Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) of nano-scale plate-shaped second phase particles
Résumé
The feasibility of accurately measuring the size and the volume fraction of nano-scale plate-shaped precipitates by atomic force microscopy (AFM) has been explored. For quantitative evaluations their unhandy geometry is conveniently described as superellipsoids. The experimental alloy Ni69Co9Al18Ti4 served as a model system: plate-shaped disordered γ-precipitates form in the L12-long-range ordered γ'-matrix. The results obtained by AFM are compared with those derived from transmission (TEM) and from high resolution scanning electron microscopy (SEM). The agreement between the AFM and the TEM results is good. In spite of the low number of SEM images taken, the same holds for the SEM results. In addition, magnetic force microscopy was applied; its results are acceptable. The main advantages of AFM are (i) the numerical output for all three dimensions, (ii) the simplicity of its operation, and (iii) the lower cost of the microscope itself. The first point allows to directly subject the numerical AFM output data to automated computer based evaluations. All present experimental and evaluation procedures are also applicable to cube-shaped particles with rounded edges and corners as found e.g. in γ'-strengthened nickel based superalloys.
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