Mechanically activated SHS of Nb5Si3 and Nb5Si3/Nb composites

JOURNAL OF ALLOYS AND COMPOUNDS

卷:826

Article

Trevino, Reina¹  Maguregui, Edgar¹  Perez, Frank¹  Shafirovich, Evgeny¹ 

[1] Univ Texas El Paso, Dept Mech Engn, El Paso, TX 79968 USA

关键词: Intermetallics;    Transition metal alloys and compounds;    Silicides;    Self-propagating high-temperature synthesis (SHS);    Mechanical activation;    Combustion;   

DOI  :  10.1016/j.jallcom.2020.154228

来源: Elsevier

【 摘 要 】

Nb5Si3 and Nb are the main components of niobium silicide-based composites, which are promising materials for high-temperature structural applications. Self-propagating high-temperature synthesis (SHS) is an attractive method for fabricating advanced materials from powders via exothermic reactions between the mixture constituents. However, to overcome kinetic difficulties of Nb-Si reaction, SHS of niobium silicides usually requires additional heat input. The present work focuses on a technique that addresses this problem by adding a mechanical activation step before SHS. Specifically, short-term ball milling was used for mechanical activation of Nb/Si mixtures with the goal of conducting SHS of Nb5Si3 and Nb5Si3/Nb composites with no preheating. The milled mixtures were compacted and ignited in an argon environment. It has been shown that a planetary mill is an effective tool for mechanical activation of Nb/Si mixtures. Milling for 10 min enabled SHS of the product that consisted of alpha-Nb5Si3 and gamma-Nb5Si3 phases with traces of Nb3Si. For the first time, Nb5Si3/Nb composites were obtained by mechanically activated SHS with no preheating. Combustion took place at an Nb/Si mole ratio as high as 3, i.e. at 25 at% Si in the mixture. At this mole ratio, a spinning propagation of the combustion wave was observed, and the content of the gamma phase, which has poor mechanical properties, was dramatically decreased. (C) 2020 Elsevier B.V. All rights reserved.

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