• 소성∙가공
• /
• 제24권1호
• /
• pp.44-51
• /
• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• 한국수소및신에너지학회논문집
• /
• 제13권3호
• /
• pp.181-189
• /
• 2002

A series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22, and 0.30) alloys are prepared and their oystal structure and P-C-T curves are examined. The electrochemical properties of these allqys such as activation conditions, discharge capacity, cycling performance are also investigated. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hot-charging treatment. The best activation conditions were the current density 120 mA/g and the hot-charging time 12h at $80^{\circ}C$ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacily just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 mAh/g at the current density 120 mA/g. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Fe_{0.15}$ is a good composition with a medium quantity of discharge capacities and a good cycling performance. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. Another series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}M_{0.15}$ (M = Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M = Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M = Al and Cu. They are 212 and 170 mAh/g, respectivety, at the current density 120mA/g. The $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Co_{0.15}$ alloy is the best one with a relatively large discharge capacity and a good cycling performance.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.933-934
• /
• 2006

The present study examines the sintering behaviour and effect of manganese addition both mechanically-blended and mechanically alloyed on Cr-Mo low alloyed steels to enhance the mechanical properties. Mn sublimation during sintering provides some specific phenomena which facilitate the sintering of alloying elements with high oxygen affinity. First step is the optimization of milling time to attain a master alloy with 50% of Mn which is diluted in Fe-1.5Cr-0.2Mo water atomized prealloyed powder by normal mixing. These mixtures are pressed to a green density of $7.1g/cm^3$ and sintered at $1120^{\circ}C$ in $90N_2-10H_2$ atmosphere.

• 한국재료학회지
• /
• 제9권9호
• /
• pp.937-942
• /
• 1999

Fe계 합금의 적층결함에너지를 감소시키는 것으로 알려진 Mn이 Fe-20Cr-1C-Si 경면처리 합금의 변형유기 상변태거동과 상온 및 고온 마모저항성에 미치는 영향에 대하여 조사하였다. 15ksi의 접촉응력에 대하여 0~25wt.% Mn을 첨가한 시편은 모두 상온에서 마모손실량이 적은 우수한 마모저항성을 보였는데 Mn 첨가량이 5wt.% 이하인 시편의 경우 마모표면에서 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태가 발생한 반면 15wt.% 이상 Mn을 첨가한 시편에서는 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태가 발생하는 것으로 나타났다. 25$0^{\circ}C$까지 고온 마모시험결과 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태가 발생한 5wt.% 이하 Mn 첨가시편은 Mn 첨가량이 증가할수록 마모손실량이 증가하는 것으로 보아 Mn 첨가는 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태에 있어서 고온 마모저항성을 저하시키는 것으로 생각되며 이는 Mn이 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태의 M(sub)d 온도를 감소시키기 때문으로 생각된다. 반면에 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태가 일어난 15wt.% 이상 Mn 첨가 시편의 경우 Mn 첨가량 증가에 따른 고온 마모손실량의 차이가 없는 것으로 보아 ${\gamma}$$\longrightarrow$$\varepsilon$변형유기 상변태는 ${\gamma}$$\longrightarrow$$\alpha$\`변형유기 상변태에 비해 온도의 존성이 적은 것으로 생각된다.

• Journal of Welding and Joining
• /
• 제19권5호
• /
• pp.506-511
• /
• 2001

Weld overlay has been developed to improve the property of material surface which is used in the severe environment. Weld overlay is the process which uses an arc heat and welds different composition of alloy on the substrate for the improvements of heat resistance and wear resistance. Weld overlay has a lot of advantages which are high hardness, good processing efficiency, easy controlling of layer thickness, good quality and low cost. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders(Cr+C+Mn+Mo+NbC) and solid wire(JIS-YGW11). Characterization of hardness and wear resistance were analyzed by EDS, EPMA, XRD and observations of microstructure were performed to investigate characteristics of overlays. The experimental results of overlaid specimens manufactured with Cr+C+Mn+Mo+NbC powders were obtained as fellows. ${\alpha}-phase$, M(Fe, Cr)3C and NbC of overlays were increased with decreasing the wire feed rates and increasing powder feed rates. Also the hardness of overlays were increased and the specific wear were decreased.

• 한국재료학회지
• /
• 제26권12호
• /
• pp.671-675
• /
• 2016

In this study, the glass-forming ability and mechanical properties of newly developed Fe-Mn-Cr-Mo-B-C-P-Si-Al bulk amorphous alloys were investigated, and metalloid elements such as B, C, and P were found to have a strong influence on the properties of the Fe-based amorphous alloys. When the total metalloid content (B, C, and P) is less than 5 %, only the crystal phase is formed, but the addition of more than 10 % metalloid elements enhances the glass forming ability. In particular, the alloys with 10 % metalloid content exhibit the best combination of very high compressive strength (~2.8 GPa) and superior fracture elongation (~30 %) because they consist of crystal/amorphous composite phases.

