Microstructure sensitivity of α-Cr phase in Ni-Cr based alloy K648

The effects of element contents and heat treatment regimes on the precipitation morphology of α-Cr phase and the mechanical properties of K648 superalloy were systematically investigated by room-temperature tension and impact tests. The precipitation law of equilibrium phases in K648 superalloy was calculated by Thermo-Calc software. The calculated results show that the main equilibrium precipitation phases are α-Cr phase, γ' phase and M₂₃C₆ carbide. Microstructure observations indicate that the precipitation morphology of α-Cr phase is sensitive to the Cr content and heat treatment regime, demonstrating its morphological variety. Mechanical property tests further testify that the room-temperature tensile properties and impact properties are significantly dependent on the morphology and distribution of α-Cr phase, meaning that the mechanical properties of the alloy have microstructure sensitivity.