Quantification of porosity and microstructure and their effect on quasi-static and dynamic behavior of additively manufactured Inconel 718

The IN718 superalloy was additively manufactured in three different heat treatment states and three loading directions (0 , 45 , 90 ). The anisotropic mechanical properties were investigated based on microstructural analysis and related to the orientation and heat treatments. The differences in mechanical performances are attributed to the precipitation hardening and the impediment of dislocation motion from δ particles. The preferential epitaxial grain growth along the building direction and the resulting ⟨100⟩ texture are considered responsible for the anisotropic tensile strength. The Weibull distribution and the area-weighted grain diameter were presented to characterize the grain distributions. The Hall-Petch relation was established to correlate the directional grain size and the yield strength of AM IN718, which further illustrated the dominance of precipitates in strengthening mechanisms and the effects of subgrain boundaries.

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“…In the HIP‐SA and forged material, the domination of twin boundaries makes balanced tensile strength 48 . The materials become equiaxed.…”

Section: Discussionmentioning

confidence: 99%

“…In the HIP-SA and forged material, the domination of twin boundaries makes balanced tensile strength. 48 The materials become equiaxed. Annealing twins could contribute to strengthening as twins in nickel form energetically-stable coherent large-angle boundaries, which as the result they could impede dislocation motion.…”

Section: Texture Analysesmentioning

confidence: 99%

Microstructural characteristics and its correlation to mechanical properties of additively manufactured nickel‐base superalloy upon heat treatments

Pei

Yuan

2022

Fatigue Fract Eng Mat Struct

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“…Comparing the sole PBF-LB/M-built and hybrid-built lattice structures, Figure 5 also shows that the in situ milled lattice structure withstands higher loads, consistently about 14-16% higher, before breaking the single layers than the PBF-LB/M-built structures. The strain and fracture behaviour of PBF-LB/M-built components is significantly influenced by the quantity and dimensions of surface defects [61][62][63]. Subsequently, the specific energy absorption (SEA) of the hybrid additive manufactured specimens is increased, scaling the applied load to the mass of the specimens [64][65][66].…”

Section: Static Testingmentioning

confidence: 99%

Static and Dynamic Mechanical Behaviour of Hybrid-PBF-LB/M-Built and Hot Isostatic Pressed Lattice Structures

2023

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We report on a comprehensive study of the mechanical properties of maraging steel body-centred cubic lattice structures fabricated by a hybrid additive manufacturing technology that combines laser powder bed fusion with in situ high-speed milling. As the mechanical properties of additive manufactured components are inferior to, e.g., cast components, surface modifications can improve the mechanical behaviour. Different hybrid additive manufacturing technologies have been designed using additive and subtractive processes, improving process quality. Following this, mechanical testing is performed with respect to static tensile properties and dynamic stress, hardness, and porosity, comparing specimens manufactured by laser powder bed fusion only to those manufactured by the hybrid approach. In addition, the influence of different heat-treatment techniques on the mechanical behaviour of the lattice structures is investigated, namely solution and aging treatment as well as hot isostatic pressing. Thus, the influence of the superior surface quality due to the hybrid approach is evaluated, leading to, e.g., an offset of about 14–16% for the static testing of HIP lattice structures. Furthermore, the dynamic load behaviour can be improved with a finished surface, heading to a shift of the different zones of fatigue behaviour in the testing of hybrid-built specimens.

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“…Haung et al [1] reported that the pinning of dislocations by releasing a larger quantity of Nb, Al, and Ti elements is the main reason for hardness improvement. Further, the presence of a few annealing twins and metal carbides helps to enhance the strength of the matrix [39]. The grain size has an inverse relation with the hardness.…”

Section: Microhardnessmentioning

confidence: 99%

Attainment of favorable microstructure for residual stress reduction through high-temperature heat treatment on additive manufactured inconel 718 alloy

Jebaraj

2022

Int J Adv Manuf Technol

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The mitigation of residual stress in additive manufactured metal parts through postheat treatment helps to enhance life during service. The present work aims to investigate the effect of the high-temperature heat treatment at 1065°C on microstructural changes, residual stress patterns, and hardness of Inconel 718 metal blocks fabricated through the Laser powder bed fusion (L-PBF) process. The non-destructive X-ray diffraction technique known as cos α method was used to measure the surface residual stress by capturing the Debye ring. It was found that the existence of columnar dendrites with laves phases in the interdendritic region along the building direction was dissolved after heat treatment. The resultant microstructure showed homogeneous equiaxed grains with the formation of annealing twins along with strengthening phases (γ' and γ'') and tiny metal carbides on the grain boundaries. Further, the residual stress magnitude in the as-built sample was found to be 77% higher on the corners compared to the center region of the top surface. The average value of residual stress on the top surface was found to be 35.5% lesser than the lateral side surface of the sample. It was observed that the distribution of residual stress is not uniform in as-built condition. The heattreated sample showed uniform distribution of compressive residual stresses in all the locations. This phenomenon happened due to the increase in diffusion of atoms present in the high-stress regions migrated to low-stress regions till attain their equilibrium condition.During this action, the stresses present in the grain interiors were altered considerably and resulted in complete recrystallization with the precipitation of more strengthening phases and annealing twins. The high-temperature post-heat treatment also affects the hardness leads to 23.03% increase in average microhardness mainly induced resistance to dislocation motion by precipitation of strengthening phases in the γ matrix.

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Quantification of porosity and microstructure and their effect on quasi-static and dynamic behavior of additively manufactured Inconel 718

Cited by 24 publications

References 48 publications

Microstructural characteristics and its correlation to mechanical properties of additively manufactured nickel‐base superalloy upon heat treatments

Microstructural characteristics and its correlation to mechanical properties of additively manufactured nickel‐base superalloy upon heat treatments

Static and Dynamic Mechanical Behaviour of Hybrid-PBF-LB/M-Built and Hot Isostatic Pressed Lattice Structures

Attainment of favorable microstructure for residual stress reduction through high-temperature heat treatment on additive manufactured inconel 718 alloy

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