• Journal of the Korean institute of surface engineering
• /
• v.53 no.3
• /
• pp.95-103
• /
• 2020

In this study, the material used in the hot dip galvanizing equipment was poorly corrosion-resistant, so it was performed to solve the cost and time problems caused by equipment replacement. The theoretical calculation was performed using the DV-Xα method(Discrete Variational Local-density approximation method). The alloy (STS4XX series) of the equipment currently used has a martensite phase. Therefore, the theoretical calculation was performed by applying P4 / mmm, which is a tetragonal structure. The new alloy was chosen by designing theoretical values close to existing materials. Considering elements that contribute to corrosion, most have high prices. Therefore, the design was completed by adjusting the content using only the components of the reference material in the theoretical design. The final design alloys were chosen as D6 and D9. Designed D6 and D9 were dissolved and prepared using an induction furnace. After the heat treatment process was completed, the corrosion rate of the alloys was confirmed by using the potentiodynamic polarization test. The surface of the prepared alloys were processed horizontally and then polished to # 1200 using sand paper to perform potentiodynamic polarization test. Domestic products: 4.735 mpy (mils / year), D6: 0.9166 mpy, D9: 0.3372 mpy, alloys designed than domestic products had a lower corrosion rate. Therefore, the designed alloy was expected to have better erosion resistance.

• Korean Journal of Metals and Materials
• /
• v.48 no.1
• /
• pp.28-38
• /
• 2010

High temperature high cycle and low cycle fatigue deformation behavior of automotive heat resistant aluminum alloys (A356 and A319 based) were investigated in this study. The microstructures of both alloys were composed of primary Al-Si dendrite and eutectic Si phase. However, the size and distribution for eutectic Si phase varied: a coarse and inhomogeneous distributed was observed in alloy B (A319 based). A brittle intermethallic phase of ${\alpha}-Fe\;Al_{12}(Fe,Mn)_3Si_2$ was detected only in B alloy. Alloy B exhibited high fatigue life only under a high stress amplitued condition in the high cycle fatigue results, whereas alloy A showed high fatigue life when stress was lowered. With regard to the low-cycle fatigue result ($250^{\circ}C$) showing higher fatigue life as ductility increased, alloy A demonstrated higher fatigue life under all of the strain amplitude conditions. Fractographic observations showed that large porosities and pores near the outside surface could be the main factor in the formation of fatigue cracks. In alloy B. micro-cracks were formed in both the brittle intermetallic and coarse Si phasese. These micro-cracks then coalesced together and provided a path for fatigue crack propagation. From the observation of the differences in microstructure and fractography of these two automotive alloys, the authors attempt to explain the high-temperature fatigue deformation behavior of heat resistant aluminum alloys.

• Journal of Electrochemical Science and Technology
• /
• v.9 no.1
• /
• pp.51-59
• /
• 2018

Various Si-Fe-Al ternary alloys were prepared with the same amount of Si by the melt spinning technique. The feasibility of the capacity prediction approach based on the estimation of the active amount of Si using the phase diagram was practically examined and reported. These predictions were verified by the electrochemical test of fabricated coin cells and other characterization methods. The capacity prediction approach using the phase diagram might be a fundamental and efficient method to accelerate the practical application of Si-based alloys as the anode material for Li-ion batteries. The details on the prediction procedure were discussed.

• Journal of the Korean Magnetics Society
• /
• v.14 no.5
• /
• pp.196-200
• /
• 2004

In order to improve dendritic formation of Nd$_2$Fe$\_$14/B phase in the strip-cast Nd-Fe-B alloys that are frequently used for production of high energy sintered magnets, effect of small substitutional additives such as Cu (0.3～1.0 at. %) and Co (0.5～1.5 at.%) on the phase formation and microstructures of the strip-cast alloys based on Nd$\_$14/Fe$\_$80/B$\_$6/ were investigated. As the amount of Cu addition increased, formation of Nd$_2$Fe$\_$14/B dendrites along the direction normal to the strip surface was suppressed with the reduction of the strip thickness mainly due to the increase of fluidity of the melt. However, both the dendrites and their <001> preferred orientation along the direction normal to the strip surface were improved with the increase of the strip thickness as the amount of Co addition increased. The dendrites became finer after small amount of Cu or Co was added. While small copper additions tended to stabilize the formation of primary Fe, small cobalt additions suppressed it. When small amount of Zr was added, however, the dendrite structures were totally collapsed with excessive grain growth of Nd$_2$Fe$\_$14/B.

