Study about the drawability, in the solid state, of the thixocast A5052 aluminium alloy and the viability of its thixodrawing / Estudo sobre a estampabilidade, no estado solido, da liga de aluminio A5052 tixofundida, e viabilidade da sua tixoestampagem

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

This work presents an analysis of the viability of drawing A5052 sheets in the semisolid state. Initially, to produce thixocast sheets, rolled commercial sheets were submitted to partial melting by different temperatures and holding times, to analyse the sheets draw ability in the solid state. The parameters utilised were: 627°C for 5 and 10 minutes, and 634°C, for 5 and 15 minutes, in sheets of 0,8 mm; 624°C for 5 and 10 minutes, and 631°C for 5 and 15 minutes, in sheets of 2,0 mm; and 625, 630 and 635°C for 15 minutes in sheets of 4,0 mm thickness. The sheets had their microstructure characterised; results showed high homogeneity of the structure throughout the test piece. Mechanical properties of the thixocast material (obtained by partial melting) were also characterised, showing significant differences when compared to the rolled condition. For drawing ability characterisation, Erichsen tests were performed and forming limit diagrams of the sheets in the rolled, annealed and thixocast states were obtained, using Marciniak´s technique and image analysis to obtain the main deformations of the alloy in the different conditions. Results showed that the thixocast material shows good formability, similar to the annealed material. Characterisation of the spatial structure of thixocast slurry showed the presence of tridimensional agglomerates of globular solid particles, with evident interaction among globules, indicating the possibility of the structure to stand tensile stresses. Therefore, for thixodrawing tests, a die was especially designed to impose severe flow conditions. The sheets were formed by thixodrawing (temperatures above the solidus) and compared to hot drawing tests. It was observed that thixodrawing is a perfectly viable process, requiring lower forces than conventional solid processing and resulting in excellent finishing products

ASSUNTO(S)

aluminium thixo-formage conformação de metais metal working estampagem (trabalhos em metal) semi-solide thixo-emboutissage embotissage blanking (metal work) aluminio

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