Abstract:The microscopic morphologies of uniaxially compressed copper bicrystals (CB) with horizontal and vertical grain boundaries (GB) were observed. Experiment results have shown that, under the same comppressive loading condition and comparing the case of CB sample with horizontal GB, a higher stress exists beside the GB for the CB sample with vertical GB, for which there are much more micro-voids and cracks, whose locations are much concentrated to or beside the slip lines.