Evolution structurale, au cours de trempes ou de revenus, d'alliages zirconium-cuivre a teneur en cuivre inferieure a 5% pds

Abstract

Various zirconium-copper alloys with 1.1–1.6 or 2.4 wt % copper were quenched from the hightemperatureβ phase and their associated phase transformation studied. According to the quenchingrate, the β phase gives rise to various metastable structures which can be subsequently decomposed by tempering. The fastest quenching-rates give rise to a ω phase of hexagonal structure ( c/ a = 0.624) which forms martensitically. If the ω phase is reheated, a linear expansion anomaly of + 0.34% is found in the range 418–455 °C approximately; this corresponds to the decomposition of the ω phase into an α s solid solution, which is a supersaturated solution of copper in hexagonal zirconium, similar to the α equilibrium solid solution. On isothermal tempering or on heating to higher temperatures, α s decomposes into equilibrium α and a precipitate of Zr 2Cu. Only the most zirconium-rich alloys among those studied give rise to the metastable ω phase. The TTT curves for the decomposition of ω have been determined over a wide temperature range.