Active eutectoid decomposition in a near-eutectoid zirconium-copper alloy

Abstract

The decomposition of the beta-phase into the α- and the Zr₂Cu-phases has been investigated in a Zr-1.6 wt pct Cu alloy. It has been observed that the decomposition process is extremely rapid and cannot be suppressed even by rapid beta quenching. The product structure obtained on fast cooling consists of a lamellar aggregate of the α-phase and a metastable phase which does not have the stoichiometry of the Zr₂Cu-phase. Structurewise, this phase is similar but not identical to the equilibrium phase. A mechanism for this rapid decomposition of the β-phase has been proposed. It has also been found that the equilibrium Zr₂Cu-phase emerges after short aging treatments at sufficiently high temperatures in the α+ Zr₂Cu field.