CHARACTERIZATION OF SYMMETRICAL (011) TILT BOUNDARIES OF COPPER FROM THE SHAPE-ANALYSIS OF BOUNDARY SIO2 PARTICLES

By internally oxidizing Cu-0.06 mass % Si bicrystals with various symmetric [011] tilt boundaries, SiO2 particles were introduced in the Cu matrix and on the grain boundaries. Transmission electron microscopy revealed that while the SiO2 particles in the Cu matrix were spherical, the boundary SiO2 particles had lenticular shapes. The boundary energies of Cu (γB) were determined with reference to the isotropic Cu-SiO2 interfacial energy (γI) by measuring the shape of the boundary SiO2 particles. When γB/γI was plotted against misorientation (θ), energy cusps were observed at θ = 39° (Σ9), 70.5° (Σ3) and 130° (Σ11) with the deepest cusp at θ = 70.5°. The effect of oxygen segregation on boundary energy was examined by applying internal oxidation and degassing treatments to the bicrystals. It was found that the boundary energy became larger as the amount of oxygen at the boundaries increased. After a short internal oxidation or degassing treatment, the γB/γI values were measured as a function of the depth from the surface for the bicrystals with θ=39° and 130° boundaries. γB/γI was found to be constant, independent of the depth from the surface, for the θ=39° boundary while it was dependent on the depth for the θ=130° boundary. Since the θ=39° boundary has a larger energy than the θ=130° boundary, it is concluded that the boundary oxygen diffusivity is larger in a higher energy boundary.