• 한국주조공학회지
• /
• 제6권1호
• /
• pp.20-26
• /
• 1986

In order to investigate the solidification characteristics of CV. graphite cast iron, decantation technique and thermal analysis test were used. Solidification characteristics were studied in the specimens with various compositions and graphite shape. The results were as follows; 1. The first surface solidifcation layer is formed along the mold wall by the growth of austenite dendrites in hypoeutectic composition and thin solid film in hypereutectic composition. 2. The mushy degree of solidifcation of hypereutiectic composition is higher than that of hypoeutectic. 3. In hypoeutectic, the effect of change of the mushy degree of solidification on the graphite shape is small, however, in hypereutectic the mushy degree of solidification becomes higher in order of flake, CV, and spheroidal graphite cast iron.

• 열처리공학회지
• /
• 제31권6호
• /
• pp.300-306
• /
• 2018

In the present study we proposed new equations to predict the liquidus temperature curve for hypoeutectic Al-Si-Cu-Mg alloy. A thermodynamic simulation was carried out to calculate the liquidus temperature, eutectic temperature and eutectic Si concentration with different Si, Cu, and Mg contents in hypoeutectic Al-Si alloys. Regressed equations were derived using the thermodynamic simulation results by multiple regression analysis. The proposed equations were compared with the equations reported previously by other researchers and agreed better with the experimental data. The addition of Cu and Mg lowered the eutectic temperature. The eutectic Si concentration was decreased by adding Cu whereas that was increased by adding Mg. Al-Si binary phase diagram was successfully predicted with a consideration of the effect of Cu and Mg addition by using the proposed equations.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2000년도 춘계학술대회논문집
• /
• pp.56-62
• /
• 2000

Semi-solid forming process has some advantages such as successful manufacturing of high quality components with less inner defects suitable for less machining high productivity and energy-saving effect. the thixotropic behavior(solid-like in the unperturbed state and liquid-like during shearing) has been the basis for the semi-solid forming process. The main focus of this article is the investigation of the effect of T6 heat treatment and alloying elements on the mechanical properties in the semi-solid formed products using thixotropic hypoeutectic (A357 and ALTHIX 86S) and hypereutectic(A390) materials. The new methods to produce semi-solid formed components with high quality are also proposed and discussed in terms of a die design and the development of a lubricant.

• 한국주조공학회지
• /
• 제24권3호
• /
• pp.145-152
• /
• 2004

The eutectic Si in Al-8.5wt.%Si alloy was changed from large flake to fine lemellar(or fibrous) shape when the Sc amount in the Al-Si alloy reaches 0.2wt.%. The optimum amount of Sc for the best modification effect was 0.8wt.% and slight decrease of modification effect occurred over this value. The study on the distribution of the modifiers(Sr, Na, and Sc) and the measurement of the surface tension of the Al-8.5wt.%Si alloy melt added with Sr, Na, and Sc modifier, respectively, reveals that Sc modifies the eutectic Si by the decrease of surface tension, while Sr and Na modify the eutectic Si mainly by impurity induced twinning mechanism.

• 한국주조공학회지
• /
• 제24권2호
• /
• pp.79-84
• /
• 2004

In this study, the electromagnetic vibration is adopted for modifying eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration(EMV), the finer the size of eutectic Si phase. The tensile strength and elongation of EMVed alloy were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000 Hz was approximately six times as high as that of the normal alloy. The mechanism for the increase in twin density due to EMV during solidification could be supposed from the fact that the preferential growth along <112> in silicon was suppressed by preventing Si atom from attaching to the growing interface of Si phase and by changing the solid/liquid interfacial energy of silicon. According to the result of UTS test, because of modification of eutectic Si, UTS and elongation are highly increased.

• 한국주조공학회지
• /
• 제9권4호
• /
• pp.327-335
• /
• 1989

The matrix structure and the morphology of CV graphite are affected by the addition of many kinds of elements, which are contained in the CV graphite cast iron, additives, fading time and cooling rate. The effects of cooling rate on the matrix structure, the shape of CV graphite, mechanical properties and propagation of ultrasonic wave in hypoeutectic CV graphite cast iron were studied. When the diameters of the samples are 50mm, 35mm and 20mm 1. CV graphite number showed average 17.9% increase and CV graphite length showed 10.3% decrease with decreasing diameter of the samples. 2. The amount of graphite and ferrite showed average 11.2, 4.1 % decrease and the amount of pearlite showed average 15.7% increase. 3. Hardness and tensile strength showed average 3.5%, 11.3% increase and impact strength showed average 1.5% decrease. 4. Ultrasonic wave velocity showed average 1.1% increase.

• 한국주조공학회지
• /
• 제24권5호
• /
• pp.290-294
• /
• 2004

The effect of carbon equivalent on the fading behavior of hypoeutectic ductile cast iron was investigated. The carbon content was slightly increased right after graphite spheroidization treatment and remained almost constant with holding at $1,490^{\circ}C$ after 4 minute. The residual magnesium content was decreased slowly with holding. The empirical equation expressing the relationship between this and holding time was proposed ; $C=C_o-P{\times}t$. The proportionality constant, P, was inversely proportional to carbon content.

• 한국주조공학회지
• /
• 제37권4호
• /
• pp.108-114
• /
• 2017

In this study, we investigated the effect of the Si content on the secondary dendrite arm spacing (SDAS) of hypoeutectic Al-Si binary alloys in the range of 4~10 wt% Si. Cooling curves were measured during the solidification of the alloy cast in a step-wise mold. We compared two kinds of solidification time: the first is the total solidification time for both dendritic and eutectic growth, and the second is the solidification time for only dendritic growth. The proportional constant in the relationship between SDAS and cooling rate was estimated, as this constant represents the stability of the cast microstructure. The proportional constant decreased with the Si contents from 4 wt% to 8 wt%, and it remains relatively uniform with up to 10 wt% of Si.

• 한국주조공학회지
• /
• 제15권3호
• /
• pp.209-219
• /
• 1995

• 대한금속재료학회지
• /
• 제50권12호
• /
• pp.897-905
• /
• 2012

Directional solidification experiments were carried out in a hypoeutectic Al-11.3Si-3.5Cu system to investigate the microstructural evolution with the solidification rate. At a fixed temperature gradient, a dendritic microstructure was observed at a constant speed of more than $25{\mu}ms^{-1}$, a cellular interface developed at $5{\mu}ms^{-1}$ and the growth rate of $0.5{\mu}ms^{-1}$ led to the stability of the planar interface. The results revealed that primary silicon phases formed among cells, even though the studied Al-Si alloy system formed the composition within a hypoeutectic silicon composition. This suggests that the liquid concentration among cells during solidification reached a higher concentration, i.e., the eutectic concentration. It is, however, interesting that primary silicon phases did not form during a dendritic growth of more than $25{\mu}ms^{-1}$. These experimental observations are explained using the theoretical models on the interface temperatures.