Hydrogen absorption in Mg-Gd alloy. (31st August 2017)

• Record Type: Journal Article
• Authors: Vlček, Marián; Čížek, Jakub; Lukáč, František; Hruška, Petr; Smola, Bohumil; Stulíková, Ivana; Kudrnová, Hana; Minárik, Peter; Kmječ, Tomáš; Vlasák, Tomáš
• Is Part Of: International journal of hydrogen energy. Volume 42:Number 35(2017)
• Page Start: 22598
• Page End: 22604
• Publication Date: 2017-08-31
• Subjects: Hydrogen -- Magnesium alloys -- Rare earth elements; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2017.04.012
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Mg-Gd alloy containing 22 wt.% Gd was studied in the present work. As cast alloy contains Mg46 Gd9 phase located at pockets along grain boundaries. In addition the as-cast alloy contains a low concentration of rectangular GdH2 particles. Solution treatment at 530° C was performed in order to dissolve Gd in the Mg matrix. The solution treatment in air enhanced the volume fraction of GdH2 particles by one order of magnitude. The formation of GdH2 particles is caused by hydrogen-induced decomposition of the Mg46 Gd9 intermetallic phase. The source of hydrogen is water vapor reacting with Mg surface. A Gd-rich oxide layer was formed during solution treatment in air. Building of the oxide layer requires diffusion of Gd solutes from bulk to the surface and leads to formation of a Gd-depleted sub-surface region. It was found that solution treatment in vacuum results in substantially lower volume fraction of GdH2 particles. Alternative methods of formation of GdH2 particles in Mg-Gd alloy were examined as well and are discussed in the paper. Highlights: Rectangular particles of GdH2 phase were observed in Mg-22wt.%Gd alloy. Solution treatment in air strongly increased volume fraction of GdH2 particles. GdH2 particles are formed by hydrogen-induced decomposition of Mg5 Gd phase. Solution treatment in vacuum leads to lower concentration of GdH2 particles. GdH2 particles are unstable against under-saturation of Mg matrix by Gd.