Effect of cooling rate on solidification characteristics of aluminium alloy AA 5182 (original) (raw)
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Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2007
Dendrite coherency point in an aluminum-silicon-copper casting alloy was determined by analyses of the variation of the thermal diffusivity. The analysis was carried out using the readings of three thermocouples inserted at equal distances in a mould holding the alloy left to solidify. The values obtained by this method are confirmed by metallographic observations on samples left to solidify to the coherency point before plunging them in water.
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2000
The wide range of operational conditions existing in foundry and casting processes generates as a direct consequence a diversity of solidification microstructures. Structural parameters such as grain size and interdendritic spacings are strongly influenced by the thermal behavior of the metal/mold system during solidification, imposing, as a consequence, a close correlation between this system and the resulting microstructure. Mechanical properties depend on the microstructural arrangement defined during solidification. Expressions correlating the mechanical behavior with microstructure parameters should be useful for future planning of solidification conditions in terms of a determined level of mechanical strength, which is intended to be attained. In the present work, analytical expressions have been developed describing thermal gradients and tip growth rate during one-dimensional unsteadystate solidification of alloys. Experimental results concerning the solidification of Al-4.5 wt pct Cu and Al-15 wt pct Cu alloys and dendritic growth models have permitted the establishment of general expressions correlating microstructure dendrite spacings with solidification processing variables. The correlation of these expressions with experimental equations relating mechanical properties and dendrite spacings provides an insight into the preprogramming of solidification in terms of casting mechanical properties. JOSÉ M.V. QUARESMA, formerly Graduate Research Assisant, Departdrite arm spacings have been linked to other solidification ment of Materials Engineering, State University of Campinas, UNICAMP, is Associate Professor, Department of Mechanical Engineering, Federal thermal parameters, such as dendritic tip velocity and tempera-University of Para, Para, Brazil. CARLOS A. SANTOS, Research Assistant, ture gradient in the solidifying material, as a function of and AMAURI GARCIA, Professor, are with the Department of Materials distance from the chill surface. Based on mathematical models Engineering, State University of Campinas, UNICAMP, 13-083-970, Camof heat transfer and dendritic growth during unsteady-state pinas-SP, Brazil.
2011
Thermal analysis technique has been used for a long time, in both ferrous and nonferrous industries for evaluating the metallurgical quality of the liquid metal before casting. However, obtaining a proper microstructure in a standard cup does not ensure that the microstructure is correct in real parts which may solidify at very different cooling rates. For this study, alloy A356 with different metal quality in terms of modification and grain refinement was tested. Different cooling rates were obtained by using cylindrical test samples with various diameters cast in sand and metallic moulds. The correlation between microstructure features such as grain size, modification rate and secondary dendrite arm spacing (SDAS) measured in the standard thermal analysis cup with those obtained in the cylindrical test parts has been investigated. Thus, knowing the thermal modulus and the mould type it is possible to establish the required grain size and modification rate in the standard cup in or...
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Thixoforming process is a metal forming process in the semi-solid condition to produce near net shaped products. The key requirement of the thixoforming process is the production of feedstock materials that consists of solid spheroids in the liquid matrix, rather than dendrites. The solid spheroidal structure could not be generated if the gravity cast alloy that consists of the dendritic structure is directly subjected to partial remelting. Cooling slope casting process is one of the simplest and cheapest methods that can be utilised to produce the nondendritic structure. In the present study, the effects of cooling slope casting process on the microstructure of Al4.8Si2.8Cu0.5Mg aluminium alloy were investigated. The alloy was melted at a superheated temperature of 700 °C before cooled down to the selected pouring temperature (650 °C) and subsequently poured onto a stainless steel plate with the cooling length of 400 mm. The plate was tilted at 60° from horizontal and was cooled wi...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2018
In the present work, the effect of processing parameters of cooling slope techniques (pouring temperature, slope angle and slope length) of ADC 12 Al alloy on its microstructural evolution has been studied in detail. A series of cooling slope casting experiments were conducted by varying the pouring temperature (580, 585 and 590°C), slope length (400, 500 and 600 mm) and slope angle (30°, 45°and 60°). The effect of processing parameters on the response factors, viz. degree of sphericity and particle size, has been investigated by applying analysis of variance (ANOVA), interaction graphs obtained using response surface methodology. The obtained results infer that optimum values of the degree of sphericity (0.865) and particle size (49.30) are observed for the following set of processing parameters, namely 585°C pouring temperature, 500 mm slope length and 45°slope angle. ANOVA results show that the pouring temperature is the most significant input variables that influence degree of sphericity and particle size followed by slope length and slope angle. The values of output variables obtained from confirmation experiment, performed at 95% confidence level, ensure that they are well within the permissible limits.
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Materials Science Forum, 2006
Effects of solidification range on macro- and microstructure of pure aluminium and binary Al–Cu alloys obtained under conditions of constant melt flow are studied experimentally. The solidification range of binary alloys was varied by changing the concentration of the alloying element. An electromagnetic pump with a specially designed melt-guiding system is used to organize controlled unidirectional melt flow along the solidification front. Temperature and melt flow velocity are controlled during the experiment. It is observed that the extent of solidification range changes the macro– and microstructure, affects width and deflection angle of columnar grains, and alters the dendrite arm spacing in the presence of melt flow. The melt flow itself is found to change the macro- and microstructure, e.g. the increase of melt flow velocity clearly decreases the dendrite arm spacing.
2009
The secondary dendrite arm spacing (SDAS) is one of the most important microstructure features of as-cast structure in hypoeutectic aluminum alloys. The size of SDAS depends on many factors such as liquid metal treatment, temperature gradient, cooling rate/solidification time and chemical composition of melt. Among them the cooling rate/solidification time have dominant impacts. In industrial production of castings, when the chemical composition of melt has been chosen, the cooling conditions will control the solidification process. In this paper the effect of various pre-heating mould temperatures and cooling conditions (with and without water cooling) on the SDAS in AlSi7Cu3 were studied. For that purpose the permanent metal mould with the cooling system incorporated in one die was designed. The solidification time was affected by the mould temperature. It was found that the influence of mould temperature on SDAS was less pronounced in the presence of water cooling. The experiment...