Recrystallization and its influence on microstructures and mechanical properties of laser solid formed nickel base superalloy Inconel 718

Recrystallization, which is often occurred in heat treated deformed materials, was examined in laser solid formed (LSFed) Inconel 718 alloy. Its influence on microstructures and mechanical properties of LSFed Inconel 718 alloy were investigated. Microstructure observation indicated that as-LSFed grains were refined and columnar grains were substituted by recrystallized equiaxed grains after recrystallization. The grain refinement mechanism was analyzed and three recrystallized grain nucleation models were found, i.e. the grain-boundary migration nucleation model, the sub-grain coalescence nucleation model and the twinning related nucleation model. The dependence of recrystallized grain size on residual thermal stress distribution was also analyzed. Higher complete recrystallization temperature, longer incubation time and larger recrystallized grain sizes were discovered when comparing with the traditional static recrystallization of deformed materials. Tensile testing results show that the anisotropy in tensile properties of LSFed Inconel 718 alloy is eliminated by the recrystallization process to a certain extent.