Thermal and Kinetic Analysis of the solidification of a near eutectic Al-Cu Alloy
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Thermal and Kinetic Analysis of the solidification of a near eutectic Al-Cu Alloy M. Morua, M.Ramirez-Argaez and C. Gonzalez-Rivera Departamento de Ingeniería Metalúrgica, Facultad de Química, UNAM, Edificio D Circuito de los Institutos s/n Cd. Universitaria Mexico D.F., Mexico. ABSTRACT In this work the thermal and kinetic analysis of the cooling and solidification of a near eutectic Al-Cu alloy is performed using inverse thermal and solidification kinetics analysis. The Fourier thermal analysis is applied to experimental cooling curves to obtain data on solid fraction evolution and latent heat of solidification. Inverse thermal analysis is applied to calculate the global heat transfer coefficients that allow correct simulation of the cooling of experimental probes. The free growth method is used to obtain the eutectic growth coefficients. All the obtained parameters are feed into a heat transfer-solidification kinetics model to validate the methodology and results generated from this work. It is found a relatively good agreement between experimental and predicted cooling curves which suggest that this methodology could be used to generate useful information needed to simulate eutectic solidification. INTRODUCTION In previous works[1-3] a new method to obtain the eutectic grain growth coefficients, the so called Free Growth (FG) method is implemented and validated using simulated cooling curves of eutectic Al-Si alloy and compared with the other two methods available to determine the grain growth kinetics, the method of Degand [4] and the method proposed by Dioszegi [5]. It is concluded that good results can be obtained using both FG and Dioszegi’s methods. In order to test the FG method using experimental data, in this work, the cooling curves and experimental probes of a near eutectic Al-Cu alloy solidified unidirectionally in the radial direction into a metallic mold, have been used to obtain information on the eutectic grain growth coefficients, the latent heat of solidification and the experimental cooling conditions. The purpose of this work is the implementation and validation of a methodology to obtain thermal and kinetic information needed to simulate solidification of eutectic alloys from the processing of experimental data associated with the cooling and solidification of a near eutectic Al-Cu alloy into a metallic mold. EXPERIMENTAL AND METHODOLOGY Melts are produced in an electric furnace with an argon atmosphere to obtain a near eutectic Al-Cu alloy using burdens of commercial purity aluminum and electrolytic cooper. Chemical composition is adjusted using spark emission spectroscopy. Thermal analysis test samples are taken by submerging a cylindrical stainless steel test cup (0.03 m inner diameter, 0.05m in height and 1.5 mm in thickness, covered with boron nitride) into the melt. The cups are kept submerged for approximately 30 seconds to allow them to reach the bath temperature. Then, they are removed from the melt and placed on a thermal analysis test stand where they are isolated thermally at the
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