Pub Date : 2023-10-05DOI: 10.3365/kjmm.2023.61.10.785
Sung-Jae Joo, Ji-Hee Son, JeongIn Jang, Bong-Seo Kim, Bok-Ki Min
Mg3Sb2-based materials are promising candidates to replace n-type Bi2Te3 for cooling and power generation at low temperatures. Generally, the thermoelectric performance of a material is sensitively affected by synthesis process parameters, and among them, sintering temperature (Ts) is a critical one. In this study, n-type Mg3SbBi0.99Te0.01 polycrystalline samples were fabricated by mechanical alloying and spark plasma sintering (SPS), and the effects of varying Ts (923 – 1073 K) on the thermoelectric properties were investigated. Sintering Mg3SbBi0.99Te0.01 at an elevated temperature of 1073 K resulted in a notable increase in electrical conductivity at low temperatures below about 423 K. This is ascribed to a sharp reduction in carrier scattering by ionized impurities. For the same reason, the carrier mobility increased sharply at a Ts of 1073 K, which is a critical temperature for sintering in this study. Moreover, the Seebeck coefficient increased and thermal conductivity decreased simultaneously by raising Ts, resulting in the maximum power factor (PFmax) of 2.2 × 10-3 W m-1K-2 and the maximum dimensionless figure of merit (zTmax) of 1.20 in the sample sintered at 1073 K. Therefore, when Ts was raised from 923 K to 1073 K, the PFmax and zTmax increased by 29 % and 64 %, respectively. This improvement in performance is attributed to the annihilation of defects generated during the mechanical alloying process, which was confirmed by microstructure analysis by transmission electron microscopy (TEM).
{"title":"Optimization of Sintering Temperature for the Synthesis of n-type Mg<sub>3</sub>SbBi<sub>0.99</sub>Te<sub>0.01</sub> Thermoelectric Materials","authors":"Sung-Jae Joo, Ji-Hee Son, JeongIn Jang, Bong-Seo Kim, Bok-Ki Min","doi":"10.3365/kjmm.2023.61.10.785","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.10.785","url":null,"abstract":"Mg3Sb2-based materials are promising candidates to replace n-type Bi2Te3 for cooling and power generation at low temperatures. Generally, the thermoelectric performance of a material is sensitively affected by synthesis process parameters, and among them, sintering temperature (<i>Ts</i>) is a critical one. In this study, n-type Mg3SbBi0.99Te0.01 polycrystalline samples were fabricated by mechanical alloying and spark plasma sintering (SPS), and the effects of varying <i>Ts</i> (923 – 1073 K) on the thermoelectric properties were investigated. Sintering Mg3SbBi0.99Te0.01 at an elevated temperature of 1073 K resulted in a notable increase in electrical conductivity at low temperatures below about 423 K. This is ascribed to a sharp reduction in carrier scattering by ionized impurities. For the same reason, the carrier mobility increased sharply at a <i>Ts</i> of 1073 K, which is a critical temperature for sintering in this study. Moreover, the Seebeck coefficient increased and thermal conductivity decreased simultaneously by raising <i>Ts</i>, resulting in the maximum power factor (<i>PFmax</i>) of 2.2 × 10-3 W m-1K-2 and the maximum dimensionless figure of merit (<i>zTmax</i>) of 1.20 in the sample sintered at 1073 K. Therefore, when <i>Ts</i> was raised from 923 K to 1073 K, the <i>PFmax</i> and <i>zTmax</i> increased by 29 % and 64 %, respectively. This improvement in performance is attributed to the annihilation of defects generated during the mechanical alloying process, which was confirmed by microstructure analysis by transmission electron microscopy (TEM).","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"300 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134947445","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 : 2023-10-05DOI: 10.3365/kjmm.2023.61.10.721
Jong-Kwan Lee, Byeong-Joo Lee, Eon-Sik Lee
Recently, strengthened environmental regulations have required the downsizing of gasoline engines, and as a result, demand for gasoline turbochargers has rapidly increased. The vane of a turbocharger controls the flow of gases toward the turbine, and it is manufactured by powder metallurgy due to its complex shape. Gasoline engines have a high exhaust gas temperature (~1000oC), and thus, Alloy1.4957 (GX15CrNiCo21-20-20) containing large amounts of Cr, Ni, and Co is used. In this study, Alloy1.4957 powders were sintered by hot isostatic pressing (HIP), and then homogenized and thermally exposed to exhaust gas temperatures. Then, a microstructural analysis was conducted to observe the changes that occurred for each process. M6X carbonitride containing Si, called Cr3Ni2SiX, was observed to be the main precipitate phase in this alloy. In general, it is known that Cr3Ni2SiX is only rarely observed in heat-resistant steel. However, in Alloy1.4957, a large amount of Cr3Ni2SiX was precipitated or dissolved depending on the process, and this is probably due to the high Si and N content of Alloy1.4957. In addition to Cr3Ni2SiX, Cr23C6 and NbX were observed. Cr23C6 was dissolved during the homogenization process, but NbX, which has high thermal stability, retained a fine size during the homogenization process and provided a nucleation site for Cr3Ni2SiX during thermal exposure.
