Bin TANG
,
Xinqiang YUAN
,
Tianfeng XUE
,
Jiacheng LI
,
Youyu FAN
材料科学技术（英文）
Crystallization behavior of the glass system AlF3-MgF2-CaF2-SrF2-BaF2-YF3-TeO2 (AMCSBY-TeO2) was studied by the nonisothermal method using differential thermal analysis. The activation energy E and Avrami exponent $n$ were determined by nonisothermal method. It is found that the value of E varies with increasing TeO2 and reaches a minimum at 10~mol~fraction TeO2, while n decreases from 3.65 to 1.78 with the addition of TeO2. X-ray diffraction shows that Ba2Te3O8, MgTe2O5, and SrTeO3 phase formed when the glasses were reheated. The addition of TeO2 changes the crystallization mechanism and improves the stability of the fluoroaluminate glass.
关键词:
Fluoroaluminate glass
,
TeO2
,
析晶
Jing TIAN
,
Xiang XUE
,
Yuebing ZHANG
,
Yalong GAO
,
Luzhi LIU
,
Qin SUN
,
Shiyou YUAN
材料科学技术（英文）
By adopting the solid modeling software SoldEdge and the enmeshment software SRIFCast as the pre-processing platform, a Ni based alloy turbine blade was three-dimensionally modeled and automatically enmeshed. A software code for numerical simulation of fluid flow and heat transfer was developed. The Xue criterion and Niyama criterion were used to predict the position of the shrinkage defects occurring in the solidification processes of the turbine blade. The results showed that both Xue and Niyama criteria could precisely predict the shrinkage defects in the Ni based alloy turbine blade. This indicates that numerical simulation is a significant tool in improving casting quality.
关键词:
Journal of Physics and Chemistry of Solids
The layered ternary ceramics Ti3SiC2 and Ti3AlC2 are isostructural and can form Ti3Si1-xAlxC2 solid solutions combining the advanced properties of both compounds [H.B. Zhang, Y.C. Zhou, Y.W. Bao, M.S. Li, Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.90Al0.1C2 solid solution, Acta Mater. 52 (2004) 3631-3637; E.D. Wu, J.Y. Wang, H.B. Zhang, Y.C. Zhou, K. Sun, Y.J. Xue, Neutron diffraction studies of Ti3Si0.9Al0.1C2 compound, Mater. Lett. 59 (2005) 2715-2719; J.Y. Wang, Y.C. Zhou, First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2 solid solution, J. Phys.: Condens. Matter 15 (2003) 5959-5968; Y.C. Zhou, J.X. Chen, J.Y. Wang, Strengthening of Ti3AlC2 by incorporation of Si to form Ti3Al1-xSixC2 solid solutions, Acta. Mater. 54 (2006) 1317-1322]. In the present work, the solid solutions of Ti3Si1-xAlxC2 (x = 0, 0.25, 0.33, 0.5, 0.67, 0.75, 1) are investigated by first-principle calculations based on pseudo-potential plan-wave method within the density functional theory framework. The results show that as Al content increases in the solid solution, all the bonds have weakened to certain extents, which lead to an unstable structure both energetically and geometrically. The calculated results are compared and discussed with the reported data for the Ti3Si1-xAlxC2 solid solutions. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
ceramics;ab initio calculations;electronic structure;electrical;conductivity;oxidation behavior;mechanical-properties;ti3sic2;temperature;ti3alc2;air;si
