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.