Semisolid A356 alloy feedstock poured through a serpentine channel

Fine spheroidal and equiaxed nondendritic microstructures required for semisolid casting can be formed through a serpentine pouring channel.Effects of the pouring temperature and the vertical section length of the serpentine pouring channel were studied.The results indicate that both favorable semisolid microstructures of A356 aluminum alloy can be generated by a serpentine pouring channel,and the solid shell inside the channel can be avoided when the pouring temperature is in the range from 660 to 680°C.It...     

Numerical simulation on reho-diecasting mould filling of an automobile master brake cylinder

An apparent viscosity model of semi-solid A356 aluminum alloy has been developed and the software Castsoft6.0 coupled with the model has been used to simulate the mould filling of an automobile master brake cylinder with the semi-solid A356 alumi-num alloy slurry.The simulation results are in agreement with the practical filling process, indicating that the apparent viscosity model is feasible and can be used to simulate the mould filling of the semisolid A356 aluminum alloy slurry and can be used to opti-mize the filling process and the design of dies.A higher injection pressure, a higher ingate flow velocity of the semi-solid slurry, and a higher slurry temperature are advantageous to the mould filling of the automobile master brake cylinder.     

Numerical simulation on the rheo-diecasting of the semi-solid A356 aluminum alloy

The effect of injection pressure, piston velocity, and the forming temperature of semisolid slurry on the filling behavior of the semi-solid A356 aluminum alloy was investigated by simulation methods. The simulation results show that these processing parameters have an important effect on the filling behavior of the semi-solid A356 aluminum alloy. The slurry flows steadily in the cavity when the injection pressure, the piston velocity, and the forming temperature are low, but it is prone to turbulent flow w...     

Performance of Semi-solid Slurry Produced by Twin-screw Stirring Mixer and Rheo-diecasting Process of AZ91D Alloy

The microstructure of semi-solid slurry of AZ91D alloy, which was produced by twin-screw stirring mixer under the different parameters, was investigated. Rheoforming by cold chamber die casting process was performed thereafter. The results indicate that with decreasing of the barrel temperature of the mixer and the pouring temperature of molten Mg alloy, the solid fraction of semi-solid slurry increases and the size of non-den-dritic grains becomes smaller. While the shear rate increases, the solid fraction of semi-solid slurry decreases. The tensile strength and elongation of metal rheoformed by die casting are higher by about 37% and 44% respectively than those produced by conventional liquid die casting.     

Filling ability of semi-solid A356 aluminum alloy slurry in rheo-diecasting

The effects of slurry temperature, injection pressure, and piston velocity on the rheo-filling ability of semisolid A356 alloys were studied by the reho-diecasting methods. The results show that the slurry temperature of the semi-solid A356 aluminum alloy has an important effect on the filling ability; the higher the slurry temperature, the better is the filling ability, and the appropriate slurry temperature for rheo-filling is in the range of 585-595℃. The injection pressure also has a great effect on the filling ability, and it is appropriate to the rheo-filling when the injection pressure is in the range of 15-25 MPa. The piston velocity also has a great effect on the filling ability, and it is appropriate to the rheo-filling when the piston velocity is in the range of 0.072-0.12 m/s. The filling ability of the slurry prepared by low superheat pouring with weak electromagnetic stirring is very good and the microstructural distribution in the rheo-formed die castings is homogeneous, which is advantageous to the high quality die casting. 2008 University of Science and Technology Beijing. All rights reserved.     

复合工艺制备的半固态A356铝合金初生相形貌分形特征研究

利用复合工艺制备了A356铝合金半固态浆料,研究了半固态A356铝合金初生相形貌的分形特征．应用编制的计算程序计算了半固态A356铝合金初生相形貌的分形维数．结果表明,复合工艺制备的半固态A356铝合金初生相的形貌可以用分形维数来表征,不同工艺参数下所获得的半固态初生相形貌具有不同的分形维数．铸锭中不同部位半固态初生相的形貌具有不同的分形维数,反映了同一铸锭不同部位的凝固条件对半固态初生相形貌的影响．凝固组织中的每个半固态初生相的分形形貌均为系统耗散性的几何表现．     

Three-dimensional analysis of the modified sloping cooling/shearing process

A self-designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. A three-dimensional simulation model was established for the analysis of preparing the semisolid Al-3wt%Mg alloy. Through simulation and experiment, it is shown that the sloping angle of the plate greatly affects temperature and velocity distributions, and the temperature and velocity of the alloy at the exit of the sloping plate increase with the increase of the sloping angle. The alloy temperature decreases linearly from the pouring mouth to the exit. The alloy temperature at the exit increases obviously with the increase of pouring temperature. To prepare the semisolid Al-3wt%Mg alloy with good quality, the sloping angle θ=45° is reasonable, and the pouring temperature is suggested to be designed above 650-660°C but under 700°C.     

