Mechanical and electrochemical properties of Al alloyed D8m-Ta5Si3 nanocrystalline coatings

JOURNAL OF ALLOYS AND COMPOUNDS

卷:749

Article

Xu, Jiang^1,2  Liu, Wei¹  Xu, Song³  Munroe, Paul³  Xie, Zong-Han^2,4 

[1] Nanjing Univ Aeronaut & Astronaut, Dept Mat Sci & Engn, 29 Yudao St, Nanjing 210016, Jiangsu, Peoples R China

[2] Wuhan Inst Technol, Sch Mech & Elect Engn, 693 Xiongchu Ave, Wuhan 430073, Hubei, Peoples R China

[3] Univ New South Wales, Sch Mat Sci & Engn, Sydney, NSW 2052, Australia

[4] Univ Adelaide, Sch Mech Engn, Adelaide, SA 5005, Australia

关键词: First-principles theoretical calculations;    Refractory metal silicides;    Electrochemical corrosion;    Mechanical properties;   

DOI  :  10.1016/j.jallcom.2018.03.156

来源: Elsevier

【 摘 要 】

In this work, the structural stability, mechanical properties and electronic structure of beta-Ta5Si3 with different Al additions were first predicted by first-principles density functional calculations. The binary and ternary beta-Ta5Si3 are thermodynamically and mechanically stable, but their thermodynamic stability slightly decreases with Al additions. The elastic constants, bulk modulus (B), shear modulus (G) and Young's modulus (E) of Al-alloyed beta-Ta5Si3 were calculated. According to the criteria involving the bulk/shear modulus (B/G ratio) and Poisson's ratio, the D8(m)-structured ternary Ta5Si3, where two Si-4a atoms are replaced by two Al atoms, shows improved ductility. Based on the theoretical analysis, the beta-Ta-5(Si0.83Al0.17)(3) nanocrystalline coating was deposited onto polished Ti-6Al-4V alloy substrates by double cathode glow discharge plasma method. The phase constitution, microstructure and composition of the coating were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) including energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The as-deposited coating was composed of nearly rounded D8(m)-beta-Ta5Si3 grains with an average size of similar to 4 nm and exhibited strong (002) and (400) preferred orientation. After Al alloying, the hardness and the compressive residual stress of the beta-Ta5Si3 decreased, and the contact damage resistance and adhesion strength increased. The electrochemical corrosion properties of the beta-Ta-5(Si0.83Al0.17)(3) nanocrystalline coating were compared to the binary beta-Ta5Si3 coating and Ti-6Al-4V in 3.5 wt% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. It was shown that the corrosion resistance of the beta-Ta5Si3 was improved through the substitution of Al for Si. (C) 2018 Elsevier B.V. All rights reserved.

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