Effect of Al addition on the microstructure and mechanical properties of IN718 alloy fabricated by laser deposition manufacturing

Abstract

The IN718 alloys with different Al content were fabricated by laser deposition manufacturing (LDM) technology. The microstructure and tensile properties of LDMed IN718 alloy with different Al contents before and after homogenization-solution-double aging (HSA) treatment were analyzed. The as-deposited samples show dendrite structure which develops with the addition of Al element. The microstructure of the as-deposited samples mainly consists of the γ matrix, Laves phases and a small amount of carbides. The HSA treatment improves the precipitation of γ'', γ' and δ strengthening phases, and with the Al content increasing, the γ' phase increases, but the γ'' phase decreases. The tensile strength of LDMed IN718 alloy increases with the increasing of Al content, but the elongation decreases. The LDMed IN718+0.5Al alloy shows the highest tensile strength and elongation for HSA-treated samples. The tensile fracture surfaces of LDMed IN718 alloys show dimpled surfaces, indicating the transgranular ductile failure mode.