Effects of CuO content in the glass on the interfacial reaction for the NiCuZn ferrites-FeSiCr alloy composites

Abstract

The effects of CuO content in Bi-B-Si-Zn glass on the interfacial reaction between the glasses and FeSiCr alloy powder and NiCuZn ferrites, microstructure, and adhesion strength were investigated. For the FeSiCr alloy and glass interface, the iron in FeSiCr alloy dissolves into the glass and is oxidized into Fe3+ during heating. The copper ions in the glass are reduced to elemental copper near the interface to maintain charge neutrality. This leads to chemical bonding between the FeSiCr alloy and glass at 750°C under air atmosphere. The CuO in the glass increases the wettability and adhesion between the FeSiCr alloy and glass. The redox reaction inhibits crack propagation from Vickers indentations in the spherical copper-rich precipitates near the interface, but the presence of pores in the glass layer would decrease the adhesion strength. In the FeSiCr alloy/glass/NiCuZn ferrites/glass/FeSiCr alloy structure, glass with 5 wt% CuO exhibited higher pulling strength. Moreover, the amount of elemental copper precipitates increased as the heat-treatment temperature was increased to 800 and 850°C, leading to an increase in the glass and FeSiCr alloy adhesion strength.