Severe plastic deformation of Mg-Fe powders to produce bulk hydrides

Abstract

We describe in the present work the production of bulk Mg hydrides by hydrogenation treatment of samples processed by severe plastic deformation. The compact bulk samples of Mg-Fe have been obtained by high pressure torsion. The ternary complex Mg2FeH6 and the binary MgH 2hydrides have been synthesized by hydrogenation treatment at 350°C, at 3 MPa during 24 h. The average grain refinement after HPT was modest as estimated by XRD. A comparison between the XRD patterns of the powders and of the HPT samples showed the formation, as expected, of a preferred orientation in the latter. The XRD of the hydride HPT samples (H-HPT) showed the presence of Mg, Fe, MgH2 and Mg2FeH6. The first de-hydrating reaction of the alloys (after H-HPT) was studied by differential scanning calorimetry (DSC). These results showed a reduction in the hydrogen dessorption temperature in comparison with commercial MgH2, indicating thermodynamic destabilization of the hydrides as a result of the high density of dislocations in the H-HPT samples. © 2009 IOP Publishing Ltd.