Phase transformations in the La1-xNdxNi3.5Al1.5-H2 (x= 0.1 and 0.2) system

Abstract Interactions in the La 1− x Nd x Ni 3.5 Al 1.5 -Н 2 ( x  = 0.1 and 0.2) system was studied from room temperature up to 950 °C at the initial hydrogen pressure of 5 MPa through differential thermal (DTA) and X-ray phase analyses. Heating two-phase alloys ( x  = 0.1 and 0.2) in hydrogen results in their disproportionation (at 530 and 560 °С, respectively) and the formation of NiAl and unidentified amorphous products. The single-phase La 0.9 Nd 0.1 Ni 3.5 Al 1.5 alloy decomposes in hydrogen at 900 °С into a hydride of rare-earth metals and an Ni 3 Al intermetallic; traces of NiAl and hydride of a phase of the CaCu 5 -type structure have also been observed. Heating the disproportionated samples in vacuum to 520–550 °С leads to their recombination into a homogenized phase with a CaCu 5 -type structure. In other words, the increase of neodymium content shifts the reaction equilibrium of La 1− x Nd x Ni 3.5 Al 1.5 alloys with hydrogen towards recombination.