物理学报2017，Vol.66Issue(19)：217-230,14.DOI:10.7498/aps.66.196101
Nb掺杂γ-TiAl金属间化合物的电子结构与 力学性能
Electronic structure and mechanical properties of Nb-doped γ-TiAl intermetallic compound
摘要
Abstract
This investigation aims at an Nb-dopedγ-TiAl intermetallic compound system in which part of Ti or Al atoms are substituted by Nb atoms. The structural parameters, the energy band structures, the electronic densities of states and the elastic constants of Nb-dopedγ-TiAl intermetallic compound are calculated and studied by using the first-principles method based on the density functional theory and other physical theory. The first-principle calculations presented here are based on electronic density-functional theory framework. The ultrasoft pseudopotentials and a plane-wave basis set with a cut-off energy of 320 eV are used. The generalized gradient approximation refined by Perdew and Zunger is employed for determining the exchange-correlation energy. Brillouin zone is set to be within 3 × 3 × 3 k point mesh generated by the Monkhorst-Pack scheme. The self-consistent convergence of total energy is at 1.0 × 10?6 eV/atom. In view of geometry optimization, it is shown that doping with Nb can change the structural symmetry of the γ-TiAl intermetallic compound. The calculated formation energies indicate that the formation energy of the system in which Ti atom is replaced by Nb atom is smaller than that of Al atom replaced by Nb atom. Accordingly, they tend to substitute Ti atom when Nb atoms are introduced into theγ-TiAl system. The calculated band structures of Nb-dopedγ-TiAl system show that they all have metallic conductivities, which implies that the brittleness ofγ-TiAl intermetallic compound could be tailored by Nb-doping. The partial densities of states of the Nb-doped and pure γ-TiAl systems indicate that the intensity of covalent bond between Ti atom and Nb atom is weaker than covalent bond between Ti atom and Al atom while the Ti atoms are replaced by Nb atoms in the γ-TiAl system. What is more, the density of states near Fermi energy increases after Al atoms has been replaced by Nb atoms in the γ-TiAl system. This is an important factor for improving the ductility ofγ-TiAl intermetallic compound. The calculated elastic constants, bulk modulus and shear modulus of Nb-doped γ-TiAl systems indicate that the ductility and the fracture strength of Nb-doped γ-TiAl system are both better than those of pure γ-TiAl system, especially in the system where part of Al atoms are replaced by Nb atoms. The plastic deformation capacity of Nb-dopedγ-TiAl system is thus improved comparatively.关键词
Nb掺杂/γ-TiAl金属间化合物/电子结构/力学性能Key words
Nb-doping/TiAl intermetallic compound/electronic structures/mechanical properties引用本文复制引用
陈治鹏,马亚楠,林雪玲,潘凤春,席丽莹,马治,郑富,汪燕青,陈焕铭..Nb掺杂γ-TiAl金属间化合物的电子结构与 力学性能[J].物理学报,2017,66(19):217-230,14.基金项目
国家自然科学基金(批准号: 11662014, 11764032)和西部一流大学重大创新项目(批准号: ZKZD2017006)资助的课题.Project supported by the National Natural Science Foundation of China (Grant Nos. 11662014, 11764032) and the Major Innovation Projects for Building First-class Universities in China's Western Region (Grant No. ZKZD2017006). （批准号: 11662014, 11764032）
