Pub Date : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.39
Tae Hoon Park
In this paper, we investigated a transparent conductive electrode (TCE) that satisfies electrical, optical, and mechanical properties, formed by depositing ultra-thin Ag metal in the form of a random grain boundary with an indium zinc oxide (IZO) layer on a PET substrate. Commonly used ITO electrodes are brittle and difficult to apply to flexible devices. In contrast, IZO-based electrodes are mechanically flexible and can be used as flexible TCE, and have high electrical and optical properties. A 90 nm thick IZO electrode has a transmittance of 90.2% at a wavelength of 460 nm and a sheet resistance of 29.5 ohm/sq. In particular, Ag metal was deposited in the form of an atypical metal island using an RF magnetron sputtering system. At 3 nm there were few metal clusters in the form of islands, and many void channels were formed, resulting in high sheet resistance as well as a decrease in optical transmittance. However, about 5 nm thickness, the number of void channels decreased and the optical path changed, improving the electrical and optical properties. Results showed that the sheet resistance was reduced to 19.8 ohm/sq, and the transmittance was also increased to 91.1%. The mechanical properties were also found to be the same for conventional IZO and Ag/IZO TCE.
{"title":"Research on Flexible Transparent Conductive Electrodes Based on Ultra-Thin Ag in the Form of Grain Boundary with IZO Layer","authors":"Tae Hoon Park","doi":"10.3365/kjmm.2024.62.1.39","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.39","url":null,"abstract":"In this paper, we investigated a transparent conductive electrode (TCE) that satisfies electrical, optical, and mechanical properties, formed by depositing ultra-thin Ag metal in the form of a random grain boundary with an indium zinc oxide (IZO) layer on a PET substrate. Commonly used ITO electrodes are brittle and difficult to apply to flexible devices. In contrast, IZO-based electrodes are mechanically flexible and can be used as flexible TCE, and have high electrical and optical properties. A 90 nm thick IZO electrode has a transmittance of 90.2% at a wavelength of 460 nm and a sheet resistance of 29.5 ohm/sq. In particular, Ag metal was deposited in the form of an atypical metal island using an RF magnetron sputtering system. At 3 nm there were few metal clusters in the form of islands, and many void channels were formed, resulting in high sheet resistance as well as a decrease in optical transmittance. However, about 5 nm thickness, the number of void channels decreased and the optical path changed, improving the electrical and optical properties. Results showed that the sheet resistance was reduced to 19.8 ohm/sq, and the transmittance was also increased to 91.1%. The mechanical properties were also found to be the same for conventional IZO and Ag/IZO TCE.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"49 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382094","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.45
S. Joo, JiHui Son, Jeongin Jang, B. Min, Bong-Seo Kim
Mg3Sb2-based n-type materials are consisted of earth-abundant elements and possess comparable thermoelectric properties with n-type Bi2Te3 at low temperatures, which make them promising candidates for cooling and power generation applications in terms of cost and performance. Substitution of Sb atom with chalcogen elements (Te, Se S) is a conventional method for n-type doping, but doping cations such as rare-earth elements and transition metals is also widely studied for its unique advantages. In this study, La and Mn were selected for co-doping of Mg3SbBi, and the thermoelectric performances of the doped materials were investigated. Mg3La0.005MnxSbBi (0 x 0.015) polycrystalline samples were made by sintering the fine powders of the mother alloy after arc melting, in which elemental Mn and LaSb compound were included for n-type dual doping. Considering the loss of Mg at elevated temperatures by vaporization, the molar ratio of Mg, Sb, and Bi in the mixture for arc melting was set to 4 : 1 : 1 with excess Mg. Analysis shows that all the samples are n-type, and the electrical conductivity of Mg3La0.005Mn0.015SbBi increased by 62% from the Mn-free Mg3La0.005SbBi at 298 K. In addition, the lattice thermal conductivity (lat) decreased with increasing Mn content in the measured temperature range of 298-623 K. The minimum value of lat was about 0.60 W m-1K-1 in Mg3La0.005Mn0.015SbBi at 523 K, which is about 19% smaller than that of the Mn-free sample. As a result of these enhancements in thermoelectric performance, the maximum figure of merit (zTmax) of 1.12 was obtained in Mg3La0.005Mn0.01SbBi and Mg3La0.005Mn0.015SbBi at 573 K, and the zT at 298 K increased by 73% to 0.35 in Mg3La0.005Mn0.015SbBi compared to Mn-free Mg3La0.005SbBi, which is beneficial to room-temperature applications.
