Abstract: The new rheology fabrication process has been developed to rheo die casting and rheo forming process. The barrel type equipment, which could continuously fabricate the rheology material, was specially designed to have a function to control cooling rate, shear rate and temperature. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed. The barrel surface has both the induction heating system and the cooling system to
control the temperature of molten metal. By using this system, the effect of the rotation speed and the rotation time on the microstructure was widely examined. The possibility for the rheoforming process was investigated with microstructural characteristic.
Abstract: Coarse grains of commercial 5052 Al and 5083 Al alloys were refined by the accumulative roll bonding (ARB) process. Average grain size of the refined microstructure was 200 nm. The 5083 Al alloy that has higher Mg content required more deformation for the refinement. Dry sliding wear behavior of the ultra-fine grained (UFG) Al alloys was investigated using a pin-on-disk wear tester at
room temperature. The UFG microstructure of the processed alloys hardly increased the wear resistance of the Al alloys in spite of the increased strength and hardness. Wear rate of the UFG Al alloys was higher than that of the non processed coarse-grained starting alloys. The SEM observation of worn surfaces revealed that surface deformation controlled the wear. The low wear resistance of
the UFG Al alloys was attributed to non-equilibrium and unstable grain boundaries and low strain hardening capability of the alloys.
Abstract: The separation system including a DC electric field with steady magnetic field was
adopted for removal of inclusion in molten Al alloy. But, very small inclusions, which less than 10 ㎛ are not eliminated. So, firstly, small inclusions are agglomerated by low frequency electromagnetic vibration. And then, we adopting the previously used electromagnetically inclusion removal process. Experiments were carried out on commercial die casting aluminum alloy A380 (JIS: ADC 10). Inclusion was separated continuously. XRF was used for compositional test and PoDFA for cleanliness test. Chemical composition of specimen was not changed and UTS,
elongation and cleanliness were increased.
Abstract: In this study, the electromagnetic vibration process is adopted for modifying the eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration (EMV), the finer the size of the eutectic Si phase. The tensile strength and elongation of EMVed alloys were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000Hz was approximately six times as high as that of the normal alloy and half of that of Sr
modified alloy. The mechanism for the increase in twin density due to EMV during solidification could be suggested from the fact that the preferential growth along <112> in silicon was suppressed by preventing the Si atom from attaching to the growing interface of the Si phase and by changing the solid/liquid interfacial energy of silicon.
Abstract: In this study, the electromagnetic vibration is adopted for control of the size of primary Si phase. The higher the current density and frequency of electromagnetic vibration (EMV), the finer the size of primary Si phase. The higher the current density but the lower frequency of EMV, the bigger the size of primary Si phase. This phenomenon considered to be related the collision, agglomeration and diffusion of silicon atoms.
Abstract: . Equal channel angular pressing (ECAP) is useful method to obtain the ultra-fine grained and the high hardened metal. The microstructure, the hardness, and the texture of the 1050 Al sheets by ECAP are changed by a severe shear deformation. The change of the microstructure, the hardness, and the texture were investigated on the 1050 Al sheets that were prepared by ECAP and annealing.
Abstract: Predictions of chromium additions to aluminum alloys to stabilize the deformation debris products were examined. Additions of 0.22 wt. % Cr to AA6063 extrusion alloys manifested enhanced formability under bending and precision-strain-rate-sensitivity tensile testing indicated that the stacking fault energy was reduced. The debris products were more resistant to dynamic recovery resulting in enhanced ductility at 27 °C and the solute-drag effect of Mg was dramatically manifested in the Haasen plot.
Abstract: The localized deformation behavior of annealed Al and Al severely deformed by ECAE process was determined by using microindentation test. Using the method proposed by Tabor, the indentation stress-strain curves of annealed Al and as-ECAE deformed Al were constructed, which display similar work-hardening behavior. For annealed Al, the altitude of the indentation stressstrain curves is a function of the indenter size. A master curve then is constructed, which displays
different work-hardening behavior. For the ECAE deformed Al, the indentation stress-strain curves are independent of the indenter size, suggesting that the microstructure inside the as-ECAE deformed Al is different from the annealed Al.
Abstract: Melt treatment is one of the most important processes in the production of casting Al
alloys. It is also a source of environmental pollution. A green and effective melt treatment with low environmental load (EI), which added with RE (Rare Earth) elements, was investigated in the paper. The research results show that this new treatment can modify, refine and purify the casting Al alloys simultaneously. Compared with the conventional treatment, the process is simplified, the metallurgic quality and mechanical properties are improved, and the environmental pollution which existed in the conventional treatment is solved thoroughly, so represented its wide applicative values.
Abstract: Aluminum foams having extremely low densities offer a large potential for lightweight
structural materials. New manufacturing process without expensive aluminum alloy powder has been developed using conventional bulk aluminum alloy sheets. Preform plate containing blowing agent particles is first manufactured through accumulative roll-bonding (ARB) process. By heating the preform plate, closed-cell aluminum foams having various porosity and cell morphology are produced. It was revealed that ARB processing condition is significantly important to produce suitable aluminum foam with high porosity and uniform pore distribution. Present manufacturing process also possesses a potential to apply to many other metal and alloy foams.