A study of plastic deformation behavior during high pressure torsion process by crystal plasticity finite element simulation

P T Wei,G Y Deng,K Tieu,C Lu

doi:10.1088/1757-899x/63/1/012045

Abstract

High pressure torsion (HPT) is an efficient technique of producing ultrafine grained materials with exceptional small grain size. In this study, a crystal plasticity finite element method (CPFEM) model has been developed to investigate the plastic deformation behavior of pure aluminum single crystal during the HPT process. The simulation results show that, the distribution and evolution of the macroscopic plastic strain and the accumulative shear strain are similar. The value increases with the increase of the distance from the center as well as the number of revolution. The simulation is capable of reflecting the anisotropic characteristics of HPT deformation, a non-homogenous deformation along the circumference of the sample could be observed. At the early stage of HPT deformation, the critical resolved shear stress (CRSS) along the radial direction presents a rapid increase, followed by a moderate increase and then reaches the near-saturate state. As the HPT deformation proceeds, there is a relatively weak increase in the quasi-saturate value and the near-steady region expands gradually towards the sample center. The orientation changes during the HPT process with increasing applied strain predicted by the developed CPFEM model are also presented.

Highlights

Severe plastic deformation (SPD) processes are capable of achieving relatively high strains without introducing any major changes in the sample shape
The Bassani and Wu hardening law has been widely used in the crystal plasticity modellings of the large deformation processes, including equal channel angular pressing (ECAP) [30, 37] and large strain torsion [38, 39]
It can be seen that all horizontal lines remain straight and are perpendicular to the axial direction, while the vertical lines have a certain angle with the Z direction and these lines are almost parallel to each other, implying a homogenous deformation across the sample thickness

Summary

Introduction

Severe plastic deformation (SPD) processes are capable of achieving relatively high strains without introducing any major changes in the sample shape. In these crystal plasticity models for large strain torsion deformation, different hardening laws were adopted. A CPFEM model, which incorporates crystal plasticity constitutive equations into a finite element framework, has been developed to simulate the deformation process of HPT.

Results

Conclusion