• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.148-151
• /
• 2004

Different kinds of feedstock of semisolid a356 aluminum alloy manufactured by EMS stirring only, inoculation of Al-5Ti-B only and combination of inoculation and EMS stirring were investigated. It is found that the grain size of these feedstock are $350{\mu}m$ for EMS casting only, $320{\mu}m$ for inoculation by Al-5Ti-B, and $100{\mu}m$ for the combination of EMS stirring and inoculation of Al-5Ti-B master alloys. The microstructure of the sample obtain by combination of inoculation and EMS system show the best homogeneousness and finest grains.

• 한국주조공학회지
• /
• 제30권1호
• /
• pp.46-51
• /
• 2010

Recently, automotive industry is attempting to replace steels for automotive parts with light-weight alloys such as aluminum alloy, because of the growing environmental regulations governing exhaust gas and the engine effectiveness of a vehicle. The low cycle fatigue (LCF) and high cycle fatigue (HCF) properties as well as the microstructure and tensile property were investigated on the low pressure cast A356 aluminum alloy wheel, which was followed by T6 heat treatment. The cast microstructure of the alloy influenced significantly on the low cycle and high cycle fatigue behaviors. The rim part of cast aluminum alloy wheel showed higher low cycle and high cycle fatigue strength compared with the spoke part, which should be caused by higher cooling rate of rim part. The spoke part of the wheel showed coarser dendrite arm spacing (DAS) and wide eutectic zone in the microstructure, which resulted in the partial brittle fracture and lower fatigue life time.

• 한국군사과학기술학회지
• /
• 제7권1호
• /
• pp.47-58
• /
• 2004

Loss factors of A356, Mn-Cu alloy and aluminum matrix composites reinforced with $SiC_p$ and Ni-coated graphite particles at various contents have been investigated using clamped-free cantilever beam method. The loss factors of half-power bandwidth of the specimens were measured over a wide range of frequencies from 50 to 3300Hz. Among the specimens, Al-10%$SiC_p$-10%$C_p$ showed the highest loss factor at the mode I, while Mn-Cu alloy showed the highest loss factors at the modes II and III. Consequently, at the mode I the Al-10%$SiC_p$--10%$C_p$ showed the loss factor of 0.00093, which is 2.64 and 1.58 times higher than those of A356 and Mn-Cu alloy, respectively.

• 한국주조공학회지
• /
• 제34권4호
• /
• pp.123-129
• /
• 2014

This work presents the results of a thixo-extrusion process applied to aluminum alloy and and reheating characteristics of semi-solid A356 Alloy using have been discussed. The reheating experiment was performed using an electric resistance furnace and multi-stage heating for uniform reheating. The thixo-extrusion was performed at the optimal reheating conditions of the semi-solid A356 alloy, the the extrusion conditions were an extrusion ratio of 33 and ram speed of 6 mm/sec. The results showed that the thixo-extrusion of semi-solid A356 alloy fabricated by the cooling slope reduced the extrusion pressure by 180% in comparison with hot extrusion, and that a sound extrusion could be obtained in spite of the same extrusion ratio and strain rate.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 춘계학술대회 논문집
• /
• pp.273-276
• /
• 2004

A356 alloy is one of the most popular casting aluminum alloys due to its good castability. It is well known that the mechanical properties of A356 alloy strongly depend on its characteristic microstructure, such as the size of eutectic Si, primary $\alpha$ dendrite and so on. These microstructural features are determined during the casting and solidification process, which implies the strong relationship with mechanical properties with solidification methods. In the present study, the mechanical characteristics of A356 alloy was investigated by using squeeze cast control arm in terms of the microstructural features, such as the size of eutectic Si, primary a dendrite. By doing so, the most favorable microstructure of A356 could be determined for Al control arm that should be one of the most reliable parts in automobile.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2005년도 추계학술대회 논문집
• /
• pp.227-230
• /
• 2005

Many rheocasting processes had been proposed because of the difficulty of recycling, the limit of material, and the high cost of raw material in thixocasting. But, these rheocasting processes also had disadvantages such as the high initial Investment cost and the lower mechanical properties than thixocasting. In this study, a continuous fabrication of rheological material with pressure rotation equipment was newly devised to overcome the disadvantages of rheocasting process. In order to investigate the thixoformability, reheating experiments were carried out with the material fabricated by the newly devised equipment. Morphological characteristics between mechanical stirring and reheating were compared.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.493-498
• /
• 2002

Friction stir welding (FSW) is a relatively new solid-state joining process which can homogenize the heterogeneous microstructure by intensely plastic deformation arising from the rotation of the welding tool. The present study applied the FSW to an A356 aluminum (AI) alloy with the as-cast heterogeneous microstructure in the T6 temper condition, and examined an effect of microstructure on mechanical properties in the weld. The base material consisted of Al matrix with a high density of strengthening precipitates, large eutectic silicon and a lot of porosities. The FSW led to fragment of the eutectic silicon, extinction of the porosities and dissolution of the strengthening precipitates in the Al alloy. The dissolution of strengthening precipitates reduced the hardness of the weld around the weld center and the transverse ultimate tensile strength of the weld. Longitudinal tensile specimen containing only the stir zone showed the roughly same strength as the base material and a much larger elongation. Moreover, Charpy impact tests indicated that the stir zone had remarkably the higher absorbed energy than the base material. The higher mechanical properties of the stir zone were attributed to a homogenization of the as-cast heterogeneous microstructure by FSW.

• 한국주조공학회지
• /
• 제30권5호
• /
• pp.174-178
• /
• 2010

In the present study, in-situ real-time observation with an X-ray radioscopic facility was carried out on pure aluminum and aluminum alloy solidification. The three kinds of aluminum alloys, such as pure aluminum, Al-8.5%Si alloy, commercial A356 (AC4C) alloys, were used in the present study. The formations of the shrinkage defects in the castings were visualized and different formation phenomena for different aluminum alloys were investigated.

• 한국주조공학회지
• /
• 제31권6호
• /
• pp.354-361
• /
• 2011

The liquid metal shearing device was constructed and assembled with a commercial high-pressure die-caster in order to induce intensive turbulent shearing force on molten aluminum alloys. The effect of the liquid metal shearing on the microstructure and tensile properties of A356 alloys was investigated with the variation of iron content. The experimental results show that dendritic primary ${\alpha}$-Al phase was effectively modified into a equiaxed form by the liquid metal shearing. It was also found that the needle-like ${\beta}$-AlFeSi phase in a Fe containing A356 alloy was changed into a blocky shape resulting in the improved mechanical properties. Based on the mechanical properties, it was suggested that the iron content in A356 alloy could be more widely tolerated by utilizing the liquid metal shearing HPDC process.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2009년도 추계학술대회 논문집
• /
• pp.371-374
• /
• 2009

Die casting process has been used widely for complex automotive products such as the knuckle, arm and etc. Generally, a part fabricated by casting has limited strength due to manufacturing defects by origin such as the dendrite structure and segregation. As an attempt to offer a solution to these problems, forging has been used as an alternative process. However, the forging process provides limited formability for complex shape products. Rheo-forging of metal offers not only superior mechanical strength but also requires significantly lower machine loads than solid forming processes. This paper presents the results of an A356 aluminum alloy sample, which were obtained by experiment and by simulation using DEFORM 3D. Samples of metal parts were subsequently fabricated by using hydraulic press machinery.