Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 11
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

We propose an empirical equation to predict the martensite start temperatures of highly alloyed steels containing more than 3 wt.% of Ni or Cr or 2 wt.% of Mo, W, or Co. The martensite start temperature calculated by the proposed equation was in good agreement with experimental data owing to not only the derivation from experimental data of alloy steels with a wide range of chemical compositions but also the interaction term between carbon and carbide-forming alloying elements.

Go to article

Authors and Affiliations

Seok-Jae Lee
ORCID: ORCID
Minsu Jung
Download PDF Download RIS Download Bibtex

Abstract

The effects of carbon content on the austenite stability and strain-induced transformation of nanocrystalline Fe-11% Ni alloys were investigated using X-ray analysis and mechanical tests. The nanocrystalline FeNiC alloy samples were rapidly fabricated using spark plasma sintering because of the extremely short densification time, which not only helped attain the theoretical density value but also prevented grain growth. The increased austenite stability resulted from nanosized crystallites in the sintered alloys. Increasing compressive deformation increased the volume fraction of strain-induced martensite from austenite decomposition. The kinetics of the strain-induced martensite formation were evaluated using an empirical equation considering the austenite stability factor. As the carbon content increased, the austenite stability was enhanced, contributing to not only a higher volume fraction of austenite after sintering, but also to the suppression of its strain-induced martensite transformation.

Go to article

Authors and Affiliations

Seung-Jin Oh
Byoung-Cheol Kim
Man-Chul Suh
In-Jin Shon
Seok-Jae Lee
Download PDF Download RIS Download Bibtex

Abstract

Cu-Sn alloys have been known as bronze since ancient times and widely used as electrode materials, ornaments, tableware and musical instruments. Cu-22Sn alloy fabrication by hot forging process is a Korean traditional forged high-tin bronze. The tin content is 22 percent, which is more than twice that of bronze ware traditionally used in China and the West. Copper and tin have a carbon solubility of several ppm at room temperature, making Cu-Sn-C alloys difficult to manufacture by conventional casting methods. Research on the production of carbon-added copper alloys has used a manufacturing method that is different from the conventional casting method. In this study, Cu-22Sn-xC alloy was fabricated by mechanical alloying and spark plasma sintering. The carbon solubility was confirmed in Cu-Sn alloy through mechanical alloying. The lattice parameter increased from A0 to C2, and then decreased from C4. The microstructural characteristics of sintered alloys were determined using X-ray diffraction and microscopic analysis. As a result of comparing the hardness of Cu-22Sn alloys manufactured by conventional rolling, casting, and forging and Cu-22Sn-xC alloy by sintered powder metallugy, B0 sintered alloy was the highest at about 110.9 HRB.
Go to article

Authors and Affiliations

Gwanghun Kim
1
ORCID: ORCID
Jungbin Park
1
ORCID: ORCID
Seok-Jae Lee
1
ORCID: ORCID
Hee-Soo Kim
2
ORCID: ORCID

  1. Jeonbuk National University, Division of Advanced Materials Engineering, 567 Baekje-daero, Deokjin-gu, Jeonju 54896, Republic of Korea
  2. Chosun University, Department of Materials Science and Engineering, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Republic of Korea
Download PDF Download RIS Download Bibtex

Abstract

The effect of TiC content on the microstructure and mechanical properties of a nanocrystalline Fe-Mn alloy was investigated by XRD analysis, TEM observation, and mechanical tests. A sintered Fe-Mn alloy sample with nano-sized crystallites was obtained using spark plasma sintering. Crystallite size, which is used as a hardening mechanism, was measured by X-ray diffraction peak analysis. It was observed that the addition of TiC influenced the average size of crystallites, resulting in a change in austenite stability. Thus, the volume fraction of austenite at room temperature after the sintering process was also modified by the TiC addition. The martensite transformation during cooling was suppressed by adding TiC, which lowered the martensite start temperature. The plastic behavior and the strain-induced martensite kinetics formed during plastic deformation are discussed with compressive stress-strain curves and numerical analysis for the transformation kinetics.

