Investigation of the Cross-Sectional Structure and Isothermal Section at 1150°C of a Nb–Re–Si Alloy Fabricated Using a Tetra-Arc Furnace

Abstract

Ternary Nb–Re–Si alloy samples were melted and pulled simultaneously in a tetra-arc furnace and rapidly water-quenched after heat treatment at 1150°C for 1200 h. The microstructures of the samples that had been water-quenched after heat treatment were observed and the Nb, Re and Si concentrations in the constituent phases were measured using an electron probe microanalyzer (EPMA). In the cross-sectional structure of the obtained alloy samples, the lower portion of the pulled part consists of Nb₅Si₃ and Nb–Re–Si ternary compound phases. By contrast, the upper portion consists of Nb₅Si₃ and Nb solid solution phases. The Nb solid-solution phase, Nb₅Si₃ and Nb–Re–Si ternary compound are in equilibrium. It was found that the solubility limit of Si in the Nb solid-solution phase ranges from 0.6 to 1.7 at%, while the solubility limit of Re in the Nb₅Si₃ phase is 1.3–2.0 at%. The maximum amount of Re in the Nb₅Si₃ phase in equilibrium with the Nb solid solution is about 0.9 at%.

 

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 82 (2018) 409–414.

Fig. 1 Photographs of the arc melting and pulling process in a tetra-arc furnace.