{"title":"Analysis of Precipitation Phase of Alloy1.4957 Heat-Resistant Steel for Gasoline Turbocharger","authors":"Jong-Kwan Lee, Byeong-Joo Lee, Eon-Sik Lee","doi":"10.3365/kjmm.2023.61.10.721","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.10.721","url":null,"abstract":"Recently, strengthened environmental regulations have required the downsizing of gasoline engines, and as a result, demand for gasoline turbochargers has rapidly increased. The vane of a turbocharger controls the flow of gases toward the turbine, and it is manufactured by powder metallurgy due to its complex shape. Gasoline engines have a high exhaust gas temperature (~1000oC), and thus, Alloy1.4957 (GX15CrNiCo21-20-20) containing large amounts of Cr, Ni, and Co is used. In this study, Alloy1.4957 powders were sintered by hot isostatic pressing (HIP), and then homogenized and thermally exposed to exhaust gas temperatures. Then, a microstructural analysis was conducted to observe the changes that occurred for each process. M6X carbonitride containing Si, called Cr3Ni2SiX, was observed to be the main precipitate phase in this alloy. In general, it is known that Cr3Ni2SiX is only rarely observed in heat-resistant steel. However, in Alloy1.4957, a large amount of Cr3Ni2SiX was precipitated or dissolved depending on the process, and this is probably due to the high Si and N content of Alloy1.4957. In addition to Cr3Ni2SiX, Cr23C6 and NbX were observed. Cr23C6 was dissolved during the homogenization process, but NbX, which has high thermal stability, retained a fine size during the homogenization process and provided a nucleation site for Cr3Ni2SiX during thermal exposure.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134947449","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 : 2023-10-05DOI: 10.3365/kjmm.2023.61.10.741
In Kyeong Jin, Dong-Geun Lee
The addition of expensive elements to β titanium alloys, which are widely used in the aerospace and automobile industries, causes their price to increase. Low-cost, high-strength alloy (Ti-12.1Mo-1.0Fe) was designed in this study and the compressive behaviors of this alloy were evaluated for application to automobile parts, etc. As a result of ambient compression in the quasi-static and dynamic strain rate range (1×10-4/s~6×103/s), twinning occurred at all strain rates, and in particular, adiabatic shear bands were observed, which cause cracks and fractures under dynamic strain rate conditions. In addition, when the relationship between these bands and mechanical characteristics was evaluated, an increase of compression strength and Vickers hardness was confirmed to occur, due to the strain rate hardening effect under compression loading. Some twins were formed by the deformation behavior during compression plastic deformation of the Ti-12.1Mo-1.0Fe alloy, and it exhibited excellent compression strength characteristics, showing a very high strain rate hardening effect at a high strain rate.
