In situ investigation on the precipitation of topologically close-packed phase in Ni-base single crystal superalloy

In situ transmission electron microscopy (TEM) investigations reveal the homogeneous nucleation of topologically close-packed (TCP) phase in Ni-base single crystal superalloy at elevated temperatures, which tends to grow toward primary γ/γ′ interface for element supply. Ru addition can decrease both the nucleation and growth rate, hence to suppress TCP precipitation effectively. Higher exposure temperature reduces the nucleation rate but increases the growth rate, finally accelerates the TCP precipitation. •In situ TEM was first applied to study the precipitation behavior of TCP phase.•The TCP phase nucleates homogeneously in γ matrix without preferential sites.•The TCP phase tends to grow toward primary γ/γ′ interface for element supply.•Ru addition can decrease both the nucleation and growth rate of TCP precipitation.•Higher temperature reduces nucleation rate but increases growth rate of TCP phase. In situ transmission electron microscopy was first applied to study the precipitation behavior of topologically close-packed (TCP) phase at elevated temperature in Ru-free and Ru-containing Ni-base single crystal superalloys. Ru addition can decrease both the nucleation and growth rate, hence to suppress TCP precipitation effectively. Higher exposure temperature reduces the nucleation rate but increases the growth rate, finally accelerates the precipitation. The TCP phases nucleate homogeneously in γ matrix without preferential sites, but tend to grow toward primary γ/γ′ interface for element supply. An orientation relationship is kept during nucleation and growth of μ phase in γ matrix, which is [110]μ // [001]γ and (001)μ // (−110)γ.