Tensile Strength and Microstructures of Samples Made of Nb-Doped IN718 Alloy Powder

The Nb-doped IN718 super-alloy powder,an advanced Ni-based aircraft engine material,was synthesized by plasma rotating electrode atomization.The influence of the Nb-doping on the microstructures and tensile behavior of the blanks,fabricated with the Nb-doped IN718 alloy powder,was investigated with scanning electron microscopy,transmission electron microscopy and tensile strength measurement at 650℃.The preliminary results show that the Nb-doping had a major impact.Specifically,the Nb-doping significantly affected the tensile properties,measured at 650℃,possibly because of formation of the cubic γ′-phase grains among γ-phased grains; as the Nb-content increased from 0.0% to 4.5%(wt),the tensile-strength/yield-strength increased by 120 MPa/170 MPa,respectively; the contraction-area at fracture changed in a decrease-increase-decrease mode and the elongation-ratio,varying in the similar manner,maximized at 3 wt.%,and the plasticity continuously decreased.We found that ductile fracture mechanism dominated.