基于 Mg3Sb2 的 n 型材料由丰富的地球元素组成，在低温条件下具有与 n 型 Bi2Te3 相当的热电特性，这使它们在成本和性能方面成为冷却和发电应用的理想候选材料。用查尔根元素（Te、Se S）取代锑原子是 n 型掺杂的传统方法，但掺杂稀土元素和过渡金属等阳离子也因其独特的优势而被广泛研究。本研究选择 La 和 Mn 作为 Mg3SbBi 的共掺杂剂，并研究了掺杂材料的热电性能。Mg3La0.005MnxSbBi (0 x 0.015) 多晶样品由电弧熔化后的母合金细粉烧结而成，其中加入了元素锰和 LaSb 复合物以实现 n 型双掺杂。考虑到镁在高温下会因汽化而损失，电弧熔化时混合物中镁、锑和铋的摩尔比被设定为 4 : 1 : 1，并加入过量的镁。分析表明，所有样品都是 n 型，在 298 K 时，Mg3La0.005Mn0.015SbBi 的导电率比无锰的 Mg3La0.005SbBi 提高了 62%。此外，在 298-623 K 的测量温度范围内，晶格热导率（lat）随着锰含量的增加而降低。在 523 K 时，Mg3La0.005Mn0.015SbBi 的 lat 的最小值约为 0.60 W m-1K-1，比无锰样品小约 19%。由于这些热电性能的提高，Mg3La0.005Mn0.015SbBi 和 Mg3La0.005Mn0.与无锰 Mg3La0.005SbBi 相比，Mg3La0.005Mn0.015SbBi 在 573 K 时的 zTmax 增加了 73%，达到 0.35，这有利于室温应用。
{"title":"Thermoelectric Properties of N-type Mg3La0.005MnxSbBi Materials Doped with La and Mn","authors":"S. Joo, JiHui Son, Jeongin Jang, B. Min, Bong-Seo Kim","doi":"10.3365/kjmm.2024.62.1.45","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.45","url":null,"abstract":"Mg<sub>3</sub>Sb<sub>2</sub>-based n-type materials are consisted of earth-abundant elements and possess comparable thermoelectric properties with n-type Bi<sub>2</sub>Te<sub>3</sub> at low temperatures, which make them promising candidates for cooling and power generation applications in terms of cost and performance. Substitution of Sb atom with chalcogen elements (Te, Se S) is a conventional method for n-type doping, but doping cations such as rare-earth elements and transition metals is also widely studied for its unique advantages. In this study, La and Mn were selected for co-doping of Mg3SbBi, and the thermoelectric performances of the doped materials were investigated. Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>x</sub>SbBi (0 <i>x</i> 0.015) polycrystalline samples were made by sintering the fine powders of the mother alloy after arc melting, in which elemental Mn and LaSb compound were included for n-type dual doping. Considering the loss of Mg at elevated temperatures by vaporization, the molar ratio of Mg, Sb, and Bi in the mixture for arc melting was set to 4 : 1 : 1 with excess Mg. Analysis shows that all the samples are n-type, and the electrical conductivity of Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi increased by 62% from the Mn-free Mg<sub>3</sub>La<sub>0.005</sub>SbBi at 298 K. In addition, the lattice thermal conductivity (<i><sub>lat</sub></i>) decreased with increasing Mn content in the measured temperature range of 298-623 K. The minimum value of <i><sub>lat</sub></i> was about 0.60 W m<sup>-1</sup>K<sup>-1</sup> in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi at 523 K, which is about 19% smaller than that of the Mn-free sample. As a result of these enhancements in thermoelectric performance, the maximum figure of merit (<i>zT<sub>max</sub></i>) of 1.12 was obtained in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.01</sub>SbBi and Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi at 573 K, and the <i>zT</i> at 298 K increased by 73% to 0.35 in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi compared to Mn-free Mg<sub>3</sub>La<sub>0.005</sub>SbBi, which is beneficial to room-temperature applications.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"27 2","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384093","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.57
Ok Kyu Park, Seulgi Han, S. Park, Jamil Ur Rahman, Sang-il Kim, Sungmo Choi
Carbon fiber reinforced polymer (CFRP) has been extensively used in civil engineering for applications such as reinforcing and retrofitting various architectural materials. Therefore, understanding the degradation of CFRP under high temperatures is important. This study aims to investigate the thermomechanical and microstructural properties of CFRP plates at elevated temperatures up to 350 oC. The platetype CFRP composites were subjected to temperatures of 50, 100, 150, 200, 250, 300, and 350 oC, and then compared with pristine CFRP samples. X-ray diffraction analysis was conducted to examine the crystal structures of the carbon fibers and epoxy resin matrices in the CFRP. At temperatures higher than 150 oC, the FWHM increased due to the degradation and softening of the resin matrix. Delamination and debonding between the matrix and fibers were observed in samples exposed to temperatures above 200 oC. The maximum tensile strength of the CFRP plates exposed at 350 oC significantly decreased to 0.605 GPa, a reduction of approximately 40% compared to the pristine sample. On the other hand, Young's modulus remained relatively unchanged across the different temperatures. This suggests that the polymer matrix degradation plays a crucial role in the mechanical properties of CFRP, as the matrix layers contribute significantly to the distribution of forces.
