Oxidation resistance of alloys at high temperatures generally depends on whether selective oxides scales are formed on the surface or not.For single phase alloys,only when the concentrate of the most active element exceeds a critical concentrate,selective oxidation occurs and the oxidation resistance is improved.For the engineering alloys are mostly multi-phase alloy,more attentions have been paid to two-phase and multi-phase alloys.As one of the most important engineering alloys,Cu-Cr alloy is an ideal material to study the oxidation behavior of binary two-phase alloys.Surface micro-crystallizing may have contribution to the oxidation resistance of alloys due to the decrease of the grain size.In this paper,Cu-50Cr two-phase alloys at both cast and micro-crystallization states were oxidized at 800 ℃ in air for 50 h.