• Journal of Korea Foundry Society
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• v.32 no.6
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• pp.296-304
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• 2012

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.480-487
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• 1997

Particle reinforced metal matrix composites(MMCs) via a centrifugal spray-cast deposition(CSD) process were fabricated by injecting second phase particles($Al_2O_3$<40${\mu}m$, W<17.3${\mu}m$) into copper melt on the atomizing disc. Compositing modes were investigated by combining microstructures and mathematical modeling between Cu droplets and the reinforced particles injected. The $Cu/W_P$ powders were shown that the W particles penetrate and get embedded in the Cu droplets. It is considered that the W particles composite preferentially in Cu melt on the atomizing disc. On the other hand, the $Al_2O_3$, particles did not penetrate into the Cu droplets on the atomizing disc but get attached in surface of Cu droplets during the flight. It is considered that the compositing may be attained in the flight distance which the relative velocity between Cu droplet and $Al_2O_3$, particle is maximum. The microstructure of the $Cu/W_P$ and the $Cu/(Al_2O_3)_p$ composite preform was strongly influenced by compositing modes of droplets, and after subsequent deposition it was comprised as it is called the dispersed type and the cell type of microstructure, respectively.

• Journal of Korea Foundry Society
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• v.27 no.6
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• pp.237-242
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• 2007

To improve the quality of the product and the cost efficiency, the joining of A356 alloy to an Al-18wt%Si alloys has been performed by centrifugal casting. The influence of the mold preheating temperature, the pouring temperature and the rotational velocity of the mold on the microstructures of the shell in the centrifugal casting was investigated using the experimental and simulation methods. In the present study, the cellular automaton (CA) technique and the finite volume method (FVM) were adopted to simulate the evolution of the macro structures and to calculate the temperature profiles, respectively. The evolution of the microstructures was also simulated using a modified cellular automaton (MCA) model. The optimal rotational speed of the mold for obtaining the sound shape of the shell was estimated experimentally to be over 1200 rpm. For the uniform microstructure, the outer shell needs to be cast with higher preheated mold temperature and lower pouring temperature, and the melt was poured at lower temperature in the inner shell. In order to obtain the sound shape of the joining, the different materials were poured simultaneously.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.203-210
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• 2002

This test is to conduct applied research the reaction area of the Ti-cast metal body which is made use of Dental Phosphate-silica alumina bonded investment material selling at a market, and the cooling method is how to effect on the acicular. The experimentation is as followings, 1. Experimental specimens After invest with Dental Phosphate-silica alumina bonded investment material, the $10{\times}10{\times}1.0mm^3$ wax pattern was casted by Dental high vacuum argon centrifugal casting machine. 2. Test We can analyze SEM/EDS, XRD utilize the fractography(an optical microscope). 3. Conclusion The pure cast metal body constituted of reaction products layer, stability layer and contamination layer. This pure cast have no connection with the cooling condition. The pure Titanium shows difference in a component distribution according to the cooling condition. Through this experimentation we can establish that acicular in the pure Ti-cast metal is consist of Hexagonal structure a=2.9505$\AA$, c=4.6826$\AA$.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.2
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• pp.72-78
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• 2014

Isothermal transformation behavior of a 10% Cr heat resistant steel fabricated by centrifugal casting process was investigated. Normalized specimen at $1100^{\circ}C$ for 1 hour was isothermally annealed at temperature range between $600^{\circ}C$ and $700^{\circ}C$ with various time. The annealed specimen had eutectoid structure which was generated along austenitic grain boundary during isothermal annealing. Areal fraction of eutectoid structure increased up to 25% after holding at $700^{\circ}C$ for 20 hours. It was observed that austenitic matrix was transformed to ferrite structure and fine $M_{23}C_6$ carbides with increase of annealing time. Time-temperature-transformation diagram of the centrifugally cast 10% Cr steel with 0.18 wt% C was plotted based on the results of isothermal transformation behavior.

