Phase diagram of the zirconium-rhenium system

Abstract

The phase diagram of the zirconium-rhenium system was constructed by x-ray and microscopic methods and by measurements of melting points, hardness and microhardness of the phases.

The region of solid solutions of rhenium in α-zirconium at 800 ° C is ∼0.5 weight %, and at the temperature of the eutectoid transition it increases to 2–3 weight %. At 1600 ° C, 14.68 weight % of rhenium dissolves in β-zirconium and at the eutectoid transition point at 550–600 ° C, 8 weight % of rhenium. The β-phase is stabilized in alloys containing more than 4 weight % of rhenium. An eutectic is formed at 1600 ° C and 25 weight % of rhenium. The presence of a metastable ω-phase in melts rich in zirconium was established.

The solubility of zirconium in rhenium at 2500 ° C is less than 2 weight %.

Three chemical compounds are formed in the system by peritectic reactions:

• 1) At 2500 ° C, Zr₅Re₂₄ of the α-Mn type with a body-centered cubic lattice (a = 9.6–9.7 kX) and a microhardness of 1000 kg/ mm²;

• 2) at 2450 ° C, ZrRe₂ with a hexagonal, close-packed lattice (a = 5.21–5.25 A; c = 8.5–8.56 A; c/a = 1.63) and a microhardness of 1200 kg/mm²;

• 3) at 1900 ° C, Zr₂Re of the σ-phase type with a tetragonal lattice (a = 10.12 A; c = 5.42 A; c/a = 0.535) and a microhardness of 700–800 kg/mm².