• Korean Journal of Metals and Materials
• /
• v.46 no.5
• /
• pp.304-309
• /
• 2008

Magnesium alloys containing $Mg_2Si$ particles, as a promising cheap heat-resistant magnesium alloy for automobile power train parts applications, are attracting more attention of both material scientists and design engineers. Modification of the Chinese script shape $Mg_2Si$ particle is a key for using this alloy in sand or permanent mould casting. In the present work, the modification effect of Sr and Sb on the corrosion properties of the Mg-5Al-2Si alloy was investigated. Sr or Sb addition promoted the formation of fine polygonal shape $Mg_2Si$ particles by providing the nucleation sites. Sr was more effective element than Sb for shape modification of Chinese script shape $Mg_2Si$. Such improved microstructure of the modified alloy resulted in large improvement in corrosion resistance as compared to unmodified Mg-5Al-2Si alloy.

• Advances in nano research
• /
• v.7 no.3
• /
• pp.169-180
• /
• 2019

Plasmonic effects of gold and platinum alloy nanoparticles (Au-Pt NPs) and their comparison to size was studied. Various factors including ratios of gold and platinum salt, temperature, pH and time of addition of reducing agent were studied for their effect on particle size. The size of gold and platinum alloy nanoparticles increases with increasing concentration of Pt NPs. Temperature dependent synthesis of gold and platinum alloy nanoparticles shows decrease in size at higher temperature while at lower temperature agglomeration occurs. For pH dependent synthesis of Au-Pt nanoparticles, size was found to be increased by increase in pH from 4 to 10. Increasing the time of addition of reducing agent for synthesis of pure and gold-platinum alloy nanoparticles shows gradual increase in size as well as increase in heterogeneity of nanoparticles. The size and elemental analysis of Au-Pt nanoparticles were characterized by UV-Vis spectroscopy, XRD, SEM and EDX techniques.

• Journal of Welding and Joining
• /
• v.1 no.2
• /
• pp.76-82
• /
• 1983

The chemical composition of deposit metal by flux cored arc welding can be easily regulated though addition of deoxidizers and alloying elements in cored flux and fluxes of flux coored wire arc analogous to those of coated electrode. It is necessary to investigate the transfer and yield efficiency due to addition of necessary alloy elements in deposit metal. This report is made to intorduce an experimental equation from the relation between welding condition and extent of penetration, deposit metal and weld melt slag and to estimate transfer and yield efficiency of alloy components in fluxes through chemical analysis of deposit metal.

• 한국전기화학회:학술대회논문집
• /
• 2003.07a
• /
• pp.83-88
• /
• 2003

PtRu alloy and $PtRu-WO_3$ nanocomposite thin-film electrodes for methanol electrooxidation were fabricated by means of a sputtering method. The structural and electrochemical properties of well-defined PtRu alloy thin-film electrodes were characterized using X-ray diffraction, Rutherford backscattering spectroscopy. X-ray photoelectron spectroscopy, and electrochemical measurements. The alloy thin-film electrodes were classified as follows: Pt-based and Ru-based alloy structure. Based on structural and electrochemical understanding of the PtRu alloy thin-film electrodes, the well-controlled physical and (electro)chemical properties of $PtRu-WO_3$, showed superior specific current to that of a nanosized PtRu alloy catalyst, The homogeneous dispersion of alloy catalyst and well-formed nanophase structure would lead to an excellent catalytic electrode reaction for high-performance fuel cells. In addition, the enhanced catalytic activity in nanocomposite electrode was found to be closely related to proton transfer in tungsten oxide using in-situ electrochemical transmittance measurement.

