A combined TEM/APFIM approach to the study of phase transformations: Phase identification in the Fe-Be system
Phase transformation investigations rely on the identification and characterization of the microstructure in order to understand the formation, development, and relative stability of the constituent phases. Although transmission and associated analytical electron microscopy techniques have made substantial contributions by providing structural and chemical data necessary for the detailed microstructural analysis, the direct atomic structure and chemistry are not readily discernable. By combining TEM techniques with atom probe field-ion microscopy (APFIM), it is possible to obtain a complete structural and chemical analysis of the constituent phases. In this paper, the microstructural development which occurs during ageing in an Fe-25 at. % Be alloy is presented to illustrate the complementary nature of the techniques and demonstrate the applicability of the combined TEM/APFIM approach in the study of phase transformations.An Fe-25 at. % Be alloy was solution annealed at 1100°C for 0.5 h and water-quenched prior to isothermal ageing at 650°C for 4 h. Thin foil specimens were examined in a Philips EM430T operated at 300 kV and in a JEOL 200CX operated at 200 kV. FIM needle specimens were electropolished and analyzed in the ORNL energy-compensated APFIM.