In-situ monitoring of internal oxidation of dilute alloys

This paper presents a non-destructive measurement method that enables identification and characterization of phenomena during internal oxidation of metallic materials as well as monitoring the kinetics of internal oxidation using "in-situ" electrical resistance measurements. A special laboratory device, based on the unique measurement cell, for the electrical resistance measurements at high temperatures and the model for electrical resistance transformation into an instantaneous microstructure were developed. To accomplish this, the process of internal oxidation was divided into the sequence of the key partial reactions that were presented in the model as the parallel and/or serial connected time variable resistors in the electrical circuit. The validity of the transformation model was experimentally confirmed by internal oxidation of Ag-Sn (2 at.% Sn) alloy at different oxidation temperatures in air atmosphere. The comparison of the results obtained by "in-situ" electrical resistance measurements with those obtained by metallographic analysis and Wagner's theory shows that the novel method presents a more effective tool for monitoring of internal oxidation kinetics. The method identifies also the microstructural defects and their influences on the kinetics of internal oxidation. (c) 2006 Elsevier Ltd. All rights reserved.