The binary system of iron and copper shows low mutual solubility and cast Cu-Fe forms an iron (bcc) and copper (fcc) dual phase structure at room temperature. In this study, tensile properties, deformation and fracture behaviour of a rolled Cu-40mass%Fe alloy have been evaluated in order to reveal the temperature dependence on tensile properties in dual phase structures. The material formed a layer structure with ultra-fine grains of 1 μm in diameter. In both iron and copper grains,

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... many precipitates of copper or iron were revealed. The strength of this material increased at low temperatures, though the elongation was hardly changed, which suggests that fcc + bcc dual phase structure is effective to improve the tensile property at low temperature. Strain was inhomogeneously distributed at low temperature regardless of Cu and Fe region, and voids and cracks tended to form inside Cu layer. These results imply that the temperature dependence on tensile properties and deformation behaviour of each phase in dual phase structure is different from that of each single phase structure, and dual phase structure materials have a potential for becoming superior cryogenic structural materials.