{"title":"Effect of Strain Rate on Deformation Behaviors of Ti-12.1Mo -1Fe Metastable Beta Alloy","authors":"In Kyeong Jin, Dong-Geun Lee","doi":"10.3365/kjmm.2023.61.10.741","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.10.741","url":null,"abstract":"The addition of expensive elements to β titanium alloys, which are widely used in the aerospace and automobile industries, causes their price to increase. Low-cost, high-strength alloy (Ti-12.1Mo-1.0Fe) was designed in this study and the compressive behaviors of this alloy were evaluated for application to automobile parts, etc. As a result of ambient compression in the quasi-static and dynamic strain rate range (1×10-4/s~6×103/s), twinning occurred at all strain rates, and in particular, adiabatic shear bands were observed, which cause cracks and fractures under dynamic strain rate conditions. In addition, when the relationship between these bands and mechanical characteristics was evaluated, an increase of compression strength and Vickers hardness was confirmed to occur, due to the strain rate hardening effect under compression loading. Some twins were formed by the deformation behavior during compression plastic deformation of the Ti-12.1Mo-1.0Fe alloy, and it exhibited excellent compression strength characteristics, showing a very high strain rate hardening effect at a high strain rate.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134947452","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 : 2023-10-05DOI: 10.3365/kjmm.2023.61.10.748
Ji Hwan Kim, Jong-Hyun Lee
To suppress Ag dewetting from around 200 oC in Ag-coated Cu (Cu@Ag) flakes, Ag and Ni-coated Cu (Cu@Ni@Ag) flakes were fabricated by successive Ni and Ag electroless plating. The Ni bath type was an important consideration to induce differences in the Ag dewetting and resultant Cu oxidation. An acid Ni bath contained succinic acid as a complexing agent and sodium hypophosphite as a reductant, and an alkaline Ni bath contained sodium citrate as a complexing agent and sodium hydroxide as a pH adjuster as well as sodium hypophosphite. A hydrazine-based Ni bath contained sodium citrate, sodium hydroxide, and hydrazine hydrate as a reductant. The acid Ni bath provided amorphous coatings with a P content of approximately 10 wt%. The Cu@Ni@Ag flakes started the Ag dewetting and Cu oxidation at 350 oC, together with the formation of the Ni3P phase. Meanwhile, the alkaline Ni bath created Ni-5 wt% P amorphous Ni coatings, which transformed into a crystalline phase after heating at 350 oC. The Ag shell was dewetted at 450 oC, which caused oxidation of the flakes. Finally, the hydrazine-based Ni bath formed crystalline coatings without P, which induced rapid mixing with the core Cu. The Ag shells on the mixed Cu-Ni alloy showed repressed dewetting behavior, and thus the dewetting and oxidation temperature was the highest, such as 500 oC. Enhancing the high oxidation resistance at approximately 300 oC will enable the use of Cu@Ni@Ag flakes as a low-cost filler material in conductive pastes, especially for long-time or high-temperature curing.
{"title":"The Effect of Ni Interlayer Formation Plating Bath on the Suppression of Oxidation of Ag-Coated Cu Flakes","authors":"Ji Hwan Kim, Jong-Hyun Lee","doi":"10.3365/kjmm.2023.61.10.748","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.10.748","url":null,"abstract":"To suppress Ag dewetting from around 200 oC in Ag-coated Cu (Cu@Ag) flakes, Ag and Ni-coated Cu (Cu@Ni@Ag) flakes were fabricated by successive Ni and Ag electroless plating. The Ni bath type was an important consideration to induce differences in the Ag dewetting and resultant Cu oxidation. An acid Ni bath contained succinic acid as a complexing agent and sodium hypophosphite as a reductant, and an alkaline Ni bath contained sodium citrate as a complexing agent and sodium hydroxide as a pH adjuster as well as sodium hypophosphite. A hydrazine-based Ni bath contained sodium citrate, sodium hydroxide, and hydrazine hydrate as a reductant. The acid Ni bath provided amorphous coatings with a P content of approximately 10 wt%. The Cu@Ni@Ag flakes started the Ag dewetting and Cu oxidation at 350 oC, together with the formation of the Ni3P phase. Meanwhile, the alkaline Ni bath created Ni-5 wt% P amorphous Ni coatings, which transformed into a crystalline phase after heating at 350 oC. The Ag shell was dewetted at 450 oC, which caused oxidation of the flakes. Finally, the hydrazine-based Ni bath formed crystalline coatings without P, which induced rapid mixing with the core Cu. The Ag shells on the mixed Cu-Ni alloy showed repressed dewetting behavior, and thus the dewetting and oxidation temperature was the highest, such as 500 oC. Enhancing the high oxidation resistance at approximately 300 oC will enable the use of Cu@Ni@Ag flakes as a low-cost filler material in conductive pastes, especially for long-time or high-temperature curing.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134947451","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 : 2023-10-05DOI: 10.3365/kjmm.2023.61.10.800
