• Title/Summary/Keyword: alloying effect

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The Effects of Si or Sn on the Sintered Properties of Fe-(Mo,Mn)-P Lean alloy (Fe-(Mo,Mn)-P계 Lean alloy의 소결특성에 미치는 Si와 Sn의 영향)

  • Jung, Woo-Young;Ok, Jin-Uk;Park, Dong-Kyu;Ahn, In-Shup
    • Journal of Powder Materials
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    • v.25 no.4
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    • pp.302-308
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    • 2018
  • A lean alloy is defined as a low alloy steel that minimizes the content of the alloying elements, while maintaining the characteristics of the sintered alloy. The purpose of this study is to determine the change in microstructure and mechanical properties due to the addition of silicon or tin in Fe-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P alloys. Silicon- or tin-added F-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P master alloys were compacted at 700 MPa and subsequently sintered under a $H_2-N_2$ atmosphere at $1120^{\circ}C$. The sintered density of three alloy systems decreases under the same compacting pressure due to dimensional expansion with increasing Si content. As the diffusion rate in the Fe-P-Mo system is higher than that in the Fe-P-Mn system, the decrease in the sintered density is the largest in the Fe-P-Mn system. The sintered density of Sn added alloys does not change with the increasing Sn content due to the effect of non-dimensional changes. However, the effect of Si addition on the transverse rupture strengthening enhancement is stronger than that of Sn addition in these lean alloys.

Effect of Ti Concentration on the Microstructure of Al and the Tunnel Magnetoresistance Behaviors of the Magnetic Tunnel Junction with a Ti-alloyed Al-oxide Barrier (Ti 첨가에 따른 Al 미세구조 변화 효과와 산화 TiAl 절연층을 갖는 자기터널접합의 자기저항 특성)

  • Song, Jin-Oh;Lee, Seong-Rae
    • Journal of the Korean Magnetics Society
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    • v.15 no.6
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    • pp.311-314
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    • 2005
  • We investigated the composition dependence of the tunneling magnetoresistance (TMR) behavior and the stability of the magnetic tunnel junctions (MTJs) with TiAlOx barrier and the microstructural evolution of TiAl alloy films. The TMR ratio increased up to $49\%$ at $5.33\;at\%$ Ti. In addition, a significant tunneling magnetoresistance (TMR) value of $20\%$ was maintained after annealing at $450^{\circ}C$, and the breakdown voltage ($V_B$) of and 1.35 V were obtained in the MTJ with $5.33\;at\%$ Ti-alloyed AlOx barrier. These results were closely related to the enhanced quality of the barrier material microstructure in the pre-oxidation state. Ti alloying enhanced the barrier/electrode interface uniformity and reduced microstructural defects. These structural improvements enhanced not only the TMR effect but also the thermal and electrical stability of the MTJs.

Effect of Cobalt Contents on the Microstructure and Charpy Impact Properties of Ferritic/martensitic Oxide Dispersion Strengthened Steel (페라이트/마르텐사이트계 산화물분산강화강의 미세조직 및 샤르피 충격특성에 미치는 코발트 함량의 영향)

  • Kwon, Daehyun;Noh, Sanghoon;Lee, Jung Gu
    • Journal of Powder Materials
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    • v.27 no.4
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    • pp.311-317
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    • 2020
  • In this study, the effects of Co content on the microstructure and Charpy impact properties of Fe-Cr-W ferritic/martensitic oxide dispersion strengthened (F/M ODS) steels are investigated. F/M ODS steels with 0-5 wt% Co are fabricated by mechanical alloying, followed by hot isostatic pressing, hot-rolling, and normalizing/tempering heat treatment. All the steels commonly exhibit two-phase microstructures consisting of ferrite and tempered martensite. The volume fraction of ferrite increases with the increase in the Co content, since the Co element considerably lowers the hardenability of the F/M ODS steel. Despite the lowest volume fraction of tempered martensite, the F/M ODS steel with 5 wt% Co shows the highest micro-Vickers hardness, owing to the solid solution-hardening effect of the alloyed Co. The high hardness of the steel improves the resistance to fracture initiation, thereby resulting in the enhanced fracture initiation energy in a Charpy impact test at - 40℃. Furthermore, the addition of Co suppresses the formation of coarse oxide inclusions in the F/M ODS steel, while simultaneously providing a high resistance to fracture propagation. Owing to these combined effects of Co, the Charpy impact energy of the F/M ODS steel increases gradually with the increase in the Co content.

