Pub Date : 2023-06-05DOI: 10.3365/kjmm.2023.61.6.404
Jin Sung Park, D. Cho, Seunggab Hong, Tae Ho Yun, Sung Jin Kim
The effect of Ni-based fillers on corrosion resistance of welded super austenitic stainless steel (SASS) was examined. The use of Ni-based fillers for gas tungsten arc welded SASS leads to the formation of fine Cr-Mo enriched phase in its weld unmixed zone, which makes it more susceptible to the localized corrosion. The metallographic observations showed that the pits were initiated around the fine Cr-Mo enriched phase precipitated in unmixed zone, and they were propagated along the base metal. The degree of corrosion damage among the welded samples using the three types of Ni-based fillers (Inconel 625, Inconel 622, Hastelloy 276) increased with the Mo contents in the fillers applied. The higher the Mo contents in the fillers, the higher the size/number ratio of Cr-Mo enriched phase with higher concentration of Mo, precipitated in unmixed zone. Based on the results, it is proposed that the Mo contents in Ni-based high alloyed fillers can have a great effect on the precipitation behavior of Cr-Mo enriched phase in unmixed zone, causing deterioration of corrosion resistance of SASS welds. Therefore, the Mo content in the filler should be optimized with the content similar to that of the base metal so as not to susceptible to localized corrosion.
{"title":"Effect of Ni-based Fillers on Corrosion Resistance of Heat Affected Zone of Super Austenitic Stainless Steel (UNS S31254) Welded by GTAW","authors":"Jin Sung Park, D. Cho, Seunggab Hong, Tae Ho Yun, Sung Jin Kim","doi":"10.3365/kjmm.2023.61.6.404","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.6.404","url":null,"abstract":"The effect of Ni-based fillers on corrosion resistance of welded super austenitic stainless steel (SASS) was examined. The use of Ni-based fillers for gas tungsten arc welded SASS leads to the formation of fine Cr-Mo enriched phase in its weld unmixed zone, which makes it more susceptible to the localized corrosion. The metallographic observations showed that the pits were initiated around the fine Cr-Mo enriched phase precipitated in unmixed zone, and they were propagated along the base metal. The degree of corrosion damage among the welded samples using the three types of Ni-based fillers (Inconel 625, Inconel 622, Hastelloy 276) increased with the Mo contents in the fillers applied. The higher the Mo contents in the fillers, the higher the size/number ratio of Cr-Mo enriched phase with higher concentration of Mo, precipitated in unmixed zone. Based on the results, it is proposed that the Mo contents in Ni-based high alloyed fillers can have a great effect on the precipitation behavior of Cr-Mo enriched phase in unmixed zone, causing deterioration of corrosion resistance of SASS welds. Therefore, the Mo content in the filler should be optimized with the content similar to that of the base metal so as not to susceptible to localized corrosion.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49463900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-05DOI: 10.3365/kjmm.2023.61.6.422
H. Kim, Il-Ho Kim
Cu–Sb–Se ternary chalcogenide compounds composed of earth-abundant low-toxicity elements are attracting attention as economical and ecofriendly semiconductors. Among them, permingeatite (Cu3SbSe4) is a potential thermoelectric material with high Seebeck coefficient and low lattice thermal conductivity. However, it is necessary to improve its thermoelectric properties through doping, as it has low electrical conductivity due to its low intrinsic carrier concentration. In this study, samples of Cu3Sb1−x−ySnxInySe4 (0.02 ≤ x ≤ 0.08 and 0.04 ≤ y ≤ 0.06) double-doped with In (group 13 element) and Sn (group 14 element) at the Sb (group 15 element) sites of permingeatite were synthesized and their thermoelectric performances were evaluated. All samples exhibited a single phase of permingeatite with tetragonal structure, and high relative densities of 97.4–98.9%. The lattice constants of the a- and c-axes were 0.5651–0.5654 and 1.1249–1.1257 nm, respectively, owing to the successful substitution of Sn and In at the Sb sites. As the doping concentrations of Sn and In increased, the carrier (hole) concentration increased. Thus, the Seebeck coefficient decreased, while the electrical and thermal conductivities increased. Sn doping was found to be more effective than In doping. Because Cu3Sb0.96−xSnxIn0.04Se4 exhibits higher Seebeck coefficients than Cu3Sb0.94−xSnxIn0.06Se4, larger power factors and higher dimensionless figures of merit (ZTs) were achieved for the Cu3Sb0.96−xSnxIn0.04Se4 specimens. Cu3Sb0.92Sn0.04In0.04Se4 achieved a maximum ZT of 0.59 at 623 K, based on its Seebeck coefficient of 161 µVK−1, electrical conductivity of 4.69 × 104 Sm−1, thermal conductivity of 0.77 Wm−1K−1, and power factor of 1.22 mWm−1K−2.
