Eco-Materials Processing and Design VIII

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Authors: Joong Hwan Jun, Geon Ha Lee, Jeong Min Kim, Ki Tae Kim, Woon Jae Jung
Abstract: Changes in microstructure and damping capacity with aging time for solutionized AZ91 (Mg-9%Al-1%Zn-0.2%Mn) alloy have been investigated based on experimental results from optical micrography, X-ray diffractometry, hardness test and damping capacity measurement vibrating in a flexural mode. Discontinuous β (Mg17Al12) precipitates form along the primary grain boundaries, the amount of which increases as the aging time increases. The hardness of α matrix with respect to aging shows a typical “S” shape, indicating a generation of fine continuous precipitation in the matrix during aging. The peak level of damping capacity for the AZ91 alloy is obtained after 1 hour of aging, over which the damping capacity becomes deteriorated continuously. The optimum density of continuous β precipitates with fine morphology, which may well act as pinning points for dislocation lines, might be responsible for the improvement of damping capacity.
Authors: Hoon Cho, Byoung Soo Lee, Jin Seok Yang, Hyung Ho Jo
Abstract: Free-cutting phosphor bronze alloy (ASTM C54400) was used as a material for automotive parts and industrial valve parts for its high strength, machinability and excellent corrosion resistance. To obtain desired mechanical strength of the alloy, the process parameters including continuous casting speed, reduction in area and annealing temperature have to be controlled. In this study, we investigated the effect of annealing on the mechanical property and machinability of free-cutting phosphor bronze alloy fabricated by continuous casting with different casting speeds of 80, 100, and 120 m/min, respectively. After annealing, the tensile strength of the alloy decreased with increasing annealing time owing to the occurrence of recrystallization and grain growth. In the cast and swaged alloy produced at casting speed of 120 m/min, the grain growth occurred rapidly. In contrast, in the alloy produced at the casting speed of 80 m/min, the grains growth rate was low. Furthermore, the effect of Pb particle in the alloy on machinability was also investigated by using a tool dynamometer installed force sensor.
Authors: Ying Nan Lin, Jian Yih Wang, Shyong Lee
Abstract: A practical and important idea regarding solid state recycling of magnesium alloys is explored. Chips of AZ91D have been put in hot air environment for accelerated oxidation to simulate the to-be-recycled state of Mg alloy scraps. These chips materials received extrusion process and subsequent annealing treatment. Tensile tests showed that the extruded plate had higher strength than that of ordinary die cast counterpart. Micro-structure investigation indicated it was probably due to finer grains of the Mg matrix as a result of extrusion. Further annealing did not seem to alter this fine structure, yet it could diminish some un-favored form of Mg17Al12 compound. Thus, post-annealed solid state recycled AZ91D showed impressive strengths and elongations.
Authors: Jee Hoon Choi, Dong Bok Lee
Abstract: Three types of L12-type Al3Ti-Cr alloys, of compositions 67Al-25Ti-8Cr, 66Al-24Ti- 10Cr, and 59Al-26Ti-15Cr in atomic percent, were corrosion tested at 900, 1000, and 1100oC in an Ar-1% SO2 gas atmosphere for up to 150 h. The alloys were resistant to corrosion because a thin Al2O3 barrier layer was formed on the alloy surface due to the high Al content in the alloys. Due to the very strong Al affinity for oxygen, virtually no sulfur was detected inside the oxide scale.
Authors: Sung Hwan Hong, Jung Hoon Kang, Jeong Whan Han
Abstract: In the continuity casting technology of steel-manufacturing process, the tundish has two important functions: the preservation and distribution of molten metal and the reaction container able to perform float-out separation of nonmetallic inclusions. The residence time affects the effective removal of the nonmetallic inclusions. In this study, a T-shaped tundish with a submerged entry nozzle (SEN) and three strands was investigated for its ability to extend the residence time. Analysis conditions were the shape of the dam which was transformed to three cases. Fluid flow and non-metallic inclusion movement were also analyzed. The movement and removal of nonmetallic inclusions was determined by residence time distribution (RTD) analysis. As a result, the number of float-out, non-metallic inclusions was increased when the deviation of mean residence time was reduced.
