Abstract:The semi-solid slurry was prepared by rolling remelting strain induced melting activation method (SIMA), and the copper alloy shaft sleeve parts at different forming stages were prepared by back extrusion. The microstructure evolution and segregation behavior of copper alloy during semi-solid back extrusion were studied. The results show that the phase structure of semi-solid ZCuSn10P1 copper alloy is mainly composed of α-Cu phase, Cu₄₁Sn₁₁ (δ) phase, Cu₃P phase and Cu_13.7Sn (β′) phase. During the semi-solid extrusion process, the slurry is filled from the bottom of the cavity to the end, and obvious solid-liquid segregation occurs during the forming process. The tendency of solid-liquid segregation and structural defects decrease with the semi-solid ZCuSn10P1 copper alloy forming. When the semi-solid extrusion is fully formed, there is no obvious defects in the structure, and the grain roundness is high and the grain distribution is uniform. The segregation of micro elements is serious in the microstructure of semi-solid extruded copper alloy, and Sn and P elements are enriched in intergranular and intragranular liquid islands, while the content of Sn and P elements in the matrix is less. With the semi-solid ZCuSn10P1 copper alloy forming, the segregation of Sn element in semi-solid copper alloy intensifies. The segregation degree decreases when the semi-solid ZCuSn10P1 copper alloy is fully formed, but the element homogeneity in the same type of area is poor.

Key words: semi-solid; copper alloy; microstructure evolution; segregation behavior; extrusion forming