• Journal of Welding and Joining
• /
• v.12 no.4
• /
• pp.85-101
• /
• 1994

Effect of Cr, Cu and Ni metal powders addition on the alloyed layer of aluminum alloy (AC2B) has been investigated with the plasma transferred arc (PTA) overlaying process. The overlaying conditions were 125-200A in plasma arc current, 150mm/min in process speed and 5-20g/min in powder feeding rate. Main results obtained are summarized as follows: 1) It was made clear that formation of thick surface alloyed layer on aluminum alloy is possible by PTA overlaying process. 2) The range of optimum alloying conditions were much wider in case of Cu and Ni powder additions than the case of Cr powder addition judging from the surface appearance and the bead macrostructure. 3) Alloyed layer with Cu showed almost the homogeneous microstructure through the whole layer by eutectic reaction. alloyed layers with Cr and Ni showed needle-like and agglomerated microstructures, the structure of which has compound layer in upper zone of bead by peritectic and eutectic-peritectic reactions, respectively. 4) Microconstituents of the alloyed layer were analyzed as A1+CrA $l_{7}$ eutectics, C $r_{2}$al sub 11/, CrA $l_{4}$, C $r_{4}$A $l_{9}$ and C $r_{5}$A $l_{*}$ 8/ for Cr addition, Al+CuA $l_{2}$(.theta.) eutectics and .theta. for Cu addition, and Al+NiA $l_{3}$ eutectics. NiA $l_{3}$, N $i_{2}$A $l_{3}$ and NiAl for Ni addition. 5) Concerning defect of the alloyed layer, many blow holes were seen in Cr and Ni additions although there was lesser in Cu addition. Residual gas contents in blow hole for Cu and Ni alloyed layer were confirmed as mainly $H_{2}$ and a littie of $N_{2}$ Cracking was observed in compound zone of the alloyed layer in case of Cr and Ni addition but not in Cu alloyed layer.r.r.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1999.10a
• /
• pp.185-189
• /
• 1999

There has been a considerable attention in Invar alloys because of its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than 10-6 near the room temperature, is attractive for precision machine tools. However, the expansion property of Invar alloys is limited below about 520。K, and mechanical properties are relatively low to apply to machine tools. In order to improve mechanical properties in this alloy, Ti alloy element was added to an invar alloy. Microstructure changes and optimum heat-treatment conditions according to Ti addition were discussed in the Ni38-Mo2-Crl-Fe Invar alloy.

• Journal of Korea Foundry Society
• /
• v.10 no.5
• /
• pp.392-398
• /
• 1990

To improve free-cutting property, fine Pb, Bi particles is necessary to be distributed evenly in Al-Cu alloy. The control of added element size and distribution are very difficult because of the physical properties of Pb, Bi. The effect of master alloy compositions on microstructure and particle distribution was investigated. The ribbon shape of Pb-50wt% Bi master alloy showed the best results. And Ti addition improved even distribution of Pb, Bi particles. Particles grown from $L_2$ phase were considered to be the Pb, Bi compound.

• Journal of Korea Foundry Society
• /
• v.23 no.2
• /
• pp.69-76
• /
• 2003

The present work was undertaken to investigate the mutual effect of the individual melt treatment commonly applied in aluminum foundries such as grain refining, modification, degassing and filtration on the microstructures and the mechanical properties. A357 alloys were fabricated through various melt treatments such as degassing by gas bubbling filtration, modification via the addition of Al-Sr master alloy, grain refining through the addition of Al-Ti-B master alloy and filtration before pouring of the melt. Each melt treatment was performed at its optimum condition reported in the literatures. The effects of each melt treatment and their interactions on the microstructures and mechanical properties of A357 alloy were examined.

• Journal of the Korean Society for Heat Treatment
• /
• v.9 no.3
• /
• pp.187-197
• /
• 1996

In this study, the properties of coil spring made by Cu-Zn-Al and B added shape memory alloys are investigated. The measurement of recovery displacement and energy with increasing weight, and thermocycling properties have been studied using displacement measuring device. Transformation temperature and phase change by thermocycling have been also investigated by DSC and X-ray diffractometer. Grain size of the alloy is refined from 1.2mm to $400{\mu}m$ by 0.06wt% of B addition. The maximum recovery energy of the coil spring for B added alloy is larger than that of no B added alloy, it is because of grain refinement. And shape memory ability of the coil spring by thermocycling decrease with increasing thermocycling after thermocycle under load. The degradation of shape memory properties of coil spring by thermocycling is improved by B addition.

• Journal of Korea Foundry Society
• /
• v.26 no.4
• /
• pp.191-196
• /
• 2006

The effects of Bi and Te on the anti-galling behaviors of Ni base alloy were investigated by SEM, galling test and wear test. Anti-galling characteristics depended on the structure of matrix and distribution of Bi-rich phase which was precipitated at grain boundary. The addition of 5 wt% Bi markably enhanced anti-galling properties. The addition of Te caused Bi-rich precipitates to disperse finely and casting structure to form equiaxed type. From the above tests, the concentration of 5 wt% Bi and 1 wt% Te was selected to optimize in this alloy.