Study of a modified ECAP die for producing nanostructured Al6060 alloy using 3D finite element simulation
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Study of a modified ECAP die for producing nanostructured Al6060 alloy using 3D finite element simulation
González-Lozano M. A. 1, Ponce-Peña P. 1, Escobedo-Bretado M.A. 1, Lara-Castro R.H.1, Ochoa-Salazar B. X. 2. 1
Depto. Ciencia de Materiales, Facultad de Ciencias Químicas, UJED, Av. Veterinaria S/N, Circuito Universitario, C.P. 34120, Durango, Dgo. México. 2 Depto. de Ingeniería Ambiental, Facultad de Ciencias Forestales, UJED, Río Papaloapan y Blvd. Durango, C.P. 34120, Durango, Dgo. México. ABSTRACT Using Finite Element Method (FEM) simulations is possible to study the homogeneity of deformation in the Equal Channel Angular Pressing (ECAP) process. In this work an investigation about the influence of a modified die on strain distribution in an ecaped Al6060 alloy was carried out. Due to that, tensile stress occurs in the vicinity of upper surface of the specimen in the severe plastic deformation zone, which increases the cracking and fracture tendency of the specimen and impedes further ECAP processing, the conventional ECAP die was modified to eliminate the tensile stress and enhance the compressive stress in the severe plastic deformation zone and reducing the cracking and fracture tendency of the specimen. Finite element analysis demonstrated that the stress state changes from tensile to strongly compressive when using the modified die. The aim of this study is to evaluate the advantages/disadvantages of the modified ECAP die and processing conditions.
INTRODUCTION
Due to their excellent mechanical and physical properties, such as high strength and ductility, Ultra-Fine Grained (UFG) materials have been widely studied in recent years. As one of the most promising Severe Plastic Deformation (SPD) techniques, Equal Channel Angular Pressing (ECAP), which was developed by Segal et al. [1], has become a more and more popular method in producing UFG materials. Compared to conventional plastic processing methods, such as forging and rolling, ECAP shows its superiority in that the cross-sectional area of the sample remains unchanged, thus the same sample may be pressed repetitively to attain exceptionally high strains, as stated by Segal [2]. However, experiments show that cracking or fracture usually occurs in the vicinity of upper surface of the extruded specimen even only after a few passes, as revealed by Semiatin et al. [3] in their experiments on the ECAP of AISI 4340 steel and a near gamma titanium aluminide alloy and by Lapovok [4] in the study on ECAP of magnesium alloy. Some researchers studied the deformation behavior of the sample during ECAP by Finite Element Method (FEM) simulation. For example, Semiatin et al. [3] investigated the effects of material constitutive behavior, tooling design, and friction conditions on metal flow, stress fields, and the tendency for tensile fracture during equal channel angular extrusion. Lapovok [4]
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