KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 15

Some of the metrics are blocked by your
consent settings
Optimizing Fabrication of Plasma-Driven CuO Shell Over Porous Al2O3 Substrate to Meet Coating Issues
(2026-07-01)
Kaentown, Sasithon
;
Wang, Wei Cheng
;
Lin, Yi Cheng
;
Chankitmunkong, Suwaree
;
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.
Some of the metrics are blocked by your
consent settings
Laser surface polishing of material extrusion additively manufactured 316L stainless steel
(2026-02-01)
Hemwat, Jirayu
;
Saetang, Viboon
;
Qi, Huan
;
Seenawat, Mongkol
;
Chankitmunkong, Suwaree
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.
Some of the metrics are blocked by your
consent settings
Improvement in the Uniformity of Bismuth Distribution in an Al-Bi Alloy by Ultrasonic Processing and Hydrogen Melt Enrichment
(2026-01-01)
Chankitmunkong, Suwaree
;
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.
Some of the metrics are blocked by your
consent settings
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.
Some of the metrics are blocked by your
consent settings
Aging-induced enhancement of corrosion resistance in Al-4Ni-1Mn alloys through Al3(Sc, Zr) precipitates
(2025-05-05)
Masthong, Anuchit
;
Eskin, Dmitry
;
Limmaneevichitr, Chaowalit
;
Pandee, Phromphong
;
Diewwanit, Onnjira
Al-Ni-Mn alloys are attractive for high-temperature, corrosive environment due to the formation of stable intermetallic compounds that can reduce corrosion susceptibility. This study showed that the additions of Mn, Sc, and Zr in Al-4 % Ni alloys significantly enhanced hardness and thermal stability through the simultaneous effect of transformation of the Al + Al<inf>3</inf>Ni to Al + Al<inf>9</inf>(Ni, Mn)<inf>2</inf> eutectic and precipitation of Al<inf>3</inf>(Sc, Zr). The thermal stability of an Al-4 % Ni-1 % Mn alloy was very good when exposed to 350 °C for 60 h. Additionally, the hardness substantially increased in an Al-4 % Ni-1 % Mn alloy with the addition of Sc and Zr, showing an approximate increase of 30 %. The highest hardness achieved was approximately 50 % higher with the optimal Sc and Zr content as compared to the Al-4Ni-1Mn alloy. Addition of 1 % Mn to an Al-4 % Ni alloy decreased the current density (I<inf>corr</inf>) and increased the corrosion potential (E<inf>corr</inf>), indicating better corrosion resistance. The effects of Sc and Zr additions on corrosion were also investigated, revealing that the increased Sc and Zr content led to more aggressive corrosion in the as-cast condition due to the eutectic coarsening and a high solid solution concentration of Sc and Zr that led to microstructural instability and electrochemical effects. However, after aging at 350 °C, the corrosion resistance significantly improved due to the Al<inf>3</inf>(Sc, Zr) precipitates that interrupted the corrosion path.
Some of the metrics are blocked by your
consent settings
Towards the Design of Highly Heterogeneous Aluminum Alloys
(2025-01-01)
Eskin, Dmitry G.
;
Chankitmunkong, Suwaree
;
Zhu, Chengbo
Modern engineering applications require new types of alloys with a unique combination of properties. Alloys with the large volume fraction of intermetallic phases started to attract the attention of researchers, for example, eutectic alloys of the Al–Fe–Ni and Al–Ce–Ni systems. Such alloys have high elasticity modulus, thermal stability, hardness and high-temperature properties, however their applications is limited to casting and mostly hypoeutectic or eutectic alloys. Formation of primary intermetallics poses a challenge unless they can be efficiently refined. Here we present a number of approaches to refine the structure of hypereutectic Al Fe, Al–Ni, Al–Ce–Ni–Mn alloys through additions, ultrasonic processing (USP) and increased cooling rates. As a result, the structure of alloys makes them suitable for deformation and additive manufacturing with extra strength gained through dispersion hardening. These approaches may pave way to the new type of alloys for demanding applications.
Some of the metrics are blocked by your
consent settings
The improvement of deformability in AA7075 alloy through cryogenic treatment and its correlation with microstructural evolution and FE modelling
(2024-12-01)
Chankitmunkong, Suwaree
;
Eskin, Dmitry G.
;
Patakham, Ussadawut
;
Chancharoen, Wares
;
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.
Some of the metrics are blocked by your
consent settings
Enhancing ambient and elevated temperature performance of hypoeutectic Al–Ce cast alloys by Al3(Sc,Zr) precipitate
(2024-01-01)
Mohammed, Abid A.
;
Chankitmunkong, Suwaree
;
Wang, Shihao
;
Eskin, Dmitry G.
;
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.
Some of the metrics are blocked by your
consent settings
Microstructure, Hardening, and Mechanical Properties of Hypoeutectic Al–Ce–Ni Alloys with Zr and Zr + Sc Additions and the Effect of Ultrasonic Melt Processing
(2023-11-01)
Chankitmunkong, Suwaree
;
Wang, Feng
;
Limmaneevichitr, Chaowalit
;
Eskin, Dmitry G.
Ternary Al–Ce–Ni alloys have a potential in the manufacture of automotive and airspace components, as well as in replacing traditional aluminum alloys in high-temperature applications, which is determined by the formation of fine and thermally stable Al<inf>11</inf>Ce<inf>3</inf> and Al<inf>3</inf>Ni eutectic. Herein, the microstructure and mechanical properties of a hypoeutectic Al<inf>4</inf>Ce<inf>2</inf>Ni alloy using Zr and Zr + Sc additions combined with ultrasonic melt processing and dispersion hardening are improved. As a result, the grain structure of the as-cast alloys is significantly refined and the annealing at 350 °C leads to a considerable hardening effect, especially in the alloys with Zr + Sc additions (doubling the hardness). Al<inf>3</inf>Zr and Al<inf>3</inf>(Zr,Sc) coherent particles are identified as hardening nanoprecipitates. The compressive mechanical testing at room and elevated temperatures shows that the additions of Zr and Zr + Sc improve the strength with the additional increase caused by ultrasonic melt processing.
Some of the metrics are blocked by your
consent settings
Effect of Zr and Sc on Intermetallic Morphology and Hardening of an Al–Fe Alloy
(2023-01-01)
Chankitmunkong, Suwaree
;
Eskin, Dmitry G.
;
Limmaneevichitr, Chaowalit
;
Pandee, Phromphong
;
Diewwanit, Onnjira
We studied the effect of zirconium and scandium on an Al-7 wt% Fe cast alloy with potential heat- and wear-resistant applications. An addition of 0.2% Zr resulted in thinning of primary Al<inf>3</inf>Fe particles, while an addition of 0.15% Zr and 0.15% Sc changed the morphology of primary intermetallics from needles to flower-like shape. While the addition of Zr did not affect the properties, the Zr + Sc joint additions increased the hardness of the as-cast Al–Fe alloy. The hardness of the base alloy increased upon annealing from 40 to 80 HV (450 °C, 2 h) and to 110 HV (350 °C, 20 h). The wear resistance of the Al–Fe alloy was also improved by Zr and Sc addition, especially after annealing. The observed effects are likely to be linked to the supersaturation of Zr and Sc in the aluminum solid solution during solidification and precipitation of dispersoids during annealing.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results