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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.55  No.2 (2014)  >  pp.298-303

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Experimental Determination of the Isothermal Section in a Ternary Re–Cr–Nb System at 1500°C

Shigeru Saito1), Toshiyuki Takashima1), Katsumi Miyama1), Toshio Narita2), Taiichi Nagata3), Ideo Masuda3), Kenichi Kajiwara3)
1) Hokkaido Institute of Technology 2) Hokkaido University 3) Japan Aerospace Exploration Agency

The compositions with tie-lines between the χ, σ, γ, α, and Nb(Cr,Re)2 phases in a ternary Re–Cr–Nb system were investigated at 1500°C by heat-treating various ternary Re–Cr–Nb alloys in vacuum for either 2 or 220 h. The microstructures of the Re–Cr–Nb alloys that had been water-quenched after heating were observed and their Re, Cr, and Nb concentration profiles were measured using an electron probe micro-analyzer (EPMA).
The tie-line compositions (at%) of each phase at 1500°C were experimentally determined, and an isothermal phase diagram was constructed. The χ phase tie-lined with the α phase (26.4 at% Re, 70.0 at% Cr, and 3.6 at% Nb) consists of 42.7 at% Re, 40.8 at% Cr, and 16.5 at% Nb. The α phase tie-lined with the Nb(Cr,Re)2 phase (28.1 at% Re, 41.9 at% Cr, and 30.0 at% Nb) consists of 24.6 at% Re, 71.2 at% Cr, and 4.2 at% Nb. The solubility limit of Re in the γ phase was 44–45 at% Re as the Cr content increased (i.e., Re content decreased) in the γ phase; the Cr content in the χ phase with a tie-line with the γ phase increased from 1.8 at% Cr to 9.8 at% Cr. The solubility limit of Nb in the σ phase tie-lined with the χ phase is 2 at% Nb.

rhenium–chromium–niobium, phase diagram, χ phase, sigma phase, diffusion barrier layer, tie-line

Received: October 01, 2013
Accepted: November 06, 2013 , Published online: January 25, 2014
Copyright © 2014 The Japan Institute of Metals and Materials



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