Microstructure and Properties of Ag-SnO2 Electrical Contact Composites with Different SnO2 Volume Fractions

Ag-SnO2 composites are widely adopted as electrical contact materials in low-voltage apparatuses. Ongoing upgrades of electrical devices impose higher standards for their mechanical strength, machinability, and electrical conductivity, among which the SnO2 volume fraction is a dominant factor regulating material performance. In this work, Ag-SnO2 electrical contact composites are reinforced with 15 μm SnO2 particles at various volume fractions. Increasing SnO2 volume fractions can improve the hardness. The ultimate tensile strength reaches a maximum value of 219.1 MPa at the SnO2 volume fraction of 18.3 vol%. Excessively high SnO2 content (26.5 vol%) leads to the brittle fracture of the composite and a sharp decline in tensile strength. Indirect strengthening dominates the overall mechanical performance, among which grain refinement serves as the primary strengthening mechanism, followed by dislocation multiplication strengthening, while the Orowan looping effect is negligible for coarse 15 μm SnO2 particles. This work clarifies the microstructure–performance correlation and strengthening mechanism of particle-reinforced Ag-SnO2 composites, providing a theoretical and experimental basis for the optimal design and performance optimization of high-performance electrical contact materials.