The effects of annealing on the microstructure and mechanical properties of Fe₂₈Ni₁₈Mn₃₃Al₂₁

Journal Article · Thu Aug 20 00:00:00 EDT 2015 · Journal of Materials Science

DOI:https://doi.org/10.1007/s10853-015-9353-x· OSTI ID:1265631

Meng, Fanling ^[1]; Qiu, Jingwen ^[2]; Baker, Ian ^[1]; Bei, Hongbin ^[3]

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1. Dartmouth College, Hanover, NH (United States). Thayer School of Engineering
2. Dartmouth College, Hanover, NH (United States). Thayer School of Engineering; Hunan Univ. of Science and Technology, Xiangtan (China). College of Electrical and Mechanical Engineering
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division

In this paper, As-cast Fe₂₈Ni₁₈Mn₃₃Al₂₁, which consists of aligned, 50 nm, (Ni, Al)-rich B2, and (Fe, Mn)-rich f.c.c. phases, was annealed at a variety of temperatures up to 1423 K and the microstructure and mechanical properties were examined. It was shown that the as-cast microstructure arises from a eutectoid transformation at ~1300 K. Annealing at temperatures ≤1073 K produces β-Mn-structured precipitates and hardness values up to 816 HV, while annealing at temperatures >1073 K leads to dramatic coarsening of the two-phase B2/f.c.c. microstructure (up to 5.5 µm after 50 h at 1273 K), but does not lead to β-Mn precipitation. Interestingly, annealing at temperatures >1073 K delays the onset of β-Mn precipitation during subsequent anneals at lower temperatures. Coarsening the B2/f.c.c. lamellar structure by annealing at higher temperatures softens it and leads to increases in ductility from fracture before yield to ~8 % elongation. Finally, the presence of β-Mn precipitates makes the very fine, brittle B2/f.c.c. microstructures even more brittle, but significant ductility (8.4 % elongation) is possible even with β-Mn precipitates present if the B2/f.c.c. matrix is coarse and, hence, more ductile.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1265631
• Journal Information: Journal of Materials Science, Vol. 50, Issue 23; ISSN 0022-2461
• Publisher: Springer
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE