The compressive creep behavior of a Pu-1 wt pct Ga δ-stabilized alloy at elevated temperatures

Abstract

Constant stress compression creep tests were performed in vacuum on a high-purity Pu-1 wt pct Ga o-stabilized alloy over the temperature range from 252° to 382°C for stresses from 700 to 2500 psi. Although the primary creep behavior could not be correlated by established techniques, the creep rates developed after true creep strains of about 0.15 provided good agreement with the temperature and stress dependence of creep for pure metals and dilute alloys. A power stress law for steady-state creep of the alloy was found forδ/E values less than 5 x 10′4, with the stress exponent being 4.0, and it was concluded that the alloy exhibits Class I solid solution behavior. For higher stress, exponential stress dependence was observed. The true activation energy for creep was found to be 38,900 cal per mole which is in good agreement with the value for self-diffus ion of plutonium in the o-stabilized alloy. The primary creep behavior could be divided into three types: 1) at low strain rates, the creep rate gradually increases to a nearly steady-state; 2) at intermediate strain rates, the creep rate first decreases and then increases to steady-state; and 3) at high strain rates, the creep rate decreases gradually to steady-state. It was concluded that the failure of established creep correlations for primary creep of Pu-1 wt pct Ga was the result of some temperature-dependent component of creep structure, possibly resulting from radiation damage byα particles.