Thermodynamic analysis of solid solution formation in the nanocrystalline Fe-Ti-Al ternary system during mechanical alloying

The nanocrystalline (Fe, Ti)(3)Al intermetallic compound was synthesized by mechanical alloying (MA) of elemental powders with the composition of Fe50Al25Ti25. The structural changes of powder particles during MA were studied by X-ray diffractometry. It was found that at early stages of MA, a nanocrystalline Fe(Ti, Al) solid solution is formed. This structure was transformed to disordered (Fe, Ti)(3)Al intermetallic compound at longer milling times. Thermodynamic analysis of this system revealed that in this ternary system, the least thermodynamic driving force for solid solution formation occurred for those compositions that contained 90% of one element. Fe substitution by Ti in Fe3Al compound decreased the Gibbs free energy change, resulting in a more stable structure. (c) 2012 Elsevier Ltd. All rights reserved.