Effect of Shear Direction on Work-Hardening Evolution of AISI 409 Steel Under Rolling/Shearing Loading

F L D Morais,E C S Corrêa,W Lopes

doi:10.1590/1980-5373-mr-2021-0398

F L D Morais, E C S Corrêa + Show 1 more

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https://doi.org/10.1590/1980-5373-mr-2021-0398

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Abstract

The mechanical behavior of metallic materials depends on several variables, such as the material structural characteristics, the process parameters, the temperature, the strain rate and the anisotropy features due to strain paths in different metal forming operations. Considering the last one, the effect of shear direction loading on the work-hardening after the rolling/shearing loading of a ferritic stainless steel, AISI 409, was investigated in this work. The annealed AISI 409 sheets were predeformed by cold rolling up 0.19 effective strain and then sheared at three different directions: at 0°, 45° and 90° from the original rolling direction. The samples were characterized through tensile, shear and Vickers microhardness tests while the study of crystallographic texture was performed using the electron backscatter diffraction (EBSD) technique. The work-hardening behaviour of the material was analyzed considering the work-hardening rate and the Hollomon work-hardening exponent after each strain path change applied to the AISI 409 steel. The results indicated the presence of preferential crystallographic orientation and the occurrence of transients on the work-hardening rate mainly for the sample sheared at 45° from the original rolling direction due to structural arrangements assumed by the AISI 409 steel after the strain path changes.

Highlights

Strain path changes are commonly observed in sheet metal forming such as in punching, bending and deep drawing operations that present linear and non-linear deformation paths
The crystallographic texture analysis has been showed a good predictive accuracy for the initial anisotropy[6] and for describing the occurrence of the plastic instability phenomenon detected during strain path changes composed by rolling/shear loading on different shear directions[7]
*e-mail: wellingtonlopes@cefetmg.br the aim of the present work is the analysis of the effects of shear direction on work-hardening behavior of AISI 409 steel during to the rolling/shear loading

Summary

Introduction

Strain path changes are commonly observed in sheet metal forming such as in punching, bending and deep drawing operations that present linear and non-linear deformation paths. A change in the strain path during a sheet metal forming process usually produces modifications on the usual mechanical response of different materials, represented by the presence of macroscopic transient effect on the flow stress curve[2], work-hardening stagnation[3], permanent softening[4] and the Bauschinger effect, i.e., a softening phenomenon after stress reversal, associated with the spring back behaviour of the materials[5]. The intensity of these anisotropic features present in sheet forming operations is significantly affected by parameters such as the amount of prestrain and the subsequent dislocation substructure and density. The loading direction was associated with the amount of permanent softening in AA3103 aluminum alloy[8]

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