Yin Z K, Chen J S, Zhang P L, Yu Z S, Zhang Y Z, Chun Y, Lu H
School of Materials Engineering, Shanghai University of Engineering Science, Shanghai, People's Republic of China.
Shanghai Collaborative Innovation Center of Laser Advanced Manufacturing Technology, Shanghai, People's Republic of China.
J Mol Model. 2020 Oct 27;26(11):320. doi: 10.1007/s00894-020-04579-y.
Phase stability, brittle-ductile transition, and electronic structures of M (M = Fe, Ru, Ge, and Sn) and content change of L10-TiAl (γ-TiAl) and B2-TiAl (β-TiAl) have been investigated using first-principle methods. It is found that M metal atoms preferentially occupy the Al (2e) sites in L10-TiAl and B2-TiAl. According to Pugh's ratio and Poisson's ratio, the brittle-ductile transition is predicted for L10-TiAl and B2-TiAl with Fe, Ru, Ge, and Sn. It is found that the brittle-ductile transition from brittle regions to ductile regions with the transition metal elements Fe and Ru in L10-TiAl and B2-TiAl at the low concentration is approximately from 0 to 6.25 at.%. However, the brittle-ductile transition of Ge and Sn at the high concentration approximates from 6.25 to 12.5 at.% in L10-TiAl, comparing with B2-TiAl which approximates from 12.5 to 18.75 at.%. Electronic structure analysis shows that the improvement of brittleness can be attributed to two factors, including different hybridizations of Al-2p (Ti-3d) orbits with Fe-3d (Ge-4p) and Ru-4d (Sn-5p) orbits and different bandwidths of pseudo-gap. Furthermore, the L10-TiAl and B2-TiAl at low concentration of Fe and Ru can increase the value of ELF, where Ge and Sn atoms become bigger at a high concentration in L10-TiAl and B2-TiAl. At last, elastic constant (C), bulk modulus (B), shear modulus (G), and Young's modulus (E) of L10 and B2-TiAl with content change are systematically given.
采用第一性原理方法研究了M（M = Fe、Ru、Ge和Sn）的相稳定性、脆韧转变及电子结构，以及L10-TiAl（γ-TiAl）和B2-TiAl（β-TiAl）的成分变化。研究发现，M金属原子优先占据L10-TiAl和B2-TiAl中的Al（2e）位点。根据普格比值和泊松比，预测了含Fe、Ru、Ge和Sn的L10-TiAl和B2-TiAl的脆韧转变。研究发现，在低浓度下，L10-TiAl和B2-TiAl中含过渡金属元素Fe和Ru时，从脆性区域到韧性区域的脆韧转变约为0至6.25原子百分比。然而，在L10-TiAl中，高浓度下Ge和Sn的脆韧转变约为6.25至12.5原子百分比，而在B2-TiAl中约为12.5至18.75原子百分比。电子结构分析表明，脆性的改善可归因于两个因素，包括Al-2p（Ti-3d）轨道与Fe-3d（Ge-4p）和Ru-4d（Sn-5p）轨道的不同杂化以及赝能隙的不同带宽。此外，低浓度的Fe和Ru掺杂在L10-TiAl和B2-TiAl中可增加ELF值，而在L10-TiAl和B2-TiAl中高浓度时Ge和Sn原子变大。最后，系统给出了成分变化时L10和B2-TiAl的弹性常数（C）、体积模量（B）、剪切模量（G）和杨氏模量（E）。
