• Korean Journal of Materials Research
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• v.32 no.10
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• pp.403-407
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• 2022

This research investigated the effect of Si addition on the microstructure, mechanical properties, electric and thermal conductivity of as-extruded Al 6013 alloys. As the content of Si increased, the area fraction of the second phase increased. As the Si content increased, the average grain size decreased remarkably, from 182 (no Si addition) to 142 (1.5Si), 78 (3.0Si) and 77 ㎛ (4.5Si) due to dynamic recrystallization by the dispersed second particles in the aluminum matrix during the hot extrusion. As the Si content increased, the yield strength and ultimate tensile strength increased. The maximum values of yield strength and ultimate tensile strength were 224 MPa and 103 MPa for the 6013-4.5Si alloy. As the amount of Si added increased, the electrical and thermal conductivity decreased. The electrical and thermal conductivity of the Al6013-4.5Si alloy were 44.0 % IACS and 165.0 W/mK, respectively. The addition of Si to Al 6013 alloy had a significant effect on its thermal conductivity and mechanical properties.

• Journal of Korea Foundry Society
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• v.20 no.2
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• pp.89-96
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• 2000

The effects of modification processing on the refinement of primary Si and the wear behavior of hyper-eutectic Al-Si alloys have been mainly investigated. Refining effects of primary Si in Al-17%Si alloy was more efficient than that of B.390 alloy. Optimum condition of getting the finest primary Si microstructure was when AlCuP modifier is added into the melt at $750^{\circ}C$ and held it at $700^{\circ}C$ for 30 minutes. Wear loss in the specimens of as-cast condition decreases as the size of primary Si decreases, in the order of B.390 alloy, B.390 alloy with AlCuP addition, Al-17%Si alloy and Al-17%Si alloy with AlCuP addition. Wear loss in the aged condition of Al-17%Si alloy, B.390 alloy and B.390 alloy with AlCuP addition decreased due to the increase of compressive residual stress in the matrix by the aging treatment. While, wear loss increased in the aged specimens of Al-17%Si alloy with AlCuP addition and Hepworth addition in which compressive residual stress decreases by the aging treatment. Therefore, it is assumed that higher compressive residual stress in the matrix can reduce the wear loss in composite materials such as hyper-eutectic Al-Si alloys.

• Journal of Korea Foundry Society
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• v.10 no.1
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• pp.43-49
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• 1990

The influences of Cu and Mg addition on wear properties of SiC particulate reinforced Al-Si metal(alloy) matrix composites were investigated. Metal matrix composites were prepared by combination of compocasting and hot pressing techniques. The main results obtained are as follows : 1) The composite with Mg addition exhibits letter wear resistance than that with Cu addition. It is considered that Mg addition improved wettability of matal matrix composite by the strong segregation to the SiC / Al matrix interface. 2) After homogenization treatment, it was found that the interfacial segregation of Mg was predominant, while that of Cu was not detected. 3) The SiC / Al-11Si eutectic composite exhibits better wear resistance than the SiC / Al-6Si hypoeutectic composite does. 4) It seems that the increase in the amount of Mg addition affects on the uniform dispersion of SiC particulates, on the refinement of microstructure and on age hardening and these effects cause wear resistance improvement of composites.

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.85-93
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• 2004

Mechanical property of hypereutectic Al-Si alloy is changed according to size and distribution of primary Si. Consequently, the study on the refinement for primary Si is progressed for a long time. But such effect of refinement comes out fading phenomena with the lapse of time. Therefore, this study investigated the optimum condition of primary Si refinement for hypereutectic Al-Si alloy. And we observed various primary Si size with P's fading phenomena. The experiment results were as follows. For experiment of primary Si refinement, we made hypereutectic Al-Si alloy with various amounts of P addition. As a result of experiment, we obtained the fine microstructure at 0.01wt.%P. And the optimum condition of P addition, for preventing from growth of primary Si by P fading, is estimated 0.1wt.%P.