Continuous Extruding Extending Forming of Semi-solid A2017 Alloy

1 IntroductionSince the pioneering work of Flemings[1-3]and hisco-workers ,semi-solid metals and their processing tech-niques ,as a near-net shape technology,have drawn con-siderable attention,especiallyinthe automobile and elec-tronic products industries[3-5].Semi-solid process can di-videintothixoformingandrheoforming.At present ,thixo-forming process has been applied successfully, such assemi-solid die casting,semi-solid extrusion and semi-sol-id dieforging.Thethixoforming processinvolves …     

Low superheat pouring with a Shear Field in rheocasting of aluminum alloys

A new rheocasting process, Low Superheat Pouring with a Shear Field （LSPSF）, was developed to produce semi-solid slurry for the rheo-forming process. The LSPSF process is one of controlled nucleation and limited growth techniques in which effective nucleation rate is controlled by passive mixing and localized rapid cooling near the liquidus temperature; dendrite growth is limited by a much slower cooling process. The experimental results of rheocast Al-Cu alloy 201 and secondary diecasting alloy A380 demonstrate that LSPSF process is capable of producing high-quality slurry in a matter of seconds. It is concluded that maximizing nucleation and nuclei survival directly lead to the grain refinement of the rheocasting microstructure, and high nuclei density combined with a slower cooling afterwards leads to a globular structure of primary phases.     

亚共晶铝硅合金半固态初生相形貌分形维数的计算

利用低过热度浇注技术制备了亚共晶铝硅合金半固态浆料,研究了半固态初生相的形貌及其分形维数和计算方法．应用图像计盒维数的算法计算了亚共晶铝硅合金半固态初生相的分形维数,并编制了相应的计算程序对亚共晶铝硅合金半固态初生相的形貌图像的计盒维数进行了计算．结果表明,不同工艺条件下制备的亚共晶铝硅合金半固态的初生相形貌有不同的分形维数;分形维数可反映初生相形貌的复杂程度．借助分形维数的计算结果可研究亚共晶铝硅合金半固态初生相的形貌及其组织性能．     

Preparation of semisolid AlSi7Mg alloy slurry through weak traveling-wave electromagnetic stirring

The semisolid AlSi7Mg alloy slurry with large capacity was prepared by low superheat pouring and week traveling-wave electromagnetic stirring.The effects of electromagnetic stirring power and frequency on the shape and distribution of primary α-Al grains in the AlSi7Mg alloy slurry were discussed.The experimental results show that the AlSi7Mg alloy slurry with fine and spherical primary α-Al grains distributed homogeneously can be obtained.Under the condition of low superheat pouring and week traveling-wave...     

Microstructure evolution of Al-Si semi-solid slurry by gas bubble stirring method

A novel technique of introducing gas bubble stirring during solidification was studied to prepare Al-Si semi-solid slurry. The microstructure evolution of the slurry during slow cooling process after stirring was investigated. The effects of the solidification rate on the microstructure of the semi-solid slurry were investigated under three different solidification conditions. The results show that fine non-dendritic slurry can be obtained using the gas bubble stirring method. Ripening and coarsening of primary Al grains are observed during the slow cooling process, and at last coarsened eutectic Si appears. Primary Al grains with different sizes and eutectic Si are obtained, corresponding to three different solidification rates.     

Effects of Extrusion Processing on Microstructure of 7075Al Alloy in the Semi-solid State

A recrystallization and partial melting(RAP) process was introduced to prepare the semi-solid 7075 aluminum alloy used for thixoforming. In order to obtain an ideal semi-solid microstructure, a series of extrusion experiments were conducted to comparatively investigate the optimum extrusion process parameters. Commercial 7075 Al alloy samples were firstly extruded with varying extrusion ratios below the recrystallization temperature followed by homogenization, then these samples were reheated to the semi-solid state and held in the range of 5 to 50 minutes. The experimental results show that varying process cause the difference in the deformation degree and microstructure for as-extruded samples, resulting in various semi-solid microstructure. It is verified that the formation of equiaxed grains in semi-solid microstructure depends on recrystallization behavior of extruded samples during partial melting. Both relative high extrusion temperature and low extrusion ratio lead to high volume fraction of recrystallized area, thus entirely equiaxed solid grains in semi-solid 7075 Al alloy samples can be obtained finally. In addition, Ostwald ripening was determined as the dominate coarsening mechanism of solid grains in semi-solid state for this 7075 Al alloy during the RAP route. The influence of predeformation on recrystallization behavior of this 7075 Al alloy was discussed in detail.     

半固态成形工艺对Sn-Bi合金性能的影响

采用机械搅拌技术制备锡铋合金半固态浆料,研究了搅拌温度、搅拌时间对锡铋半固态合金组织和力学性能的影响.试验结果表明:搅拌速度为320 r/min、搅拌时间为10 min、搅拌温度为145℃时的搅拌效果相对较好,得到了近球形的半固态锡铋合金金相组织,固相颗粒的尺寸较小,分布较均匀.半固态铸造挤压制备温度保险丝的抗拉强度和延伸率与一般普通铸造挤压法相比分别提高了23%和28%;半固态锡铋合金浸润性良好,可以达到温度保险丝的使用要求.     

