Abstract
One of the most applied severe plastic deformation processes is ECAP (equal-channel angular pressing) which is suitable to produce ultrafine-grained metallic materials with high mechanical performance. A variant of the ECAP process was proposed in 2009, which consists in reducing the diameter of the exit channel of the die; it is named the nonequal-channel angular pressing (NECAP) process. A flow line function was also proposed to describe the material flow and the deformation field during NECAP. In the present work, an improved version of that flow function is presented containing two additional parameters compared to the previously proposed function. The new parameters permit to control precisely the shapes and the positions of the flow lines. The new flow function was applied to 90° NECAP of commercially pure aluminum to characterize the deformation field and the extent of the plastic deformation zone. The crystallographic texture evolution is also simulated using the new function. Excellent agreements with experiments were obtained for both the flow line trajectories and the crystallographic texture.
Highlights
Severe plastic deformation (SPD) processes have been recognized in the last decades as the most feasible and convenient methods to achieve submicron grain-sized bulk materials with superior strengths [1]
A modified equal-channel angular pressing (ECAP) process has been proposed [4, 5], in which the thickness of the exit channel (c) is smaller compared to the width of the entry channel (p); it is named nonequalchannel angular pressing (NECAP)
Successful modeling of the texture development can provide support for the proposed flow function, so we have carried out texture simulations using the velocity gradient defined in equation (8) for the Al NECAP testing originally published in reference [4]. e viscoplastic self-consistent (VPSC) model was employed [10] in its version further tuned with the help of finite element results in references [11, 12]
Summary
Severe plastic deformation (SPD) processes have been recognized in the last decades as the most feasible and convenient methods to achieve submicron grain-sized bulk materials with superior strengths [1]. It is practical to reduce the number of ECAP passes to obtain the same stage of grain refinement. For this purpose, a modified ECAP process has been proposed [4, 5], in which the thickness of the exit channel (c) is smaller compared to the width of the entry channel (p); it is named nonequalchannel angular pressing (NECAP). It is possible to carry out such an experiment successfully [8] At such a high strain, the material can reach the limiting steady stage with minimum grain size, replacing 10 ECAP steps. It will be shown in the present work that, by introducing two additional parameters, this flow function can be significantly improved to obtain much better results for both the material trajectory and the texture evolution
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