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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
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    Pandee, Phromphong
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    Diewwanit, Onnjira
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    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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    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.
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    Rakhmonov, J. U.
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    Pandee, P.
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    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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    Laser surface polishing of material extrusion additively manufactured 316L stainless steel
    (2026-02-01)
    Hemwat, Jirayu
    ;
    Saetang, Viboon
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    Qi, Huan
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    Seenawat, Mongkol
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    Material extrusion additive manufacturing (MEX) provides a cost-effective pathway for fabricating metallic components; however, its industrial use remains limited by surface defects and high roughness. This study evaluates nanosecond laser polishing (LP) as a post-processing method to improve the surface characteristics of 316L stainless steel produced by Bound Metal Deposition (BMD). The objective is to understand how laser beam diameter, scan speed, and processing atmosphere (air vs. argon) influence surface integrity. Polishing experiments were performed using 50 W and 100 W laser power with beam diameters of 200 and 400 μm at scanning speeds of 100–400 mm/s. Areal roughness (S<inf>a</inf>), surface waviness (W<inf>a</inf>), surface chemistry, subsurface microstructure, and electrochemical response were systematically characterized. Laser polishing reduced S<inf>a</inf> from 2.003 μm to 0.371 μm (81 % reduction) and W<inf>a</inf> by up to 43 %. Polishing in argon produced cleaner melt tracks with minimal oxidation, a refined remelted layer, and enhanced passive film formation, leading to improved corrosion resistance (E<inf>corr</inf> improved from −0.466 V to −0.062 V). These findings demonstrate that LP effectively mitigates the surface limitations of BMD-fabricated stainless steel and provide process guidelines for achieving high-quality functional surfaces in MEX metal components.
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    Characterization of the Anodic Film and Corrosion Resistance of an A535 Aluminum Alloy after Intermetallics Removal by Different Etching Time
    (2022-07-01) ;
    Eskin, Dmitry
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    Limmaneevichitr, Chaowalit
    ;
    Kengkla, Nattarat
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    Diewwanit, Onnjira
    The objective of this study was to improve the corrosion resistance of an A535 alloy by removing intermetallics on the alloy surface by alkaline etching to improve the morphologies and properties of the anodic film that was sealed with different sealants. It was found that alkaline etching for 4 min was suitable for dissolving intermetallic particles and simultaneously providing sufficient roughness for the adhesion of an oxide film to the Al matrix. The effect of alkaline etching revealed that a decrease in the intermetallic fraction from 21% to 16% after etching for 2 and 4 min, respectively, corresponded to the increase in the surface roughness, thickness, and consistency of the anodic film. It was also demonstrated that the surface morphology of the anodic films after stearic acid sealing was more uniform and compact than that after nickel fluoride sealing. The electrochemical polarization curves and salt spray test proved that the alloy etched for 4 min and sealed with stearic acid had better corrosion resistance as compared with the aluminum alloy sealed with nickel fluoride.
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    The improvement of deformability in AA7075 alloy through cryogenic treatment and its correlation with microstructural evolution and FE modelling
    (2024-12-01) ;
    Eskin, Dmitry G.
    ;
    Patakham, Ussadawut
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    Chancharoen, Wares
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    Seehanam, Saran
    Cryogenic treatment has high potential for improving the deformation behavior through the recrystallization at a low temperature. In this work, true stress–strain curves were obtained via compression tests to understand the deformation behavior of an AA7075 under cryogenic conditions. Results showed a significant improvement in the flow stress of AA7075, increasing from 260 to 560 MPa at the yield point. The strain hardening exponent (n) also increased from 0.25 to 0.35 after deformation at cryogenic temperatures. The presence of Al<inf>2</inf>CuMg phase influenced the deformation texture of the tested aluminum alloy, resulting in more elongated grains and fine sub-grains after deformation at cryogenic temperatures, due to the hindered recrystallization. Microstructure evolution after deformation at room and cryogenic temperatures was investigated using EBSD technique to characterize texture and recrystallized grains. The results indicated that the spacing of the high-angle grain boundaries (HAGBs) in the sample deformed at room temperature was slightly larger than in the cryogenically treated sample. The alloy deformed at the cryogenic temperature exhibited a higher strain hardening exponent (n = 0.35) compared to room temperature deformation (n = 0.25). Furthermore, finite element analysis supported the experimental findings, showing that the Plastic Equivalent Strain (PEEQ) of the model tested at cryogenic temperature was higher than at room temperature, attributed to grain refinement during low-temperature deformation. The calculated effective stress responses at cryogenic temperatures for the investigated flow stress aligned well with the experimental results. These new aspects and mechanisms of deformation of aluminum alloys at cryogenic temperatures can improve the formability of high-strength alloys in the future production of more complex and integrated lightweight components.
