Invited Speaker

Dr. Yanli Lu

Dr. Yanli Lu

Professor, School of Materials Science and Engineering, Northwestern Polytechnical University, China
Speech Title: Study on the Interface Properties and Associated Void of the Nanoscale Al Precipitates in Al-Si Alloys

Abstract: The properties of the interface between nanoscale Al precipitate and Si matrix were studied by the first-principles calculations combined with high-resolution transmission electron microscopy (HRTEM) observation. The purpose of this work is to reveal its role on the mechanical properties of the eutectic Si particle in Al-Si alloys. Meanwhile, the formation mechanisms of the void associated with every Al precipitate were also discussed in depth. The calculation results show that the bonding of the Al/Si interface has strong covalent feature, which makes the interface stronger than the bulk Al and weaker than Si matrix. Therefore, the microcracks tend to form and expand in the interior of nanoscale Al precipitates instead of Al/Si interface. The nanoscale Al precipitates will improve the toughness of eutectic Si particles by releasing part of stress through lattice distortion and promote the formation of nano-deformation twins. In order to explain the interesting phenomenon that there is always a void associated with every Al particle, the diffusion barrier of Al atom in the Si matrix and the binding energy of solute atom and a vacancy were calculated. The results indicate that the vacancies can be introduced by the change of the volume and the migration of the solute-vacancy pair during the diffusion and precipitation progress. Then these vacancies will be discharged along the close-packed direction (Al<111>) and gather at the Al{111}/Si{001} interface, forming the visible void. This agrees very well with the experimental observation.

Keywords: First-principles, High-resolution transmission electron microscopy, Al/Si interface, Solute-vacancy pair, Void, Formation mechanism.

Biography: Lu Yanli is the professor and doctoral supervisor from School of Materials Science and Engineering, Northwestern Polytechnical University. She is mainly engaged in multi-scale research on the microstructure and properties of advanced metal materials and functional materials. She served as the reviewer for SCI journals such as Computational Materials Science and "Science China Series". She has won Shaanxi Science and Technology Award, Chinese Society of Aeronautics and Astronautics Science and Technology Award, Aviation Society of Youth Science and Technology Award in Shaanxi Province, etc.