The semi-solid 6061 aluminum alloy slurry was prepared by a serpentine channel pouring process. The effects of pouring temperature, bend number and bend diameter on the microstructures were investigated. Microstructur...The semi-solid 6061 aluminum alloy slurry was prepared by a serpentine channel pouring process. The effects of pouring temperature, bend number and bend diameter on the microstructures were investigated. Microstructural evolution mechanism of the semi-solid slurry during the pouring process was also analyzed. The results show that the grain is refined and the grain roundness is improved by controlling the pouring temperature close to the liquidus temperature, and the nucleation rate of primary α(Al) grains is effectively increased via increasing the bend number and decreasing the bend diameter. The primary grains are not only formed directly from the alloy melt via chilling nucleation and heterogeneous nucleation, but also evolved from the fractured dendrite fragments. Meanwhile, the heat exchange between the melt and the serpentine channel is increased by the “self-stirring” effect in the melt, which also promotes the refinement and spheroidization of primary α(Al) grains.展开更多
以6061铝合金磁控钨极氩弧焊(GTAW)的焊接电弧为研究对象,建立GTAW三维模型,对比分析了无外加磁场和外加横向磁场作用下焊接电弧的电流密度、洛伦兹力以及温度场的变化规律。结果表明,未施加磁场时,电弧具有高度的对称性,内部电流密度...以6061铝合金磁控钨极氩弧焊(GTAW)的焊接电弧为研究对象,建立GTAW三维模型,对比分析了无外加磁场和外加横向磁场作用下焊接电弧的电流密度、洛伦兹力以及温度场的变化规律。结果表明,未施加磁场时,电弧具有高度的对称性,内部电流密度最大值达到了2.66×10^(7)A/m^(2),洛伦兹力最大值达到了1.21×10^(5)N,电弧最高温度达到14862.4 K,径向上电流密度呈单峰分布,洛伦兹力呈双峰分布。随着横向磁场的施加,电弧发生偏转,洛伦兹力迅速增大,在磁场强度为0.2 m T时,洛伦兹力最大值增大到1.51×10^(5)N。偏转后电弧弧长增加,电势增大。展开更多
The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator.The relationship between the true stress and t...The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator.The relationship between the true stress and the true strain at different temperatures and strain rates was studied with the deformation degree of 70%.The microstructures during the deformation process were characterized.The deformation mechanism and thixo-forming properties of the semi-solid alloys were analyzed.The results show that the homogeneous and non-dendrite microstructures of semi-solid 6061Al alloy manufactured by near-liquidus casting technology could be transformed into semi-solid state with the microstructure suitable for thixo-forming which are composed of near-spherical grains and liquid phase with eutectic composition through reheating process.The deformation temperature and strain rate affect the peak stress significantly rather than steady flow stress.The resistance to deformation in semi-solid state decreases with the increase of the deformation temperature and decrease of the strain rate.At steady thixotropic deformation stage, the thixotropic property is uniform, and the main deformation mechanism is the rotating or sliding between the solid particles and the plastic deformation of the solid particles.展开更多
6061Al matrix composites reinforced by 5vol.%ABOw and 15vol.%SiCp were fabricated by semi-solid stirring technique successfully at 640 ℃ for 40min with the stirring rate of 300 rpm,and the composites were extruded at...6061Al matrix composites reinforced by 5vol.%ABOw and 15vol.%SiCp were fabricated by semi-solid stirring technique successfully at 640 ℃ for 40min with the stirring rate of 300 rpm,and the composites were extruded at a temperature of 500 ℃ using an extrusion ratio of 25:1 subsequently.Tensile tests were performed on as-casted and as-extruded(ABOw+SiCp)/6061Al composites at room temperature,and microstructures were observed by scanning electron microscope(SEM).SEM investigation showed that the as-extruded composite exhibited reduced porosity as well as a more uniform distribution of the reinforcements compared with the as-casted composite.The tensile tests results showed that the ultimate tensile strength and tensile elongation of as-extruded composite are higher than that of as-casted composite.展开更多
基于热锻条件,使用销-盘摩擦设备对6061热锻铝合金和H13钢基自润滑模具材料进行了高温对磨实验,通过电子探针和能谱仪分析了不同工况下工件和模具的磨损机理。结果表明,随着载荷的增加,工件和模具之间的摩擦因数与磨损率先降低后升高;...基于热锻条件,使用销-盘摩擦设备对6061热锻铝合金和H13钢基自润滑模具材料进行了高温对磨实验,通过电子探针和能谱仪分析了不同工况下工件和模具的磨损机理。结果表明,随着载荷的增加,工件和模具之间的摩擦因数与磨损率先降低后升高;随着转速的增加,工件和模具之间的摩擦因数增大,磨损率呈倍数增加;当载荷为12 N、转速为100 r·min^(-1)时,工件和模具之间的摩擦因数最小,其值为0.416,磨损率仅为24.591 mm 3·N^(-1)·m^(-1);随着转速和载荷的增加,工件和模具之间的粘着磨损加重并且逐渐出现磨粒磨损和氧化磨损。展开更多
文摘The semi-solid 6061 aluminum alloy slurry was prepared by a serpentine channel pouring process. The effects of pouring temperature, bend number and bend diameter on the microstructures were investigated. Microstructural evolution mechanism of the semi-solid slurry during the pouring process was also analyzed. The results show that the grain is refined and the grain roundness is improved by controlling the pouring temperature close to the liquidus temperature, and the nucleation rate of primary α(Al) grains is effectively increased via increasing the bend number and decreasing the bend diameter. The primary grains are not only formed directly from the alloy melt via chilling nucleation and heterogeneous nucleation, but also evolved from the fractured dendrite fragments. Meanwhile, the heat exchange between the melt and the serpentine channel is increased by the “self-stirring” effect in the melt, which also promotes the refinement and spheroidization of primary α(Al) grains.