• Transactions of the Korean hydrogen and new energy society
• /
• v.5 no.2
• /
• pp.99-109
• /
• 1994

To develop high capacity hydrogen storage alloys for secondary Ni/MH batteries, electrochemical charge/discharge characteristics of $Zr_{1-x}Ti_xMn_{1-y}V_yNi_{1-z}M_z$ (M=Al,Co,Fe) alloys were investigated, in which $0.2{\leq}x{\leq}0.6$, $0.2{\leq}y{\leq}0.8$, $0.2{\leq}z{\leq}0.4$. With increasing Ti content(x) and/or decreasing V content(y), lattice constants and maximum theoretical capacities of the alloys were decreased and equilibrium pressure of hydrogen absorption were increased. Electrochemical discharge capacities were increased with increasing Ti content(x). Especially, the alloys of x= 0.4~0.6 showed better charge/discharge efficiencies than those of x<0.4. Discharge capacities of $Zr_{0.4}Ti_{0.6}Mn_{0.4}V_{0.6}Ni_{0.8}Fe_{0.2}$, $Zr_{0.4}Ti_{0.6}Mn_{0.4}V_{0.6}Ni_{0.8}Al_{0.2}$ and $Zr_{0.5}Ti_{0.5}Mn_{0.4}V_{0.6}Ni_{0.6}Co_{0.4}$ were 385, 328 and 333mAh/g, respectively. These alloys were fully activated within five charge/discharge cycles and had a good charge and discharge rate capabilities and temperature characteristics.

• Applied Microscopy
• /
• v.47 no.1
• /
• pp.50-54
• /
• 2017

The microstructure, the crystallization behavior, and magnetic properties of FeSi-based soft magnetic alloys (FINEMET) were investigated using transmission electron microscopy, X-ray diffraction, and coercive force measurements. The amorphous $Fe_{73.28}Si_{13.43}B_{8.72}Cu_{0.94}Nb_{3.63}$ alloys particles, prepared in $10^{-4}$ torr by gas atomization process, were heat treated at $530^{\circ}C$, $600^{\circ}C$, and $670^{\circ}C$ for 1 hour in a vacuum of $10^{-2}$ torr. Nanocrystalline Fe precipitation was first formed followed by the grain growth. Phase formation and crystallite sizes was compared linked to its magnetic behavior, which showed that excellent soft magnetic property can directly be correlated with its microstructure.

• Journal of Korea Foundry Society
• /
• v.31 no.6
• /
• pp.354-361
• /
• 2011

The liquid metal shearing device was constructed and assembled with a commercial high-pressure die-caster in order to induce intensive turbulent shearing force on molten aluminum alloys. The effect of the liquid metal shearing on the microstructure and tensile properties of A356 alloys was investigated with the variation of iron content. The experimental results show that dendritic primary ${\alpha}$-Al phase was effectively modified into a equiaxed form by the liquid metal shearing. It was also found that the needle-like ${\beta}$-AlFeSi phase in a Fe containing A356 alloy was changed into a blocky shape resulting in the improved mechanical properties. Based on the mechanical properties, it was suggested that the iron content in A356 alloy could be more widely tolerated by utilizing the liquid metal shearing HPDC process.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.1
• /
• pp.82-88
• /
• 2019

Here, we report on nanocrystalline Si-Al-M (M = Fe, Cu, Ni, Zr) alloys for use as an anode for lithium-ion batteries, which were fabricated via a melt-spinning method. Based on the XRD and TEM analyses, it was found that the Si-Al-M alloys consist of nanocrystalline Si grains surrounded by an amorphous matrix phase. Among the Si-Al-M alloys with different metal composition, Ni-incorporated Si-Al-M alloy electrode retained the high discharge capacity of 2492 mAh/g and exhibited improved cyclability. The superior $Li^+$ storage performance of Si-Al-M alloy with Ni component is mainly responsible for the incorporated Ni, which induces the formation of ductile and conductive inactive matrix with crystalline Al phase, in addition to the grain size reduction of active Si phase.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1030-1031
• /
• 2006

Titanium alloys and Titanium alloy-based particulate composites were synthesized using the blended elemental P/M route. First, processing conditions such as the fabrication of master alloy powder were investigated. Ti-6Al-4V, Ti-5Al-2.5Fe, Ti-6Al-2Sn-4Zr-2Mo, IMI685, IMI829, Timetal 1100 and Timetal 62S, and Ti-6Al-2Sn-4Zr-2Mo/ 10%TiB and Timetal 62S/10%TiB were then synthesized using the optimal processing conditions obtained. The microstructures and mechanical properties such as tensile strength and high cycle fatigue strength were evaluated.

• Korean Journal of Metals and Materials
• /
• v.50 no.7
• /
• pp.531-538
• /
• 2012

In this study, we evaluated the fluidity of the Al-Zn based alloys which exhibit excellent mechanical properties. We conducted computer simulations of fluid flow using the results of DSC, DTA analysis and Java-based Materials Properties software (J. Mat. Pro). Such computer simulations were then compared with the results obtained from experimental observations. The computer simulation results and the experimental results were very similar in fluidity length. It was found that the fluidity length of Al-Zn alloys is improved by increasing the Zn content while decreasing the solidus temperature of an alloy. In addition, we elucidate the effect of Zn addition on variations in different mechanical properties and the microstructure characteristics of (Al-xZn3Cu0.4Si0.3Fe) x=20, 30, 40, and 45 wt% alloys fabricated by gravity casting.