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Metals 2016, 6(6), 127;

The Effects of Al and Ti Additions on the Structural Stability, Mechanical and Electronic Properties of D8m-Structured Ta5Si3

Department of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China
School of Mechanical & Electrical Engineering, Wuhan Institute of Technology, 693 Xiongchu Avenue, Wuhan 430073, China
School of Materials Science and Engineering, University of New South Wales, Sydney NSW 2052, Australia
School of Mechanical Engineering, University of Adelaide, Adelaide SA 5005, Australia
Authors to whom correspondence should be addressed.
Academic Editor: Ana Sofia Ramos
Received: 6 January 2016 / Revised: 26 April 2016 / Accepted: 30 April 2016 / Published: 26 May 2016
(This article belongs to the Special Issue Intermetallics 2016)
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In the present study, the influence of substitutional elements (Ti and Al) on the structural stability, mechanical properties, electronic properties and Debye temperature of Ta5Si3 with a D8m structure were investigated by first principle calculations. The Ta5Si3 alloyed with Ti and Al shows negative values of formation enthalpies, indicating that these compounds are energetically stable. Based on the values of formation enthalpies, Ti exhibits a preferential occupying the Ta4b site and Al has a strong site preference for the Si8h site. From the values of the bulk modulus (B), shear modulus (G) and Young’s modulus (E), we determined that both Ti and Al additions decrease both the shear deformation resistance and the elastic stiffness of D8m structured Ta5Si3. Using the shear modulus/bulk modulus ratio (G/B), Poisson’s ratio (υ) and Cauchy’s pressure, the effect of Ti and Al additions on the ductility of D8m-structured Ta5Si3 are explored. The results show that Ti and Al additions reduce the hardness, resulting in solid solution softening, but improve the ductility of D8m-structured Ta5Si3. The electronic calculations reveal that Ti and Al additions change hybridization between Ta-Si and Si-Si atoms for the binary D8m-structured Ta5Si3. The new Ta-Al bond is weaker than the Ta-Si covalent bonds, reducing the covalent property of bonding in D8m-structured Ta5Si3, while the new strong Ti4b-Ti4b anti-bonding enhances the metallic behavior of the binary D8m-structured Ta5Si3. The change in the nature of bonding can well explain the improved ductility of D8m-structured Ta5Si3 doped by Ti and Al. Moreover, the Debye temperatures, ΘD, of D8m-structured Ta5Si3 alloying with Ti and Al are decreased as compared to the binary Ta5Si3. View Full-Text
Keywords: transition metal silicides; D8m-Ta5Si3; first principle calculation; mechanical properties transition metal silicides; D8m-Ta5Si3; first principle calculation; mechanical properties

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Liu, L.; Cheng, J.; Xu, J.; Munroe, P.; Xie, Z.-H. The Effects of Al and Ti Additions on the Structural Stability, Mechanical and Electronic Properties of D8m-Structured Ta5Si3. Metals 2016, 6, 127.

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