文摘以6061铝合金磁控钨极氩弧焊(GTAW)的焊接电弧为研究对象,建立GTAW三维模型,对比分析了无外加磁场和外加横向磁场作用下焊接电弧的电流密度、洛伦兹力以及温度场的变化规律。结果表明,未施加磁场时,电弧具有高度的对称性,内部电流密度最大值达到了2.66×10^(7)A/m^(2),洛伦兹力最大值达到了1.21×10^(5)N,电弧最高温度达到14862.4 K,径向上电流密度呈单峰分布,洛伦兹力呈双峰分布。随着横向磁场的施加,电弧发生偏转,洛伦兹力迅速增大,在磁场强度为0.2 m T时,洛伦兹力最大值增大到1.51×10^(5)N。偏转后电弧弧长增加,电势增大。
基金Project(50874049) supported by the National Natural Science Foundation of ChinaProject(2008DFB50020) supported by International Science and Technology Cooperation of Ministry of Science and Technology of China
文摘The 6061 semi-solid aluminium alloy feedstocks prepared by near-liquidus casting were compressed in semi-solid state by means of Gleeble-3500 thermal-mechanical simulator.The relationship between the true stress and the true strain at different temperatures and strain rates was studied with the deformation degree of 70%.The microstructures during the deformation process were characterized.The deformation mechanism and thixo-forming properties of the semi-solid alloys were analyzed.The results show that the homogeneous and non-dendrite microstructures of semi-solid 6061Al alloy manufactured by near-liquidus casting technology could be transformed into semi-solid state with the microstructure suitable for thixo-forming which are composed of near-spherical grains and liquid phase with eutectic composition through reheating process.The deformation temperature and strain rate affect the peak stress significantly rather than steady flow stress.The resistance to deformation in semi-solid state decreases with the increase of the deformation temperature and decrease of the strain rate.At steady thixotropic deformation stage, the thixotropic property is uniform, and the main deformation mechanism is the rotating or sliding between the solid particles and the plastic deformation of the solid particles.
基金Funded by the Nationd Natural Science Foundation of China (No.2006CB605 203-3)
文摘6061Al matrix composites reinforced by 5vol.%ABOw and 15vol.%SiCp were fabricated by semi-solid stirring technique successfully at 640 ℃ for 40min with the stirring rate of 300 rpm,and the composites were extruded at a temperature of 500 ℃ using an extrusion ratio of 25:1 subsequently.Tensile tests were performed on as-casted and as-extruded(ABOw+SiCp)/6061Al composites at room temperature,and microstructures were observed by scanning electron microscope(SEM).SEM investigation showed that the as-extruded composite exhibited reduced porosity as well as a more uniform distribution of the reinforcements compared with the as-casted composite.The tensile tests results showed that the ultimate tensile strength and tensile elongation of as-extruded composite are higher than that of as-casted composite.
文摘基于热锻条件,使用销-盘摩擦设备对6061热锻铝合金和H13钢基自润滑模具材料进行了高温对磨实验,通过电子探针和能谱仪分析了不同工况下工件和模具的磨损机理。结果表明,随着载荷的增加,工件和模具之间的摩擦因数与磨损率先降低后升高;随着转速的增加,工件和模具之间的摩擦因数增大,磨损率呈倍数增加;当载荷为12 N、转速为100 r·min^(-1)时,工件和模具之间的摩擦因数最小,其值为0.416,磨损率仅为24.591 mm 3·N^(-1)·m^(-1);随着转速和载荷的增加,工件和模具之间的粘着磨损加重并且逐渐出现磨粒磨损和氧化磨损。