{"title":"Thermomechanical Behavior and Microstructure Properties of Carbon Fiber Reinforced Polymer at Elevated Temperatures","authors":"Ok Kyu Park, Seulgi Han, S. Park, Jamil Ur Rahman, Sang-il Kim, Sungmo Choi","doi":"10.3365/kjmm.2024.62.1.57","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.57","url":null,"abstract":"Carbon fiber reinforced polymer (CFRP) has been extensively used in civil engineering for applications such as reinforcing and retrofitting various architectural materials. Therefore, understanding the degradation of CFRP under high temperatures is important. This study aims to investigate the thermomechanical and microstructural properties of CFRP plates at elevated temperatures up to 350 oC. The platetype CFRP composites were subjected to temperatures of 50, 100, 150, 200, 250, 300, and 350 oC, and then compared with pristine CFRP samples. X-ray diffraction analysis was conducted to examine the crystal structures of the carbon fibers and epoxy resin matrices in the CFRP. At temperatures higher than 150 oC, the FWHM increased due to the degradation and softening of the resin matrix. Delamination and debonding between the matrix and fibers were observed in samples exposed to temperatures above 200 oC. The maximum tensile strength of the CFRP plates exposed at 350 oC significantly decreased to 0.605 GPa, a reduction of approximately 40% compared to the pristine sample. On the other hand, Young's modulus remained relatively unchanged across the different temperatures. This suggests that the polymer matrix degradation plays a crucial role in the mechanical properties of CFRP, as the matrix layers contribute significantly to the distribution of forces.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"43 16","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382458","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.22
Kyeong-Min Kim, Yejin Jeong, D.V. Kiran, Suk-Hwan Kwon, Seong-Moon Seo, Eun-Joon Chun
Single-crystal superalloys have been popularly employed in high-temperature parts of gas turbines, such as blades. However, the welds of such alloys are highly susceptible to solidification cracking, which limits their applicability to high-temperature turbine blades. In this study, the effects of characteristics of weld solidification on solidification cracking susceptibilities (solidification brittle temperature range, BTR) were fundamentally investigated for the CMSX-4 single-crystal superalloy. We applied a transverse-Varestraint test procedure for both the linear and oscillated arc welds by changing the weld solidification characteristics, such as the degree of single crystal growth and formation of solidification grain boundaries. The BTR for the CMSX-4 alloy is 336 K for linear welding condition, whereas the values are 434 K and 342 K for 0.6 and 1.5 Hz oscillated welds. Interestingly, the BTR continuously increases with the weld oscillation frequency. By contrast, almost no changes in the weld mushy-zone temperature range are theoretically calculated for each welding condition via the diffusion-controlled Scheil model. The mechanism underlying the increase in BTR under oscillation welding is clarified based on the relationship between the achievement ratio of the weld single crystal growth and fraction of high-angle (>15o) solidification boundaries, which affect severe dendrite coalescence undercooling. The lower fraction of the high-angle weld solidification grain boundaries attributed to the superior achievement ratio of weld single crystal growth, which reduces the dendrite coalescence undercooling and BTR. Consequently, it enhances the solidification crack propagation resistance.