Numerical simulation of the preparation of semi-solid metal slurry with damper cooling tube method

In semi-solid forming process, preparing the slurry with rosette or globular microstructure is very important. A new ap- proach named the damper cooling tube method (DCT), to produce the semi-solid metal slurry, has been introduced. To optimize the technical parameters in designing the apparatus, the finite volume method was adopted to simulate the flow process. The temperature effects on the rheological properties of the slurries were also considered. The effects of the technical parameters on the slurry proper- ties were studied in detail.     

水冷多联分离式热管数据机房节能潜力分析

水冷多联分离式热管系统被提出用于冷却数据机房,该系统综合了自然冷却技术和变频技术的优点,能够有效地降低制冷系统的能耗。为了探索水冷多联分离式热管系统相对于传统空调系统的节能潜力:首先,建立了水冷多联分离式热管系统的传热模型并且利用实验进行了验证,得知其相对误差在±10%以内;其次,通过建立的水冷多联分离式热管系统的能耗模型确定了系统的最佳送风温度设定值和供水温度设定值,其值分别是24?C和15?C;最后,对比分析冷却系统#1～#3的全年运行能耗,获得了水冷多联分离式热管系统(#3)相对于是否利用湖水源的传统空调系统(#2与#1)的节能率,其节能率分别为11.3%和68.8%。     

New method for the preparation of semi-solid AISi7Mg alloy slurry

The effects of pouring temperature and short electromagnetic stirring with low strength on the microstructures of AlSi7Mg alloy were investigated.The results show that if liquid AlSi7Mg alloy is poured at 630 or 650 ℃,many primary α-Al grains in the solidified melt are rosette-like,and only a small number of them are spherical.However,if liquid AlSi7Mg alloy is poured at a lower superheat and meanwhile is stirred by an electromagnetic field at a low power for a short time,then most primary α-Al grains in the solidified melt become spherical,and only a few are rosette-like.The theoretical analysis indicates that the strengthened melt flow motion induced by the short electromagnetic stirring makes the temperature field more homogeneous in the melt,which is poured at a lower superheat,and makes the primary α-Al grains deposit in a larger region at the same time,so this new solidification kinetic condition leads to the microstructure of spherical primary α-Al grains.The experiments also demonstrate that pouring at an appropriate superheat and stirring by an electromagnetic field at a low power for a short time is a good new method for preparing the semi-solid slurry or billet of AlSi7Mg alloy.     

铝合金的半固态成形技术

金属材料的半固态成形是一种能够获得致密组织及高性能零部件的近净成形技术,被认为是一项绿色成形新技术。在简要介绍半固态成形技术研究现状的基础上,着重叙述了作者进行高能超声波制备铝合金半固态浆料、半固态浆料流变压铸成形的试验研究。研究表明,超声制浆及半固态压铸成形工艺适合于铝合金零件的成形制造。含20％Si 的高硅铝合金Al-20Si-2Cu-1Ni经过半固态压铸成形,T6热处理后抗拉强度可达到310MPa,比传统液态压铸提高34％。     

Microstructural formation of semi-solid AZ91D alloy stirred by electromagnetic field

With the help of an electromagnetic stirring device, alloy melt quenching and EBSD (electron back scatter diffraction)analysis technology, the microstructure of the semi-solid AZ91D magnesium alloy slurry stirred by rotational electromagnetic field under different stirring power conditions has been studied. The results show that the size of primary α-Mg phase is reduced obviously when the solidifying alloy melt is stirred by rotational electromagnetic field, moreover, the primary α-Mg grains are changed to fine rosette grains or spherical grains which are proved to belong to the different grains in three-dimension by the EBSD analysis technology. The results also show that the stirring power is an important processing parameter in the preparation of the semi-solid AZ91D magnesium alloy slurry. The larger the stirring power, the finer the primary α-Mg grains, the less the rosette primary α-Mg grains, and the more the spherical primary α-Mg grains. Theoretical analysis indicates that a stronger flow motion leads to a more even temperature field and solute field and a stronger man-made temperature fluctuation in the alloy melt so that the specially fine rosette and/or spherical primary α-Mg grains are formed in the semi-solid AZ91D magnesium alloy slurry.     

New method for the preparation of semi-solid AlSi7Mg alloy slurry

The effects of pouring temperature and short electromagnetic stirring with low strength on the microstructures of AlSi7Mg alloy were investigated. The results show that if liquid AlSi7Mg alloy is poured at 630 or 650℃, many primary α-Al grains in the solidified melt are rosette-like, and only a small number of them are spherical. However, if liquid AlSi7Mg alloy is poured at a lower superheat and meanwhile is stirred by an electromagnetic field at a low power for a short time, then most primary α-Al grains in the solidified melt become spherical, and only a few are rosette-like. The theoretical analysis indicates that the strengthened melt flow motion induced by the short electromagnetic stirring makes the temperature field more homogeneous in the melt, which is poured at a lower superheat, and makes the primary α-Al grains deposit in a larger region at the same time, so this new solidification kinetic condition leads to the microstructure of spherical primary α-Al grains. The experiments also demonstrate that pouring at an appropriate superheat and stirring by an electromagnetic field at a low power for a short time is a good new method for preparing the semi-solid slurry or billet of AlSi7Mg alloy.