The effects of microstructure on the U-13at.%Nb alloy hydriding for 500 °C/2 h aged

The microstructure and hydriding properties of as-quenched and 500 degrees C/2 h aged U-13at.%Nb alloys were investigated. After suffering 500 degrees C/2 h process, the as-quenched alloy with single metastable alpha" phase partially decomposed into lamellar pearlite along prior-gamma grain boundaries and around impurities accompanied by the redistribution of niobium. The as -quenched U-13at.%Nb alloy performed perfect corrosion resistance to hydrogen while the aged poor owing to their different microstructure. The hydriding reaction order for the aged alloy in this work was determined to be 0.62. The decomposed areas had relatively lower Volta potential than the non-decomposed areas, which decreased the hydrogen corrosion resistance. In addition, the conclusion that Nb-poor alpha-like-U reacted with hydrogen preferentially than Nb-rich phase was confirmed by KFM results that Nb-poor phase had relatively lower Volta potential. (C) 2017 Elsevier B.V. All rights reserved.