• Journal of Korea Foundry Society
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• v.15 no.6
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• pp.588-595
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• 1995

SiC particles reinforced Mg-Zr, Mg-Zn and Mg-Zn-Zr composites were manufactured by Rheocompocasting method. Effects of Zn, Zr addition on microstructures and hardness were investigated by using the micro Vickers hardness tester, the optical and scanning electron microscopy. By the Zr addition to the pureMg/SiCp composites, SiC particles become more homogeneously dispersed and grain refined so that the micro hardness of the composite increased. In case of Zn addition, although grain refinement and homogeneous dispersion effects of SiC particles were not obtained, hardness was more increased than the only Zr added composite by the formation of many Mg-Zn intermetallic compounds at grain boundary. In the Mg-Zn-Zr/SiCp composite, the highest value of hardness was obtained by triple effects such as grain refining, dispersion hardening of SiC particles and Mg-Zn compounds.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.2
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• pp.82-86
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• 2011

The influences of Bi addition on morphological modification of $Mg_2Si$ phase and mechanical properties were investigated in Mg-7%Al-0.5%Si casting alloy. It was found that the addition of 0.3%Bi changed the $Mg_2Si$ morphology from coarse Chinese script type to polygonal type, and significantly decreased the size to ~5 ${\mu}m$ or less with the increase of number density. The modification of $Mg_2Si$ phase by the addition of Bi resulted in the improvement of tensile properties of the Mg-Al-Si alloy at RT and $175^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.257-263
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• 2019

Lightweight geopolymers were fabricated with non-milled IGCC slag and Si sludge as a bloating material. The relationship between addition amount of Si sludge and physical/chemical properties of lightweight geopolymers was investigated. When the geopolymers were made by mixing IGCC slag, alkali activator, and more than 10 wt.% Si sludge, the temperature of the geopolymer pastes reached higher than 130℃ in a few minutes. This exothermic reaction accelerated the geopolymer reaction; however, it was difficult to make geopolymer specimens because of a rapid bloating reaction. Both compressive strength and density of the specimens tend to decrease with an addition of Si sludge; however, there was little difference in both compressive strength and density with addition of Si sludge more than 10 wt.%. Because there was a limit to get low density geopolymers by simply increasing the addition of Si sludge, the control of pore size and distribution of geopolymer is more important by controlling flow rate of the paste through the control of W/S ratio. Therefore, it is important to control process conditions, appropriate W/S ratio for the bloating than the control of Si sludge. The optimum W/S ratio was 0.20 for the addition of Si sludge less than 30 wt.% and W/S ratio should be more than 0.28 for the addition of Si sludge more than 30 wt.%, although there was no practical application in fact.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.347-355
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• 1997

It is well known that the coarse primary Si in hypereutectic Al-Si alloys deteriorate castability, machinability, and mechanical properties. So, many treatment has been tried to refine the primary Si increasing cooling rate and adding refinement agent. Therefore. the purpose of our work was the observation of the effect on the refinement of primary Si and the analysis of the trend to apply to the casting process by changing the amount of P addition and the cooling rate while fixing the temperature at $750^{\circ}C$ of P addition and the type of AlCuP. In the condition of amount of P addition was fixed, primary Si was finer as cooling rate increased but in case of cooling rate was fixed, the effect of refinement was resisted as incersed the amount of P addition. At a relatively slow cooling rate of $22^{\circ}C/sec$, refinement was governed by the amount of P addition rather than cooling rate. At elevated cooling rate of $51^{\circ}C/sec$ and $99^{\circ}C/sec$, the undercooling due to faster cooling rate promoted nucleation of primary Si rather than P addition more significantly.

• Transactions of Materials Processing
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• v.13 no.7
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• pp.608-613
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• 2004

Mechanical properties of hypereutectic Al-Si alloy are influenced by the size and distribution of primary Si. To investigate the effects of P addition and holding time, hypereutectic Al-Si alloys with various amount of P content were produced in the lab. Then, the size and distribution of primary Si were examined respectively. Mechanical properties of hardness, tensile strength and wear resistance were analyzed in conjunction with the microstructural variations in alloys.

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.747-754
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• 1989

The effects of CuO and SiO2 on the sintered density, grain growth and magnetic properties of Sr-ferrite were investigated. The sintered density of Sr-ferrite is increased with increasing the amount of CuO or SiO2 addition. The grain of Sr-ferrite grow uniformly with the addition of CuO, so remanence increases and coercivity decreases. The addition of SiO2 increase coercivity but does not affect remanence prominently. The sintering temperature above 125$0^{\circ}C$ and SiO2 addition above 0.8wt% causes abnormal grain growth in Sr-ferrite. When CuO and SiO2 are added simultaneouly, remanence does not decrease but coercivity shows low value.