期刊
METALS
卷 11, 期 2, 页码 -出版社
MDPI
DOI: 10.3390/met11020266
关键词
laser metal powder bed fusion (L-PBF); Inconel 718; microstructure; hardness; heat treatment; recrystallization; annealing twins
The study found that a longer hold time at 1100 degrees C during solid solution heat treatment has a significant impact on complete recrystallization and hardness retention. A high density of annealing twins evolved during the 3-hour solid solution treatment, with slight variations as the treatment time increases.
The widely adopted temperature for solid solution heat treatment (ST) for the conventionally fabricated Inconel 718 is 1100 degrees C for a hold time of 1 h or less. This ST scheme is, however, not enough to dissolve Laves and annihilate dislocations completely in samples fabricated with Laser metal powder bed fusion (L-PBF) additive manufacturing (AM)-Inconel 718. Despite this, the highest hardness obtained after aging for ST temperatures (970-1250 degrees C) is at 1100 degrees C/1 as we have ascertained in our previous studies. The unreleased residual stresses in the retained lattice defects potentially affect other properties of the material. Hence, this work aims to investigate if a longer hold time of ST at 1100 degrees C will lead to complete recrystallization while maintaining the hardness after aging or not. For this study, L-PBF-Inconel 718 samples were ST at 1100 degrees C at various hold times (1, 3, 6, 9, 16, or 24 h) and aged to study the effects on microstructure and hardness. In addition, a sample was directly aged to study the effects of bypassing ST. The samples (ST and aged) gain hardness by 43-49%. The high density of annealing twins evolved during 3 h of ST and only slightly varies for longer ST.
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