In recent year, various rheo-forming methods have been developed to produce higher mechanical property products. In particular, Rheo-forging of metal offers not only high mechanical strength but also much lower machine loads than solid forming processes. However, there are many problems such as indr...
In recent year, various rheo-forming methods have been developed to produce higher mechanical property products. In particular, Rheo-forging of metal offers not only high mechanical strength but also much lower machine loads than solid forming processes. However, there are many problems such as indraft of air during stirring in molten metal and the starting materials are still expensive. As a result, the commercial semi-solid products are still limited. Semi-solid materials are produced with a special microstructure by stirring during solidification from their molten state.
First, A356 and Al6061 rheological aluminum materials was manufactured by EMS(electromagnetic stirring system). The principal parameters for EMS system were stirring current, stirring time and pouring temperature which had an effect on controlling the microstructure. After stirring, the equivalent diameter and roundness were measured to find the optimal stirring conditions. Moreover, T6 heat treatment conditions according to the ageing time for rheological material was carried out about A356 and Al6061 aluminum alloys.
In addition, the rheological material of A356 casting aluminum was fabricated by electromagnetic stirrer (EMS) in vacuum to prevent air from coming into the rheological material. It is very important to find the optimal fabrication condition that is composed of stirring time, stirring current and solid fraction. The experimental parameters, in vacuum state of 760~ 38 Torr, were stirring time (0 ~ 930 sec), stirring current (0 ~ 40 A), and solid fraction (30 ~ 60 %). The rheological material fabricated by the evacuated electromagnetic stirring system was compared with the previously fabricated rheological material without vacuum at the view point of microstructure aspect such as porosities and mechanical properties.
Furthermore, this paper presents the results of the influence of air control during stirring and direct and indirect forging. A356 and Al6061 aluminum alloys were manufactured by electromagnetic stirring with a vacuum pump and fabricated by hydraulic press machinery. Both the manufacture of billet and the fabrication of sample were used by the vacuum pump to prevent the indraft of air. To compare of air control, two type samples were fabricated. One sample was fabriated with vacuum pump. The other sample was fabricated without air control system. The shape of product was selected to observe the deformation behavior. It is similar to alphabet H. In addition, to predict the deformation behavior, the finite element simulations of forging of Al6061 and A356 aluminum alloy were performed using the DEFORM-3D software.
Finally, in this paper, thin aluminum plate for bipolar plate was studied by low rheo-casting process with EMS system. The total of weight of biopolar plate being used in automobile fuel cell, which stacks 880 units of a bipolar plate whose single unit of weight is 83g, becomes 73kg when using 0.2mm thickness stainless steel for automobile fuel cell. However, when using aluminum bipolar plate for fuel cell, the bipolar plate weighs 30 g and the total weight of the fuel cell would be 27kg which is one third of use of stainless steel. However, the conventional manufacturing process such as a press forming to form the light metal like aluminum is difficult to be employed to form the bipolar plater because they have disadvantages at the aspects of the material properties, cost, and mass production. In order to overcome these difficulties, we develop the complex rheoforming process, called semisolid processing, which can control the crystal size and its movement of high strengthened-light material. Using this process, we develop the bipolar plate through the semi-continuous forming process which can control the crystal grain by electromagnetic stirring and which can produce thin aluminum plate under vacuum-evacuation and gas pressure.
In recent year, various rheo-forming methods have been developed to produce higher mechanical property products. In particular, Rheo-forging of metal offers not only high mechanical strength but also much lower machine loads than solid forming processes. However, there are many problems such as indraft of air during stirring in molten metal and the starting materials are still expensive. As a result, the commercial semi-solid products are still limited. Semi-solid materials are produced with a special microstructure by stirring during solidification from their molten state.
First, A356 and Al6061 rheological aluminum materials was manufactured by EMS(electromagnetic stirring system). The principal parameters for EMS system were stirring current, stirring time and pouring temperature which had an effect on controlling the microstructure. After stirring, the equivalent diameter and roundness were measured to find the optimal stirring conditions. Moreover, T6 heat treatment conditions according to the ageing time for rheological material was carried out about A356 and Al6061 aluminum alloys.
In addition, the rheological material of A356 casting aluminum was fabricated by electromagnetic stirrer (EMS) in vacuum to prevent air from coming into the rheological material. It is very important to find the optimal fabrication condition that is composed of stirring time, stirring current and solid fraction. The experimental parameters, in vacuum state of 760~ 38 Torr, were stirring time (0 ~ 930 sec), stirring current (0 ~ 40 A), and solid fraction (30 ~ 60 %). The rheological material fabricated by the evacuated electromagnetic stirring system was compared with the previously fabricated rheological material without vacuum at the view point of microstructure aspect such as porosities and mechanical properties.
Furthermore, this paper presents the results of the influence of air control during stirring and direct and indirect forging. A356 and Al6061 aluminum alloys were manufactured by electromagnetic stirring with a vacuum pump and fabricated by hydraulic press machinery. Both the manufacture of billet and the fabrication of sample were used by the vacuum pump to prevent the indraft of air. To compare of air control, two type samples were fabricated. One sample was fabriated with vacuum pump. The other sample was fabricated without air control system. The shape of product was selected to observe the deformation behavior. It is similar to alphabet H. In addition, to predict the deformation behavior, the finite element simulations of forging of Al6061 and A356 aluminum alloy were performed using the DEFORM-3D software.
Finally, in this paper, thin aluminum plate for bipolar plate was studied by low rheo-casting process with EMS system. The total of weight of biopolar plate being used in automobile fuel cell, which stacks 880 units of a bipolar plate whose single unit of weight is 83g, becomes 73kg when using 0.2mm thickness stainless steel for automobile fuel cell. However, when using aluminum bipolar plate for fuel cell, the bipolar plate weighs 30 g and the total weight of the fuel cell would be 27kg which is one third of use of stainless steel. However, the conventional manufacturing process such as a press forming to form the light metal like aluminum is difficult to be employed to form the bipolar plater because they have disadvantages at the aspects of the material properties, cost, and mass production. In order to overcome these difficulties, we develop the complex rheoforming process, called semisolid processing, which can control the crystal size and its movement of high strengthened-light material. Using this process, we develop the bipolar plate through the semi-continuous forming process which can control the crystal grain by electromagnetic stirring and which can produce thin aluminum plate under vacuum-evacuation and gas pressure.
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