Numerical Investigation of Plastic Strain Homogeneity during Equal-Channel Angular Pressing of a Cu-Zr Alloy

Jittraporn Wongsa-Ngam,Terence G. Langdon,Chaosuan Kanchanomai,Nitikorn Noraphaiphipaksa

doi:10.3390/cryst11121505

Abstract

A three-dimensional finite element method (3D FEM) simulation was carried out using ABAQUS/Explicit software to simulate multi-pass processing by equal-channel angular pressing (ECAP) of a circular cross-sectional workpiece of a Cu-Zr alloy. The effective plastic strain distribution, the strain homogeneity and the occurrence of a steady-state zone in the workpiece were investigated during ECAP processing for up to eight passes. The simulation results show that a strain inhomogeneity was developed in ECAP after one pass due to the formation of a corner gap in the outer corner of the die. The calculations show that the average effective plastic strain and the degree of homogeneity both increase with the number of ECAP passes. Based on the coefficient of variance, a steady-state zone was identified in the middle section of the ECAP workpiece, and this was numerically evaluated as extending over a length of approximately 40 mm along the longitudinal axis for the Cu-Zr alloy.

Highlights

The fabrication of bulk ultrafine-grained (UFG) materials has been widely investigated over the last two decades due to the potential to produce metals with superior mechanical and physical properties
Several techniques are available for fabricating these materials, but major emphasis has been placed on the use of equal-channel angular pressing (ECAP), in which a sample is pressed through a die constrained within an internal channel that is bent through a sharp angle [1]
There are only limited reports related to multi-pass ECAP processing using 3D finite element method (FEM) for circular cross-sectional workpieces, and all of these reports are directed at the deformation of aluminum and aluminum alloys [16,17,18]

Summary

Introduction

The fabrication of bulk ultrafine-grained (UFG) materials has been widely investigated over the last two decades due to the potential to produce metals with superior mechanical and physical properties. Several techniques are available for fabricating these materials, but major emphasis has been placed on the use of equal-channel angular pressing (ECAP), in which a sample is pressed through a die constrained within an internal channel that is bent through a sharp angle [1] In this procedure, a shear strain is introduced as the sample passes through the bend in the channel, and this is a very effective severe plastic deformation (SPD) processing method for producing bulk UFG materials for use in engineering applications. There are only limited reports related to multi-pass ECAP processing using 3D FEM for circular cross-sectional workpieces, and all of these reports are directed at the deformation of aluminum and aluminum alloys [16,17,18] Because of this deficiency, the present investigation was initiated in order to use a 3D. FEM simulation to investigate the deformation behavior and homogeneity evolution of the multi-pass ECAP processing, up to eight passes, of a copper alloy of Cu-0.1 wt.% Zr with billets with circular cross-sections

The Principles of Finite Element Simulations

Results and Discussion

Equivalent plastic variation

Steady-State