Microstructural Feature and Evolution of Rapidly Solidified Ni₃Al-Based Superalloys

The Ni₃Al-based superalloy was rapidly solidified in the form of droplets with varying diameters. The cooling rate (R_c) is a function of diameter (D) of droplet. With the decrease in droplet sizes (increase in the cooling rates), the volume fraction of γ′ + γ eutectic structure increases from 21.31 (D = 1400 μm, R_c = 3.6 × 10² K s⁻¹) to 36.31% (D = 270 μm, R_c = 2.3 × 10³ K s⁻¹). Moreover, unimodal size distribution of nano-γ′ exists in the droplets instead of bimodal dual-size distributions of γ′ precipitates that are normal in as-cast alloys.