Étude du comportement mécanique de l'alliage d'aluminium 5182 à faible fraction liquide
|Abstract:||Numerical thermomechanical simulations are necessary to predict the occurrence of hot tears, occurring at the end of solidification, in direct casting processes of aluminum smelters. However, these simulations require several inputs including mechanical properties and behavior laws at different temperatures. For this project, a dynamic mechanical analyzer is used to characterize these inputs for an aluminum alloy 5182 (4.5wt% Mg). Dynamic bending analysis is used for the first time to study the evolution of the elastic modulus with the liquid fraction in the microstructure. Also, series of creep tests are performed in tensile mode to propose behavioral laws. The use of a calculation model of solidification path considering the back diffusion allows to estimate the liquid fraction during the tests according to the temperature. The specimens used for the various mechanical tests were machined from a AA5182 ingot cast by the direct casting process. In order to study the effect of the microstructure, test specimens were machined from three positions according to the width of the ingot. The closer the specimen is to the surface, the more refined the microstructure. The fine microstructures appear to be less rigid when liquid is present in the microstructure. Also, three heating rates were studied for dynamic analyses (10⁰C/min, 20⁰C/min and 30⁰C/min). The solidus temperature decreases with increasing heating rate since the partial homogenization during heating is smaller. A design of experiment was performed for creep tests with test specimens from two positions in the ingot (surface, center), tested at three temperature levels (555⁰C, 560⁰C, 565⁰C) and at two stress levels (0.25MPa and 0.50 MPa). Five creep behaviors were observed: uniform creep, partial cracking, localization followed by failure, brittle failure, and deformation recovery. High temperatures and high stresses increase the occurrence of localization and failure while deformation recovery is observed only at low temperatures and stresses. The uniform creep and partial cracking curves were modeled by mechanical behavior laws.|
|Document Type:||Mémoire de maîtrise|
|Open Access Date:||25 July 2022|
|Collection:||Thèses et mémoires|
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