Effect of Deformation Path on the Microstructure and Mechanical Behavior of TWIP980 Steel

Recent technological advances have made it possible to manufacture steels with both high strength and high ductility. This is the case for Twinning-Induced Plasticity (TWIP) steels which are characterized by a twinning deformation mechanism, which is responsible for its excellent properties. In this work, TWIP980 steel was tested under tensile loading along the rolling direction until pre-deformations of 10%, 20%, and 30% were reached. In order to assess the effect of the deformation path, the pre-deformed samples were reloaded in directions of 0°, 45° and 90° against the rolling direction. Microstructural analysis was performed by means of optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The yield stress increased with the imposed deformation for all the tested directions. As the strain path changed from 0° to 90°, the yield stress for reload decreased, and the Bauschinger effect and permanent softening was observed. The yield plateau was observed as being directly influenced by deformation path without influence by strain rate and temperature.

Modelling of Strain-Path Transients in Commercially Pure Aluminium

In the current work, the recently proposed homogeneous anisotropic hardening (HAH) model, featuring a distorted yield surface, is applied to commercially pure aluminium. A dislocation-based hardening rule is incorporated into the HAH model to describe the transient stagnation of the hardening rate during strain reversal. A cast and homogenized material with random texture previously investigated by Mánik et al. [1] is selected. The material is prestrained either by compression or rolling, and then tested in uniaxial tension to acquire either reverse softening or orthogonal hardening. The Bauschinger effect, the permanent softening during reverse loading and the hardening in the course of orthogonal loading are captured by the model. However, the permanent softening during orthogonal loading cannot be predicted, and the transient variations of the R-value predicted by the HAH model are neither in qualitative nor quantitative agreement with the experimental data.