Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 723, Issue -, Pages 89-96Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2018.03.046
Keywords
Microstructure; Directional solidification; Nb-doped; NiAl-Cr(Mo) hypereutectic alloy; Compression properties; Fracture morphology
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Funding
- National Natural Science Foundation of China [51704232, 51604222]
- Natural Science Basic Research Plan in Shaanxi Province of China [2016JQ5018]
- fund of the State Key Laboratory of Solidification Processing in NWPU [SKLSP201626]
- Doctoral Starting Fund of Xi'an University of Technology [101-451115009]
- scientific research program - Shaanxi Provincial Education Department [16JK1538]
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Solidification microstructures and compression properties of NiAl-32Cr-6Mo hypereutectic alloys containing different contents of Nb were investigated. The addition of Nb did not change the basic phase constituents, though a new phase of Laves Nb(Cr1-x-yNixAly)(2) was observed. However, the primary Cr(Mo) phase no longer showed obvious dendritic morphology, the formation of lamellae was disturbed and the eutectic cellular microstructure degenerated. When the Nb content was 5%, eutectic lamellae coarsened and became spherical and poorly aligned. Fully eutectic microstructures were obtained in the directionally solidified hypereutectic alloys grown at 6 mu m/s regardless of the addition amount of Nb. With the increasing content of Nb addition, the volume fraction of Laves phase located at the NiAl/Cr(Mo) boundary became more. The yield strength of directionally solidified NiA1-32Cr-6Mo-3Nb alloy reached to 2072 MPa, which is the highest value in the NiAl-based eutectic alloy at present. Well-aligned microstructure and more strengthening phase are conducive to the improvement of properties. All the alloys exhibited brittle quasi-cleavage fracture mode, cleavage in the NiAl phase and de bonding of the NiAl/Cr(Mo) interface accompanied by Cr(Mo) lamellae and Cr2Nb phase pulled out were observed in the fracture surface.
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