Castability of Ti-6Al-7Nb alloy for dental casting.
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Castability of Ti-6Al-7Nb alloy, CP Ti, and Co-Cr alloy was examined for mesh type and plate type specimens. The casting was carried out with a pressure type casting machine and commercial molding material. The castability of the mesh type specimen was evaluated in terms of the number of cast segments (castability index), and that of the plate type was evaluated by the area of the specimen (casting rate). X-ray images processed by a digital imaging technique were used to identify the casting porosity. The casting rate of the specimens increased with increasing thickness of the specimens. It was concluded that the castability index and the casting rate of Ti-6Al-7Nb alloy was slightly lower than that of CP Ti, and higher than that of Co-Cr alloy, were as Ti-6Al-7Nb alloy showed fewer casting porosities than CP Ti and smaller ones than Co-Cr alloy, which was advantageous for increasing the reliability of the casting properties.Keywords:
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Together with porosity, the problems created by the formation of iron intermetallics in Al-Si alloys pose serious concerns in regard to their use in structural components. The presence of these intermetallics, particularly the brittle β-Al5FeSi phase, tends to reduce the alloy properties and casting quality. In order to optimise the iron intermetallics in Al-6.5% Si-3.5% Cu-Fe alloys, the effects of cooling rate, Sr modification, other melt additions, and heat treatment were studied, with a view to determining the means of their formation and dissolution, in relation to their effect on porosity formation and alloy properties. The iron levels selected for study were 0.5%, 1.0% and 1.5%, covering the range of levels normally observed in foundry alloys. Castings were prepared using a cooling fin sand mould (DAS range: 25–85 μm) for microstructural analysis, and a Stahl permanent mould for tensile testing purposes. Samples of molten metal quenched in cold water provided much smaller DASs. Microstructural characterisation was carried out using optical microscopy and thermal, image and electron microprobe analyses. Tensile properties (T6 condition) were determined at room temperature and a strain rate of 4 × 10−4/s using an Instron Universal testing machine. The results show that at any Fe level, the average β-Al5FeSi platelet length is strongly determined by the DAS. Strontium (250–350 ppm) is effective in reducing the β-platelet size through its fragmentation/dissolution effect on the latter. At higher Sr concentrations, both coarsening of the β-platelets (i.e., "overmodification") and their decomposition (through Si rejection ahead of the platelets) occur. Addition of P increases β-phase formation (due to the presence of AIP particles that act as possible nucleation sites). Melt superheating (900 °C) thereafter reduces the effect. At Fe levels of 1% or more, α-Chinese script or sludge particles form only at slow cooling rates or with superheating. Tensile properties of alloys containing up to 1 % Fe are improved with Mn, Mn + Cr, Sr or Be additions. Best overall properties are achieved with Mn at Mn/Fe = 0.7. Also, Sr additions of 200–300 ppm are best, higher levels giving rise to increased porosity levels and, hence, lower properties. For a given Fe level, the optimum Sr concentration depends on the cooling rate and Si content of the alloy. Iron levels of 1.5% are not recommended for Al-6.5% Si-3.5% Cu (319.2) alloys as the properties cannot be improved by any of the above means.
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The present article describes the effect of adding iron into melt, and its impact on the microstructure, chemical composition and mechanical properties of AlSi7Mg0.3 alloy. Higher iron content is typical of the so-called secondary alloy, which becomes increasingly used by a growing number of manufacturers in the production process of high-quality castings. The behaviour of AlSi7Mg0.3 alloy with high Fe content has not been scientifically investigated and sufficiently described, therefore working with secondary alloy is very problematic when focusing on high-sophistication castings for the automotive industry. In general, iron is unwanted in aluminium alloys, and its content should be kept as low as possible. The only exception is the process of pressure die casting where we can tolerate iron content up to 1 wt. %. In gravity casting of Al-Si-based alloys, the critical iron content changes mainly depending on the silicon content. The experimental part of this article investigates the impact of gradual addition of iron into AlSi7Mg0.3 alloy on the content of the main alloying elements such as, in particular, Si and Mg. In order to eliminate the negative effect of iron in the alloy, we used in the experiment the correctors Ni and Cr in the form of AlNi20 and AlCr20 master alloys.
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This paper describes a vertical type twin roll strip casting process for producing aluminum alloy strip of ADC12, A3003 and A7075. Twin roll casting process is able to produce a strip from molten metal directly. Thus this process has a possibility to reduce total cost of sheet making comparing to conventional rolling process. Aluminum alloy ADC12 is a casting material that is used for die casting. A3003 is known as a wrought aluminum alloy for aluminum can body sheet. The A3003 sheet is generally produced by rolling, so it is effective for reducing a process cost to produce the strip by twin roll casting process. Aluminum alloy A7075 has high tensile strength, and it is known as a material for aerospace application. The sheet is manufactured in small quantities comparing to the other sheet aluminum alloy. It is supposed that the demand of high tensile strength aluminum sheet such as A7075 is going to increase for weight saving of structural material. In this study, twin roll casting experiment was performed to produce these three aluminum alloy strip in same experimental conditions. Castability, surface conditions and strip thickness were estimated. It was possible to cast these aluminum alloy strip.
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Alonizing
6063 aluminium alloy
Die casting
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Refractory metals
Nickel alloy
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Spark Plasma Sintering
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Powder Metallurgy
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The relationship between the porosity formation and various influence factors such as die - casting process, solidification time, cooling rate, hydrogen content, alloying constituent, modificater, degassing method, etc. in an AlSigCu3 alloy is studied. The function mechanisms of different influence factors are also analysed.
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Bismuth-bearing bronze alloy is drawing attention as a lead-free copper alloy substitute for CAC406 alloy. Effects of the bismuth content and cooling rate on the casting structure and mechanical properties of bronze alloys were investigated. The decrease in the liquidus line reduced with increasing bismuth content, resulting in a large change in the alloying components such as zinc and bismuth. The bismuth content of 3 mass% is appropriate for controlling composition and obtaining a good castability under the same casting conditions as CAC406 alloy. Small pores are formed in the bismuth-bearing bronze alloy. The amount of pores was found to increase with increasing bismuth content. In addition, higher cooling rates of the alloy during casting diminished the amount of pores and increased bulk density. Uniform dispersion of fine bismuth particles (about 10 μm) and grain refinement led to higher strength and higher elongation of the alloy. A 3 mass% bismuth-bearing bronze alloy of 2 mm in thickness showed more than 50% elongation and 300 MPa tensile strength.
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