Effects of Isothermal Heat-treatment on Microstructure Evolution and Mechanical Properties of K4169 Super-alloy in Semi-solid State

The microstructure evolution and mechanical properties of K4169 super-alloy during semi-solid isothermal heat treatment are studied.The results show that the semi-solid isothermal heat-treatment can turn the dendritic structure of K4169 super-alloy into spheroids.The process is as following:during the increasing of temperature,the partial γ phase at grain interface of eutectic structure is dissolved;then with the further increasing of temperature,the γ+γ'phase begin to remelt successively and the γ phase gradually evolves into spheroidal shape during the holding.The higher the isothermal temperature,the faster the semi-solid remelting and the γ phase evolution process.When the isothermal temperature is much higher or the holding time is much longer,the samples are susceptible to deformation and the spheroidal structure is also susceptible to grow up.Holding temperature 1310℃,holding time 90-120min or holding temperature 1320℃,holding time 45-60min.are the best isothermal heat-treatment of k4169 super-alloy.The effects of isothermal heat-treatment on compress strength of K4169 super-alloy relate to the form of the microstructure.The hardness of K4169 super-alloy in semi-solid state is lower than the casting's.