Microstructural characteristics and its correlation to mechanical properties of additively manufactured nickel-base superalloy upon heat treatments

The IN718 superalloy was additively manufactured in three different heat treatment states and three loading directions (0 degrees, 45 degrees, 90 degrees). The anisotropic mechanical properties were investigated based on microstructural analysis and related to the orientation and heat treatments. The differences in mechanical performances are attributed to the precipitation hardening and the impediment of dislocation motion from delta$$ \delta $$ particles. The preferential epitaxial grain growth along the building direction and the resulting ⟨100⟩$$ \left\langle 100\right\rangle $$ texture are considered responsible for the anisotropic tensile strength. The Weibull distribution and the area-weighted grain diameter were presented to characterize the grain distributions. The Hall-Petch relation was established to correlate the directional grain size and the yield strength of AM IN718, which further illustrated the dominance of precipitates in strengthening mechanisms and the effects of subgrain boundaries.

Automated summary

This study investigated the anisotropic mechanical properties of IN718 superalloy in three different heat treatment states and three loading directions. The differences in mechanical performances were attributed to precipitation hardening and the impediment of dislocation motion from delta particles. Preferential epitaxial grain growth and resulting ⟨100⟩ texture were considered responsible for the anisotropic tensile strength. Weibull distribution and area-weighted grain diameter were used to characterize the grain distributions. Hall-Petch relation was established to correlate directional grain size and yield strength, illustrating the dominance of precipitates in strengthening mechanisms and the effects of subgrain boundaries.