Go to article

Authors and Affiliations

Junhyub Jeon
ORCID: ORCID
Seunggyu Choi
Namhyuk Seo
ORCID: ORCID
Young Hoon Moon
In-Jin Shon
Seok-Jae Lee
ORCID: ORCID
Download PDF Download RIS Download Bibtex

Abstract

In this study, a non-equiatomic high entropy alloy was fabricated using the spark plasma sintering method, and its microstructural features and mechanical properties were investigated. The chemical composition of FeMnCoCr was determined by using the entropy calculation related to the design of high entropy alloys. A bulk sample with the same composition was also prepared using the conventional metallurgical processes of casting and hot rolling. The microstructures of the samples fabricated by these different processes were compared by microscope observation, and a quantitative phase analysis was carried out using FE-SEM. Hardness measurement was used to evaluate mechanical properties. Particular attention was paid to microstructural changes due to heat treatment, which was analyzed by considering how austenite stability is affected by grain refinement.

Go to article

Authors and Affiliations

Namhyuk Seo
ORCID: ORCID
Junhyub Jeon
ORCID: ORCID
Seunggyu Choi
Young Hoon Moon
In-Jin Shon
Seok-Jae Lee
ORCID: ORCID
Download PDF Download RIS Download Bibtex

Abstract

We investigated the austenite stability and mechanical properties in FeMnNiC alloy fabricated by spark plasma sintering. The addition of Mn, Ni, and C, which are known austenite stabilizing elements, increases its stability to a stable phase existing above 910°C in pure iron; as a result, austenitic microstructure can be observed at room temperature, depending on the amounts of Mn, Ni, and C added. Depending on austenite stability and the volume fraction of austenite at a given temperature, strain-induced martensite transformation during plastic deformation may occur. Both stability and the volume fraction of austenite can be controlled by several factors, including chemical composition, grain size, dislocation density, and so on. The present study investigated the effect of carbon addition on austenite stability in FeMnNi alloys containing different Mn and Ni contents. Microstructural features and mechanical properties were analyzed with regard to austenite stability.

Go to article

Authors and Affiliations

Seunggyu Choi
Junhyub Jeon
ORCID: ORCID
Namhyuk Seo
ORCID: ORCID
Young Hoon Moon
In-Jin Shon
Seok-Jae Lee
ORCID: ORCID
Download PDF Download RIS Download Bibtex

Abstract

A Si-Fe-Al ternary oxide-based micropowder coating was used to prevent the formation of a Zn coating on steel during the hot-dip Zn galvanizing process to reduce the welding fume and defects generated during the welding of Zn-galvanized steel. The composition ratio of the oxide powder was optimized and its microstructure and weldability were evaluated. The optimized oxide coating was stable in the hot-dip galvanizing bath at 470°C and effectively inhibited the formation of Zn coating. The Zn residue could be easily removed with simple mechanical impact. The proposed coating reduced Zn fume and prevented the residual Zn from melting in the weld bead during high-temperature welding, thus reducing the number of welding defects. The results indicated that this pretreatment can simplify the manufacturing process and shorten the process time cost-effectively.
Go to article

Authors and Affiliations

Seong-Min So
1
Ki-Yeon Kim
1
Il-Song Park
1
ORCID: ORCID
Seok-Jae Lee
1
ORCID: ORCID
Dong-Jin Yoo
2
Yeon-Won Kim
3
ORCID: ORCID
Min-Suk Oh
1
ORCID: ORCID

  1. Jeonbuk National University, Division of Advanced Materials Engineering, Jeonju, Republic of Korea
  2. Jeonbuk National University, Department of Energy Storage/Conversion Engineering Of Graduate School, Department of Life Science, Hydrogen and Fuel Cell Research Center, Jeonju, Republic of Korea
  3. Mokpo National Maritime University, Division of Marine Mechatronics, Mokpo, Republic of Korea
Download PDF Download RIS Download Bibtex

Abstract

The austenitic stability and strain-induced martensitic transformation behavior of a nanocrystalline FeNiCrMoC alloy were investigated. The alloy was fabricated by high-energy ball milling and spark plasma sintering. The phase fraction and grain size were measured using X-ray diffraction. The grain sizes of the milled powder and the sintered alloy were confirmed to be on the order of several nanometers. The variation in the austenite fraction according to compressive deformation was measured, and the austenite stability and strain-induced martensitic transformation behavior were calculated. The hardness was measured to evaluate the mechanical properties according to compression deformation, which confirmed that the hardness increased to 64.03 HRC when compressed up to 30%.
Go to article