• 한국재료학회지
• /
• 제9권3호
• /
• pp.327-332
• /
• 1999

중성자에 조사 $(fluence: 2.3\times10^{19}ncm^{-2}, 553 K, E\geq1.0 MeV)$된 Mn-Mo-Ni 저 합금강 모재의 열처리 회복 거동을 조사하기 위하여 등시소둔과 등온소둔을 수행하여 회복 활성화에너지, 회복 반응차수 그리고 회복 반응률상수를 결정하였다. 열처리 후 회복은 비커스 미세 고온경도기로 측정하였고 실험결과를 이용, 열처리 회복단계, 회복결함들의 거동 및 회복 kinetics을 분석하였다. 실험결과 2단계의 회복구간(stage I : 703-753K, stage II : 813K-873K)이 나타났으며 각 단계의 회복활성화 에너지는 2.50 eV(1단계) 및 2.93 eV(2단계)이었다. 조사재와 비조사재의 등시소둔 곡선의 비교를 통하여 813K에서 RAH(radiation anneal hardening) 피크를 확인할 수 있었다. 743K 및 833K에서 수행한 등온소둔 결과, 회복의 60%가 모두 120분 이내에 일어나는 것으로 관찰되었다. 회복 반응차수는 두 회복구간에서 모두 2로 나타났으며 회복 반응율상수는 $3.4\times10^{-4}min^{-1}$(1단계)과 $7.1\times10^{-4}min^{-1}$(2단계) 이었다. 이상의 결과와 기 발표된 자료들을 함께 분석한 결과, 본 재료의 회복은 오랜 중성자조사로 형성된 점결함 집합체들이 열처리에 의한 분해와 Fe 기지에 격자간 원자로 존재하던 self-interstitial들과 vacancy들의 재결합에 의해 일어나는 것으로 해석된다.

• 열처리공학회지
• /
• 제3권4호
• /
• pp.23-40
• /
• 1990

This study has been carried out to investigate into some effects of Mn content with varying amounts and austenite grain size on hardenability in boron-added Fe-C-Cr-Mo alloy systems. (1) Austenite grains have been found to hardly grow in the temperature range of $900^{\circ}C$ to $950^{\circ}C$, whereas they grow rapidly in the temperature range of $975^{\circ}C$ to $1100^{\circ}C$. (2) Austenite grain growth is considerably small with increasing holding time at a given austenitizing temperature and is, in particular, hardly found to occur at a temperature of $900^{\circ}C$. (3) The hardenability improves ramarkably as Mn content is increased at three different austenitizing temperatures $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. (4) The maximum hardenability is obtained from steels A, B and C austenitized at the $900^{\circ}C$, although Mn content is varied in each specimen.

• Nuclear Engineering and Technology
• /
• 제32권4호
• /
• pp.372-378
• /
• 2000

The effect of alloying elements on the creep resistance of Zr alloys was investigated using thermal creep tests that were performed as a part of advanced fuel cladding development. The creep tests were conducted at 40$0^{\circ}C$ and 150 MPa for 240 hr. A statistical model was derived from the relationship between the steady-state creep rate and the content of individual alloying elements. The creep strengthening effect decreased in the following sequence : Nb, Sn, Mn, Cr, Mo, Fe and Cu. The high creep resistance of Sn and the opposite effect of Fe on zirconium alloys seem to be associated with their lowering and enhancing, respectively, the self-diffusivity of the zirconium matrix.

• 대한기계학회논문집A
• /
• 제28권5호
• /
• pp.554-562
• /
• 2004

An empirical relationship between parameters from SP curves and tensile properties has been systematically investigated by experimental tests and FEM simulations. A series of SP and tensile tests were performed. SP tests were also simulated by FE analysis with various tensile properties. It was found that the yield loads(Py) and the maximum loads( $P_{MAX}$) in SP curves were linearly related with the yield strength($\sigma$$_{o}$) and the tensile strength($\sigma$$_{UTS}$), respectively. The yield loads defined from the intersection point of two lines tangent to the elastic bending region and plastic bending region showed better relation to the yield strength than those from offset line. The maximum loads in SP curves showing plastic instability region was linearly related with the tensile strengths. The slope of SP curves in simulation results had a close correlation with the hardening coefficient and hardening strength as well.l.l.l.