{"title":"Effect of Single Crystal Growth and Solidification Grain Boundaries on Weld Solidification Cracking Behavior of CMSX-4 Superalloy","authors":"Kyeong-Min Kim, Yejin Jeong, D.V. Kiran, Suk-Hwan Kwon, Seong-Moon Seo, Eun-Joon Chun","doi":"10.3365/kjmm.2024.62.1.22","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.22","url":null,"abstract":"Single-crystal superalloys have been popularly employed in high-temperature parts of gas turbines, such as blades. However, the welds of such alloys are highly susceptible to solidification cracking, which limits their applicability to high-temperature turbine blades. In this study, the effects of characteristics of weld solidification on solidification cracking susceptibilities (solidification brittle temperature range, BTR) were fundamentally investigated for the CMSX-4 single-crystal superalloy. We applied a transverse-Varestraint test procedure for both the linear and oscillated arc welds by changing the weld solidification characteristics, such as the degree of single crystal growth and formation of solidification grain boundaries. The BTR for the CMSX-4 alloy is 336 K for linear welding condition, whereas the values are 434 K and 342 K for 0.6 and 1.5 Hz oscillated welds. Interestingly, the BTR continuously increases with the weld oscillation frequency. By contrast, almost no changes in the weld mushy-zone temperature range are theoretically calculated for each welding condition via the diffusion-controlled Scheil model. The mechanism underlying the increase in BTR under oscillation welding is clarified based on the relationship between the achievement ratio of the weld single crystal growth and fraction of high-angle (>15o) solidification boundaries, which affect severe dendrite coalescence undercooling. The lower fraction of the high-angle weld solidification grain boundaries attributed to the superior achievement ratio of weld single crystal growth, which reduces the dendrite coalescence undercooling and BTR. Consequently, it enhances the solidification crack propagation resistance.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"1 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381277","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.12
Byeong Jo Han, Sang Ho Cho, Kang Rok Jeon, Jong-Hyun Lee
To ensure the high-temperature stability of a bondline under next-generation power devices such as SiC semiconductors, a die bonding test was performed by transient liquid-phase (TLP) sinter-bonding using a Sn-coated Cu (Cu@Sn) particle-based preform. Compared to the existing 20 min-bonding result using a 30 μm Cu@Sn particle-based preform, a 5 μm Cu@Sn particle-based preform was used to significantly reduce the bonding time to 5 min, and the optimal levels of the amount of Sn in the Cu@Sn particles, the thicknesses of Sn surface finish layers on the chip and substrate, and compression pressure during the bonding were investigated. The Sn content in the Cu@Sn particles significantly changed the microstructure, including the porosity of the prepared preform. The preform porosity of 0.01% was confirmed after the formation of sufficient Sn shells with an average thickness of about 602 nm at Sn 30 wt%. In addition, in the preform with Sn 30 wt% content, the Sn phase was almost depleted after 3 min after annealing at 250 °C. The Sn finish layer was evaluated in the thickness range of 0.63−4.12 µm, and it was observed that the shear strength of the formed bondline tended to increase with increasing pressure for all Sn layer thicknesses. In particular, when the bonding was carried out at a pressure of 2 MPa using a dummy Cu chip and substrate coated with a 1.53 μm thick Sn layer, the best shear strength value of 36.89 MPa was achieved. In this case, all the Sn phases transformed into intermetallic compound phases of Cu6Sn5 and Cu3Sn, and all the phases formed within the bondline, including Cu, exhibited high melting-point characteristics. Therefore, it was determined that there would be no remelting of the bondline or a drastic decrease in mechanical properties in a high-temperature environment below 300 oC, as initially intended. By increasing the content of the Sn shell up to 30 wt%, it was possible to achieve a nearly full density (porosity: 0.3%) bondline structure, due to the rearrangement behavior of particles, by maintaining liquid Sn for a long time during the bonding process. In conclusion, the optimal Sn finish thickness was determined to be at the level of 1.5 µm, and the optimal pressure was at the level of 2 MPa. The short bonding time of 5 min represents a significant advance in TLP bonding processes, and it is expected to contribute to a substantial improvement in the die bonding of future SiC power devices.
