期刊
MATERIALS CHARACTERIZATION
卷 106, 期 -, 页码 420-427出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.matchar.2015.06.027
关键词
Energy input; Microstructure evolution; Direct laser fabrication; IN718
类别
资金
- National High Technology Research and Development Program of China [2013AA031606]
- Fundamental Research Funds for the Central Universities [HUST-2014QT006]
In this study IN718 samples were deposited by direct laser fabrication (DLF) technology in argon atmosphere from pre-alloyed powders. The microstructural evolution of the samples and the effects of energy input (E-v) on microstructural architectures, dendritic morphology, precipitated phases and thus microhardness were investigated in detail. For microstructure of the as-DLFed samples, at a lower E-v, the columnar grains were very continuous and uniform, while at a higher E-v, the columnar grains were no longer continuous and a layer banded structure was present. With increasing E-v, there was a dendrite to cell transition (DCT) in dendritic morphology evolution of the as-DLFed IN718 samples. Also, two critical points of E-v to determine whether the dendritic morphology of the as-DLFed IN718 sample is dendrites, cells or both were found to be about 220 J/mm(3) and 550 J/mm(3) respectively in this study. For precipitated phases, the size and the amount of the Laves phase within interdendritic boundaries were increased with increasing E-v, while the volume fraction of precipitated gamma '' and gamma' phases in matrix gamma of the as-deposited IN718 samples was getting small. As a consequence, the microhardness of the sample increases by decreasing E-v for a constant overlap rate between two neighbor cladding tracks, similarly, the microhardness also increases by decreasing E-v for a constant laser scanning velocity. (C) 2015 Elsevier Inc. All rights reserved.
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