A laser powder bed fusion (LPBF) Inconel 718 (IN718) alloy was fabricated under different process parameters, and the samples with optimal process parameters were treated by subsequent heat treatment. The outcomes demonstrated that the pores’ size and shape were influenced by the process parameters. The porosity of the samples first grew and subsequently reduced as the volume energy density increased, and the types of pores changed from lack-of-fusion pores to gas holes and keyhole pores. The porosity of the samples with three process parameters were 3.46%, 0.15% and 1.26%, respectively. The sample of 60.0 J/mm³ was chosen for a single solution (heat treatment at 980 °C for 1 h, SS) and direct aging (heat treatment at 720 °C for 8 h and then 620 °C for 8 h, DA), and the microstructure evolution of the samples was examined. Because of the segregation of the elements Nb and Mo, the Laves phase was distributed among the dendrites in the as-built (AB) sample. The solution heat treatment dissolved the Laves phase and precipitated the δ phase, while aging heat treatment precipitated the γ′/γ” phases. Additionally, the impact of the second phase on the tensile characteristics was looked into. The DA sample had the highest strength, with a tensile strength of 1458 MPa and a yield strength of 1271 MPa. With tensile and yield strengths of 980 MPa and 620 MPa, respectively, the AB sample had the lowest strength due to the Laves phase’s role as the crack initiator. The Laves phase dissolved and the γ′/γ”-strengthened phase precipitated, leading to an increase in the strength of the heat-treated specimens.

In this paper, the microstructure analysis and performance research of dual laser beam welded 2060-T8/2099-T83 aluminum–lithium alloys were carried out. First, the macroscopic morphology and microstructure characteristics of T-joint aluminum–lithium alloys under different welding conditions were observed. Then the effect of welding parameters and pore defects on tensile and fatigue properties of the weld were carried out and the experimental results were analyzed. It was found that the weld heat input has a significant influence on the penetration of the welded aluminum–lithium alloys joint. When the laser power is too high, the weld will absorb more laser energy and the increase in the evaporation of magnesium will further increase the weld penetration. When the penetration depth increases, the transverse tensile strength tends to decrease. There is no obvious rule for the effect of pore defects on the tensile strength of the weld. At the same time, the heat input of the weld is inversely proportional to the porosity. When the weld heat input increases from 19.41 to 23.33 kJ/m, the porosity decreases from 5.35% to 2.08%. During the fatigue test, it was confirmed that the existence of pore defects would reduce the fatigue life of the weld. In addition, from the analysis of the fatigue fracture morphology it can be found that when the porosity is low, the weld toe is the main source of fatigue cracks. The crack propagation zone shows a typical beach pattern and the final fracture of the base metal presents the characteristics of a brittle fracture. While, when the porosity is high, the crack source is mainly located at the pore defects. T-joint fractures from the inside of the weld and the fracture in the final fracture zone have obvious pore defects and dimples.

Improving the high-temperature stress rupture properties of Inconel 718 (IN718) alloys is crucial for enhancing aircraft engine performance. By using the laser powder bed fusion (LPBF) technique, IN718 alloys were crafted at varying volumetric energy densities (VED) in this study. The dendrite growth mode, reinforcing phase distribution and high temperature stress rupture properties of various VED samples were investigated. The results showed that the stress rupture life and the uniform elongation of the samples both first increased and then decreased with the increase in VED. When the VED was 60 J/mm³, the maximum rupture life and elongation of the sample were 43 h and 3.8%, respectively. As the VED increased, the angle of dislocation in the dendrite decreased while the spacing between primary dendrite arms increased, resulting in an increase in the size and volume fraction of the Laves phase. Following a heat treatment, the δ phase would nucleate preferentially around the dissolved Laves phase causing an increase in the volume fraction of the δ phase with the increase in VED. The creep voids readily formed around the δ phase are distributed along the grain boundaries, while the inhomogeneous δ phase and fine grains facilitated crack initiation and propagation. Furthermore, a significant quantity of the δ phase consumed the Nb element, thereby hindering adequate precipitation in the γ″ phase and causing cracks.