In order to achieve a low-expansion GH6783 alloy with favorable microstructure and comprehensive mechanical properties

heat treatment experiments were conducted on GH6783 ring forgings. Optical microscopy (OM)

scanning electron microscope (SEM) analysis

and fracture analysis were employed to investigate the microstructure and mechanical properties of the alloy under various secondary aging heat treatment processes. The results show that with the increase in the heating temperature of the first stage in secondary-aging process

both the fraction and particle size of primary γ′ phases increase obviously

while the fraction of secondary γ′ phases decreases gradually. Notably

when the temperature of the first stage of secondary aging reaches 780 ℃

only one larger-sized γ′ phase precipitates within the crystal. With the increase of the first stage in secondary-aging temperature

the strength

plasticity and stress-rupture life of the alloy show an initial increase followed by a decrease. At a temperature of 720 ℃ during the first stage of secondary aging

the tensile strength at room temperature and at 750 ℃ reaches its maximum

while the durability and tensile plasticity of the alloy are also notably superior at this aging temperature. This suggests that maintaining the alloy at 720 ℃ during the first stage of secondary aging can yield optimal microstructure and comprehensive mechanical properties.