Prediction Model for the Microstructure and Properties in Weld Heat Affected Zone: V. Prediction Model for the Phase Transformation Considering the Influence of Prior Austenite Grain Size and Cooling Rate in Weld HAZ of Low Alloyed Steel (용접 열영향부 미세조직 및 재질 예측 모델링: V. 저합금강의 초기 오스테나이트 결정립크기 및 냉각 속도의 영향을 고려한 용접 열영향부 상변태 모델)

  • Kim, Sang-Hoon;Moon, Joon-Oh;Lee, Yoon-Ki;Jeong, Hong-Chul;Lee, Chang-Hee
    • Journal of Welding and Joining
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    • v.28 no.3
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    • pp.104-113
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    • 2010
  • In this study, to predict the microstructure in weld HAZ of low alloyed steel, prediction model for the phase transformation considering the influence of prior austenite grain size and cooling rate was developed. For this study, six low alloyed steels were designed and the effect of alloying elements was also investigated. In order to develop the prediction model for ferrite transformation, isothermal ferrite transformation behaviors were analyzed by dilatometer system and 'Avrami equation' which was modified to consider the effect of prior austenite grain size. After that, model for ferrite phase transformation during continuous cooling was proposed based on the isothermal ferrite transformation model through applying the 'Additivity rule'. Also, start temperatures of ferrite transformation were predicted by $A_{r3}$ considering the cooling rate. CCT diagram was calculated through this model, these results were in good agreement with the experimental results. After ferrite transformation, bainite transformation was predicted using Esaka model which corresponded most closely to the experimental results among various models. The start temperatures of bainite transformation were determined using K. J. Lee model. Phase fraction of martensite was obtained according to phase fractions of ferrite and bainite.

Effect of Effective Grain Size on Charpy Impact Properties of High-Strength Bainitic Steels (베이나이트계 고강도강의 샤르피 충격 특성에 미치는 유효결정립도 영향)

  • Shin, Sang Yong;Han, Seung Youb;Hwang, Byoungchul;Lee, Chang Gil;Lee, Sunghak
    • Korean Journal of Metals and Materials
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    • v.46 no.10
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    • pp.617-626
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    • 2008
  • This study is concerned with the effect of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels. Six kinds of steels were fabricated by varying alloying elements and hot-rolling conditions, and their microstructures and tensile and Charpy impact properties were investigated. Their effective grain sizes were also characterized by the electron back-scatter diffraction analysis. The tensile test results indicated that the B- or Cu-containing steels had the higher yield and tensile strengths than the B- or Cu-free steels because their volume fractions of bainitic ferrite and martensite were quite high. The B- or Cu-free steels had the higher upper shelf energy than the B- or Cu-containing steels because of their higher volume fraction of granular bainite. In the steel containing 10 ppm B without Cu, the best combination of high strengths, high upper shelf energy, and low energy transition temperature could be obtained by the decrease in the overall effective grain size due to the presence of bainitic ferrite having smaller effective grain size.

Effect of Dewpoints on Annealing Behavior and Coating Characteristics in IF High Strength Steels Containing Si and Mn (Si, Mn함유 IF 고강도강의 소둔거동 및 도금특성에 미치는 이슬점 온도의 영향)

