Lattice defects are unavoidable structural units in materials and play an important role in determining material properties.Compared with the periodic structure of crystals,the atomic configurations of the lattice def...Lattice defects are unavoidable structural units in materials and play an important role in determining material properties.Compared with the periodic structure of crystals,the atomic configurations of the lattice defects are determined by the coordinates of a large number of atoms,making it difficult to experimentally investigate them.In computational materials science,multiparameter optimization is also a difficult problem and experimental verification is usually required to determine the possibility of obtaining the structure and properties predicted by calculations.Using our recent studies on oxide surfaces as examples,we introduce the method of integrated aberration-corrected electron microscopy and the first-principles calculations to analyze the atomic structure of lattice defects.The atomic configurations of defects were measured using quantitative high-resolution electron microscopy at subangstrom resolution and picometer precision,and then the electronic structure and dynamic behavior of materials can be studied at the atomic scale using the firstprinciples calculations.The two methods complement each other and can be combined to increase the understanding of the atomic structure of materials in both the time and space dimensions,which will benefit materials design at the atomic scale.展开更多
As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1...As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1Nd-0.5Zr alloy, the β pre- cipitate phase was assumed to he one of the main strengthening phases in peak-aged samples. This study aimed to determine the crys- tal structure and orientation relationship of the β precipitate phase in Mg-7Gd-5Y-INd-0.5Zr alloy using transmission electron mi- croscopy and high-resolution electron microscopy. The results indicated that the β precipitate had a face-centered cubic structure with a lattice parameter of a=2.22 nm. The orientation relationship between the β precipitate phase and the ct-Mg matrix was （i-12）β（1-100）α, [110]β[0001 ]α. Theβ plates formed on prismatic planes could play an important role in alloy strengthening by proving effective barriers to gliding dislocations. A single β plate often contained several domains of （1 11）β twin-related variants. A composition of Mgs（Y0.4Gdo.4Nd0.2） was suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.展开更多
基金supported by the National Basic Research Program of China(2009CB623701,2011CB606406)the National Natural Science Foundation of China(51371102,51390475,51071092,11374174,and 51390471)+2 种基金the Foundation for the Author of National Excellent Doctoral Dissertation of Chinathe Program for New Century Excellent Talents in Universitythe Scientific Foundation for Returned Overseas Chinese Scholars,Ministry of Education
文摘Lattice defects are unavoidable structural units in materials and play an important role in determining material properties.Compared with the periodic structure of crystals,the atomic configurations of the lattice defects are determined by the coordinates of a large number of atoms,making it difficult to experimentally investigate them.In computational materials science,multiparameter optimization is also a difficult problem and experimental verification is usually required to determine the possibility of obtaining the structure and properties predicted by calculations.Using our recent studies on oxide surfaces as examples,we introduce the method of integrated aberration-corrected electron microscopy and the first-principles calculations to analyze the atomic structure of lattice defects.The atomic configurations of defects were measured using quantitative high-resolution electron microscopy at subangstrom resolution and picometer precision,and then the electronic structure and dynamic behavior of materials can be studied at the atomic scale using the firstprinciples calculations.The two methods complement each other and can be combined to increase the understanding of the atomic structure of materials in both the time and space dimensions,which will benefit materials design at the atomic scale.
基金supported by the National "Twelfth Five-Year Plan" Key Technologies Program of China (2011DAE22B01)
文摘As reported in our previous works, a Mg-7Gd-5Y-1Nd-0.5Zr alloy recently developed exhibited remarkable age-hardening responses and excellent mechanical properties at both room and elevated temperatures. In Mg-7Gd-5Y-1Nd-0.5Zr alloy, the β pre- cipitate phase was assumed to he one of the main strengthening phases in peak-aged samples. This study aimed to determine the crys- tal structure and orientation relationship of the β precipitate phase in Mg-7Gd-5Y-INd-0.5Zr alloy using transmission electron mi- croscopy and high-resolution electron microscopy. The results indicated that the β precipitate had a face-centered cubic structure with a lattice parameter of a=2.22 nm. The orientation relationship between the β precipitate phase and the ct-Mg matrix was （i-12）β（1-100）α, [110]β[0001 ]α. Theβ plates formed on prismatic planes could play an important role in alloy strengthening by proving effective barriers to gliding dislocations. A single β plate often contained several domains of （1 11）β twin-related variants. A composition of Mgs（Y0.4Gdo.4Nd0.2） was suggested for the β phase in Mg-7Gd-5Y-1Nd-0.5Zr alloy.