{"title":"Transient Liquid-Phase Sinter-Bonding Characteristics of a 5 um Cu@Sn Particle-Based Preform for High-Speed Die Bonding of Power Devices","authors":"Byeong Jo Han, Sang Ho Cho, Kang Rok Jeon, Jong-Hyun Lee","doi":"10.3365/kjmm.2024.62.1.12","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.12","url":null,"abstract":"To ensure the high-temperature stability of a bondline under next-generation power devices such as SiC semiconductors, a die bonding test was performed by transient liquid-phase (TLP) sinter-bonding using a Sn-coated Cu (Cu@Sn) particle-based preform. Compared to the existing 20 min-bonding result using a 30 μm Cu@Sn particle-based preform, a 5 μm Cu@Sn particle-based preform was used to significantly reduce the bonding time to 5 min, and the optimal levels of the amount of Sn in the Cu@Sn particles, the thicknesses of Sn surface finish layers on the chip and substrate, and compression pressure during the bonding were investigated. The Sn content in the Cu@Sn particles significantly changed the microstructure, including the porosity of the prepared preform. The preform porosity of 0.01% was confirmed after the formation of sufficient Sn shells with an average thickness of about 602 nm at Sn 30 wt%. In addition, in the preform with Sn 30 wt% content, the Sn phase was almost depleted after 3 min after annealing at 250 °C. The Sn finish layer was evaluated in the thickness range of 0.63−4.12 µm, and it was observed that the shear strength of the formed bondline tended to increase with increasing pressure for all Sn layer thicknesses. In particular, when the bonding was carried out at a pressure of 2 MPa using a dummy Cu chip and substrate coated with a 1.53 μm thick Sn layer, the best shear strength value of 36.89 MPa was achieved. In this case, all the Sn phases transformed into intermetallic compound phases of Cu6Sn5 and Cu3Sn, and all the phases formed within the bondline, including Cu, exhibited high melting-point characteristics. Therefore, it was determined that there would be no remelting of the bondline or a drastic decrease in mechanical properties in a high-temperature environment below 300 oC, as initially intended. By increasing the content of the Sn shell up to 30 wt%, it was possible to achieve a nearly full density (porosity: 0.3%) bondline structure, due to the rearrangement behavior of particles, by maintaining liquid Sn for a long time during the bonding process. In conclusion, the optimal Sn finish thickness was determined to be at the level of 1.5 µm, and the optimal pressure was at the level of 2 MPa. The short bonding time of 5 min represents a significant advance in TLP bonding processes, and it is expected to contribute to a substantial improvement in the die bonding of future SiC power devices.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"53 6","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381796","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.1
Hyun-Uk Jun, Jae-Hun Kim, Wonho Kim, Jooyong Cheon, Ki-Man Bae, Eun-Kyung Lee, Yeong-Do Park, Changwook Ji
This study was performed to compare the resistance spot weldability of Al 5052-H32 alloy and Al 6014-T4 alloy, and the cause of the differences in the weldability was investigated. In general, the surface of the aluminum alloy has an oxide film several nm thick, and local heat input is generated at the electrode-sheet interface and the sheet-sheet interface during resistance spot welding. XPS analysis proved that the Al 5052- H32 alloy has a relatively thick magnesium oxide film on the surface and contains a large amount of magnesium solute element. As a result, Al 5052-H32 has a higher resistance, in both the contact resistance of the electrodesheet interface and sheet-sheet interface, compared with the Al 6014-T4 alloy. Therefore, the Al 5052-H32 alloy has a larger nugget diameter at the same welding current as compared to the Al 6014-T4 alloy, but the surface contamination of the electrode is aggravated due to local heat input. The results indicated that a difference in oxide film type and thickness can significantly influence resistance heat generation and electrode cooling effects, as well as produce welds with different weld morphology and microstructure. In addition, the Al 5052-H32 alloy had more pores and shrinkage in the weld than Al 6014-T4 alloy, and longitudinal cracks were observed in the center of the nugget, but had relatively excellent mechanical properties.