{"title":"Improved Thermoelectric Performance of Cu3Sb1−x−ySnxInySe4 Permingeatites Double-Doped with Sn and In","authors":"H. Kim, Il-Ho Kim","doi":"10.3365/kjmm.2023.61.6.422","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.6.422","url":null,"abstract":"Cu–Sb–Se ternary chalcogenide compounds composed of earth-abundant low-toxicity elements are attracting attention as economical and ecofriendly semiconductors. Among them, permingeatite (Cu<sub>3</sub>SbSe<sub>4</sub>) is a potential thermoelectric material with high Seebeck coefficient and low lattice thermal conductivity. However, it is necessary to improve its thermoelectric properties through doping, as it has low electrical conductivity due to its low intrinsic carrier concentration. In this study, samples of Cu<sub>3</sub>Sb<sub>1−x−y</sub>Sn<sub>x</sub>In<sub>y</sub>Se<sub>4</sub> (0.02 ≤ <i>x</i> ≤ 0.08 and 0.04 ≤ <i>y</i> ≤ 0.06) double-doped with In (group 13 element) and Sn (group 14 element) at the Sb (group 15 element) sites of permingeatite were synthesized and their thermoelectric performances were evaluated. All samples exhibited a single phase of permingeatite with tetragonal structure, and high relative densities of 97.4–98.9%. The lattice constants of the a- and c-axes were 0.5651–0.5654 and 1.1249–1.1257 nm, respectively, owing to the successful substitution of Sn and In at the Sb sites. As the doping concentrations of Sn and In increased, the carrier (hole) concentration increased. Thus, the Seebeck coefficient decreased, while the electrical and thermal conductivities increased. Sn doping was found to be more effective than In doping. Because Cu<sub>3</sub>Sb<sub>0.96−x</sub>Sn<sub>x</sub>In<sub>0.04</sub>Se<sub>4</sub> exhibits higher Seebeck coefficients than Cu<sub>3</sub>Sb<sub>0.94−x</sub>Sn<sub>x</sub>In<sub>0.06</sub>Se<sub>4</sub>, larger power factors and higher dimensionless figures of merit (ZTs) were achieved for the Cu<sub>3</sub>Sb<sub>0.96−x</sub>Sn<sub>x</sub>In<sub>0.04</sub>Se<sub>4</sub> specimens. Cu<sub>3</sub>Sb<sub>0.92</sub>Sn<sub>0.04</sub>In<sub>0.04</sub>Se<sub>4</sub> achieved a maximum ZT of 0.59 at 623 K, based on its Seebeck coefficient of 161 µVK<sup>−1</sup>, electrical conductivity of 4.69 × 10<sup>4</sup> Sm<sup>−1</sup>, thermal conductivity of 0.77 Wm<sup>−1</sup>K<sup>−1</sup>, and power factor of 1.22 mWm<sup>−1</sup>K<sup>−2</sup>.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45461608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-05DOI: 10.3365/kjmm.2023.61.6.449
Hoseop Song, S. Song, Jaiyoung Cho, G. Song
High entropy alloys (HEAs) are defined as a multi-element alloy including more than 4 elements with near equi-atomic percentage. In general, the configurational entropy of the HEAs is known to be sufficient to stabilize a single solid solution, such as body-centered cubic (BCC), face-centered cubic (FCC) and hexagonal-closed pack (HCP). Compared to BCC single-phase alloys, FCC single-phase alloys draw extensive attention because they are advantageous in manufacturing and processing. FCC-based HEAs show excellent ductility but limited strength, so many research on improving strength has been conducted. Outstanding mechanical properties with a balance of strength and ductility are rarely achieved in single-phase FCC-based HEAs. This is why most alloys for structural applications exhibit a multi-phase microstructure. In this study, we aimed to develop multi-phase FCC-based HEA with superior mechanical properties than single-phase CoCrFeMnNi HEA, via Co substitution in CoCrFeMnNi HEA by Cu, which has a high mixing enthalpy. It was found that the CuCrFeMnNi HEA is composed of two FCC phases and one BCC phase. The CuCrFeMnNi HEA was cold-rolled, and subsequently aged at 500, 700, 900oC for 1 hour. As the annealing temperature increased, the volume fraction of the FCC phase (FCC1 + FCC2) increased and the residual stress was gradually relieved by recrystallization. Furthermore, small amount of sigma phase was formed at 900oC. The effect of the microstructural evolution on the mechanical properties, such as hardness and tensile properties at room temperature, will be discussed.
