[en] This article presents a microstructural study of three different pairs of dissimilar materials (copper with an aluminum alloy, X70 steel with duplex stainless steel and an aluminum alloy with alumina) welded by a diffusion bonding process. The bonded area was examined by light microscopy. Despite the difference in the physicochemical properties of the base materials, microstructural observation revealed that the three pairs of dissimilar materials were successfully joined by a solid state diffusion bonding process.