Processamento de uma liga Pb-4%Sb por extrusão angular em canais iguais

Abstract

This work has covered all stages from alloy preparation by melting, processing by Equal Channel Angular Pressing-ECAP, microstructural characterization and mechanical properties determination before and after processing and the finite element modelling simulation of the process. An ECAP die, with 16mm edge square cross section, was manufactured using ABNT 1045 steel. A Pb-4%Sb cast alloy was prepared by melting the pure elements and processed by ECAP. Some specimens fractured during the first pressing and others were succesfully processed up to 8 passes. Compression and microhardness tests were performed in the alloy before and after processing in order to determine its mechanical properties. Optical microscopy andscanning electron microscopy were used to determine the alloy microstructure before and after ECAP. The alloy was found to be subjected to dynamic recristallization when strained at room temperature, leading to a reduction of its mechanical resistance. The structure was refined by recrystallization and the antimony precipitates were broken.Strain localization was observed during ECAP straining. FEM simulations employing the Pb-4%Sb alloy flow curve indicated the appearence of a dead metal layer in the external curvature of the deformation zone, when friction between the specimen and the die was considered. Strain localization was also observed in simulations with finer mesh.