{"title":"Influence of Heat-Treatment on Microstructures and Mechanical Properties of CuCrFeMnNi High-Entropy Alloy","authors":"Hoseop Song, S. Song, Jaiyoung Cho, G. Song","doi":"10.3365/kjmm.2023.61.6.449","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.6.449","url":null,"abstract":"High entropy alloys (HEAs) are defined as a multi-element alloy including more than 4 elements with near equi-atomic percentage. In general, the configurational entropy of the HEAs is known to be sufficient to stabilize a single solid solution, such as body-centered cubic (BCC), face-centered cubic (FCC) and hexagonal-closed pack (HCP). Compared to BCC single-phase alloys, FCC single-phase alloys draw extensive attention because they are advantageous in manufacturing and processing. FCC-based HEAs show excellent ductility but limited strength, so many research on improving strength has been conducted. Outstanding mechanical properties with a balance of strength and ductility are rarely achieved in single-phase FCC-based HEAs. This is why most alloys for structural applications exhibit a multi-phase microstructure. In this study, we aimed to develop multi-phase FCC-based HEA with superior mechanical properties than single-phase CoCrFeMnNi HEA, via Co substitution in CoCrFeMnNi HEA by Cu, which has a high mixing enthalpy. It was found that the CuCrFeMnNi HEA is composed of two FCC phases and one BCC phase. The CuCrFeMnNi HEA was cold-rolled, and subsequently aged at 500, 700, 900oC for 1 hour. As the annealing temperature increased, the volume fraction of the FCC phase (FCC1 + FCC2) increased and the residual stress was gradually relieved by recrystallization. Furthermore, small amount of sigma phase was formed at 900oC. The effect of the microstructural evolution on the mechanical properties, such as hardness and tensile properties at room temperature, will be discussed.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47258286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.330
R. Kim, H. Jeong, Y. Son, Sorokina Si, S. Ryu, S. K. Ko, H. Hong
The effect of TiO2 additive concentration and sintering temperatures on the densification of alumina (Al2O3 ) ceramics were investigated. Densified alumina specimens were prepared by uniaxial pressing at a pressure of 60 MPa followed by isothermal heating at either 1400, 1500, or 1600 o C for 2 h. The relative density, microstructure, crystallinity, and hardness were investigated, and the correlation between properties and structure was discussed in relation to TiO2 addition and sintering temperature. The densities of the 0.05wt%-TiO2 specimens sintered at 1500 and 1600 o C had higher values than the pure alumina specimens. Adding more than 5.0wt% TiO2 lowered the relative density. The maximum achieved density was 99.7% at 0.05wt% TiO2 addition. Shrinkage and hardness analyses confirmed that the sintering temperature for the Al2O3 insulator could be lowered by adding TiO2. The optimal concentration to obtain a dense alumina with high hardness for insulator use was determined to be in the range of 0.05 to 1.0 wt% of TiO2 . These results provide fundamental composition and process optimization data for the development of high-dielectric alumina insulators.