本研究对 Al 5052-H32 合金和 Al 6014-T4 合金的电阻点焊性进行了比较，并探究了焊接性差异的原因。一般来说，铝合金表面有一层数 nm 厚的氧化膜，电阻点焊时在电极-薄板界面和薄板-薄板界面会产生局部热输入。XPS 分析证明，Al 5052- H32 合金表面有一层较厚的氧化镁膜，并含有大量的镁溶质元素。因此，与 Al 6014-T4 合金相比，Al 5052-H32 在电极板界面和板-板界面的接触电阻方面都具有更高的电阻。因此，与 Al 6014-T4 合金相比，在相同的焊接电流下，Al 5052-H32 合金的金块直径更大，但由于局部热输入，电极表面污染加剧。结果表明，氧化膜类型和厚度的不同会显著影响电阻发热和电极冷却效果，并产生不同焊接形态和微观结构的焊缝。此外，与 Al 6014-T4 合金相比，Al 5052-H32 合金在焊缝中具有更多的气孔和收缩，并在焊块中心观察到纵向裂纹，但具有相对优异的机械性能。
{"title":"Comparison of Weldability and Microstructure in Resistance Spot Welding of Aluminum 5052-H32 Alloy and Al 6014-T4 Alloy","authors":"Hyun-Uk Jun, Jae-Hun Kim, Wonho Kim, Jooyong Cheon, Ki-Man Bae, Eun-Kyung Lee, Yeong-Do Park, Changwook Ji","doi":"10.3365/kjmm.2024.62.1.1","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.1","url":null,"abstract":"This study was performed to compare the resistance spot weldability of Al 5052-H32 alloy and Al 6014-T4 alloy, and the cause of the differences in the weldability was investigated. In general, the surface of the aluminum alloy has an oxide film several nm thick, and local heat input is generated at the electrode-sheet interface and the sheet-sheet interface during resistance spot welding. XPS analysis proved that the Al 5052- H32 alloy has a relatively thick magnesium oxide film on the surface and contains a large amount of magnesium solute element. As a result, Al 5052-H32 has a higher resistance, in both the contact resistance of the electrodesheet interface and sheet-sheet interface, compared with the Al 6014-T4 alloy. Therefore, the Al 5052-H32 alloy has a larger nugget diameter at the same welding current as compared to the Al 6014-T4 alloy, but the surface contamination of the electrode is aggravated due to local heat input. The results indicated that a difference in oxide film type and thickness can significantly influence resistance heat generation and electrode cooling effects, as well as produce welds with different weld morphology and microstructure. In addition, the Al 5052-H32 alloy had more pores and shrinkage in the weld than Al 6014-T4 alloy, and longitudinal cracks were observed in the center of the nugget, but had relatively excellent mechanical properties.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"43 22","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382434","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.32
Jeonyoung Song, Jiho Gu, Won Hui Jo, Cho Hyeon Lee, Jae Bok Seol, Youngwha Ma
Here, we investigated the influence of δ-precipitate (orthorhombic D0a Ni3Nb-ordered phase) on the room- and high-temperature tensile properties in wrought nickel-based Inconel 625 superalloys subjected to solution and aging heat treatment. Typically, solution heat-treatment temperatures in these alloys affect the solid-state precipitation of δ-phase, which governs high-temperature tensile properties. While precipitation of fine D0a δ-phase is known to have beneficial effects on the mechanical properties owing to the retardation of grain coarsening, Widmanstätten δ precipitation plays a deleterious influence on the fracture toughness, tensile ductility, and fatigue resistance. Therefore, to enhance the mechanical properties of this alloy series, it is key to generate a high number density of fine D0a δ precipitate by adjusting solid solution treatment temperatures. In this study, solution heat treatments were conducted above and below δ-phase solvus temperatures. By applying solution heat treatment at 900°C and 970°C, this alloy was confirmed to have a Widmanstätten δ phase and is composed similarly to the annealed microstructure. This Widmanstätten δ precipitate was densely distributed at both intergranular and intragranular grains. On the other hand, when solution treatment was applied at 1040 and 1100°C, more coarse particles (approximately 30 μm) with a significant reduction of Widmanstätten type δ phase were obtained. We found that grain size and Widmanstätten δ-phases have an important role in the high-temperature tensile properties of Inconel 625 superalloy series.
{"title":"Effect of Heat Treatment Temperature on Microstructure, Tensile Properties and δ-Precipitate Phase in Ni-based Superalloy","authors":"Jeonyoung Song, Jiho Gu, Won Hui Jo, Cho Hyeon Lee, Jae Bok Seol, Youngwha Ma","doi":"10.3365/kjmm.2024.62.1.32","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.32","url":null,"abstract":"Here, we investigated the influence of δ-precipitate (orthorhombic D0a Ni3Nb-ordered phase) on the room- and high-temperature tensile properties in wrought nickel-based Inconel 625 superalloys subjected to solution and aging heat treatment. Typically, solution heat-treatment temperatures in these alloys affect the solid-state precipitation of δ-phase, which governs high-temperature tensile properties. While precipitation of fine D0a δ-phase is known to have beneficial effects on the mechanical properties owing to the retardation of grain coarsening, Widmanstätten δ precipitation plays a deleterious influence on the fracture toughness, tensile ductility, and fatigue resistance. Therefore, to enhance the mechanical properties of this alloy series, it is key to generate a high number density of fine D0a δ precipitate by adjusting solid solution treatment temperatures. In this study, solution heat treatments were conducted above and below δ-phase solvus temperatures. By applying solution heat treatment at 900°C and 970°C, this alloy was confirmed to have a Widmanstätten δ phase and is composed similarly to the annealed microstructure. This Widmanstätten δ precipitate was densely distributed at both intergranular and intragranular grains. On the other hand, when solution treatment was applied at 1040 and 1100°C, more coarse particles (approximately 30 μm) with a significant reduction of Widmanstätten type δ phase were obtained. We found that grain size and Widmanstätten δ-phases have an important role in the high-temperature tensile properties of Inconel 625 superalloy series.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"113 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383441","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.65
