Prakt. Met. Sonderband 41 (2009) 311
Characterization of high-temperature oxidation of metallic materials
by in-situ electrical resistance measurements
M. Bruncko'?, A.C. Kneissl?, I. Anzel'
"University of Maribor, Faculty of Mechanical Engineering, Slovenia
“University of Leoben, Department Physical Metallurgy and Materials Testing, Austria
Abstract
'C und 1070°C
This research work deals with problems of non-destructive monitoring and characterization of high-
temperature oxidation of metallic materials. For this purpose a special laboratory device that
enables identification and characterization of phenomena during high-temperature oxidation of
metallic materials using in-situ electrical resistance measurements was set up. Furthermore, the
behandlung im algorithms that transform the electrical resistance into an instantaneous microstructure defined by
dass 75% der the parameters of high-temperature oxidation kinetics were determined. To accomplish this, the
ser fiir diese process of high-temperature oxidation was divided into the sequence of the key partial reactions that
Wihrend der are presented in the model as the parallel and/or serial connected time variable resistors in the
(5mer immer electrical circuit. With the novel measurement method we monitored the high-temperature oxidation
roBer, was als of Ag-Sn (2 at. % Sn) and Cu-Al (1.25 at % Al) alloys at different oxidation temperatures in air
wert fiir die atmosphere.
1 Introduction
Practically all metals and alloys survive high-temperature exposure by growing oxide scales and/or
by precipitation of the oxide particles in the matrix. Formed products can grow in shape of external
oxide layers on surfaces, or as discrete oxide particles precipitated in a metal matrix. The first case
:chnische represents external oxidation, and the other case is called internal oxidation. These processes are
very important, because they determine the properties and applicability of metallic materials.
Generally, they are undesired, because they cause deterioration of the mechanical properties and
decomposition of metallic material. On the other side, the controlled process of external oxidation
could be used for formation of protective coatings and the internal oxidation for dispersion
strengthening of materials [1-5]. Oxide dispersion strengthened (ODS) metal matrix composites
have not only good electrical and heat conductivity but also very good mechanical properties even
at high temperature. Two of the most widely used groups of contact materials are internally
oxidized dispersion hardened silver and copper alloys. A unique combination of high strength and
p.L3-L7 conductivity at elevated temperatures makes ODS Cu and Al alloys best candidates for high
temperature electric materials, such as electrodes, lead wires, connectors, high heat flux
143-350 components, frictional brake parts, integrated circuit sealing materials etc. . The principle of their
29 production involves selective oxidation of less noble solute elements (e.q. Mg, Al, Sn, Cd, Zn etc.)
001, p. 881 forming a fine dispersion of oxide particles in the solvent metal matrix. In order for monitoring and
„422 controlling the proceeding of high-temperature oxidation of metals and alloys several destructive
and non-destructive methods can be applied [1,6-8].