{"title":"Effect of added TiO2 on the mechanical properties of sintered Al2O3 insulator","authors":"R. Kim, H. Jeong, Y. Son, Sorokina Si, S. Ryu, S. K. Ko, H. Hong","doi":"10.3365/kjmm.2023.61.5.330","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.330","url":null,"abstract":"The effect of TiO2 additive concentration and sintering temperatures on the densification of alumina (Al2O3 ) ceramics were investigated. Densified alumina specimens were prepared by uniaxial pressing at a pressure of 60 MPa followed by isothermal heating at either 1400, 1500, or 1600 o C for 2 h. The relative density, microstructure, crystallinity, and hardness were investigated, and the correlation between properties and structure was discussed in relation to TiO2 addition and sintering temperature. The densities of the 0.05wt%-TiO2 specimens sintered at 1500 and 1600 o C had higher values than the pure alumina specimens. Adding more than 5.0wt% TiO2 lowered the relative density. The maximum achieved density was 99.7% at 0.05wt% TiO2 addition. Shrinkage and hardness analyses confirmed that the sintering temperature for the Al2O3 insulator could be lowered by adding TiO2. The optimal concentration to obtain a dense alumina with high hardness for insulator use was determined to be in the range of 0.05 to 1.0 wt% of TiO2 . These results provide fundamental composition and process optimization data for the development of high-dielectric alumina insulators.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48384191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.355
Steven Yun, Il-Ho Kim
Famatinite (Cu3SbS4 ) is a promising p-type thermoelectric material because of its low lattice thermal conductivity and high Seebeck coefficient. In this study, famatinite powders, double-doped with Sn (a BIV group element) and In (a BIII group element) to give Cu3Sb1-x-ySnxInyS4 (0.02 ≤ x ≤ 0.12 and 0.06 ≤ y ≤ 0.10), were synthesized by mechanical alloying and then consolidated by hot pressing. Phase analysis and microstructure observations were conducted over a range of doping levels, and the charge transport parameters and thermoelectric properties were evaluated. Except for the specimen with y = 0.10, in which the secondary phase CuInS2 was found, all the specimens exhibited a tetragonal famatinite phase without secondary phases. The Sn/In double doping increased the unit cell a-axis to 0.5387–0.5389 nm and changed the c-axis to 1.0744–1.0752 nm. As the temperature increased, the electrical conductivity decreased while the Seebeck coefficient increased, which indicates that the Sn/In double-doped famatinites have degenerate semiconductor characteristics. With increasing Sn and In content, the carrier concentration increased, so that the electrical conductivity increased and the Seebeck coefficient decreased. Cu3Sb0.80Sn0.12In0.08S4 exhibited the highest power factor, 0.87 mW m-1 K-2 at 623 K, with greatly increased thermal conductivity. Cu3Sb0.86Sn0.08In0.06S4 showed the highest value for the dimensionless figure of merit, ZT = 0.53 at 623 K, with a power factor of 0.78 mW m-1 K-2 and thermal conductivity of 0.90 W m-1 K-1.
Famatinite（Cu3SbS4）具有晶格热导率低、塞贝克系数高等优点，是一种很有前途的p型热电材料。在本研究中，通过机械合金化合成了双掺杂Sn（一种BIV族元素）和In（一种BIII族元素）得到Cu3Sb1-x-ySnxInyS4（0.02≤x≤0.12和0.06≤y≤0.10）的法马汀矿粉末，然后通过热压固结。在一系列掺杂水平上进行了相分析和微观结构观察，并评估了电荷传输参数和热电性能。除了y=0.10的试样中发现了二次相CuInS2外，所有试样都呈现出不含二次相的四方法马锡矿相。Sn/In双掺杂使晶胞a轴增加到0.5387–0.5389 nm，c轴改变到1.0744–1.0752 nm。随着温度的升高，电导率降低，而塞贝克系数增加，这表明Sn/In双掺杂法马替石具有简并半导体特性。随着Sn和In含量的增加，载流子浓度增加，电导率增加，塞贝克系数降低。Cu3Sb0.80Sn0.12In0.08S4在623K下表现出最高的功率因数，为0.87mW m-1 K-2，热导率大大提高。Cu3Sb0.86Sn0.08In0.06S4显示出无量纲品质因数的最高值，在623K下ZT=0.53，功率因数为0.78mW m-1 K-2，热导率为0.90 W m-1 K-1。
{"title":"Effects of Sn and In Double-Doping on the Thermoelectric Performance of Cu3Sb1-x-ySnxInyS4 Famatinites","authors":"Steven Yun, Il-Ho Kim","doi":"10.3365/kjmm.2023.61.5.355","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.355","url":null,"abstract":"Famatinite (Cu<sub>3</sub>SbS<sub>4</sub> ) is a promising p-type thermoelectric material because of its low lattice thermal conductivity and high Seebeck coefficient. In this study, famatinite powders, double-doped with Sn (a B<sup>IV</sup> group element) and In (a B<sup>III</sup> group element) to give Cu<sub>3</sub>Sb<sub>1-x-y</sub>Sn<sub>x</sub>In<sub>y</sub>S<sub>4</sub> (0.02 ≤ x ≤ 0.12 and 0.06 ≤ y ≤ 0.10), were synthesized by mechanical alloying and then consolidated by hot pressing. Phase analysis and microstructure observations were conducted over a range of doping levels, and the charge transport parameters and thermoelectric properties were evaluated. Except for the specimen