Abstract
The effects of small additions of 0.25 at.% Mn and 0.11 at.% Mo to a cast, dilute Al-0.08Zr-0.02Sc-0.01Er-0.10Si (at.%) alloy were investigated by Vickers microhardness, electrical conductivity, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Isochronal aging experiments revealed that the Mn/Mo-modifications allowed the alloy to achieve a 30 MPa higher peak microhardness, which was maintained at higher temperatures (475 °C vs. 400 °C). This is attributed to α-Al(Mn,Mo)Si submicron precipitates forming at 450–475 °C, following precipitation of L12-Al3(Zr,Sc,Er) nanoprecipitates at 350–425 °C. Isothermal aging experiments at 400 °C indicated that the Mn/Mo addition improved the coarsening resistance of the L12-precipitates to yield a coarsening rate about four times slower than that found in Mn/Mo-free alloys. Compared to the base alloy, this results in a 30% reduction in the nanoprecipitate radii after six months of aging. The α-phase consists mainly of coherent plate-like precipitates, with a minority of cuboidal semi-coherent precipitates, displaying well-defined crystallographic orientation relationships with the matrix. Increasing the Mn concentration to 0.40 at.%, led to the formation of primary Al12(Mn,Mo) precipitates, which are too coarse to provide any strength benefit.
Original language | English (US) |
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Article number | 110585 |
Journal | Materials Characterization |
Volume | 169 |
DOIs | |
State | Published - Nov 2020 |
Funding
This research was sponsored by the Ford-Northwestern University Alliance. The authors kindly thank Drs. J. Boileau and B. Ghaffari (Ford Research Laboratory), Prof. D.C. Dunand and Dr. A. R. Farkoosh (Northwestern University) for numerous useful discussions. This work made use of the MatCI Facility and the EPIC facility (NUANCE Center) at Northwestern University. NUCAPT, MatCI and NUANCE received support from the MRSEC program (NSF DMR-1720139) through Northwestern's Materials Research Center; NUCAPT and NUANCE also from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205). NUANCE received support from the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. DNS discloses that he has a financial interest in Braidy Industries, which is active in the area of aluminum alloys. This research was sponsored by the Ford-Northwestern University Alliance . The authors kindly thank Drs. J. Boileau and B. Ghaffari (Ford Research Laboratory), Prof. D.C. Dunand and Dr. A. R. Farkoosh (Northwestern University) for numerous useful discussions. This work made use of the MatCI Facility and the EPIC facility (NUANCE Center) at Northwestern University. NUCAPT, MatCI and NUANCE received support from the MRSEC program (NSF DMR-1720139) through Northwestern's Materials Research Center; NUCAPT and NUANCE also from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205). NUANCE received support from the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. DNS discloses that he has a financial interest in Braidy Industries, which is active in the area of aluminum alloys.
Keywords
- Al-Zr-Sc-Er-Si-Mn-Mo alloy
- High-temperature alloy
- Precipitation strengthening
- Transmission electron microscopy
ASJC Scopus subject areas
- General Materials Science
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering