Origin of substantial plastic deformation in Gum Metals

The elastic property and structure of dislocation in Gum Metal are investigated by anisotropic elastic theory and high-resolution transmission electron microscopy (HRTEM). The results show that the elastic energy coefficients for the 1/2 < 111 > perfect dislocations nearly equal to zero as the shear modulus along < 111 >{110}, {112}, {123} when the valence electron number e/a reaches 4.2, which implies a low intrinsic critical resolved shear stress for dislocation glide. HRTEM observations further revealed 70.53 degrees dislocations in Gum Metal after severe cold working. The substantial plastic deformation is considered to originate from the conventional dislocation mechanism, rather than from the dislocation-free mechanism in Gum Metals. (C) 2008 American Institute of Physics.