Jaeho Choi
To select materials suitable for products, material perception, which is the feeling consumers have about materials, has been studied. Material perception data were obtained through surveys using digital logic for bipolar adjective pairs. The material perception data were analyzed through unsupervised learning of data mining. Prior to data analysis, to increase the reliability of the data, the homogeneity of the data between surveys was tested using clustering analysis, correlation analysis and chi-squared test. After checking the homogeneity of the data between surveys, the data were merged. The merged material perception data were analyzed using relative frequencies, hierarchical clustering, and association rules. The relative frequencies obtained from survey participants' selections were used to determine the prevailing perceptions of each material and as basic data for other analyses. In the hierarchical clustering analysis, hierarchy was identified using distances within clusters and distances between clusters. Through association rule analysis, the consumer's simultaneous perceptions of the material can be known, so not only the individual characteristics of the material but also the relational characteristics can be considered when selecting materials based on consumer's perception. The analyzed characteristics were designed into a material perception map, and this material perception map will be a powerful tool to help product designers make better choices that match consumers' perception and experience when selecting materials.
{"title":"Material Selection: Material Perception Data Analysis Using Clustering Analysis and Association Rule Analysis of Data Mining","authors":"Jaeho Choi","doi":"10.3365/kjmm.2024.62.1.65","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.65","url":null,"abstract":"To select materials suitable for products, material perception, which is the feeling consumers have about materials, has been studied. Material perception data were obtained through surveys using digital logic for bipolar adjective pairs. The material perception data were analyzed through unsupervised learning of data mining. Prior to data analysis, to increase the reliability of the data, the homogeneity of the data between surveys was tested using clustering analysis, correlation analysis and chi-squared test. After checking the homogeneity of the data between surveys, the data were merged. The merged material perception data were analyzed using relative frequencies, hierarchical clustering, and association rules. The relative frequencies obtained from survey participants' selections were used to determine the prevailing perceptions of each material and as basic data for other analyses. In the hierarchical clustering analysis, hierarchy was identified using distances within clusters and distances between clusters. Through association rule analysis, the consumer's simultaneous perceptions of the material can be known, so not only the individual characteristics of the material but also the relational characteristics can be considered when selecting materials based on consumer's perception. The analyzed characteristics were designed into a material perception map, and this material perception map will be a powerful tool to help product designers make better choices that match consumers' perception and experience when selecting materials.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"6 7","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381337","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.51
Yoon Hwan Moon, Jong Geun Park, Yong Jun Oh
Immiscible Au-Ni alloy thin films undergo phase separation and dewetting because of thermodynamic and morphological instability at elevated temperatures below the miscibility gap. We report the formation and assembly of bimetallic nanoparticles (BNPs) on topographic Si templates. An ordered array of inverted pyramidal pits were produced via solid-state and liquid-state dewetting of a 12-nm-thick Au-Ni thin film by respectively using thermal annealing and laser irradiation. Upon direct thermal annealing at 600 and 800 oC, the thin film on the templates self-assembled into an ordered array of BNPs composed of Au-rich and Ni-rich sub-clusters in pits. But the relative proportions of the two sub-clusters varied with annealing temperature due to the additional formation of smaller Ni-rich NPs that were scattered around the BNPs. Laser irradiation of the film, in contrast, formed an ordered array of fully mixed alloy NPs on the template and left no other residues on the surface. Subsequent thermal annealing induced the elements within the NPs to segregate, resulting in Au-rich and Ni-rich sub-clusters. In brief, the combination of solid-state and liquidstate dewetting processes on a topographic template not only enabled the 2-dimesional self-assembly of BNPs but also allowed control of the mixing of alloying elements within the BNPs. These results offer insights into the tailored fabrication of BNPs, which have potential applications in bio-functional catalysts, and plasmonic and chemical sensors.
