Effect of SiO<SUB>2</SUB> Volume Fraction on High-Temperature Deformation and Fracture Behavior of Cu-SiO<SUB>2</SUB> Bicrystals

High-temperature deformation and fracture behavior of Cu-SiO2 bicrystals with different misorientation angles of 8° and 30°, and SiO2 volume fractions of 0.43% and 1.7% were studied. Though typical intermediate-temperature embrittlement was observed in all the bicrystals, their deformation and fracture behavior depended strongly on the misorientation angle and the volume fraction. The elongation to fracture decreased and the temperature range of low ductility became wider with increase in misorientation angle. The strength increased with increasing volume fraction. Although the elongation to fracture in the 8° bicrystal decreased with increasing SiO2 volume fraction, the elongation to fracture in the 30° bicrystal was almost constant independent of SiO2 volume fraction. These differences in deformation and fracture behavior were reasonably understood by considering the dependence of grain-boundary sliding and stress relaxation on the grain-boundary character.