Solid state phase transformation study on a series of Pu–Ga alloys containing 0.18–0.63wt.% Ga

Abstract

• Solid state phase transformation behaviours of Pu–Ga alloys were investigated. • Effects of Ga content and starting condition on Pu–Ga alloy were found significant. • The nature of as cast α-phase is independent of the nominal Ga content. • The ε → δ transformation happens through two mechanisms when Ga < 0.63 wt.%. • Increase of thermal expansion coefficient of δ-phase with increasing Ga confirmed. The effects of Ga concentration and starting condition of Pu–Ga alloys on their solid-state phase transformation behaviours in a set of Pu–Ga alloys containing 0.18–0.63 wt.% Ga were studied under non-equilibrium conditions with a heating/cooling rate of 10 °C/min in the temperature range of 25–560 °C by a dilatometry method. The characteristic abrupt slope changes shown in the dilatometry tracks during heating and cooling are ascribed to the known phase transformations in the Pu–Ga alloys. The rationale for such an ascription is discussed. The study showed that, as expected, Ga concentration and the starting condition of the Pu–Ga alloy have significant effects, demonstrated by the variety of the onset and completion temperatures of a phase transformation. We find that the nature of as cast α-phase is independent of the nominal Ga content. The ε → δ transformation happens through two mechanisms when Ga < 0.63 wt.%. Furthermore, the increase of thermal expansion coefficient of δ-phase with increasing Ga is also confirmed.