Preparation and Investigation of Internally Oxidised Ag-based Electrical Contact Materials

摘要

The aim of our work was to synthesised Ag-based contact material by the internal oxidation of two or more component alloys of elements with high affinity to oxygen. Such Ag-based alloys can be internally oxidised successfully if they are exposed to oxidation atmosphere at elevated temperatures. If the volume of formed surface oxide layer increases to such extent that further oxygen supply to the reaction front is reduced, the actual oxygen content is chemically not equivalent to the content of alloying element to be oxidised. In this way, the oxidation in the zone of internal oxidation, from the surface towards interior, can be gradually reduced or even completely halted. On the basis of results of our kinetics and metallographic investigations, the oxidation conditions for undisturbed internal oxidation without surface passivation of Ag-Zn based alloys with small additions of Mg were determined. Actually, boundary concentrations of micro-alloying elements for undisturbed internal oxidation were determined. The concentrations of micro-alloying element below 0.005 vol.% do not create the conditions with enough large number of oxidation nuclei. On the other side, the alloy compositions with the concentrations of micro-alloying element above 1.2 vol. % lead to defect microstructures because of a local or general passivation.