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Recycling of Aluminum Alloy from Al-Cu Metal Matrix Composite Reinforced with SiC Particulates
Sharma, Ashutosh,Ahn, Byungmin Materials Research Society of Korea 2018 한국재료학회지 Vol.28 No.12
In this study, we investigate the recycling of aluminum-based metal matrix composites(AMCs) embedded with SiC particulates. The microstructure of the AMCs is characterized by X-ray diffraction and scanning electron microscopy. The possibility of recycling the composite scrap is attempted from the melted alloy and SiC particulates by re-melting, holding and solidification in crucibles. The recovery percentage of the matrix alloy is calculated after a number of holding times, 0, 5, 10, 15, 20, 25 and 30 minutes and for different particulate sizes and weight fractions in the Al matrix. The results show that the recovery percentage of the matrix alloy, as well as the time required for maximum recovery of the matrix, is dependent on the size and weight fraction of SiC particulates. In addition, the percentage recovery increases with particulate size but drops with the particulate fraction in the matrix. The time to reach maximum recovery falls rapidly with an increase in particulate size and fraction.
Using high-pressure torsion to process an aluminum-magnesium nanocomposite through diffusion bonding
Kawasaki, Megumi,Ahn, Byungmin,Lee, HanJoo,Zhilyaev, Alexander P.,Langdon, Terence G. Cambridge University Press (Materials Research Soc 2016 Journal of materials research Vol.31 No.1
<▼1><B>Abstract</B><P/></▼1><▼2><P>Disks of commercial Al-1050 and ZK60A alloys were stacked together and then processed by conventional high-pressure torsion (HPT) through 1 and 5 turns at room temperature to investigate the synthesis of an Al-Mg alloy system. Measurements of microhardness and observations of the microstructures and local compositions after processing through 5 turns revealed the formation of an ultrafine multi-layered structure in the central region of the disk but with an intermetallic β-Al3Mg2 phase in the form of nano-layers in the nanostructured Al matrix near the edge of the disk. The activation energy for diffusion bonding of the Al and Mg phases was estimated and it is shown that this value is low and consistent with surface diffusion due to the very high density of vacancy-type defects introduced by HPT processing. The results demonstrate a significant potential for making use of HPT processing in the preparation of new alloy systems.</P></▼2>
Ashutosh Sharma,Hansung Lee,Byungmin Ahn 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9
In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and sparkplasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFex(x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSnalloy contained FCC with CuxSnywhile AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr andAlCuSiFeMn showed the formation of BCC + FCC with additional σ- and μ-phases in the HEA matrix. The calculated thermodynamicparameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mngive rise to major BCC with brittle σ- and μ-phase, which further improves their mechanical strength.
Ashutosh Sharma,Ashok K. Srivastava,Kwan Lee,Byungmin Ahn 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
Lead-free Sn–58Bi– x CeO 2 ( x in wt% = 0, 0.3, 0.6 and 0.9) composite solder was prepared via mechanical blending andmelting route. The ceria nanoparticles (CeO 2 ) were prepared from chemical precipitation method. Further, the variationin microstructure and phase composition, melting point, wetting and mechanical properties were studied through scanningelectron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diff erential scanning calorimetry,spreading ratio, contact angle and tensile testing, respectively. It was shown that Sn–58Bi– x CeO 2 composite solders show16.66 and 32.05% increase in spread ratio and wetting angle, respectively, due to the enhanced melt fl uidity up to x = 0.6. The fraction of hard Bi-phase was also refi ned simultaneously. The tensile results showed a slight decrease in ultimatetensile strength and enhancement in ductility up to x = 0.3 and 0.6 except at x = 0.9. High temperature aging also demonstrateda reduced intermetallic compounds thickness when fraction of ceria nanoparticles in the matrix was up to x = 0.6. Itis suggested that for optimum set of soldering properties, the concentration of the nanoparticles should be at 0.6 wt% in themonolithic Sn–58Bi alloy.
Choi, In-Chul,Lee, Dong-Hyun,Ahn, Byungmin,Durst, Karsten,Kawasaki, Megumi,Langdon, Terence G.,Jang, Jae-il Elsevier 2015 Scripta materialia Vol.94 No.-
<P>A Mg–Zn–Zr alloy was processed by high-pressure torsion for up to 2 turns at room temperature to produce significant grain refinement together with enhanced plasticity and strength. Measurements were performed to determine the strain-rate sensitivity, shear yield strength and activation volume as a function of the processing conditions. The results suggest there is a significant contribution from grain boundary sliding to the flow process and the onset of plasticity is associated with heterogeneous dislocation nucleation.</P>
고속열차 점착계수 향상을 위한 신규 복합재료 분말 마찰조절재 개발 및 점착력 특성 평가
오민철,안병민,Oh, Min Chul,Ahn, Byungmin 한국분말재료학회 (*구 분말야금학회) 2018 한국분말재료학회지 (KPMI) Vol.25 No.6
With the recent remarkable improvements in the average speeds of contemporary trains, a necessity has arisen for the development of new friction modifiers to improve adhesion characteristics at the wheel-rail interface. The friction modifier must be designed to reduce slippage or sliding of the trains' wheels on the rails under conditions of rapid acceleration or braking without excessive rolling contact wear. In this study, a novel composite material consisting of metal, ceramic, and polymer is proposed as a friction modifier to improve adhesion between wheels and rails. A blend of Al-6Cu-0.5Mg metallic powder, $Al_2O_3$ ceramic powder, and Bakelite-based polymer in various weight-fractions is hot-pressed at $150^{\circ}C$ to form a bulk composite material. Variation in the adhesion coefficient is evaluated using a high-speed wheel-rail friction tester, with and without application of the composite friction modifier, under both dry and wet conditions. The effect of varying the weighting fractions of metal and ceramic friction powders is detailed in the paper.