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Subject: search.filters.subject.Precipitation hardening

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    Enhancing the properties of a hypereutectic Al-Fe alloy through recycled aluminum scrap and ultrasonic melt processing
    (2025-10-01)
    Tangsuksan, Tawatchai
    ;
    Pandee, Phromphong
    ;
    Diewwanit, Onnjira
    ;
    Limmaneevichitr, Chaowalit
    ;
    Tyurnina, Anastasia V.
    This paper focuses on the effects of using recycled aluminum beverage cans and ultrasonic melt processing (USP) on the microstructure and properties of a hypereutectic Al-Fe alloy that has potential in structural and electric applications. The proportion of recycled aluminum scrap used as the starting material varied, and its influence on grain refinement, intermetallic phase formation, precipitation hardening, and mechanical performance was examined. Ultrasonic melt processing (USP) was applied to refine the microstructure and improve phase distribution. The experimental results showed that both the addition of recycled aluminum scrap and USP significantly increased the hardness and tensile strength of the alloys, with further improvements observed after optimal aging treatments, although ductility slightly decreased. Additionally, the presence of alloying elements from the recycled scrap, such as Mg, Mn, Si, and Cu, led to a reduction in electrical conductivity while improving the precipitation hardening response. This study highlights the potential of using recycled materials and advanced processing techniques to develop sustainable, high-performance aluminum alloys for various industrial applications.
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    Precipitation hardening and structure evolution in hypereutectic Al-6 % Fe-Zr alloys subjected to ultrasonic melt processing
    (2024-01-05)
    Chankitmunkong, S.
    ;
    Wang, F.
    ;
    Pandee, P.
    ;
    Limmaneevichitr, C.
    ;
    Eskin, D. G.
    The objective of this research was to study the influence of Zr concentration and ultrasonic melt processing (USP) on the microstructure and precipitation hardening of a hypereutectic Al-6% Fe alloy. Such alloys have a good potential in high-temperature, wear-resistant, and conducting applications but suffer from coarse structure and low strength/ductility, which prevents their processing. The microstructure of the studied alloys consisted of primary Al<inf>13</inf>Fe<inf>4</inf> intermetallics and (Al)+Al<inf>13</inf>Fe<inf>4</inf> eutectic colonies, which were successfully refined by adding Zr and performing USP. The mechanisms of USP and Zr were confirmed for the Al-6 % Fe alloys with a range of Zr additions. The structure refinement led to improved hardness and tensile properties of the alloys. All studied alloys demonstrated strong precipitation hardening effect with hardness increasing 4–5 times, reaching 170 HV for the alloy with 0.4 % Zr after annealing at 400 ℃ for 20 hrs. The electrical conductivity increased from 25 % IACS in the as-cast alloy to 40% IACS in the annealed Al-6% Fe-0.4 % Zr alloy. The prime novelty of this work is a considerable increase of hardness upon annealing, i.e. more than 100 HV, in the Al-6 % Fe alloy with only minute traces of Zr (<0.01 %). The precipitation phenomena were investigated by transmission electron microscopy. The precipitation of the semi-coherent Al<inf>13</inf>Fe<inf>4</inf> phase with Zr segregated to its surface was observed for the first time. All studied alloys (with minute and larger Zr additions) showed the precipitation of this phase, while the alloys with the larger amount of Zr also demonstrated the precipitation of the metastable L1<inf>2</inf> Al<inf>3</inf>Zr phase. Therefore, the properties improvement was attributed to the structure refinement and the formation of Zr-modified Al<inf>13</inf>Fe<inf>4</inf> and Al<inf>3</inf>Zr precipitates in the microstructure.
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    Ambient- and elevated temperature properties of Sc- and Zr-modified Al–6Ni alloys strengthened by Al3Ni microfibers and Al3(Sc,Zr) nanoprecipitates
    (2022-04-28)
    Suwanpreecha, C.
    ;
    Rakhmonov, J. U.
    ;
    Chankitmunkong, S.
    ;
    Pandee, P.
    ;
    Dunand, D. C.
    The eutectic Al–6Ni (wt.%) alloy exhibits excellent strength at ambient and elevated temperature, provided by a high volume fraction of Al<inf>3</inf>Ni microfibers formed during solidification. Here, Al–6Ni is micro-alloyed with Sc and Zr (with 0.1Sc+0.2Zr, 0.2Sc+0.4Zr and 0.3Sc+0.2Zr, wt.%), creating two additional populations of primary and secondary Al<inf>3</inf>(Sc,Zr) precipitates. The fully eutectic microstructure (α-Al + Al<inf>3</inf>Ni) observed in Al–6Ni alloy changes, with Sc and Zr addition to hypoeutectic microstructure with primary α-Al grains nucleated on solidification by primary Al<inf>3</inf>(Sc,Zr) precipitates. Upon subsequent aging, fully-coherent Al<inf>3</inf>(Sc,Zr) nanoprecipitates form in the α-Al matrix between Al<inf>3</inf>Ni microfibers, providing substantial precipitation strengthening, which is maintained for up to 1 month at 350 °C. Alloy strength - both at ambient temperature and during creep at 300 °C - can be quantitatively described through a superposition of precipitation strengthening by Al<inf>3</inf>(Sc,Zr) nanoprecipitates and load-transfer strengthening by Al<inf>3</inf>Ni microfibers.
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    Microstructure Evolution of an Al–Fe–Ni Alloy with Zr and Sc Additions Upon Different Cooling Rates During Solidification for Improving the Mechanical and Electrical Conductivity Properties
    (2021-01-01)
    Chankitmunkong, Suwaree
    ;
    Eskin, Dmitry G.
    ;
    Limmaneevichitr, Chaowalit
    Al–Fe–Ni eutectic alloys have high potential for being alternative aluminum alloys for various electronic and electrical applications instead of conventional low-conductivity Al casting alloys. Furthermore, the addition of Zr and Sc up to 0.3–0.6 wt% improves the hardness for high temperature applications, which is a result of the finer Al–Fe–Ni eutectic structure, and precipitation hardening of Al<inf>3</inf>Zr and/or Al<inf>3</inf>Sc nanoprecipitates. Thus, the aim of the present contribution is to analyze the microstructure features changes in an Al-1.75Fe–1.25Ni eutectic alloy upon different cooling rates during solidification. The features of Al–Fe–Ni eutectics and intermetallics were studied quantitatively, and the mechanical properties and electrical conductivity were measured.