Phase transformations and phase equilibria in the La–Ni and La–Ni–Fe systems. Part 1: Liquidus & solidus projections

Abstract

Phase equilibria in the La–Ni and La–Ni–Fe systems were studied using DTA, X-ray diffraction, SEM and EPMA. La–Ni phase diagram, liquidus and solidus projections, melting diagram and a Scheil reaction scheme for the La–Ni–Fe system over the whole concentration range were constructed. Among binary compounds LaNi5, La5Ni19 and La2Ni7 have large homogeneity ranges and dissolve at the solidus temperature up to 21.9, 16.1 and 14.0 at.% Fe, respectively. The homogeneity ranges of the remaining phases are smaller. No ternary compounds have been identified in the La–Ni–Fe system. Liquidus projection is characterized by 13 fields of primary solidification of the component-based solid solutions (γFe,Ni), (δFe), (αFe), (βLa), (γLa) and solid solutions based on binary phases LaNi5, La5Ni19, La2Ni7, LaNi3, La7Ni16, La2Ni3, LaNi, La7Ni3 and La3Ni. The solidus projection is characterized by ten three-phase fields, which result from invariant four-phase equilibria, three are of eutectic type and seven of transition type.