Effect of High Density Current Pulses on Microstructure and Mechanical Properties of Dual-Phase Wrought Superalloy

Abstract

In this study, high density electric current pulse (ECP) treatment was introduced instead of the conventional solution treatment, and the γ′ phase was completely dissolved under the ECP treatment within only several milliseconds at 1148 °C. Due to the extremely short treatment time and high cooling rate, the growth of γ-phase matrix grain and γ′ phase precipitate was effectively retarded. By comparing with the conventional heat process, the grain size of ECP treated sample was controlled to about 15 μm, the size of the re-precipitated γ′ phase reduced from 65 to 35 nm, and the number density of γ′ precipitate increased from 1.46 × 108 to 3.03 × 108/mm2. The Vickers hardness, ultimate tensile strength and yield strength of the ECP treated sample were significantly improved. According to the theoretical derivation of kinetics, the ECP treatment introduces an extra electrical free energy which promoted the dissolution of γ′ phase. The ECP treatment may provide a new method for solution treatment of the Ni-based superalloy.