Authors and Affiliations

Jungbin Park
1
ORCID: ORCID
Junhyub Jeon
1
ORCID: ORCID
Namhyuk Seo
1
ORCID: ORCID
Gwanghun Kim
1
ORCID: ORCID
Seung Bae Son
1
ORCID: ORCID
Jae-Gil Jung
1
ORCID: ORCID
Seok-Jae Lee
1
ORCID: ORCID

  1. Jeonbuk National University, Research Center for Advanced Materials Development, Division of Advanced Materials Engineering, Jeonju 54896, Republic of Korea
Download PDF Download RIS Download Bibtex

Abstract

The effects of the sintering holding time and cooling rate on the microstructure and mechanical properties of nanocrystalline Fe-Cr-C alloy were investigated. Nanocrystalline Fe-1.5Cr-1C (wt.%) alloy was fabricated by mechanical alloying and spark plasma sintering. Different process conditions were applied to fabricate the sintered samples. The phase fraction and grain size were measured using X-ray powder diffraction and confirmed by electron backscatter diffraction. The stability and volume fraction of the austenite phase, which could affect the mechanical properties of the Fe-based alloy, were calculated using an empirical equation. The sample names consist of a number and a letter, which correspond to the holding time and cooling method, respectively. For the 0A, 0W, 10A, and 10W samples, the volume fraction was measured at 5.56, 44.95, 6.15, and 61.44 vol.%. To evaluate the mechanical properties, the hardness of 0A, 0W, 10A, and 10W samples were measured as 44.6, 63.1, 42.5, and 53.8 HRC. These results show that there is a difference in carbon diffusion and solubility depending on the sintering holding time and cooling rate.
Go to article

Bibliography

[1] E . Yajima, T. Miyazaki, T. Sugiyama, H. Terajima, Trans. JIM 15, 173 (1974).
[2] E .C. Santos, K. Kida, T. Honda, J. Rozwadowska, K. Houri, Adv. Mater. Res. 217, 982 (2011).
[3] I . Yoshida, K. Yamamoto, K. Domura, K. Mizobe, K. Kida, Mater. Sci. Forum 867, 55 (2016).
[4] O . Grassel, L. Kruger, G. Frommeyer, L.W. Meyer, Int. J. Plast. 16, 1391 (2000).
[5] G. Frommeyer, U. Brux, P. Neumann, ISIJ Int. 43, 438 (2003).
[6] D.S. Park, S.J. Oh, I.J. Shon, S.J. Lee, Arch. Metall. Mater. 63, 1479 (2018).
[7] S.G. Choi, J.H. Jeon, N.H. Seo, Y.H. Moon, I.J. Shon, S.J. Lee, Arch. Metall. Mater. 65, 1001 (2020).
[8] S.J. Lee, S. Lee, B.C. De Cooman, Scr. Mater. 64, 649 (2011).
[9] Y. Sakuma, O. Matsumura, H. Takechi, Met. Trans. A 22, 489 (1991).
[10] Y. Matsuoka, T. Iwasaki, N. Nakada, T. Tsuchiyama, S. Takaki, ISIJ Int. 53, 1224 (2013).
[11] K. Sugimoto, M. Misu, M. Kobayashi, H. Shirasawa, ISIJ Int. 33, 775 (1993).
[12] S.J. Lee, S. Lee, B.C. De Cooman, Int. J. Mater. Res. 104, 423 (2013).
[13] J.S. Benjamin, T.E. Volin, Met. Trans. 5, 1929 (1974).
[14] S.I. Cha, S.H. Hong, B.K. Kim, Mater. Sci. Eng. A 351, 31 (2003).
[15] H .W. Zhang, R. Gopalan, T. Mukai, K. Hono, Scr. Mater. 53, 863 (2005).
[16] G.K. Williamson, W.H. Hall, Acta Metall. 1, 22 (1953).
[17] B.L. Averbach, M. Cohen, Trans. AIME 176, 401 (1948).
[18] H . Luo, J. Shi, C. Wang, W. Cao, X. Sun, H. Dong, Acta Mater. 59, 4002 (2011).
[19] S.J. Oh, J.H. Jeon, I.J. Shon, S.J. Lee, J. Korean Powder Metall. Inst. 26, 389 (2019).
[20] I . Seki, K. Nagata, ISIJ Int. 45, 1789 (2005).
[21] G. Dini, R. Ueji, A. Najafizadeh, S.M. Monir-Vaghefi, Mater. Sci. Eng. A 527, 2759 (2010).
[22] F. Martin, C. Garcia, Y. Blanco, M.L. Rodriguez-Mendez, Mater. Sci. Eng. A 642, 360 (2015).
Go to article

