The effect of interdendritic δ phase on the mechanical properties of Alloy 718 built up by additive manufacturing

δ precipitates at interdendritic region in each additive manufactured 718 specimens ((a), (b), (c)). The tensile strengths of the heat-treated specimen were comparable to those of cast and wrought specimens ((d)); however, the horizontal specimen exhibited one fourth ductility compared to the vertical specimen at 650 °C ((e)). It was found that the unexpected interdendritic δ phase would provide the initial site and path of cracking during tensile test.280