{"title":"Control of Self-Assembly and Elemental Mixing of AuNi Bimetallic Nanoparticles via Solid-State and Liquid-State Dewetting of Metal Thin Films","authors":"Yoon Hwan Moon, Jong Geun Park, Yong Jun Oh","doi":"10.3365/kjmm.2024.62.1.51","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.51","url":null,"abstract":"Immiscible Au-Ni alloy thin films undergo phase separation and dewetting because of thermodynamic and morphological instability at elevated temperatures below the miscibility gap. We report the formation and assembly of bimetallic nanoparticles (BNPs) on topographic Si templates. An ordered array of inverted pyramidal pits were produced via solid-state and liquid-state dewetting of a 12-nm-thick Au-Ni thin film by respectively using thermal annealing and laser irradiation. Upon direct thermal annealing at 600 and 800 oC, the thin film on the templates self-assembled into an ordered array of BNPs composed of Au-rich and Ni-rich sub-clusters in pits. But the relative proportions of the two sub-clusters varied with annealing temperature due to the additional formation of smaller Ni-rich NPs that were scattered around the BNPs. Laser irradiation of the film, in contrast, formed an ordered array of fully mixed alloy NPs on the template and left no other residues on the surface. Subsequent thermal annealing induced the elements within the NPs to segregate, resulting in Au-rich and Ni-rich sub-clusters. In brief, the combination of solid-state and liquidstate dewetting processes on a topographic template not only enabled the 2-dimesional self-assembly of BNPs but also allowed control of the mixing of alloying elements within the BNPs. These results offer insights into the tailored fabrication of BNPs, which have potential applications in bio-functional catalysts, and plasmonic and chemical sensors.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"28 15","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382601","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 : 2023-12-05DOI: 10.3365/kjmm.2023.61.12.909
Yong-min Jeon, S. Ryu, Min Jun Kim, Seong Eui Lee
In this study, a composition-gradient thin film was applied for the formation of intermediate layer of Ti seed layer for an stable electrode stack Ag metal layer. Various composition of Ag-Ti hetero metal layer were simultaneously deposited by using the sputtering process with Ti and Ag target, respectively. An intermediate layer was deposited at a gradient composition ratio such as 5:5 and 7:3. In addition, the optimal deposition conditions were evaluated by confirming the plasma codition such as density of plasma ion, plasma potential with the Langmuir Probe (Hiden ESPion). Flow rate, power, and composition ratio were optimized as variables for thin film structures of compositional gradient thin films. In addition, thin film samples were heat treated at 200 ℃, 300 ℃, and 400 ℃ to relieve the residual stress between the interface of laminated thin films. Under these conditions, a composition-gradient thin film was evaluated by XRD (X-Ray Diffraction, SmartLab Rigaku 9kW), SEM (Scanning Electron Microscope, Nova NanoSEM 450), and EDS (energy dispersive X-ray spectroscopy). As a result of the measurement, it was confirmed that interfacial diffusion occurred due to the composition gradient thin film. When the composition gradient intermediate layer was applied to thin film stack, the residual stress increased more than that of single thin film stack. However, after stress relief annealing, residual stress was dramatically decreased compared to single stack.
{"title":"Study on Ag-Ti Thin Film Structure with Compositional Gradient Fabricated by Sputtering Process","authors":"Yong-min Jeon, S. Ryu, Min Jun Kim, Seong Eui Lee","doi":"10.3365/kjmm.2023.61.12.909","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.12.909","url":null,"abstract":"In this study, a composition-gradient thin film was applied for the formation of intermediate layer of Ti seed layer for an stable electrode stack Ag metal layer. Various composition of Ag-Ti hetero metal layer were simultaneously deposited by using the sputtering process with Ti and Ag target, respectively. An intermediate layer was deposited at a gradient composition ratio such as 5:5 and 7:3. In addition, the optimal deposition conditions were evaluated by confirming the plasma codition such as density of plasma ion, plasma potential with the Langmuir Probe (Hiden ESPion). Flow rate, power, and composition ratio were optimized as variables for thin film structures of compositional gradient thin films. In addition, thin film samples were heat treated at 200 ℃, 300 ℃, and 400 ℃ to relieve the residual stress between the interface of laminated thin films. Under these conditions, a composition-gradient thin film was evaluated by XRD (X-Ray Diffraction, SmartLab Rigaku 9kW), SEM (Scanning Electron Microscope, Nova NanoSEM 450), and EDS (energy dispersive X-ray spectroscopy). As a result of the measurement, it was confirmed that interfacial diffusion occurred due to the composition gradient thin film. When the composition gradient intermediate layer was applied to thin film stack, the residual stress increased more than that of single thin film stack. However, after stress relief annealing, residual stress was dramatically decreased compared to single stack.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"13 8","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138598577","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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