Mechanical behaviour of borosilicate glass-copper composites

Abstract

Borosilicate glass matrix composites with a dispersed Cu content of 10 and 40 vol% were processed through a Powder Metallurgy route and their mechanical behaviour at room and elevated temperatures was studied. To promote a stronger particle/matrix interfacial bond, composites were also processed with oxidized Cu powder. The glass transition temperature of borosilicate glass increased by 40°C for 40 vol% Cu addition. Both the flexural strength and fracture toughness increased with the addition of ductile particles to borosilicate glass. The gain in fracture toughness at room temperature is considerably smaller than the value expected from the dispersion of metallic particles in a brittle matrix. Microcracking at the interfaces (due to thermal expansion mismatch stresses) appears to be responsible for the poor toughness. At elevated temperatures, the rate sensitivity of composites decreased with increasing addition of Cu and decreasing temperature. Cu addition lowered the strength of the composites at lower temperatures. However, there was a strengthening effect at 700°C. Composites with oxidized Cu exhibited higher flow stress than others. A maximum of 550% elongation was observed in tensile tests of 40 vol% Cu composites at 675°C. The apparent viscosity of composites at a given temperature was not influenced by the dispersed phase content. Trends in the variations of flow stress and viscosity of composites can be attributed to the soft and ductile nature of dispersed Cu in the glass matrix.