with y = 0.10, in which the secondary phase CuInS<sub>2</sub> was found, all the specimens exhibited a tetragonal famatinite phase without secondary phases. The Sn/In double doping increased the unit cell a-axis to 0.5387–0.5389 nm and changed the c-axis to 1.0744–1.0752 nm. As the temperature increased, the electrical conductivity decreased while the Seebeck coefficient increased, which indicates that the Sn/In double-doped famatinites have degenerate semiconductor characteristics. With increasing Sn and In content, the carrier concentration increased, so that the electrical conductivity increased and the Seebeck coefficient decreased. Cu<sub>3</sub>Sb<sub>0.80</sub>Sn<sub>0.12</sub>In<sub>0.08</sub>S<sub>4</sub> exhibited the highest power factor, 0.87 mW m<sup>-1</sup> K<sup>-2</sup> at 623 K, with greatly increased thermal conductivity. Cu<sub>3</sub>Sb<sub>0.86</sub>Sn<sub>0.08</sub>In<sub>0.06</sub>S<sub>4</sub> showed the highest value for the dimensionless figure of merit, ZT = 0.53 at 623 K, with a power factor of 0.78 mW m<sup>-1</sup> K<sup>-2</sup> and thermal conductivity of 0.90 W m<sup>-1</sup> K<sup>-1</sup>.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47333712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.338
H. Kang, Soo-Kyoung Kim, B. Jang, H. Kim
AA 2026 is an improved version of AA 2024, an alloy with added Zr to reduce Fe and Si content and inhibit recrystallization during hot working. Al 2026 alloy has high strength and high damage resistance, so it is widely used in aircraft parts. In this study, in order to investigate the hot workability of AA 2026 and to optimize the hot forming parameters, hot compression tests were conducted in the temperature range of 300 to 450 o C, at a strain rate of 0.01 to 10 and in the 50% strain section. The true stress–true strain curve showed a dynamic softening phenomenon while the stress increased rapidly at a small strain and then remained steady. In order to evaluate its high temperature processability, the constitutive equations for flow stress, temperature, and strain were quantified based on the Arrhenius equation, and a process strain map was prepared. The peak stress accuracy of the constitutive equation was about 98.2%, which was consistent with the experimental data of AA 2026 under strain rate and temperature conditions. In addition, scanning electron microscopy (SEM) and backscattered electron diffraction pattern analyzer (EBSD) analyses were conducted to confirm the mechanism of the dynamic softening phenomenon. The CDRX phenomenon was confirmed under the high strain condition in the low temperature region and the DDRX phenomenon in the low strain condition in the high temperature region.
AA 2026是AA 2024的改进版本，加入Zr可以降低铁和硅含量，抑制热加工过程中的再结晶。al2026合金具有高强度和高抗损伤性，因此广泛应用于飞机零部件。为了研究AA 2026的热加工性，优化热成形参数，在300 ~ 450℃的温度范围内，在0.01 ~ 10的应变速率下，在50%应变截面进行了热压缩试验。真应力-真应变曲线表现为动态软化现象，应力在小应变下迅速增大后趋于稳定。为了评价其高温加工性能，基于Arrhenius方程，量化了流动应力、温度和应变的本构方程，并绘制了工艺应变图。在应变速率和温度条件下，本构方程的峰值应力精度约为98.2%，与AA 2026的实验数据一致。此外，通过扫描电镜(SEM)和背散射电子衍射分析仪(EBSD)分析证实了动态软化现象的机理。在低温区高应变条件下证实了CDRX现象，在高温区低应变条件下证实了DDRX现象。
{"title":"High Temperature Deformation and Microstructural Evolution of Homogenized AA 2026 Alloy","authors":"H. Kang, Soo-Kyoung Kim, B. Jang, H. Kim","doi":"10.3365/kjmm.2023.61.5.338","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.338","url":null,"abstract":"AA 2026 is an improved version of AA 2024, an alloy with added Zr to reduce Fe and Si content and inhibit recrystallization during hot working. Al 2026 alloy has high strength and high damage resistance, so it is widely used in aircraft parts. In this study, in order to investigate the hot workability of AA 2026 and to optimize the hot forming parameters, hot compression tests were conducted in the temperature range of 300 to 450 o C, at a strain rate of 0.01 to 10 and in the 50% strain section. The true stress–true strain curve showed a dynamic softening phenomenon while the stress increased rapidly at a small strain and then remained steady. In order to evaluate its high temperature processability, the constitutive equations for flow stress, temperature, and strain were quantified based on the Arrhenius equation, and a process strain map was prepared. The peak stress accuracy of the constitutive equation was about 98.2%, which was consistent with the experimental data of AA 2026 under strain rate and temperature conditions. In addition, scanning electron microscopy (SEM) and backscattered electron diffraction pattern analyzer (EBSD) analyses were conducted to confirm the mechanism of the dynamic softening phenomenon. The CDRX phenomenon was confirmed under the high strain condition in the low temperature region and the DDRX phenomenon in the low strain condition in the high temperature region.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44756278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.311