  • Jeon, Sun-Ho;Shin, Kwang-Soo;Sohn, Ho-Sang;Kim, Dai-Ryong
    • Korean Journal of Metals and Materials
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    • v.46 no.7
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    • pp.427-436
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    • 2008
  • The effect of dewpoints on annealing behavior and coating characteristics such as wettability and galvannealing kinetics was studied by annealing 0.3wt%Si - 0.1~0.4wt% Mn added interstitial-free high strength steels(IF-HSS). The 0.3wt%Si-0.1wt%Mn steel exhibited good wettability with molten zinc and galvannealing kinetics after annealing when the dewpoint of $H_2-N_2$ mixed gas was above $-20^{\circ}C$. It is shown that the wettability and galvannealing kinetics are directly related to the coverage of the external(surface) oxide formed by selective oxidation during annealing. At $N_2-15%H_2$ annealing atmosphere, the increase of dewpoint results in a gradual transition from external to internal selective oxidation. The decrease of external oxidation of alloying elements with a concurrent increase of their subsurface enrichment in the substrate, showing a larger surface area that was free of oxide particles, contributed to the improved wettability and galvannealing kinetics. On the other hand, the corresponding wettability and galvannealing kinetics were deteriorated with the dewpoints below $-20^{\circ}C$. The continuous oxide layer of network and/or film type was formed on the steel surface, leading to the poor wettability and galvannealing kinetics. It causes a high contact angle between annealed surface and molten zinc and plays an interrupting role in interdiffusion of Zn and Fe during galvannealing process.

Mechanical Alloying and the Consolidation Behavior of Nanocrystalline $Ll_2$ A$1_3$Hf Intermetallic Compounds (Cu 첨가에 따른 nanocrystalline ${Ll_2}{Al_3}Hf$ 금속간 화합물의 기계적 합금화 거동 및 진공열간 압축성형거동)

  • Kim, Jae-Il;O, Yeong-Min;Kim, Seon-Jin
    • Korean Journal of Materials Research
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    • v.11 no.8
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    • pp.629-635
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    • 2001
  • To improve the ductility of $A1_3Hf$ intermetallics, which are the potential high temperature structural materials, the mechanical alloying behavior. the effect of Cu addition on the $Ll_2$ phase formation and the behavior of vacuum hot-pressed consolidation were investigated. During the mechanical alloying by SPEX mill, the $Ll_2 A1_3Hf$ intermetallics with the grain size of 7~8nm was formed after 6 hours of milling in Al-25at.%Hf system. The $Ll_2$ Phase of Al_3Hf$ intermetallics with the addition of 12.5at.%Cu, similar to that of the binary Al-25at.% Hf, was formed, but the milling time necessary for the formationof the $Ll_2$ phase was delayed form 6 hours to 10 hours. The lattice parameter of ternary $Ll_2(Al+Cu)_3Hf$ intermetallics decreased with the increase of Cu content. The onset temperature of $Ll_2$ to $D0_{23}$ phase in $Al_3Hf$ intermetallics was around 38$0^{\circ}C$, the temperature upon completion varied from 48$0^{\circ}C$ to 5$50^{\circ}C$ as the annealing time. The onset temperature of $Ll_2$ to $D0_{23}$ phase transformation in $(Al+ Cu)_3Hf$ intermetallics increased with the amount of Cu and the highest onset temperature of $700^{\circ}C$ was achieved by the Cu addition of 10at.%. The relative density increased from 89% to 90% with the Cu addition of 10at.% in $Al_3Hf$ intermetallics hot-pressed in vacuum under 750MPa at 40$0^{\circ}C$ for 3 hours. The relative density of 92.5% was achieved without the phase transformation and the grain growth as the consolidation temperature increased from 40$0^{\circ}C$ to 50$0^{\circ}C$ in $(Al+Cu)_3Hf$ intermetallics hot-pressed in vacuum under 750MPa for 3 hours.

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Material Life Cycle Assessment on Mg2NiHx-5 wt% CaO Hydrogen Storage Composites (Mg2NiHx-5 wt% CaO 수소 저장 복합재료의 물질전과정평가)

