ABSOLUTE ATOMIC-SCALE MEASUREMENTS OF THE GIBBSIAN INTERFACIAL EXCESSOF SOLUTE AT INTERNAL INTERFACES

A method consistent with the Gibbs' formalism is presented for measuri ng the Gibbsian interfacial excess of solute (GAMMA) at an internal in terface using atom-probe field-ion microscopy (APFIM). The values of G AMMA are measured directly, that is, without deconvolution procedures. The relationships between GAMMA and the thermodynamic-state variables of an internal interface are studied using the techniques of APFIM an d transmission electron microscopy (TEM). Examples are given of the ap plication of APFIM-TEM to the measurement of GAMMA at grain boundaries in an Fe(Si) alloy.