Se Woong Lee, Seulgi Han, Okmin Park, Sang-il Kim, Sungmo Choi
Glass fiber-reinforced polymers (GFRPs) have attracted significant attention as structural materials because of their high fatigue resistance, corrosion resistance, strength, and stiffness. This study examined the effect of elevated temperatures (150, 250, 350, and 450oC) on the microstructural and mechanical properties of GFRP plates. The number of bubbles increased as the firing temperature increased, and the bubbles burst at 250oC or higher, forming pores on the surface. A tensile test was conducted, and the maximum stress of the GFRP plates fired at 150, 250, and 350oC was reduced from 54.2 to 52.2, 40.3, and 24.0 MPa, respectively, compared to that of the unfired GFRP plate. Meanwhile, the elastic moduli of the GFRP plates fired at 150, 250, and 350oC reduced from 19.1 to 18.3, 16.1, and 12.1 GPa, respectively, compared to that of the unfired GFRP plate. This reduction in the mechanical properties of the GFRP plates at elevated temperatures was attributed to the degradation of the mechanical properties of the resin matrix due to glass transition and decomposition, debonding, and an increase in surface defects. The maximum strain decreased gradually with increasing firing temperature, suggesting that the brittleness of the GFRP plates increased at elevated temperatures.
{"title":"Influence of Elevated Temperature on the Mechanical and Microstructural Properties of Glass Fiber-Reinforced Polymers","authors":"Se Woong Lee, Seulgi Han, Okmin Park, Sang-il Kim, Sungmo Choi","doi":"10.3365/kjmm.2023.61.10.800","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.10.800","url":null,"abstract":"Glass fiber-reinforced polymers (GFRPs) have attracted significant attention as structural materials because of their high fatigue resistance, corrosion resistance, strength, and stiffness. This study examined the effect of elevated temperatures (150, 250, 350, and 450oC) on the microstructural and mechanical properties of GFRP plates. The number of bubbles increased as the firing temperature increased, and the bubbles burst at 250oC or higher, forming pores on the surface. A tensile test was conducted, and the maximum stress of the GFRP plates fired at 150, 250, and 350oC was reduced from 54.2 to 52.2, 40.3, and 24.0 MPa, respectively, compared to that of the unfired GFRP plate. Meanwhile, the elastic moduli of the GFRP plates fired at 150, 250, and 350oC reduced from 19.1 to 18.3, 16.1, and 12.1 GPa, respectively, compared to that of the unfired GFRP plate. This reduction in the mechanical properties of the GFRP plates at elevated temperatures was attributed to the degradation of the mechanical properties of the resin matrix due to glass transition and decomposition, debonding, and an increase in surface defects. The maximum strain decreased gradually with increasing firing temperature, suggesting that the brittleness of the GFRP plates increased at elevated temperatures.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134947447","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.652
Seong-Hee Lee
A cold roll-bonding (CRB) process is applied to study the effects of stacking number on the microstructure and mechanical properties of roll-bonded and age-treated Al sheets. Commercial AA1050 and AA6061 sheets with a thickness of 2 mm were stacked alternately on each other to two and four layers, and roll-bonded by multi-pass cold rolling. The roll-bonded Al sheets were then subjected to natural aging (T4) and artificial aging (T6) treatments. The as roll-bonded Al sheets showed a typical deformation structure, where the grains are elongated in the rolling direction regardless of the stacking number. However, after the T4 and T6 aging treatments, the Al sheets had a recrystallization structure consisting of coarse grains in both the AA5052 and AA6061 regions with different grain sizes in each. In addition, the sheets showed an inhomogeneous hardness distribution in the thickness direction, with higher hardness in AA6061 than in AA1050 after the T4 and T6 age treatments. The tensile strength of the T6-treated specimen was higher than that of the T4-treated one for both the 2 and 4-layer CRBs. In addition, both the tensile strength and elongation of the specimens processed by the 4-layer stack CRB were higher than those of the 2-layer stack CRB for all experimental conditions.
