable radial pressure was proposed to overcome difficulties in the forming of low plastic materials and large height-to-diameter ratio workpieces. A typical 5A06 aluminum alloy dome was numerically and experimentally investigated. The reasons for typical defects were analyzed under different radial pressures. Effects of radial pressure on the thickness distribution were discussed and optimal radial pressure was determined. It is shown by numerical simulations and experiment that a cup with a drawing ratio of 2.4 is formed by the new process of hydroforming with controllable radial pressure. It is significantly effective for the forming of low plastic materials and large height-to-diameter ratio workpieees. Two typical thinning points exit along the dome wall. With the radial pressure, thinning is decreased effectively at the two points, the dome forming is achieved and thickness distribution is more uniform.展开更多
基金Project(51175138) supported by the National Natural Science Foundation of ChinaProjects(2012HGZX0030,2013HGCH0011) supported by the Fundamental Research Funds for the Central Universities,China
文摘Powder mixture of pure A1 and oxidized SiC was consolidated into 10% （mass fraction） SiCp/AI composites at 523 K by equal channel angular pressing and torsion （ECAP-T）. The interfacial bonding of the composites was characterized by transmission electron microscopy （TEM） and high resolution transmission electron microscopy （HRTEM）. The selected area electron diffraction （SAED） for the interface was investigated. The elements at the interface were scanned by energy dispersive spectroscopy （EDS） and the EDS mapping was also obtained. X-ray diffraction （XRD） analysis was carried out for the composites fabricated by 1 pass, 2 passes and 4 passes ECAP-T. According to the XRD analysis, the influences of ECAP-T pass on the Bragg angle and interplanar spacing for AI crystalline planes were studied. The results show that after ECAP-T, the interface between A1 and SiC within the composites is a belt of amorphous SiO2 containing a trace of A1, Si and C which diffused from the matrix and the reinforcement. With the growing ECAP-T pass, the Bragg angle decreases and interplanar spacing increases for A1 crystalline planes, due to the accumulated lattice strain. The increasing lattice strain of A1 grains also boosts the density of the dislocation within A1 grains.
基金Project(06-13) supported by the Foundation of State Key Laboratory of Plastic Forming Simulation and Die & Mould Technology, China
文摘In order to improve the prediction capability of spring-back in aluminum sheet metal forming, the influence of the plastic deformation on elastic modulus is considered when the material undergoes a large plastic deformation. The present work focused on establishing a new model to accurately describe the relation of elastic modulus and plastic deformation. The tensile tests were performed to investigate the influence of plastic deformation on elastic modulus at low strain rate. Two different aluminum sheets were used, AA2024-T3 and LY12-CZ, and the thickness of sheet metals was 1.3 mm and 2.0 mm, respectively. In order to overcome the drawback, which is directly measuring the slope of tension curve to obtain elastic modulus, an extrapolation method was adopted. The proposal macroscopic piecewise sinusoidal function can accurately model the elastic modulus variation.
基金Supported by the Key Program of National Natural Science Foundation of China(11432003)the Key Research Project for Henan Universities(15A430009)
文摘For most strip-like plastic injection molded parts, whose cross section size is much smaller than their length, the traditional Hele-Shaw model and three-dimensional model do not work well in the prediction of the warpage be- cause of their special shape. A new solution was suggested in this work. The strip-like plastic part was regarded as a little-curved beam macrnscopically, and was divided into a few one-dimensional elements. On the section of each elemental node location, two-dimensional thermal finite element analysis was made to obtain the non- uniform thermal stress caused by the time difference of the solidification of the plastic melt in the mold. The stress relaxation, or equivalently, strain creep was dealt with by using a special computing model. On the bases of in-mold elastic stress, the final bending moment to the beam was obtained and the warpage was predict- ed in good a^reement with practical cases.
基金This work was financially supported by the National High-Tech Research and Development Program of China (No.2002AA334070)
文摘Diffusion bonding is one of the most important techniques for composite materials, while bonding temperature, holding time,and rolling reduction are the key parameters that affect the bonding strength of sandwich plates. To study the effect of plastic deformation on the bonding strength, laboratory experiments were carried on a Gleeble Thermal Simulator to imitate the diffusion-rolling bonding under different reductions for steel sandwich plates. The bonding strength and interlayer film thickness were measured, and the element diffusion was analyzed using line scanning. The relationship between the bonding strength and “diffused interlayer” thickness was investigated. It has been found that the bonding strength increases with reduction, whereas the interlayer film thickness decreases gradually as the reduction increases. The diffusion under plastic deformation is obviously enhanced in comparison with that of nil reduction. The mechanism of plastic deformation effect on the diffusion bonding and related models have been discussed.
基金Project(50725413)supported by the National Natural Science Foundation of ChinaProject(2007CB613704)supported by the National Basic Research Program of ChinaProject(2008DFR50040)supported by the International Cooperation Program of Ministry of Science and Technology of China
文摘Many researchers in China are actively engaged in the development of new types of wrought magnesium alloys with low cost or with high-performances and novel plastic processing technologies.The research activities are funded primarily through four government-supported programs:the Key Technologies R&D Program of China,the National Basic Research Program of China,the National High-tech R&D Program of China,and the National Natural Science Foundation of China.The key R&D activities for the development of new wrought magnesium alloys in China are reviewed,and typical properties of some new alloys are summarized. More attentions are paid to high-strength wrought magnesium alloys and high-plasticity wrought magnesium alloys.Some novel plastic processing technologies,emerging in recent years,which aim to control deformation texture and to improve plasticity and formability especially at room temperature,are also introduced.
基金Projects(50525516, 50875062 ) supported by the National Natural Science Foundation of China
文摘A new process of hydroforming with controllable radial pressure was proposed to overcome difficulties in the forming of low plastic materials and large height-to-diameter ratio workpieces. A typical 5A06 aluminum alloy dome was numerically and experimentally investigated. The reasons for typical defects were analyzed under different radial pressures. Effects of radial pressure on the thickness distribution were discussed and optimal radial pressure was determined. It is shown by numerical simulations and experiment that a cup with a drawing ratio of 2.4 is formed by the new process of hydroforming with controllable radial pressure. It is significantly effective for the forming of low plastic materials and large height-to-diameter ratio workpieees. Two typical thinning points exit along the dome wall. With the radial pressure, thinning is decreased effectively at the two points, the dome forming is achieved and thickness distribution is more uniform.
