Juntao Zou

Arc erosion behaviors of AgSnO2 contact materials prepared with different SnO2 particle sizes

To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag–4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag–4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag–4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag–4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag–4%SnO2 contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.

Microstructure and properties of Cu–Ti–Ni alloys

The effects of Ni addition and aging treatments on the microstructure and properties of a Cu–3Ti alloy were investigated. The microstructure and precipitation phases were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; the hardness, electrical conductivity, and elastic modulus of the resulting alloys were also tested. The results show that Ni addition increases the electrical conductivity and elastic modulus, but decreases the hardness of the aged Cu–3Ti alloy. Within the range of the experimentally investigated parameters, the optimal two-stage aging treatment for the Cu–3Ti–1Ni and Cu–3Ti–5Ni alloy was 300°C for 2 h and 450°C for 7 h. The hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–1Ni alloy were HV 205, 18.2% IACS, and 146 GPa, respectively, whereas the hardness, electrical conductivity, and elastic modulus of the Cu–3Ti–5Ni alloy were HV 187, 31.32% IACS, and 147 GPa, respectively. Microstructural analyses revealed that β′-Ni3Ti and β′-Cu4Ti precipitate from the Cu matrix during aging of the Cu–3Ti–5Ni alloy and that some residual NiTi phase remains. The increased electrical conductivity is ascribed to the formation of NiTi, β′-Ni3Ti, and β′-Cu4Ti phases.