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.108-114
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• 2004

$Al_2O_3$, SiC reinforced Al matrix composites were fabricated by centrifugal spray casting method and their wear resistance characteristics have been studied. Particles are generally uniformly distributed in the microstructure of as-cast specimens. In order to investigate the effect of secondary deformation, hot rolling was performed for each specimen of pure Al matrix composites with a reduction of 10, 20, 30, 40 and 50% at $400{\sim}500^{\circ}C$, respectively. Microstructure of specimen showed that particle distribution density and hardness increased because of increasing of reduction ratio. Wear test with a various sliding velocity of 1.98, 2.38, 2.88 and 3.53m/sec showed that the wear resistance characterization of composite improved remarkably compared to the normal alloy and performs without reinforced particles. Microstructural observation for the worn surface of pure Al specimens without particles showed that a change in wear mechanism seemed to separate layer by surface fatigue. In other case of Al composite reinforced with $Al_2O_3$ and SiC, the grinder type of wear mechanism was shown.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.5
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• pp.195-200
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• 2019

For expanding the applications and workability of TiAl alloy, elongation is very important property. Fine microstructure is needed for elongation and physical properties of TiAl alloys. In this study, The effects of cyclic heat treatment process for fine microstructure of Ti-46Al-Nb-W-Cr-Si-C alloy, which was made by VAR (vacuum arc remelting) and VIM(vacuum induction melting) centrifugal casting process, was investigated. Cycle heat treatment process was very effective for recrystallization of this TiAl system, which has microstructure size of $50{\sim}100{\mu}m$ through pre-heat treatment, cyclic heat treatment in ${\alpha}+{\gamma}$ phase region and solution heat treatment respectively. Refined grain size was finally confirmed by photos of optical microscope and scanning electron microscope.

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.450-457
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• 1997

Effects of Ti addition and homogenizing heat treatment on the mechanical properties in Cu-Zn-Al alloy (high strength yellow brass) were investigated. Grain refinement was successfully achieved by Ti addition. The microstructure, which was composed of island or fine feather-like branched Ti compounds was changed to feather-like eutectic microstructure as the content of Ti increased. The highest hardness value was obtained for 0.5 wt.% Ti specimen and the second was Ti non-added specimen in as-cast condition. The highest tensile strength was obtained for 0.5 wt.% Ti specimen. Because of the presence of cast defects and worse castability, tensile strength decreased as the content of Ti increased. Elongation increased with increasing homogenizing time and temperature; remarkable increase was obtained for $400^{\circ}C$ homogenizing temperature in the 0.5 wt.% Ti specimen. For $500^{\circ}C$ and $600^{\circ}C$ homhgenizing, temperature, high elongation was obtained in 2 and 4 wt.% Ti specimen.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.229-234
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• 2017

In this study, TiAl alloy was fabricated by a centrifugal casting method for turbo charge of automotive. Optimum conditions for defectless morphology using various ceramic mold were investigated. The crystal structure, microstructure, and chemical composition of the TiAl prepared by centrifugal casting were studied by X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS), microvickers hardness analyzer (HV). Two kinds of dendrite structures were observed with 4-fold and 6-fold symmetries. The FE-SEM, EDS and HV examinations of the as-cast TiAl showed that the thickness of the oxide layer (${\alpha}$-case) was typically less than $50{\mu}m$.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.97-104
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• 2011

Modified C95600 bronze contains Fe component of 0.7 weight percentage besides Cu-7Al-2.5Si composition. The shape of centrifugal cast is a circular pipe with thick wall. Specimens machined from the centrifugal cast were quenched in oil after isothermal holding at a given heat treatment temperature in the range of $700{\sim}900^{\circ}C$. Mechanical properties and structural morphology are depended on the quenching heat treatment temperature regardless of isothermal holding time. Tensile strength or Brinell hardness is increased with increasing heat treatment temperature. The microstructure caused by quenching contains mixing phases of ${\alpha}+{\beta}'+FeSi+{\kappa}$ which martensite of ${\beta}'$ phase has been transformed from ${\beta}$ phase. Effect of isothermal holding temperature on mechanical properties in case of quenching heat treatment attributes to the change of volume fraction of ${\beta}'$ on the structural morphology. Mechanical characteristics of specimen, initially quenched from $850^{\circ}C$, and then tempered at $500^{\circ}C$, does not show an obvious softening indication, because disappearance of ${\beta}'$ during tempering process can be compensated by precipitation of brittle phase ${\gamma}$.