Authors: Sung Wi Koh, Hyung Jin Kim, Jae Dong Kim, Byung Tak Kim, Sun Oug Hwang, Woo Seok Choi
Abstract: In the present study, the influences of load on the abrasive wear properties of silica-filled epoxy resin composites were investigated at ambient temperature. The friction coefficient, wear rate and specific wear rate against SiC abrasive paper were determined experimentally. The sliding wear tests of the materials demonstrated that the friction coefficient and the wear rate of silica filled epoxy composites were lower than those of the pure epoxy. The cumulative wear volume tended to increase nonlinearly with increase of sliding distance and depended on diameter of the silica particle for all these composites. The friction coefficient and wear rate were raised substantially with an increase in applied load.
Authors: Shae K. Kim
Abstract: Driven largely by the never ending quest for weight reduction to decrease fuel consumption and emission, the automotive industry is predicting significant growth in the use of aluminum alloys. Generally, cold chamber type die casting process is utilized for aluminum alloys. In order to comply with the growing demand for life cycle environmental effect, life cycle assessment (LCA) was carried out for producing A356 aluminum alloy by cold chamber type die casting process, based on what has been experienced as needed for LCA study. The main emphasis of this study is to evlauate the effect of trial of improving die casting process and product quality on the environmental value obtained by LCA. Also the results will be compared by the trial of life cycle improvement. In LCA, the process evaluated was based on yields of finished parts relative to the metal input. This is important both in environmental point of view and in commercial point of view, because the environmental data are sensitive to the design of the cast part and the efficiency of the die casting operation.
Authors: Jin Yong Zhang, Gang Bai, Ke Ke Zhang, Yu Hang He, Shun Yang
Abstract: In the paper, the Sn2.5Ag0.7Cu solder alloy is selected out by comprehensive comparison. Minute a mount of rare earth (RE) was added into Sn2.5Ag0.7Cu solder aiming at examining the effect of different a mount of RE on microstructure,the physical properties and mechanical properties of Sn2.5Ag0.7Cu solder.the aim is to define the optimization range of the RE addition.
Authors: Hyung Jin Kim, Sung Wi Koh, Jae Dong Kim, Byung Tak Kim
Abstract: In this study, the mechanical properties of silica-filled epoxy resin composites with average silica particle diameter of 6-33m were investigated at ambient temperature and pin-ondisc friction test was conducted for this. Experimental results demonstrated that mechanical properties such as flexural strength, flexural modulus and critical stress intensity factor depend on average particle diameter. The flexural strength decrease with increase of particle size whereas the critical stress intensity factor increases with increases of particle size. Wear rates of silica-filled composites are below a half those of unfilled epoxy. Fracture surface analysis was discussed based on SEM examination.
Authors: Han Sol Kim, Won Yong Kim
Abstract: This work describes the effect of microstructures on elastic modulus in Ti-26Nb-xSi alloy (x=0.5~1.5at.%) prepared by arc melting, cold rolling and recrystallization heat treatment. OM observation and x-ray diffraction analysis revealed that the microstructure of as-quenched sample appeared to mixture appearance consisting of mostly bcc-structured β phase and small amount of orthorhombic-structured α″ phase. After cold rolling, elongated structure parallel to the rolling direction was observed, and equiaxed structure with the average grain size of about 20~30μm was developed for the sample after recrystallization heat treatment. In as-quenched sample randomly distributed feature of pole figure was characterized without showing a specific texture component. In cold-rolled sample α-fiber, γ-fiber and rotated cube texture components were detected. After recrystallization heat treatment the intensity of α-fiber texture component was markedly decreased, while the rotated cube component becomes sharpened and γ-fiber component remains relatively unchanged. The elastic modulus increased by cold rolling and then decreased by recrystallization over the entire chemical composition range investigated. The variation of elastic modulus values was interpreted in terms of changes in texture components depending on thermomechanical processing.

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