Microstructure evolution and coarsening kinetics of semisolid CuSn10P1 alloy under short-time isothermal treatment

The key success of semisolid rheology is to prepare high-quality semisolid slurries. To achieve that it is necessary to be able to characterize the microstructure, element distribution, and coarsening mechanism during short-time isothermal treatment. This present work applied the enclosed cooling slope channel (ECSC) to make a semisolid slurry of CuSn10P1 alloy. Effects of short-time isothermal treatment (0, 5, 10, 15, 20, 25 s) on microstructure characteristics, element distribution, grain stability, and coarsening kinetics of semisolid CuSn10P1 alloy were studied. The equiaxed or near-globular microstructure can be prepared and improved intergranular segregation of CuSn10P1 alloy through the semisolid slurry short-time isothermal treatment. The mean diameter of primary α-Cu phase gradually increases with soaking time prolonged, but shape factor shows a wavy trend. The mean size and shape factor changes caused by the instability of primary α-Cu phase during short-time isothermal treatment can be described by the melting mechanism and the coarsening mechanism. The relationship between the high Tin layer thickness of primary α-Cu and soaking time is consistent with the linear equation. The relationships of the Sn mass fraction in intergranular microstructure and primary α-Cu phase center versus soaking time are consistent with an exponential equation. The suitable isothermal treatment parameters for the semisolid CuSn10P1 alloy is the soaking time 15 s to 20 s at 990 °C. (paper)