Estudo comparativo de estrutura/propriedades da liga A1-Si5-Cu3-Mg nos estados fundido e tixoconformado, para utilização em componentes de motores / Comparative study of structure-properties from A1-Si5-Cu3-Mg alloy by casting and thixoforged, for use in engine components

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

30/07/2010

RESUMO

The goal of this work was the comparative study between the Al-Si5-Cu3-Mg alloy obtained by die casting and thixoforging, based on a commercial accessories bracket used in diesel engines. The die casting commercial part was characterized in terms of structure and mechanical properties, and the final sample obtained by thixoforging was characterized in the same terms, in order to have a comparative base. For thixoability analysis, in other words, the capacity to obtain thixotropic slurries of the alloy under study, it was evaluated by thermal analysis through DSC techniques and thermodynamic simulations using THERMOCALC® software. Transformations temperatures and ranges are discussed, proposing thixoforging windows. The alloy was submitted for globularization thermal treatments under 120 and 300s, and solid fractions 45 and 60%, beyond the influence evaluation of a preliminary cold forming before the thixoforging process. The alloy proved to be interesting to produces thixotropic slurries, with solidification range around 100°C, besides a favorable liquid fraction vs temperature to define the thixoforging window. This thixotropic behavior allowed the complete matrix filling and thixoforged samples were obtained with a good quality, highlighting the porosity decreasing in comparison with the die casting component (around 17 times less). Reduced globules sizes were obtained with previous cold forming, due to the involved globularization mechanism of the recrystallization, and consequent mechanical properties improving in face of non cold forming material. Thixoforged product presents mechanical properties according to the studied alloy specifications, although for some manufacturing conditions present lower tensile strength and hardness when compared with die casted component

ASSUNTO(S)

motores ligas tixotropia ligas (metalurgia) fundição engines alloys tixotropy alloys (metallurgy) foundry

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