Fig. 1 a Microstructure of as-cast Ni3Al-based superalloy, b morphology of γ′ particles (in primary dendrites), c enlarged image of γ′II particles

Fig. 2 a DSC result of as-cast Ni3Al-based superalloy, b enlarged area C in Fig. 2a

Fig. 3 Calculated relationship between diameter (D) and cooling rate (Rc)

Fig. 4 Images of eutectic structures extracted by ImageJ software: aD = 1300 μm (Rc = 3.9 × 102 K s-1), bD = 1000 μm (Rc = 5.2 × 102 K s-1), cD = 700 μm (Rc = 7.7 × 102 K s-1), dD = 270 μm (Rc = 2.3 × 103 K s-1)

Fig. 5 Average volume fraction of eutectic phase versus droplet diameter

Fig. 6 Morphology of γ′ particles (precipitating from dendritic γ solid solution) of the droplet sample with different diameters: a 1000 μm (Rc = 5.2 × 102 K s-1), b 700 μm (Rc = 7.7 × 102 K s-1)

Fig. 7 a TEM micrograph of γ′ particles in the droplet sample with diameter of 1000 μm (Rc = 5.2 × 102 K s-1), b corresponding SAED pattern showing the γ matrix, γ′ precipitates of the alloys. Z = [001]

Fig. 8 a DSC heating curves obtained from as-cast alloy and droplet sample (D = 1000 μm, Rc = 5.2 × 102 K s-1), b enlarged areas A1, A2 in Fig. 8a, cγ′ precipitation rate (df/dt) as function of temperature (T)