Effect of Heat Treatment on Mechanical Properties of Inconel 718

The effect of gamma" (Ni3Nb) particle size on the mechanical properties and deformation mechanism of Inconel 718 was investigated. In this study, two kinds of aging heat treatment were used to obtain different gamma" particle size. The effect of gamma" size on the tensile/compressive-proof, creep and fatigue strengths at 24 degrees C and 650 degrees C were studied. When the average size of gamma" particle was 18 nm, they were considered to be sheared by the group of 1/2 < 110 > dislocations during tensile deformation. When the average size of gamma" particle was 42 nm, the tensile deformation was occurred by the passage of deformation twins at 650 degrees C. The creep and fatigue strengths were considered to be decreased as the deformation mechanism changed from dislocation's shearing of gamma" particle to deformation twins. The tension/compression anisotropy in single crystal Ni-base superalloys has been reported when the deformation twin is observed. However, in the polycrystalline Inconel 718, in spite of existence of the deformation twin, the anisotropy in yield strengths was not observed.