A close observation on the deformation behavior of bicrystal copper under tensile loading

• Mechanical behavior of copper bicrystal was studied by DIC and in situ tension.
• The full-field displacement and strain were acquired.
• Strengthening effect of the grain boundary was discovered by DIC.
• The high-angle grain boundary impeded slip bands.
• Double-necking phenomenon of the sample was observed.

Tensile deformation behavior of a copper bicrystal with a perpendicular grain boundary was investigated. The deformation distribution on specimen surface during test was obtained by using digital image correlation (DIC) method. Experimental results show that the specimen deforms in a ‘double-necking’ mode. Both the displacement and strain distributions on specimen surface are inhomogeneous, and strain level at the grain boundary is lower than that within the grains. The specimens always fracture at the interior of the grain with soft orientation. In situ tension tests by scanning electron microscopy (SEM) indicate that slip bands cannot pass through the grain boundary. The above results suggest that the tensile deformation behavior of copper bicrystal is determined by the orientation of each grain as well as the grain boundary property. Grain with soft orientation tends to deform plastically and fracture first. Large-angle grain boundary could impede slip bands and hence strengthen the material.