Heterogeneous Distribution of Microstrain Evolved During Tensile Deformation of Polycrystalline Plain Low Carbon Steel

Hai Qiu,Rintaro Ueji,Yuuji Kimura,Tadanobu Inoue

doi:10.3390/met10060774

Abstract

On a macroscale, the stress–strain curve of polycrystalline steel exhibits perfectly linear behavior in the elastic tension region. We observed that the strain distribution within grains is inhomogeneous in the range of the elastic deformation region. Microstrain concentrates at some local sites which are at and near the grain boundaries or in the interior of the grains. The microstrain is pseudo-periodic, and its period increases with applied stress, tending to approach the grain size. In addition to the tension-strain concentration, the compression-strain concentration is even present in the elastic region. The pseudo-periodic and inhomogeneous microstrain is attributed to the orientation heterogeneity of grains in polycrystalline steel.

Highlights

In a polycrystalline steel, grain boundary has significant influence on its mechanical properties.There are many studies [1,2,3,4,5,6] clarifying the mechanism by which the grain boundary affects plastic deformation, and these studies have been conducted by various methods
Hook and Hirth designed a sample with bicrystals of a high purity Fe-3% Si alloy [4]. They investigated the dislocation slip occurring in the bicrystals subjected to small plastic strains by experiment and verified that heterogeneous deformation occurred at grain boundaries
It can be seen that the ferrite has equi-axed grains and the average grain size is 30.4 μm

Summary

Introduction

There are many studies [1,2,3,4,5,6] clarifying the mechanism by which the grain boundary affects plastic deformation, and these studies have been conducted by various methods. Elastic incompatibility occurs due to different crystal orientations, resulting in heterogeneous deformation at grain boundaries [1,2]. Hook and Hirth designed a sample with bicrystals of a high purity Fe-3% Si alloy [4]. They investigated the dislocation slip occurring in the bicrystals subjected to small plastic strains by experiment and verified that heterogeneous deformation occurred at grain boundaries. Raabe et al found that grain-to-grain plastic strain heterogeneity and in-grain plastic strain heterogeneity occurred in large macroscopic plastic strains [5,6]

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