Improving mechanism of both strength and ductility of GH4169 alloy induced by electric-pulse treatment

The microstructure characteristics of GH4169 alloy aged with electric-pulse treatment (EPT) at 800 °C were investigated and tensile properties were examined at high temperature. The tensile test results indicate that the ultimate stress, yield stress and fracture elongation increase simultaneously in the alloy aged with EPT compared with that of normal aged alloy. The vacancy concentration of the alloy aged with EPT increases proved by positron annihilation spectrometer compared with that of normal aged alloy. Vacancy concentration increase leads to increasing of yield stress at the initial stage of tensile deformation. Farther, vacancy induces ultrafine nm-sized γ′′ phase to precipitate during tensile deformation at high temperature, which is the key factor on strength and ductility improvement. Meanwhile, EPT induces parts of γ′′ phase (precipitating during aged treatment) to precipitate around dislocation which impedes dislocation motion.