• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.3
• /
• pp.796-805
• /
• 1996

A fabrication process using Semi-Solid Material(SSM) for casting alloy has been studied to demonstrate the possibility for mass production with controlled solid fraction. The SSM was fabricated under the various solid fractions and preheating temperatures of mold. The behaviour of a semi-solid global microstructure has been investigated under the various heating and die temperatures for solid fraction. The effect of reheating time on the globularization of SSM microstructure has been investigated in detail. And the behavior of SSM which has the solid fraction 0.5 was observed under compression. The stress strain relationship was also obtained for the compression test of semi-solid materials. The rheological behaviour of semi-solid with globule microstructure was investigated as a function of the compression velocity under isothermal holing conditions.

• Journal of the Korean Society of Industry Convergence
• /
• v.21 no.1
• /
• pp.29-36
• /
• 2018

Low pressure casting process for unidirectional carbon fiber reinforced aluminum (UD-CF/Al) composites which is an infiltration route of molten Al into porous UD-CF preform has been a cost-effective way to obtain metal matrix composites (MMCs) but, easy to cause non-uniform fiber distribution as CF clustering. Such clustered CFs have been a problem to decrease the density and thermal conductivity (TC) of composites, due to the existence of pores in the clustered area. To obtain high thermal performance composites for heat-sink application, the relationship between fiber distribution and porosity has to be clearly investigated. In this study, the CF distribution was evaluated with quantification approach by using two-dimensional spatial distribution method as local number 2-dimension (LN2D) analysis. Note that the CFs distribution in composites sensitively changed by sizes of Cu bridging particles between the CFs added in the UD-CF preform fabrication stage, and influenced on only $LN2D_{var}$ values.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.1
• /
• pp.173-177
• /
• 2013

The purpose of this paper is to investigate the influences on mechanical properties of two-stroke cycle motor pistons manufactured by casting, conventional forging and powder forging, through the comparison of characteristics, merits and disadvantages of each forming technology. For each forming technology, the optimal process parameters were determined through the experiments for several conditions, and microstructure, hardness, tensile strength and elongation of pistons are compared and analyzed. In conventional forging process, material temperature was $460^{\circ}C$ and the die temperature was $210^{\circ}C$ for the Al 4032. The optimal condition was found as solution treatment under $520^{\circ}C$ for 5 hours, quenching with $23^{\circ}C$ water, and aging under $190^{\circ}C$ for 5 hours. In powder forging process, the proper composition of material was determined and optimal sintering conditions were examined. From the experiment, 1.5% of Si contents on the total weight, $580^{\circ}C$ of sintering temperature, and 25 minutes of sintering time were determined as the optimal process condition. For the optimal condition, the pistons had 76.4~78.3 [HRB] of hardness, and 500 [MPa] of tensile strength after T6 heat treatment.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.262-267
• /
• 2007

In this paper, we study about wear properties for the metal matrix composites fabricated by low pressure infiltration process. Metal fiber preform reinforced aluminum alloy composite were fabricated by low pressure casting process under 0.4MPa. Infiltration condition was changed the pressure infiltration time of 1 s, 2 s and 5 s under a constant pressure of 0.4MPa. The molten alloy completely infiltrated the FeCrSi metal perform regardless of the increase in the pressure acceleration time. However, the infiltration time at the pressure acceleration time of 1s was shorter than at the pressure acceleration time of 2s or 5s. The FeCrSi/A366.0 composite was investigated the porosity. The porosity is reducing as the pressure acceleration time compared with the pressure acceleration time of 2s and 5s. The FeCrSi/A366.0 composites were investigated the wear resistance. FeCrSi/A366.0 composite at pressure acceleration time of 1s has excellent wear resistance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2004.11a
• /
• pp.66-74
• /
• 2004

The sliding wear behavior of $ZrO_2-22wt\%MgO\;(MZ)\;and\;ZrO_2-8wt\%Y_2O_3\;(YZ)$ deposited on a casting aluminum alloy with bond layer (NiCrCoAlY) by plasma spray against an SiC ball was investigated under dry test conditions at room temperature. At all load conditions, the wear mechanisms of the MZ and the YZ coatings were almost the same. The wear mechanisms involved the forming of a smooth film by material transferred on the sliding surface and pullout. The wear rate of the MZ coating was less than that of the YZ coating. With an increase normal load the wear rate of the studied coatings increased. The SEM was used to examine the sliding surfaces and elucidate likely wear mechanisms. The EDX analysis of the worn surface indicated that material transfer was occurred from the SiC ball to the disk. It was suggested that the material transfer played an important role in the wear performance.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.10a
• /
• pp.139-142
• /
• 2002