Tae-Ung Song, Jamin Koo, Seung-Byeong Jeon, C. Jeong
Cast A356(Al-Si-Mg) alloys are widely used in automotive and general applications because of their mechanical properties and castability. Al-Si-Mg-(Cu) alloys typically lose their strength above 170 o C due to coarsening of precipitates, which limits their application to components. To maintain their strength at elevated temperature, Al-Si-Mg-(Cu) alloys are modified by adding transitional metals. Several studies have been carried out to evaluate the effect of Zr addition on the high temperature mechanical properties of cast Al-Si alloys because Zr can form thermally stable phases such as Al3Zr. Despite the relative studies on the influence of Cu and Zr on the mechanical properties of cast Al-Si-Mg-(Cu) alloys, investigations of the effect of Zr on the phase transformations and the mechanical properties during heat treatment remains limited. In this study, the effects of added Cu and Zr on the phase transformations and the mechanical performance during heat treatment of A356 cast alloy were investigated. Needle-like and block-like (Al,Si)3(Ti,Zr) dispersoids formed as some Si and Ti replaced Al and Zr in Al3Zr crystal structures were generally observed. Furthermore, with increasing solution treatment time, the size of Zr dispersoids was reduced, and smaller Zr particles were precipitated at the same time, which caused a decrease in the area fraction of the Zr dispersoids. In addition, the metastable L12 structures of Zr dispersoids in Al-Si-Mg-Cu-Zr alloys were transformed into stable D023 during solution heat treatment as the Cu addition accelerated the transformation. Tensile and low-cycle fatigue (LCF) tests were performed to reveal the effects of (Al,Si)3(Ti,Zr) dispersoids on mechanical properties. As a result, elongation at elevated temperature was highly increased, while maintaining strength, according to the increase in solution heat treatment time, which improved low-cycle fatigue properties.
{"title":"Investigation of Phase Transformation and Mechanical Properties of A356 Alloy with Cu and Zr Addition during Heat Treatment","authors":"Tae-Ung Song, Jamin Koo, Seung-Byeong Jeon, C. Jeong","doi":"10.3365/kjmm.2023.61.5.311","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.311","url":null,"abstract":"Cast A356(Al-Si-Mg) alloys are widely used in automotive and general applications because of their mechanical properties and castability. Al-Si-Mg-(Cu) alloys typically lose their strength above 170 o C due to coarsening of precipitates, which limits their application to components. To maintain their strength at elevated temperature, Al-Si-Mg-(Cu) alloys are modified by adding transitional metals. Several studies have been carried out to evaluate the effect of Zr addition on the high temperature mechanical properties of cast Al-Si alloys because Zr can form thermally stable phases such as Al3Zr. Despite the relative studies on the influence of Cu and Zr on the mechanical properties of cast Al-Si-Mg-(Cu) alloys, investigations of the effect of Zr on the phase transformations and the mechanical properties during heat treatment remains limited. In this study, the effects of added Cu and Zr on the phase transformations and the mechanical performance during heat treatment of A356 cast alloy were investigated. Needle-like and block-like (Al,Si)3(Ti,Zr) dispersoids formed as some Si and Ti replaced Al and Zr in Al3Zr crystal structures were generally observed. Furthermore, with increasing solution treatment time, the size of Zr dispersoids was reduced, and smaller Zr particles were precipitated at the same time, which caused a decrease in the area fraction of the Zr dispersoids. In addition, the metastable L12 structures of Zr dispersoids in Al-Si-Mg-Cu-Zr alloys were transformed into stable D023 during solution heat treatment as the Cu addition accelerated the transformation. Tensile and low-cycle fatigue (LCF) tests were performed to reveal the effects of (Al,Si)3(Ti,Zr) dispersoids on mechanical properties. As a result, elongation at elevated temperature was highly increased, while maintaining strength, according to the increase in solution heat treatment time, which improved low-cycle fatigue properties.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41393832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.324
I. Shon
