Phase reversion kinetics of thermally decomposed (α plus γ′) phases to γ-phase in U-10 wt% Mo alloy

JOURNAL OF NUCLEAR MATERIALS

卷:530

Article

Newell, Ryan^1,3  Mehta, Abhishek¹  Keiser, Dennis D., Jr.²  Sohn, Yongho¹ 

[1] Univ Cent Florida, Adv Mat Proc & Anal Ctr, Dept Mat Sci & Engn, Orlando, FL 32816 USA

[2] Idaho Natl Lab, POB 1625, Idaho Falls, ID 83401 USA

[3] Aerojet Rocketdyne Inc, Jupiter, FL 33478 USA

关键词: Uranium alloy;    Decomposition;    Phase reversion;    Kinetics;   

DOI  :  10.1016/j.jnucmat.2019.151983

来源: Elsevier

【 摘 要 】

Thermally induced phase reversion kinetics of decomposed alpha + gamma' phases toy phase was investigated for the U - 10 wt% Mo (U-10Mo) hypoeutectoid alloy using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The as-cast U-10Mo alloy was homogenized to the gamma phase at 1073 K for 96 h, and decomposed at sub-eutectoid temperature of 773 K as a function of time from 240 to 1200 h. The decomposition of gamma phase initiated via two mechanisms: (1) discontinuous precipitation (DP) or cellular precipitation along the grain boundaries and inclusions; and (2) continuous precipitation (CP) within the gamma grains as gamma' needles. After 720 h at 773 K, the DP colonies completely consumed the continuous y matrix, after which discontinuous coarsening (DC) was observed. The completely-decomposed U-10Mo alloy samples were then annealed at 843, 853, and 863 K as a function of time to document the kinetics of alpha+gamma' -> gamma phase reversion. The reference intensity ratio analysis was employed to XRD patterns to quantify the phase amount after each heat treatment. A combinatorial kinetic model, consisting of the classical JMAK nucleation and growth, and spherical particle dissolution, was employed to describe the alpha+gamma' -> gamma phase reversion as a function of time and temperature. This phenomenological model provided a good approximation for the phase reversion within the temperature and time ranges examined in this study. Furthermore, a diffusion enhancement approach was employed for a set of typical irradiation parameters to estimate the irradiation effect on the alpha+gamma' -> gamma phase reversion kinetics. (C) 2020 Elsevier B.V. All rights reserved.

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