PHASE-EQUILIBRIA IN THE FE-RICH CORNER OF THE ND-FE-TI TERNARY ALLOY SYSTEM AT 1100-DEGREES-C

High-temperature phase relations in the Fe-rich corner of the Nd-Fe-Ti ternary allay system have been investigated and an equilibrium phase diagram has been constructed at 1100 degrees C. Arc-melted and anneale d alloys of systematically varying compositions were characterized uti lizing scanning electron microscopy, an energy dispersive x-ray microa nalysis system (EDS), x-ray diffraction, and optical metallography. Th ree major phases have been identified, the well known Nd(Fe,Ti)(12) '' 1:12'' (ThMn12-type structure) and Nd-2(Fe,Ti)(17) ''2:17'' (Th2Zn17-t ype structure) compounds, and a phase with approximate composition Nd- 2(Fe,Ti)(19) ''2:19.'' The crystal structure of the latter phase has v ery recently been solved, and the ''ideal'' composition shown to be Nd -3(Fe,Ti)(29) ''3:29.'' Quantitative EDS data has been used to identif y the compositional limits for the three major phases. Annealing the ' '1:12'' and ''3:29'' ternary phases at 900 degrees C results in a slow decomposition into Nd-2(Fe,Ti)(17), Fe2Ti, and alpha-Fe(Ti).