TiB2 is considered candidate materials for ultra-high temperature ceramics and cutting tools because of its a high thermal conductivity, a low coefficient of thermal expansion, a high hardness and high melting temperature. Despite these attractive properties, TiB2 applications are limited because it has a low fracture toughness below the brittle-ductile transition temperature. To improve on its mechanical properties, the approach universally utilized has been to add secondary materials to form a composite and to fabricate an ultra - fine material. A dense ultra - fine TiB2- ZrO2 composite was rapidly sintered using pulsed high current activated heating (PHCAH) methods within 3 min in one step from the mechanically synthesized the powders of TiB2 and ZrO2 . Consolidation was reached using an effective combination of mechanical pressure and the pulsed high current. A highly dense TiB2-ZrO2 material with relative density of 97.2% was made by the simultaneous application of 75 MPa pressure and a pulsed 2500 A current. The grain sizes of TiB2 and ZrO2 in the composite were 135 nm and 84 nm, respectively. The fracture toughness and hardness of the TiB2 -ZrO2 composite were 11.2 MPa.m1/2 and 957 kg/mm2 , respectively. The fracture toughness of the TiB2 -ZrO2 composite was three times higher than that of monolithic TiB2 .
{"title":"Synthesis and Rapid Sintering of Ultra Fine TiB2-ZrO2 Composite","authors":"I. Shon","doi":"10.3365/kjmm.2023.61.5.324","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.324","url":null,"abstract":"TiB<sub>2</sub> is considered candidate materials for ultra-high temperature ceramics and cutting tools because of its a high thermal conductivity, a low coefficient of thermal expansion, a high hardness and high melting temperature. Despite these attractive properties, TiB2 applications are limited because it has a low fracture toughness below the brittle-ductile transition temperature. To improve on its mechanical properties, the approach universally utilized has been to add secondary materials to form a composite and to fabricate an ultra - fine material. A dense ultra - fine TiB<sub>2</sub>- ZrO<sub>2</sub> composite was rapidly sintered using pulsed high current activated heating (PHCAH) methods within 3 min in one step from the mechanically synthesized the powders of TiB<sub>2</sub> and ZrO<sub>2</sub> . Consolidation was reached using an effective combination of mechanical pressure and the pulsed high current. A highly dense TiB<sub>2</sub>-ZrO<sub>2</sub> material with relative density of 97.2% was made by the simultaneous application of 75 MPa pressure and a pulsed 2500 A current. The grain sizes of TiB<sub>2</sub> and ZrO<sub>2</sub> in the composite were 135 nm and 84 nm, respectively. The fracture toughness and hardness of the TiB<sub>2</sub> -ZrO<sub>2</sub> composite were 11.2 MPa.m<sup>1/2</sup> and 957 kg/mm<sup>2</sup> , respectively. The fracture toughness of the TiB<sub>2</sub> -ZrO<sub>2</sub> composite was three times higher than that of monolithic TiB<sub>2</sub> .","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46377795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.379
Junyang Jung, Hee-Soo Kim
We constructed a convolutional neural network to estimate average grain size from microstructure images. In the previous study from our research group, the network was trained using GB-type images in which the grain matrix and grain boundary were represented in white and black, respectively. The model well estimated the same GB-type images, but did not properly predict CL-type images where grain boundaries were defined by color contrast between grains. In the present study, the convolutional neural network was trained using CL-type microstructure images, and evaluated the average grain size, for comparison with the previous GB-type model. The relationship between the microstructure image and the average grain size was determined using regression rather than classification. Then, the results were compared with the previous ones. Finally, the proposed approach was used for actual microstructural image analysis. Mid-layer images were extracted to examine how the network recognizes the characteristics of microstructures, such as grain color and grain boundary. Like the previous GB-type model, the present CL-type model seems to estimate the average grain size from the curvature of the grain boundary through edge detection of the grain boundaries. However, the GB- and CL-type models only properly predicted the grain size from the same kind of images as the training data, because the definitions of the grain boundaries of the two models were different.
