MEchanics GAthering -MEGA- Seminar: Precipitation strengthening of Al-Mg-Si alloys from mesoscale to atomistics
Abstract Aluminum alloys are important light alloys that find a lot of applications in industry and with precipitation the yield strength of the material can be improved greatly. In the current study, we first use mesoscale simulations, i.e. Discrete Dislocation Dynamics (DDD), to study peak-aged Al–Mg–Si alloys strengthened by β'' precipitates. In the process of dislocation-precipitate interaction, dislocation can either shear the precipitates (Shearing mechanism) or loop around them (Orowan mechanism), and for peak-aged material, two mechanisms are thought to give the same result, hence we only model the looping mechanism in strength prediction. Careful simulations using experimental characterizations and proper material parameters show an overestimate of uniaxial tensile yield strength. And the detailed force analysis on individual precipitates indicates that shearing happens in the strengthening process. To further understand the strengthening process, we carry out atomistic simulations using a curated Al–Mg–Si Neural Network Potential (NNP), and the result shows that both shearing and looping can take place atomistically depending on the shearing energy and precipitate internal misfit stress. Theoretical shearing models and Discrete Dislocation Dynamics are used for critical resolved shear stress prediction and agree well with the atomistic results. A yield strength prediction based on the atomistic knowledge and several corrections gives a much reasonable result to the strength of real material.
Bio Yi Hu did his bachelor study in Shanghai at Tongji University in the field of Civil Engineering. Then he moved to Stuttgart, Germany for his master study focusing on Computational Mechanics but mainly on continuum scale. At EPFL, he works in the lab of Multiscale Mechanics Modeling and has learned dislocation theory and atomistic detail of crystal plasticity. He is going to finish his PhD soon in November.
Bio Yi Hu did his bachelor study in Shanghai at Tongji University in the field of Civil Engineering. Then he moved to Stuttgart, Germany for his master study focusing on Computational Mechanics but mainly on continuum scale. At EPFL, he works in the lab of Multiscale Mechanics Modeling and has learned dislocation theory and atomistic detail of crystal plasticity. He is going to finish his PhD soon in November.
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- MEGA.Seminar Organizing Committee