Projeto e análise do desempenho de uma matriz-protótipo para deformação plástica severa de metais por extrusão em canal angular com torção
Resumen
The emphasis of this work was to develop a prototype of a Twist Equal-Channel
Angular Pressing die (T-ECAP). ECAP consists of pressing a metallic billet
through two sequential channels with same cross-section area forming an
angle, imposing large shear strains on the material without significant changes
on their initial dimensions. In addition, it is widely studied due to its ability to
produce ultrafine-grained materials (< 1 μm). T-ECAP has a twist zone in
addition to the sequential channels, so that in each pass a combined shear
strain is applied, increasing equivalent strain per pass. In this study, in an
original die for T-ECAP, extrusions were made with Cu-0.7Cr-0.07Zr alloy and
pure copper, which are very ductile at room temperature, for comparison with
the results from numerical simulation obtained by finite element method in a
Deform® software. The processed materials had their microstructure studied by
metallography and strain distribution was evaluated by Vickers hardness
mappings. Performance analysis of the T-ECAP die were also carried out with
numerical simulations being performed with different combinations of
geometries. The results indicated that in the original ECA-T die a single pass
resulted in an equivalent strain of approximately 0.61, using the combination φ
= 120° and Φ = 44° in the ECAP zone and ω = 45° and β = 23° in the twist
zone. For T-ECAP die optimization, among analyzed combinations, the one that
resulted in a smaller heterogeneity in the distribution of stresses and strains
with a smaller pressing load was a die with φ = 120°, Φ = 22°, ω = 90° and β =
25°, imposing an average equivalent strain of 1.12 per pass. Thus, based on
these findings, a mechanical design of a new T-ECAP prototype die was
proposed.
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