Predicting The Hall Petch Effect In Fcc Metals Using Non Local Crystal Plasticity

Author : Chaitali Shridhar Patil
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (135 download)

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Download or read book Influence of Constitutive Laws on the Evolution of Micromechanical Field Variables During Deformation of FCC Metals written by Chaitali Shridhar Patil and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding spatial evolution of micromechanical fields like effective stress or effective strain during deformation of polycrystalline materials is important for the whole life cycle of structural components, starting from process optimization to damage predictions. For this purpose, crystal plasticity modelling and simulation is an important predictive tool. Validity and accuracy of these simulations depend on the choice of the constitutive law. Therefore, this study assesses influence of the constitutive laws on the full field predictions of the crystal plasticity simulations. In this regard, we analysed two different aspects of the constitutive law. Firstly, one of the main components of the constitutive law for the plastic deformation is the hardening law. In this study, therefore, we compare full field predictions using the phenomenological Voce hardening law and the dislocation density based hardening law. As functional form of these two hardening laws is different, evolution of the critical resolved shear stress of the two laws need not to be same for all orientations during the deformation. Hence, we quantified differences in the local effective stress and texture predictions of the two laws during tensile deformation of copper. Crystal plasticity simulations were performed using a three dimensional (3D) fast Fourier transform-based elasto-viscoplastic (EVP-FFT) micromechanical solver. Simulation results show that the local distribution of stress strongly depends on the hardening rule. Average texture predicted by both the laws do not vary significantly. However, spatial orientation evolution (micro-texture) varies with increasing strain. This can be attributed to the spatially different shear strain accumulation between the two laws. Dislocation densities back calculated from the critical resolved shear stress are more homogeneous in the Voce hardening law than the predictions of the dislocation density based hardening law. Finally, dislocation density based law predicts higher accumulation of the dislocation density for the grains near the 001 orientation compared to grains with other orientations. Multiple slip activity within the 001 grains can result in higher accumulation of the dislocation density, which requires further experimental validation in the future. Secondly, cross slip of the screw dislocations is one of the important mechanisms of dislocation evolution during the deformation of medium to high stacking fault energy FCC metals. In the recent literature, it has been proposed that activation energy for the cross slip depends on the applied stress state. As a result, cross slip mediated dynamic recovery of the screw dislocations will also be influenced by the applied stress state. Hence, we incorporated the stress dependent dynamic recovery of the screw dislocations in the constitutive law. We analysed influence of the dynamic recovery on the evolution of the dislocation density and the micro-texture during the tension, compression as well as plane strain compression of polycrystalline aluminium. Even with the incorporation of the stress state dependent dynamic recovery, grain average dislocation density accumulation of the 001 grains is the highest during uniaxial deformation. Hence, detailed experimental and simulation analysis of these grains is required. In case of plane strain compression, dynamic recovery of the screw dislocations increases nucleation propensity of the cube orientation ({001}100). As the sharp cube texture is commonly observed after static recrystallization of FCC materials, our results highlight importance of dynamic recovery of the screw dislocations in the dislocation density based hardening laws.