Thermal contraction of the casting and the thermal expansion of the mold result in gap formation at the mold-casting interface, which affects greatly the heat transfer between the mold and casting. Information on the movements of the mold and casting during solidification and cooling is also the basis for the investigation of the casting deformation.Movements of the casting and mold were analyzed simultaneously using coupled thermo-mechanical contact boundary model for the plate casting of aluminum alloy. The calculated displacement and temperature distributions of the casting and mold were compared with the previous measured data. It was confirmed that the mold and the casting moved together until the air gap formed by the calculation. Comparing the air gap curve with the displacement curve of the casting just before and after air gap formation made it apparent that the growth of the air gap was mainly due to contraction of the casting because the change in the mold displacement was not significant. Gap formation time increased with increase in initial mold temperature.KEY WORDS: coupled thermo-mechanical contact boundary model; air gap formation; mold bending; plate casting; mold and casting displacement.boundary model for the aluminum alloy plate casting. Figure 1 shows the meshes of the mold and of the casting used for thermal and stress analysis, performed by twodimensional thermo-mechanical coupled analysis. Half of the transverse section at the mid-height of the mold and casting was chosen for analysis. Dimensions of the casting were 100 mm wide by 12.5 mm thick, and the mold 150 mm wide by 37.5 mm thick. Size and shape of the casting and mold were chosen to compare the calculated results in the present study with the measured ones in the previous papers. 2,6,21,23,25) Each number in the figure shows locations where temperature and displacement are checked. Location 2 and 3 in the figure look like the same node, but two nodes are overlapped. Computational Procedure Model DescriptionA four-node quadrilateral element was used, one mesh being 2.5 by 1.25 mm for the mold, and 3.3 by 2.5 mm for the casting. The mold material was cast iron, the cast alloy being Al-7%Si-0.3%Mg alloy. Casting was treated as an elastic-plastic deformable body, mold as an elastic deformable one and plane strain was assumed.Mold material properties were assumed to be constant independent of temperature. Casting material properties were temperature dependent. Thermal conductivity and modulus of elasticity with temperature are given in Tables 1 and 2. 21) Density of the casting is 2 700 kg/m 3 . The latent heat was converted into the change of specific heat over the solidification range. However Al-7%Si-0.3%Mg alloy includes eutectic, latent heat during primary and eutectic solidification was evaluated using the ratio measured by a differential scanning calorimeter. In eutectic solidification, a temperature of 1 K was set as the range for latent release.Constant linear thermal contraction during solidification of the cast metal was co...
This study demonstrates the feasibility of a novel casting process called tailored additive casting (TAC). The TAC process involves injecting the melt several times to fabricate a single component, with a few seconds of holding between successive injections. Using TAC, we can successfully produce commercial-grade automotive steering knuckles with a tensile strength of 383 ± 3 MPa and an elongation percentage of 10.7 ± 1.1%, from Al 6061 alloys. To produce steering knuckles with sufficient mechanical strength, the composition of an Al 6061 alloy is optimized with the addition of Zr, Zn, and Cu as minor elements. These minor elements influence the thermal properties of the melt and alloy, such as their thermal stress, strain rate, shrinkage volume, and porosity. Optimal conditions for heat treatment before and after forging further improve the mechanical strength of the steering knuckles produced by TAC followed by forging.
Pure silicon can be obtained from Al-Si alloys by a combination of solvent refining and centrifugation. Primary silicon crystals are separated in the form of a foam after centrifugation. A vertical centrifugal separator is used which needs no more effort for further separation since each part of the high and low silicon content is divided automatically into two pieces after centrifugation. This centrifugal method does not use the density difference between two phases as in other methods, but uses the order of solidification in Al-Si alloys. How to make the Si foam, its characteristics including its density and strength, and purity of the extracted Si particles after acid leaching are reviewed.
Solvent refining of silicon from Al-Si melts assisted by a centrifugation was investigated for three alloys in the Al-Si system. Silicon was successfully separated from aluminum-rich phase in the form of a foam by centrifugation. As the silicon content increased, the recovery decreased because less aluminum-rich phases remained in the silicon foam. The weight ratio before and after acid leaching of the silicon foam was inversely related to its apparent density before acid leaching. The purity of the extracted silicon decreased slightly with increased silicon content. The purity of the silicon flakes obtained from the Al - 30% Si alloy was 4N, except aluminum. Boron and phosphorus in the silicon flakes could be lowered effectively by decreasing the silicon content in the Al-Si alloys
To develop Cu alloy with tensile strength of 800 MPa and electrical conductivity of 80 %IACS (International Annealed Copper Standard), the variation of mechanical strength and electrical conductivity in Cu-Ag alloy during fabrication processes including casting, solid solution and ageing treatment were investigated. Solid solution hardening leads to a large drop in electrical conductivity of Cu-Ag alloys due to super-saturation of Ag solute in Cu matrix. Ageing hardening gives rise to enhance both of the mechanical strength and the electrical conductivity. Therefore, it can be mentioned that the electrical conductivity of Cu-Ag alloys was affected dominantly by Ag solute in Cu matrix.
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