Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, R...Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, Re, and Os. Among the studied systems, lattice reorientation energy increases in the order of Mg, Gd, Tb, Dy, Zr, Tc, Ti, Ho, Y, Co, Er, Sc, Be, Tin, Lu, Hf, Re, Ru and Os. The reorientation process consists of shear and shuffle components. Concerning the significance of shuffle, these hexagonal metals fall into two groups. In the first group, which includes Mg, Co, Ru, Re and Os, regardless of the shear amount, subsequent shuffle is an energy-uphill process, while in the second group, which includes Ti, Tc, Be, Y. Gd, Tb, Dy, Ho, Zr, Er, Sc, Hf, Lu and Tin, shuffle becomes an energy-downhill process if shear component reaches an adequate level (at least 60%). These results qualitatively explain the present observation of lattice reorientation in hexagonal metals, and shed light upon a general understanding on the [1012] twinning behavior in the aim of improving materials properties.展开更多
High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), whi...High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works,a further study indicates that the C_(44)/C_(44)ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.展开更多
In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopi...In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. A global analysis of constitutive parameters based on the Latin Hypercube Sampling method and the Spearman's rank correlation method is adopted in order to improve the identification efficiency of parameters. Then, an optimal solution of constitutive parameters as a whole is obtained by using a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and the local accurate search techniques. It is concluded that the proposed constitutive modal can accurately describe the Ti-6Al-4V alloy's dynamic behavior because the prediction results of the model are in good agreement with the experimental data.展开更多
基金supported financially by the National Key Research and Development Program of China(No.2016YFB0701304)the National Natural Science Foundation of China(No.51671195)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2015151)
文摘Employing ab initio calculations, we systematically investigated tile energy paths of [1012] twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tin, Lu, Hf, Re, and Os. Among the studied systems, lattice reorientation energy increases in the order of Mg, Gd, Tb, Dy, Zr, Tc, Ti, Ho, Y, Co, Er, Sc, Be, Tin, Lu, Hf, Re, Ru and Os. The reorientation process consists of shear and shuffle components. Concerning the significance of shuffle, these hexagonal metals fall into two groups. In the first group, which includes Mg, Co, Ru, Re and Os, regardless of the shear amount, subsequent shuffle is an energy-uphill process, while in the second group, which includes Ti, Tc, Be, Y. Gd, Tb, Dy, Ho, Zr, Er, Sc, Hf, Lu and Tin, shuffle becomes an energy-downhill process if shear component reaches an adequate level (at least 60%). These results qualitatively explain the present observation of lattice reorientation in hexagonal metals, and shed light upon a general understanding on the [1012] twinning behavior in the aim of improving materials properties.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 11774247 and U2030107)Sichuan University Innovation Research Program of China (Grant No. 2020SCUNL107)。
文摘High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works,a further study indicates that the C_(44)/C_(44)ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.
基金the financial support by the National Natural Science Foundation of China Academy of Engineering Physicsthe jointly set-up"NSAF"joint fund under Contract No.U1430119
文摘In this paper, a new physically based constitutive model is developed for hexagonal close-packed metals, especially the Ti-6Al-4V alloy, subjected to high strain rate and different temperatures based on the microscopic mechanism of plastic deformation and the theory of thermally activated dislocation motion. A global analysis of constitutive parameters based on the Latin Hypercube Sampling method and the Spearman's rank correlation method is adopted in order to improve the identification efficiency of parameters. Then, an optimal solution of constitutive parameters as a whole is obtained by using a global genetic algorithm composed of an improved niche genetic algorithm, a global peak determination strategy and the local accurate search techniques. It is concluded that the proposed constitutive modal can accurately describe the Ti-6Al-4V alloy's dynamic behavior because the prediction results of the model are in good agreement with the experimental data.