  • Shin, Hyo-Won;Hwang, June-Hyeon;Kim, Eun-A;Hong, Tae-Whan
    • Clean Technology
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    • v.27 no.2
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    • pp.107-114
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    • 2021
  • Material Life Cycle Assessment (MLCA) was performed to analyze the environmental impact characteristics of the Mg2NiHx-5 wt% CaO hydrogen storage composites' manufacturing process. The MLCA was carried out by Gabi software. It was based on Eco-Indicator 99' (EI99) and CML 2001 methodology. The Mg2NiHx-5 wt% CaO composites were synthesized by Hydrogen Induced Mechanical Alloying (HIMA). The metallurgical, thermochemical characteristics of the composites were analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), specific surface area analysis (Bruner-Emmett-Teller, BET), and thermogravimetric analysis (TGA). As a result of the CML 2001 methodology, the environmental impact was 78% for Global Warming Potential (GWP) and 22% for Eutrophication Potential (ETP). In addition, as a result of applying the EI 99' methodology, the acidification was the highest at 43%, and the ecotoxicity was 31%. Accordingly, the amount of electricity used in the manufacturing process may have an absolute effect on environmental pollution. Also, it is judged that the leading cause of Mg2NiHx-5 wt% CaO is the addition of CaO. Ultimately, it is necessary to research environmental factors by optimizing the process, shortening the manufacturing process time, and exploring eco-friendly alternative materials.

Effect of Niobium and Tin on Mechanical Properties of Zirconium Alloys (Zr 합금의 기계적 특성에 미치는 Nb와 Sn의 영향)

  • Kim, Gyeong-Ho;Choe, Byeong-Gwon;Baek, Jong-Hyeok;Kim, Seon-Jae;Jeong, Yong-Hwan
    • Korean Journal of Materials Research
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    • v.9 no.2
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    • pp.188-194
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    • 1999
  • To investigate the effect of niobium and tin on the mechanical properties of zirconium alloys, the tensile test and the microstructural analysis were performed on the Zr-based binary(Zr-xNb, Zr-xSn) and ternary(Zr-0.8Sn-xNb, Zr-0.4Nb-xSn) alloys. As the content of Nb or Sn element increased, the strengths of the Zr-based alloys tended to gradually increase. The increase of mechanical strength was remarkable strength was remarkable in the range more than the solubility of Nb and Sn. The strengthening effects were discussed on the basis of the solid solution hardening, the precipitate hardening, the grain size effect, and the texture effect. The mechanical strength is mainly controlled by the solid solution hardening and additionally by the precipitate hardening in the content more than solubility limit of Nb and Sn. The grain refinement also has a slight effect on the strength of the zirconium alloys with the addition of Nb and Sn. However, the texture effect can be excluded due to the same Kearns number regardless of the content of alloying elements.

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Effect of Ni or Cu content on Microstructure and Mechanical Properties of Solution Strengthened Ferritic Ductile Cast Iron (고용강화 페라이트계 구상흑연주철의 미세조직 및 기계적 성질에 미치는 Ni 및 Cu의 영향)

  • Bang, Hyeon-Sik;Kim, Sun-Joong;Song, Soo-Young;Kim, Min-Su
    • Journal of Korea Foundry Society
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    • v.41 no.5
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    • pp.411-418
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    • 2021
  • In order to experimentally investigate the effect of Ni or Cu addition on microstructure and mechanical properties of high Si Solution Strengthened Ferritic Ductile cast Iron (SSF DI), a series of lab-scale sand casting experiment were conducted by changing initial concentration of Ni up to 3.0wt% or Cu up to 0.9wt% in the alloy. It was found that increase in Ni or Cu content in the alloy leads to increase in strength properties and hardness as well as decrease in ductility. The higher Ni or Cu content the SSF DI has, the higher fraction of pearlite was observed. At similar levels of Ni or Cu contents in the alloy, higher pearlite area fraction was observed in the Cu-containing SSF DI than that in the Ni-containing SSF DI. When the effect of the microstructure on the mechanical properties of Ni-containing SSF DI was considered, Ni-containing SSF DI was found to have excellent strength and hardness as well as good elongation when the pearlite fraction was controlled less than 10%. As the pearlite fraction in the Ni-containing SSF DI exceeds 10%, however, it shows drastic decrease in elongation. Meanwhile, gradual increase in strength and hardness, and decrease in elongation with respect to increase in pearlite fraction were observed in Cu-containing SSF DI. The different microstructure-mechanical property relationships between Ni-containing and Cu-containing SSF DI were due to the combined effect of the relatively weak pearlite stabilizing effect of Ni compared to that of Cu in high Si SSF DI, and matrix strengthening effect caused by the different amounts of those alloying elements required for similar pearlite fraction.