Retention of metastable beta phase in a two-phase quaternary zirconium alloy

This study investigates the retention of greater than equilibrium beta phase in a two-phase zirconium alloy. We provide experimental data exploring two factors that impact the retention of beta phase following heat treatment of a two-phase quaternary zirconium alloy, Zr-3.5Sn-0.8Mo-0.8Nb. Heat treatment temperature and quenching rate are varied to establish a criterion for metastable beta phase retention and determine the excess free energy of the metastable phase as a function of solutionizing temperature. It is possible to retain a microstructure with up to 46 vol% beta phase at room temperature in this alloy, which has a stable room temperature beta phase content of 8 vol%. (C) 2018 Published by Elsevier Ltd.