A crystal-plasticity model of extruded AM30 magnesium alloy

An enhanced crystal-plasticity finite-element model is developed to model the effects of texture, grain size and loading direction on asymmetrical tension-compression behaviour of AM30 magnesium alloy. A constitutive description of plastic deformation in the suggested scheme accounts for contributions from deformation slip and twinning. The calibrated model was employed to investigate the effects of texture and grain size on the yield stress and strain- - hardening behaviour of AM30 magnesium alloy at room temperatures under various loading conditions. The study reveals that grain refinement and initial texture significantly influence the mechanical behaviour of AM30. Results show that the key factor controlling the tension compression asymmetry is deformation twinning. Two techniques, which could be used to reduce this asymmetry, are grain refinement and weakening of the initial texture in extruded AM30

Modelling strain localization in Ti-6Al-4V at high loading rate: a phenomenological approach

A phenomenological approach based on a combination of a damage mechanism and a crystal plasticity model is proposed to model a process of stain localization in Ti-6AI-4V at a high strain rate of 103 s-1. The proposed model is first calibrated employing a 3D representative volume element model. The calibrated parameters are then employed to investigate the process of onset of strain localization in the studied material. A suitable mesh size is chosen for the proposed model by implementing a mesh-sensitivity study. The influence of boundary conditions on the initiation of the strain localization is also studied. A variation of crystallographic orientation in the studied material after the deformation process is characterized, based on results for different boundary conditions. The study reveals that the boundary conditions significantly influence the formation of shear bands as well as the variation of crystallographic orientation in the studied material. Results also indicate that the onset of strain localization can affect considerably the material’s behaviour

Deformation characteristics in micromachining of single crystal 6H-SiC: Insight into slip systems activation

ABSTRACTSilicon carbide (SiC) is ideally suitable as a sensor material in harsh environments. Despite the brittleness in the macroscopic scale, plasticity in SiC is observed at small component length-scales. Previous nanoindentation based study combining experiment and numerical approaches of single-crystal 6H-SiC has shown that slip activation is rather complex, and that non-basal slip could potentially dominate the plastic deformation behaviour. In this study, we investigated the local deformation response evolution of shear strain directly under and in the vicinity of the indenter tip. The results show the pyramidal slip families contribute significantly to the deformation process

Supplementary information files for 'A crystal-plasticity model of extruded AM30 magnesium alloy'

Supplementary information files for 'A crystal-plasticity model of extruded AM30 magnesium alloy'Abstract:An enhanced crystal-plasticity finite-element model is developed to model the effects of texture, grain size and loading direction on asymmetrical tension-compression behaviour of AM30 magnesium alloy. A constitutive description of plastic deformation in the suggested scheme accounts for contributions from deformation slip and twinning. The calibrated model was employed to investigate the effects of texture and grain size on the yield stress and strain- - hardening behaviour of AM30 magnesium alloy at room temperatures under various loading conditions. The study reveals that grain refinement and initial texture significantly influence the mechanical behaviour of AM30. Results show that the key factor controlling the tension compression asymmetry is deformation twinning. Two techniques, which could be used to reduce this asymmetry, are grain refinement and weakening of the initial texture in extruded AM30.</div

Shear band widening mechanism in Ti–6Al–4V under high strain rate deformation

In this study, mechanical properties and microstructural investigation of Ti64 at high strain rate are studied using a split-Hopkinson pressure bar method under compression for temperatures up to 800 °C. Flow softening in the mechanical response of material to such loading conditions hints at instability in compression, which increases with an increase in temperature. Microstructural characterization of the deformed material is characterized using the electron-backscattered diffraction technique. It reveals the presence of instabilities in Ti64 in the form of a fine network of shear bands. The shear band width grows with an increase in temperature along with the area fraction of shear band in the material, displaying its improved capacity to contain microstructural instabilities at higher temperature. After a detailed microstructural investigation, a mechanism for shear band widening is proposed. Based on this mechanism, a path generating nuclei within shear bands is discussed