Abstract
T-shaped equal channel angular pressing (T-shaped ECAP) is a novel process of severe plastic deformation (SPD). The maximum effective strain per pass in the T-shaped ECAP is larger than that in the ECAP. Deformation models of the T-shaped ECAP have been proposed by a designed grids deformation experiment considering the deformation dead zone (DDZ) formation or without it. Based on the deformation models, an upper bound approach has been used to analyse the T-shaped ECAP process. The effects of the plastic deformation zone (PDZ) angles and the friction factor on the relative pressing pressure and the DDZ are analysed. It is found that the relative pressing pressure increases with an increase of the angle and the friction factor m, however, the DDZ decreases. The upper bound solution for the T-shaped ECAP with the DDZ is more close to the experimental load than that without the DDZ. The results show that there is a good agreement between the theoretical value and the measured maximum load required for the T-shaped ECAP conducting.
Highlights
Equal channel angular pressing (ECAP) is an effective route to refining coarse grains intoultrafine-grained or nanostructured states with the grain size of 0.1~1μm by means of large plastic shear deformation [1].The most advantage of ECAP is that the billet undergoes severe plastic deformation (SPD) with the maximum strain arriving at 1.15 after one single pass but the same cross-sectional geometry of the billet remains
5 Conclusions An upper bound approach has been used to analyse the T-shaped ECAP process based on the proposed deformation models
The following conclusions can be outlined: 1. Deformation models taking into account the existence or absence of deformation dead zone (DDZ) in the T-shaped ECAP process are proposed based on the results of a designed grids deformation experiment
Summary
Equal channel angular pressing (ECAP) is an effective route to refining coarse grains intoultrafine-grained or nanostructured states with the grain size of 0.1~1μm by means of large plastic shear deformation [1].The most advantage of ECAP is that the billet undergoes severe plastic deformation (SPD) with the maximum strain arriving at 1.15 after one single pass but the same cross-sectional geometry of the billet remains. In order to optimize the ECAP process and obtain homogeneous nanostructured billets, many attempts have been made to analyse the ECAP process using deformation mechanics and finite element simulations [2,3,4,5,6]. Effects of the PDZ shape on the material flow during the ECAP were analysed by the FEM and the grid deformation patterns [8,9,10,11,12,13]
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