Deformation and strain localization in polycrystals with plastically heterogeneous grains

Abstract

A model of a polycrystalline material is studied, where each grain consists of several zones with different plastic properties. The size and configuration of the zones as well as their properties are mimicking the situation inside the crystals of artificially aged Al alloys with precipitate free zones (PFZs). The properties of the different zones are conjectured based on micromechanical models and experimental observations of the AA6000 series of Al alloys. A periodic patch of such a composite material, subjected to plane-strain tension, is modelled using the finite element method. The material behaviour is described by a single crystal plasticity model. The results of the simulations show a number of characteristic features emerging in composite material systems, including sliding and distortion of grain boundaries and shear band formation at grain boundary triple points. The assumptions made about the properties of the different zones in the crystals are evaluated. The distributions of plastic strain and deviatoric and hydrostatic stresses in the composite crystalline systems are discussed.

Nano-scale characterisation of sheared β” precipitates in a deformed Al-Mg-Si alloy

“…The AA6060 aluminium alloy used in this study has been investigated in several other studies, and the reader is referred to these previous works for details, while a short summary is presented here 32–34 . The alloy contained 0.422 wt% Si and 0.468 wt% Mg, and was extruded as a 10 mm thick profile measuring 83 mm in width.…”

“…All of the observed precipitates were consistent with the β″ phase, except for relatively few inhomogeneously nucleated precipitates that were of an over-aged character. The material has an equiaxed grain structure with a strong cube texture and minor Goss components 32,33 .…”

Lattice rotations in precipitate free zones in an Al-Mg-Si alloy

“…In addition to Schwellinger [4] there are several studies that have reported on dislocation structures in PFZs of aluminium alloys [15][16][17][18]. Styczyńska et al [15] observed by in situ TEM straining experiments that dislocation sources at GBs became active before sources inside the grain interiors.…”

“…Watanabe et al [17] did not study PFZs specifically, but noted that some PFZs in an Al-Mg-Sc alloy under cyclic loading became misoriented relative to their parent grains. Khadyko et al [18] observed several different dislocation structures in PFZs and their vicinity in an Al-Mg-Si alloy stretched to fracture in uniaxial tension. In most PFZs, both inside and outside the neck, dislocations spanned the PFZs and appeared almost perpendicular to the GB plane.…”

Ductile damage mechanism under shear-dominated loading: In-situ tomography experiments on dual phase steel and localization analysis

“…These activities contribute to the understanding of the failure mechanisms (e.g. Baczmanski et al 2016, Kim and Yoon (2015), Matsuno et al (2015), De Geus et al 2016, Daehli et al (2016), Khan and Bhasin (2017), Khadyko et al (2016), Lee et al (2015), Scales et al, 2016) and the development of enhanced porous plasticity models to predict ductile failure (Tutyshkin et al (2015), Zhai et al (2016), Shutov et al (2015), Ling et al (2016)). In real materials, the effect of anisotropy on ductile failure is also often relevant.…”