This study presents a mathematical model predicting the stress-strain behavior of fiber reinforced (FMMCs) and fiber/particle reinforced metal matrix composites (F/P MMCs). MMCs were fabricated by squeeze casting method using Al2O3 short fiber and particle as reinforcement, and A356 aluminum alloy as matrix. The fiber/particle ratios of F/P MMCs were 2:1, 1:1, 1:2 with the total reinforcement volume fraction of 20 vol.%, and the FMMCs were reinforced with 10 vol,%, 15 vol. %, 20 vol. % of fibers. Tensile tests were conducted and compared with predictions which were derived using laminate analogy theory and multi-failure model of reinforcements. Results show that the tensile strength of FMMCs with 10 vol.% of fiber was well matched with prediction, and as the fiber volume increases, predictions become larger than experimental results. The difference between the prediction and experiment is considered to be a result of matrix allowance of fiber damage in tensile loading. As the fiber volume fraction in FMMCs increases, the fiber damage increases and so that the tensile strength is reduced. The strength of F/P MMCs approaches more closely to the prediction than FMMCs reinforced with 20 vol.% of fibers because F/P MMCs contains small quantity of fibers and thus has a positive effect in fiber strengthening.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.61-66
• /
• 2003

In this paper, the effect of binder additive on the fracture toughness was metal matrix composite produced by squeeze casting method. In this study using the matrix is AC4CH and reinforcement used Aluminum borate whisker. Each MMC was produced by add inanimate binder ($SiO_2,\;Al2O_3,\;TiO_2$) to whiskers for increase the binding together of whiskers. Fracture toughness test were carry out in accordance with the ASTM E-399 standard test method, W=25mm, b=12.5mm CT(half size) specimen. However Base metal AC4CH was not meet the qualification of $P_m/P_Q<1.1$, so that test were performed $J_{IC}$ test. $K_{J_{IC}}$ value was measuring by $J_{IC}$ value change into $K_{IC}$. $J_{IC}$ test was carry out in accordance with the ASTM 1820.

• Journal of Korea Foundry Society
• /
• v.13 no.3
• /
• pp.248-258
• /
• 1993

A semi-solid alloy in which solid and liquid phase are co-existing is obtained by stirring of A17075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semisolid alloy. The fabrication possibility of fiber-reinforced aluminum alloy containing $Al_2O_3$ short fibers with vigorous agitation of short fibers were obtained by control of stirring time, solid fraction and impeller speed in extrusion billet fabrication processes. The microstructure to extrusion billet fabricated by low pressure casting was investigated for fiber dispersion state. The relationship between the extrustion force and velocity at hot extrustion, the flow strain and extrusion ratio were theoretically described. The surface defects with lubricants and without lubricant after hot extrusion were investigated. The composites materials after hot extrusion were measured by vickers hardness with extrusion ratio. It has become clear that the secondary working such as hot extrusion was very useful to obtained improved the mechanical properties of metal matrix composites.

• Journal of Korea Foundry Society
• /
• v.31 no.6
• /
• pp.336-341
• /
• 2011

Recently, aluminium usage in the automobile industry has been increased cause of its lightweight. The aluminium has a melting-solidification process in producing line and another melting process was needed in manufacturing process. Two times of melting process for making ingot and casting not only makes the loss of time and money but contaminates the air with Sox, Nox. For this reason, the holding furnace with laminated adiabatic material was developed. This holding furnace can deliver the molten aluminium directly to the industry needing molten aluminium. Recent holding furnace has above $15^{\circ}C/h$ of cooling rate and that causes solidification of molten aluminium. The ANSYS software was used to analysis the heat transfer. The adiabatic materials were laminated with optimized arrangement and holding furnace shape was changed with optimized modelling by ANSYS analysis for reducing the cooling rate of molten aluminium in holding furnace.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2002.05a
• /
• pp.113-199
• /
• 2002

In this study, the toughness was evaluated by using the instrumented Charpy impact testing procedures for A15083-O aluminum alloy used in the LNG carrying and storing tank. The specimens were GMAW welded with four different mixing shield gas ratios (Ar100%+He0%, Ar67%+He33%, Ar50%+He50%, and Ar33%+He67%), and tested at four different temperatures(+25, -30, -85, and -196$^{\circ}C$ ) in order to investigate the influence of the mixing shield gas ratio and the low temperature. The specimens were divided into base metal, weld metal, fusion line, and HAZ specimen according to the worked notch position. From experiment, the maximum load increased a little up to -85$^{\circ}C$, and the maximum load and maximum displacement were shown the highest and the lowest at -196$^{\circ}C$ than the other test temperatures. The absorption energy of weld metal notched specimens was not nearly depends on test temperature and mixing shield gas ratio because the casting structure was formed in weld metal zone. In the other hand, the others specimens was shown that the lower temperature, the higher absorption energy slightly up to -85$^{\circ}C$ but the energy was decreased so mush at -196$^{\circ}C$