SHAPE CHANGE OF LIQUID B2O3 PARTICLES IN COPPER SINGLE-CRYSTALS DEFORMED AT HIGH-TEMPERATURES

The flow characteristics of copper single crystals containing spherica l B2O3 particles have been examined by tensile tests between room temp erature and 800 degrees C. The B2O3 particles become liquid like at hi gh temperatures and the shape change of the particles due to plastic d eformation of the copper matrix is observed by electron microscopy. Di ffusional relaxation around the liquid B2O3 particles is discussed on the basis of the results of the observations. A comparison between the effects of dispersed particles on the stress-strain curves for copper single crystals containing the liquid B2O3 and those for plastically non-deformable SiO2 particles is made. The work-hardening rate and its temperature dependence for the Cu-SiO2 alloy are similar to those for the Cu-B2O3 alloy. The similarity is explained by the active diffusio nal relaxation during deformation around the plastically non-deformabl e particles.