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

• Published in: Journal of non-crystalline solids 2008-10, Vol.354 (35-39), p.4418-4422
• Main Authors: Trostianchyn, А.М., Bulyk, І.І., Trostianchyn, I.V., Mudry, S.I.
• Format: Article
• Language: English
• Subjects: Alloys; Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Cross-disciplinary physics: materials science; rheology; Crystallization; Exact sciences and technology; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2008.06.062

Interactions in the La1−xNdxNi3.5Al1.5-Н2 (x=0.1 and 0.2) system was studied from room temperature up to 950°C at the initial hydrogen pressure of 5MPa 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 La0.9Nd0.1Ni3.5Al1.5 alloy decomposes in hydrogen at 900°С into a hydride of rare-earth metals and an Ni3Al intermetallic; traces of NiAl and hydride of a phase of the CaCu5-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 CaCu5-type structure. In other words, the increase of neodymium content shifts the reaction equilibrium of La1−xNdxNi3.5Al1.5 alloys with hydrogen towards recombination.