2019-Sustainable Industrial Processing Summit
SIPS2019 Volume 3: Kobe Intl. Symp. / Science of Innovative and Sustainable Alloys and Magnets (SISAM)
| Editors: | F. Kongoli, M. Calin, J.M. Dubois, K. Zuzek-Rozman |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2019 |
| Pages: | 156 pages |
| ISBN: | 978-1-989820-02-5 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Nanocrystal-amorphous dispersions in Al-based and high-entropy alloys
A. Lindsay Greer1; Akihisa Inoue2;1UNIVERSITY OF CAMBRIDGE, Cambridge, United Kingdom; 2TIANJIN UNIVERSITY, Tianjin, China;
Type of Paper: Regular
Id Paper: 250
Topic: 42
Abstract:
We review recent advances in the development of two types of rapidly quenched alloys that show promise as structural materials. In each case, the focus of interest is the dispersions of nanocrystals in the residual amorphous matrix that can be achieved by treating initially fully amorphous melt-spun ribbons.
The first alloy type is Al-based with compositions such as Al90Y10 (at.%) and Al84Y8.5Ni4Co2Pd1Fe0.5 [1,2]. Remarkably, when amorphous ribbons are cold-rolled, this induces partial crystallization to nanoscale fcc-Al (alpha-Al). By contrasting this crystallization with the apparently similar crystallization induced by annealing, progress has been made in understanding the mechanisms of hardening and softening. Polymorphic crystallization induced by cold-rolling avoids the formation of compound phases associated with brittleness, and is therefore promising for the development of high-solute Al-based alloys as structural materials.
The second alloy type is metal-metalloid, with a complex (high-entropy) mixture of metals and relatively low metalloid content. An example is the alloy series (Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)86-89B11-14 [3]. Initially amorphous alloys when annealed show complex crystallization sequences. Nanoscale (5-15 nm) particles of fcc and bcc phases are formed and show very high thermal stability (resistance to coarsening). It is of particular interest that ultrahigh hardness of 1500-1550 Hv can be achieved without the formation of any boride phases. The hardening and thermal stability are unusually high for such low boron content and encouraging for the development of ultrahard coatings.
Prospects for further alloy development are considered.
Keywords:
Alloys; Amorphous Materials; Magnetic Materials;References:
1. F.F. Han, A. Inoue, Y. Han, F.L. Kong, S.L. Zhu, E. Shalaan, F. Al-Marzouki, A.L. Greer, Novel heating-induced reversion during crystallization of Al-based glassy alloys, Sci. Reports 7 (2017) 46113.2. H.W. Bi, A. Inoue, F.F. Han, Y. Han, F.L. Kong, S.L. Zhu, E. Shalaan, F. Al-Marzouki, A.L. Greer, Novel deformation-induced polymorphic crystallization and softening of Al-based amorphous alloys, Acta Mater. 147 (2018) 90-99.
3. F. Wang, A. Inoue, F.L. Kong, S.L. Zhu, E. Shalaan, F. Al-Marzouki, W.J. Botta, C.S. Kiminami, Yu.P. Ivanov, A.L. Greer, Formation, stability and ultrahigh strength of novel nanostructured alloys by partial crystallization of high-entropy (Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)86-89B11-14 amorphous phase, Acta Mater. 170 (2019) 50-61.