The effect of quenching rate on the temperatures of the allotropic phase changes in plutonium

Abstract

A gas-quenching apparatus has been used to determine the temperatures of the allotropie phase changes of unalloyed plutonium, at cooling rates varying from 20 to 5000 °C/sec. Helium gas was used as the quenching medium, and the cooling curves were recorded using a cathode ray oscilloscope. The ε → δ → γ, the δ → γ and the γ → α transformations were independently studied. The results show that with increasing cooling rate the temperatures of all the phase changes are increasingly depressed, thus ruling out athermal mechanisms as possible modes of transformation.