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    Primary Si refinement and eutectic Si modification in Al-20Si via P-Ce addition
    (2022-03-01)
    Chokemorh, Peerawit
    ;
    Pandee, Phromphong
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    ;
    Patakham, Ussadawut
    ;
    Limmaneevichitr, Chaowalit
    Enhancing the mechanical properties of hypereutectic Al-Si alloys by refining the primary and eutectic Si morphology is very challenging. In this study, the refinement mechanism of primary and eutectic Si morphologies via the simultaneous addition of P-Ce into the Al-20Si alloy was studied. Microstructural analysis revealed that the primary and eutectic Si morphologies were significantly refined, which increased the tensile strength. Furthermore, the addition of Ce, up to 0.6 wt%, can result in the formation of Ce-rich intermetallic phases, which may lead to a significantly increased tensile strength while retaining the ductility of the alloy. The ultimate tensile strength of the Al-20Si alloy increased from 96 to 175 MPa, and the elongation increased from 1.0% to 1.7% with the addition of P-Ce. Moreover, the wear resistance of the alloy improved. The added P and Ce did not react with each other to form an intermetallic compound; therefore, this method can simultaneously refine primary and eutectic Si.
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    Enhancing ambient and elevated temperature performance of hypoeutectic Al–Ce cast alloys by Al3(Sc,Zr) precipitate
    (2024-01-01)
    Mohammed, Abid A.
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    Wang, Shihao
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    Eskin, Dmitry G.
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    Patakham, Ussadawut
    This study explored the consequences of incorporating Sc and Zr into hypoeutectic Al–9Ce cast alloys, specifically investigating their influence on microstructure and mechanical properties. The findings demonstrated the significant reduction in the grain size of the Al–9Ce alloy while successfully maintaining the distinctive shape of the eutectic Al<inf>11</inf>Ce<inf>3</inf> phase through the incorporation of Sc and Zr additions. During aging treatments, Al<inf>3</inf>(Sc,Zr) coherent precipitates formed both at the interface between the α-Al and Al<inf>11</inf>Ce<inf>3</inf> phases and within the α-Al matrix. Remarkably, this led to optimal hardness achieved within a short duration of 3 h at 350 °C. Peak-aged quaternary Al–9Ce–xSc–yZr alloys showed significantly better tensile strength than the binary Al–Ce alloy at both ambient and elevated temperatures. Overall, the study underscored promising prospects of Al–Ce–Sc–Zr alloys for use in high-temperature applications, as they exhibited enhanced mechanical properties.
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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) ;
    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.
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    Improvement in the Uniformity of Bismuth Distribution in an Al-Bi Alloy by Ultrasonic Processing and Hydrogen Melt Enrichment
    (2026-01-01) ;
    Eskin, Dmitry G.
    ;
    Diewwanit, Onnjira
    Manufacturing of immiscible metallic alloysMetallic alloys, such as aluminumAluminum-bismuth, faces challenges in achieving uniform distribution of secondary phase droplets/particles due to their higher density and tendency to agglomerate/coalesce, which negatively affects mechanical propertiesMechanical properties. Recent studies on emulsification of immiscible liquids showed that ultrasonic treatment (UST) of gas-saturated systems improved the droplet distribution. In this work we tested this approach on Al-Bi alloys with melts saturated with hydrogenHydrogen. It was demonstrated that this combination resulted in the uniform distribution of fineFines Bi droplets in the aluminumAluminum matrix. UST had a dual role in the process: (a) increased cavitation facilitated by dissolved hydrogenHydrogen improved the efficiency of droplet formation and distribution and (b) ultrasonic degassing eliminated the adverse effects of gas porosity. Finer and evenly distributed Bi particles enhanced the wear resistance of the alloy.
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    Optimizing Fabrication of Plasma-Driven CuO Shell Over Porous Al2O3 Substrate to Meet Coating Issues
    (2026-07-01)
    Kaentown, Sasithon
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    Wang, Wei Cheng
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    Lin, Yi Cheng
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    Diewwanit, Onnjira
    A plasma-driven in situ conversion strategy was developed in which Cu<inf>2</inf>O nanoparticles introduced into an alkaline phosphate–hydroxide electrolyte undergo oxidative transformation to CuO within plasma micro-discharge channels during plasma electrolytic oxidation (PEO) of AA6061 aluminum alloy. The positive duty cycle was systematically varied from 10% to 40% under constant mean current density to regulate dielectric breakdown behavior, discharge energy input, and interfacial oxidation conditions. Voltage transient analysis, X-ray diffraction, field emission scanning electron microscopy, and scratch adhesion testing were employed to correlate discharge characteristics with phase evolution and coating integrity. A progressive increase in the duty cycle was found to reduce the dielectric breakdown transition voltage, promote more spatially distributed microdischarges, and facilitate charge-transfer-driven oxidation of Cu<inf>2</inf>O to CuO within the active oxide growth zone. This plasma-assisted redox mechanism enables CuO to form co-spatially with Al<inf>2</inf>O<inf>3</inf> melting and rapid re-solidification, producing a CuO shell structure distributed over the porous alumina matrix rather than as a passively entrapped particulate phase. The resulting microstructural densification suppresses discharge-crater porosity, reduces surface roughness, and improves coating–substrate adhesion by nearly twofold relative to particle-free PEO coatings. These findings establish that duty-cycle-controlled discharge behavior provides a mechanistically grounded and dispersant-free route for fabricating CuO-modified oxide coatings with enhanced structural integration and interfacial adhesion on aluminum alloys.