Authors and Affiliations

Gwanghun Kim
1
ORCID: ORCID
Junhyub Jeon
1
ORCID: ORCID
Namhyuk Seo
1
ORCID: ORCID
Seunggyu Choi
1
Min-Suk Oh
1
ORCID: ORCID
Seung Bae Son
1
ORCID: ORCID
Seok-Jae Lee
1
ORCID: ORCID

  1. Jeonbuk National University, Division of Advanced Materials Engineering, 567 Baekje-daero, Deokjin-gu, Jeonju, 54896, Republic of Korea
Download PDF Download RIS Download Bibtex

Abstract

Artificial intelligence operated with machine learning was performed to optimize the amount of metalloid elements (Si, B, and P) subjected to be added to a Fe-based amorphous alloy for enhancement of soft magnetic properties. The effect of metalloid elements on magnetic properties was investigated through correlation analysis. Si and P were investigated as elements that affect saturation magnetization while B was investigated as an element that affect coercivity. The coefficient of determination R2 (coefficient of determination) obtained from regression analysis by learning with the Random Forest Algorithm (RFR) was 0.95 In particular, the R2 value measured after including phase information of the Fe-Si-B-P ribbon increased to 0.98. The optimal range of metalloid addition was predicted through correlation analysis method and machine learning.
Go to article

Authors and Affiliations

Min-Woo Lee
1
ORCID: ORCID
Young-Sin Choi
1
ORCID: ORCID
Do-Hun Kwon
1
ORCID: ORCID
Eun-Ji Cha
1
ORCID: ORCID
Hee-Bok Kang
2
ORCID: ORCID
Jae-In Jeong
2
ORCID: ORCID
Seok-Jae Lee
3
ORCID: ORCID
Hwi-Jun Kim
1
ORCID: ORCID

  1. Smart Liquid Processing R&D Department of Korea Institute of Industrial Technology, Incheon 21999, Korea
  2. R&D Center of Youngin Electronic, Youngin 1033, Korea
  3. Jeonbuk National University, Division of Advanced Materials Engineering, Jeonju 54896, Korea
Download PDF Download RIS Download Bibtex

Abstract

The soft magnetic properties of Fe-based amorphous alloys can be controlled by their compositions through alloy design. Experimental data on these alloys show some discrepancy, however, with predicted values. For further improvement of the soft magnetic properties, machine learning processes such as random forest regression, k-nearest neighbors regression and support vector regression can be helpful to optimize the composition. In this study, the random forest regression method was used to find the optimum compositions of Fe-Si-B-C alloys. As a result, the lowest coercivity was observed in Fe80.5Si3.63B13.54C2.33 at.% and the highest saturation magnetization was obtained Fe81.83Si3.63B12.63C1.91 at.% with R2 values of 0.74 and 0.878, respectively.
Go to article

Authors and Affiliations

Young-Sin Choi
1 2
ORCID: ORCID
Do-Hun Kwon
1
ORCID: ORCID
Min-Woo Lee
1
ORCID: ORCID
Eun-Ji Cha
1
ORCID: ORCID
Junhyup Jeon
3
ORCID: ORCID
Seok-Jae Lee
3
ORCID: ORCID
Jongryoul Kim
2
ORCID: ORCID
Hwi-Jun Kim
1
ORCID: ORCID

  1. Smart Liquid Processing R&D Department, Korea Institute of Industrial Technology, 156, Gaetbeol-ro, Yeonsu-Gu, Incheon 21999, Korea
  2. Hanyang Univ., Department of Materials Science and Chemical Engineering, Ansan 15588, Korea
  3. Jeonbuk National Univ., Division of Advanced Materials Engineering, Jeonju 54896, Korea

This page uses 'cookies'. Learn more