Papers by Keyword: Semisolid Casting

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Authors: Safar Rostamzadeh, Behzad Niroumand, Ali Maleki
Abstract: In the present research, the possibility of single stage semi-solid casting of a hypereutectic gray cast iron in a sand mold was investigated. For this purpose, a specially designed chilled sprue sand mold rigged to a vertical centrifugal casting machine was used. The molten cast iron was poured in the chilled sprue sand mold at 1275 oC at a rotation speed of 400 rpm. Two control samples were also poured at 1275 oC under gravity and centrifugal casting conditions in the same mold without sprue chilling. Microstructures and mechanical properties of the specimens were then characterized. The results showed that the average length and thickness of the primary solid phase, i.e. the Kish graphite, and those of the eutectic flake graphite were smaller in semi-solid centrifuged castings and their hardness were higher than those of the control samples. The results are discussed in terms of the shearing and chilling effects of the designed sprue during the initial stages of pouring.
Authors: Hong Xing Lu, You Feng He, Stephen P. Midson, Da Quan Li, Qiang Zhu
Abstract: Surface blistering during T6 heat treating is an artifact that is essentially unique to high pressure casting processes such as semi-solid casting and die casting. It is believed that the blistering originates from subsurface defects present in the castings. When the castings are exposed to elevated temperatures during solution heat treatment, the strength of the aluminum is reduced, and the defects expand to deform the surfaces of the castings. There are three potential sources for the subsurface defects - entrapped air, die lubricant or shot sleeve lubricant.This paper will report on a study to determine the origin of the defects present in the castings that produce the blisters. Along with attempting to separate the influence of air and the two types of lubricants on blister formation, the study will also examine the impact of a number of process parameters on blistering.
Authors: Ryoji Nakamura, Hisaki Watari, Shinji Kumai
Abstract: Two kinds of roll casters, which were suitable for high speed roll casting, were devised. One was a vertical type twin roll caster, and the other was an unequal diameter twin roll caster. The semisolid roll casting using a cooling slope was adopted to these roll casters. The solid fraction was smaller than 5%. 3 mm thickness of 6111 strip was cast at 60 m/min by the vertical type twin roll caster, and 5 mm thickness of 6111 strip was cast at 30 m/min by the unequal diameter twin roll caster. The microstructure of the as-cast strip was equiaxed and spherical, not columnar. The mechanical properties of the strip rolled from roll-cast strip were almost as same as that of the strip made from cast ingot.
Authors: Khaled A. Ragab, Mohamed Bouazara, Amine Bouaicha, Hatem Mrad
Abstract: The diversity of physical and mechanical properties of aluminum alloys leads to develop a variety of manufacturing processes including the semi-solid casting process. Fatigue failure is considered the most common problem occurred in automotive engineering applications by which the vehicle components, mainly suspension system parts, fail under conditions of dynamic loading. It is well known that the fatigue life of aluminum castings, mainly A357, is very sensitive to casting design as well as to casting defects and microstructure constituents. The fatigue characteristics of automotive lower suspension arm made of semi-solid A357 aluminum castings have been investigated using metallurgical and analytical approaches. The critical stress areas capable of initiating cracks during fatigue tests are detected by using fatigue experimental design for real part materials by the installation of strain gages on the suspension arm to calculate maximum stress; further more, analytical approach is applied using modelling software. Microstructure characteristics of the semisolid A357 under T6 heat treatment conditions are examined using scanning electron microscope. The results show that using the SEED casting technology (Swirled Enthalpy Equilibration Device) has an efficient effect on the mechanical and metallurgical characteristics of real part materials that are also affected by castings design.
Authors: Futoshi Kido, Tetsuichi Motegi
Abstract: In order to produce AZ91 and AZ31 magnesium alloy billets semisolid continuous casting by using an inclined cooling plate was carried out. The molten magnesium alloy in an electric furnace was flowed on the inclined cooling plate and then poured in a tundish. The slurry prepared using this process was solidified by drawing a dummy bar from a water-cooled copper mold, consequently producing a billet. As a result, we could produce the magnesium alloy billets by semisolid continuous casting. Magnesium alloy billets with refined and globular primary α crystals were successfully and continuously cast by optimizing the solidification conditions. In this case, the grain size of AZ91 billets was about 55μm and that of AZ31 billets was 50μm. The AZ91 billets produced by semisolid continuous casting were employed in thixocasting experiments. The experiments revealed that thixocasting could produce the mobile phone casings with spherical primary α crystals at 858K. Moreover, we proved that the difference of shot cycle did not influence the microstructures for up to 251 shots.
Authors: Yoshiki Tsunekawa, Shinpei Suetsugu, Masahiro Okumiya, Yuichi Furukawa, Naoki Nishukawa, Yoshikazu Genma
Abstract: Hypereutectic Al-Si-Cu alloys which are typical light-weight wear-resistant materials, are required to improve the ductility as well as the strength and wear-resistance for the wider applications. Increase in amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys, however, it leads to the poor strength and ductility. It is known that dual phase steels composed of hetero-structure have succeeded to bring contradictory mechanical properties of high strength and ductility concurrently. In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance, ultrasonic irradiation to molten metal during the solidification, which is named sono-solidification, was carried out from its molten state to just above the eutectic temperature. The sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure, that is, hard primary silicon particles, soft non-equilibrium α-Al phase and eutectic region. Rheocasting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk specimen. After the rheocasting with modified sono-solidified slurry held for 45s at 570oC, the quantitative optical microscope observation exhibits that the microstructure is composed of 18area% of hard primary silicon particles and 57area% of soft α-Al phase, in contrast there exist only 5area% of primary silicon particles and no α-Al phase rheocast with normally solidified slurry. Hence the tensile tests of T6 treated rheocast specimens with modified sono-solidified slurry exhibit the improved strength and 5% of elongation, regardless of more than 3 times higher amounts of primary silicon particles compared to that rheocast with normally solidified slurry.
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