{"title":"Machine Learning-Based Prediction of Grain Size from Colored Microstructure","authors":"Junyang Jung, Hee-Soo Kim","doi":"10.3365/kjmm.2023.61.5.379","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.379","url":null,"abstract":"We constructed a convolutional neural network to estimate average grain size from microstructure images. In the previous study from our research group, the network was trained using GB-type images in which the grain matrix and grain boundary were represented in white and black, respectively. The model well estimated the same GB-type images, but did not properly predict CL-type images where grain boundaries were defined by color contrast between grains. In the present study, the convolutional neural network was trained using CL-type microstructure images, and evaluated the average grain size, for comparison with the previous GB-type model. The relationship between the microstructure image and the average grain size was determined using regression rather than classification. Then, the results were compared with the previous ones. Finally, the proposed approach was used for actual microstructural image analysis. Mid-layer images were extracted to examine how the network recognizes the characteristics of microstructures, such as grain color and grain boundary. Like the previous GB-type model, the present CL-type model seems to estimate the average grain size from the curvature of the grain boundary through edge detection of the grain boundaries. However, the GB- and CL-type models only properly predicted the grain size from the same kind of images as the training data, because the definitions of the grain boundaries of the two models were different.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41619756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-05DOI: 10.3365/kjmm.2023.61.5.347
T. Woo, I. Park
The amount and kind of additives in electrolytes play a very important role on the electroplating of Cu foil, which is used as a cathode materials for secondary batteries. As the use of Cu foil increased, various studies on the electroplated Cu foil are urgently needed. We studied surface characteristics and changes in structural properties due to the addition of inhibitors under electroplating conditions with high current density. The surface layer was observed, to analyze the effect of the amount of potassium carbonate as an inhibitor. When the potassium carbonate was added at 5~25 ppm without any other additives, the initial plating voltage was observed to decrease. To uniformly distribute crystals without agglomeration at the initial stage of electroplating, it is reasonable to add potassium carbonate within the range of 20~25 ppm. There was no significant difference in surface roughness and specific resistance due to the amount of potassium carbonate, when the additives were added complexly. There was an increase in the relative strength of the preferred growth orientation of (220) in a group with 20 ppm potassium carbonate, compared to the group with 10 ppm potassium carbonate. The grain size decreased with the amount of potassium carbonate added with other additives. However, there was no significant difference in tensile strength and elongation (p-value: 0.000). To ensure uniform properties with a combination of 4 kinds of additives it is reasonable to add potassium carbonate in the range of 10~20 ppm.
{"title":"Effect of Potassium Carbonate Additives on the Properties of Copper Foils Electroplated at High Current Density","authors":"T. Woo, I. Park","doi":"10.3365/kjmm.2023.61.5.347","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.5.347","url":null,"abstract":"The amount and kind of additives in electrolytes play a very important role on the electroplating of Cu foil, which is used as a cathode materials for secondary batteries. As the use of Cu foil increased, various studies on the electroplated Cu foil are urgently needed. We studied surface characteristics and changes in structural properties due to the addition of inhibitors under electroplating conditions with high current density. The surface layer was observed, to analyze the effect of the amount of potassium carbonate as an inhibitor. When the potassium carbonate was added at 5~25 ppm without any other additives, the initial plating voltage was observed to decrease. To uniformly distribute crystals without agglomeration at the initial stage of electroplating, it is reasonable to add potassium carbonate within the range of 20~25 ppm. There was no significant difference in surface roughness and specific resistance due to the amount of potassium carbonate, when the additives were added complexly. There was an increase in the relative strength of the preferred growth orientation of (220) in a group with 20 ppm potassium carbonate, compared to the group with 10 ppm potassium carbonate. The grain size decreased with the amount of potassium carbonate added with other additives. However, there was no significant difference in tensile strength and elongation (p-value: 0.000). To ensure uniform properties with a combination of 4 kinds of additives it is reasonable to add potassium carbonate in the range of 10~20 ppm.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42508869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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