Investigating the thermal stability of nanocrystalline aluminum-lithium alloy by combining different mechanisms: Reinforcing with graphene and alloying with Sr

Interest in nanocrystalline (nc) aluminum-lithium (Al-Li) alloys is motivated by the demand for lightweight and high-performance materials for light-weighting applications and superior fuel consumption. Nonetheless, nc metals, including Al are thermally unstable, which hinders their technological ap...

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Bibliographic Details
Published in:Journal of alloys and compounds 2022-09, Vol.914, p.165348, Article 165348
Main Authors: Ahmad, Sara I., Hamoudi, Hicham, Zekri, Atef, Youssef, Khaled M.
Format: Article
Language:English
Subjects:
Alloying
Alloys
Aluminum
Aluminum carbide
Aluminum-lithium alloys
Annealing
Ball milling
Grain boundaries
Grain growth
Grain size
Graphene
Hardness
Investigations
Isothermal annealing
Nanocrystalline
Nanocrystals
Second phase
Thermal stability
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Summary:Interest in nanocrystalline (nc) aluminum-lithium (Al-Li) alloys is motivated by the demand for lightweight and high-performance materials for light-weighting applications and superior fuel consumption. Nonetheless, nc metals, including Al are thermally unstable, which hinders their technological applications. In this study, we explore the effect of combining dilute amounts of strontium (1.0 at% Sr) and graphene nanoplatelets (1.0 wt% GNPs) to investigate the thermal stability of a nc Al-Li alloy. Ball milling was used to prepare four samples: Al-Li, Al-Li-Sr, Al-Li-GNPs, and Al-Li-Sr-GNPs, to systematically investigate the role of each added element. Isothermal annealing was conducted at different temperatures to investigate the thermal stability. Despite maintaining a nanometric grain size and high hardness of 70 nm and 1.1 GPa, respectively, after annealing at 773 K for 1 h, the Al-Li-Sr-GNPs sample suffered the most significant grain growth and the highest drop in hardness when compared to the Al-Li-Sr and Al-Li-GNPs samples. Microstructural investigations suggested that competing effects resulting from the spontaneous reaction of both Sr and GNPs with Al at higher temperatures resulted in a declining thermal stability efficiency. The formation and distribution of the rod-like Al4C3 phase at the grain boundaries stood in the way of proper Sr diffusion after annealing and caused the agglomeration of the Al4Sr phase. [Display omitted] •The thermal stability of nc Al-Li alloy was studied through Sr and GNPs additions.•The Al4Sr and Al4C3 formed at the GBs contributed to the improved thermal stability.•Rod-like Al4C3 formed at the grain boundaries prevented the proper Sr segregation.•Agglomeration of the Al4Sr resulted in a declined thermal stability efficiency.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2022.165348