Designing heterogeneous microstructure in PM nickel superalloys via dual-alloy powder blending: A combined experimental and computational study

Heterogeneous microstructure design holds promise to overcome the inherent trade-off between high-temperature strength and dwell crack growth (DCG) resistance in powder metallurgy (PM) nickel-based superalloys for aero-engine disks. Herein, a dual-alloy powder blending strategy is presented to engineer and control microstructure heterogeneity. Two master alloy powders with distinct compositions and γ’ solvus temperatures—a low-solvus alloy (S1) and a high-solvus alloy (S2)—were blended (20 wt% S1), consolidated via hot isostatic pressing, and subjected to supersolvus solution treatment. Multi-scale characterization revealed that compositional inheritance produced a stable heterogeneous microstructure: S1-derived regions containing finer γ’ precipitates (∼190 nm, ∼53 vol%) and coarse grains (∼76 µm) embedded within an S2 matrix featuring coarser γ’ (∼310 nm, ∼63 vol%) and finer grains (∼38 µm). This heterogeneity originates from differential γ’ dissolution kinetics and limited interdiffusion of slow-diffusing elements (Cr, W, Mo, Ta), as validated by thermodynamic and kinetic simulations. The degree of heterogeneity is highly sensitive to initial powder size and cooling rate: simulations established a critical S1 particle radius of ∼ 20 µm below which compositional inheritance is lost, while rapid cooling (3 °C/s) intensified non-equilibrium precipitation. These findings provide quantitative design criteria for engineering heterogeneous PM superalloys with enhanced damage tolerance.