Phase equilibria in the Fe-rich corner of the Nd-Fe-Ti ternary alloy system at 1100 °C

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Abstract
High‐temperature phase relations in the Fe‐rich corner of the Nd‐Fe‐Ti ternary alloy system have been investigated and an equilibrium phase diagram has been constructed at 1100 °C. Arc‐melted and annealed alloys of systematically varying compositions were characterized utilizing scanning electron microscopy, an energy dispersive x‐ray microanalysis system (EDS), x‐ray diffraction, and optical metallography. Three major phases have been identified, the well known Nd(Fe,Ti)12 ‘‘1:12’’ (ThMn12‐type structure) and Nd2(Fe,Ti)17 ‘‘2:17’’ (Th2Zn17‐type structure) compounds, and a phase with approximate composition Nd2(Fe,Ti)19 ‘‘2:19.’’ The crystal structure of the latter phase has very recently been solved, and the ‘‘ideal’’ composition shown to be Nd3(Fe,Ti)29 ‘‘3:29.’’ Quantitative EDS data has been used to identify the compositional limits for the three major phases. Annealing the ‘‘1:12’’ and ‘‘3:29’’ ternary phases at 900 °C results in a slow decomposition into Nd2(Fe,Ti)17, Fe2Ti, and α‐Fe(Ti).