{"title":"Effects of Stacking Number on Microstructure and Mechanical Properties for Cold Roll Bonding Process of Dissimilar Aluminum Alloy Sheets","authors":"Seong-Hee Lee","doi":"10.3365/kjmm.2023.61.9.652","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.652","url":null,"abstract":"A cold roll-bonding (CRB) process is applied to study the effects of stacking number on the microstructure and mechanical properties of roll-bonded and age-treated Al sheets. Commercial AA1050 and AA6061 sheets with a thickness of 2 mm were stacked alternately on each other to two and four layers, and roll-bonded by multi-pass cold rolling. The roll-bonded Al sheets were then subjected to natural aging (T4) and artificial aging (T6) treatments. The as roll-bonded Al sheets showed a typical deformation structure, where the grains are elongated in the rolling direction regardless of the stacking number. However, after the T4 and T6 aging treatments, the Al sheets had a recrystallization structure consisting of coarse grains in both the AA5052 and AA6061 regions with different grain sizes in each. In addition, the sheets showed an inhomogeneous hardness distribution in the thickness direction, with higher hardness in AA6061 than in AA1050 after the T4 and T6 age treatments. The tensile strength of the T6-treated specimen was higher than that of the T4-treated one for both the 2 and 4-layer CRBs. In addition, both the tensile strength and elongation of the specimens processed by the 4-layer stack CRB were higher than those of the 2-layer stack CRB for all experimental conditions.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42527679","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.704
Ju-Hyun Park, Myoung-Nam Kim, Se-Rin Park, Sun-Myung Lee
Azurite is an inorganic pigment commonly used in traditional painting arts and even today. This pigment has two types: natural azurite and synthetic artificial azurite, called blue verditer or blue bice. Because they have the same structure and similar appearance they are difficult to distinguish. The purpose of this study is to compare these two types pigments, focusing on material properties and accelerated weathering behavior. Natural azurite consist of copper carbonate and mineral compounds like quartz, kaolinite. On the other hand, artificial azurites are synthesized using azurite and calcite. As a result of thermal analysis, unlike natural azurite, the calcite in artificial azurite resulted in weight loss at three temperatures, at approximately 350 ℃, 650 ℃, and 840 ℃. According to the microscope analysis results, natural azurites have clearly blue angular particles with sharp edges, produced by crushing. Artificial azurite showed spherules and aggregates with tiny rounded or fibrous particles. After accelerated weathering tests, the natural azurites had no change in color, particle shape or original components, but the artificial azurites noticeably changed color and shape. The color changes of artificial azurites occurred due to the growth of calcite crystallite, a slight new product formation, and change in particle shape. Even though natural azurites are more expensive pigments, they provide superior color durability and particle shape stability compared to artificial azurites.
{"title":"Properties and Lightfastness of Natural and Artificial Azurite Used As Painting Pigment","authors":"Ju-Hyun Park, Myoung-Nam Kim, Se-Rin Park, Sun-Myung Lee","doi":"10.3365/kjmm.2023.61.9.704","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.704","url":null,"abstract":"Azurite is an inorganic pigment commonly used in traditional painting arts and even today. This pigment has two types: natural azurite and synthetic artificial azurite, called blue verditer or blue bice. Because they have the same structure and similar appearance they are difficult to distinguish. The purpose of this study is to compare these two types pigments, focusing on material properties and accelerated weathering behavior. Natural azurite consist of copper carbonate and mineral compounds like quartz, kaolinite. On the other hand, artificial azurites are synthesized using azurite and calcite. As a result of thermal analysis, unlike natural azurite, the calcite in artificial azurite resulted in weight loss at three temperatures, at approximately 350 ℃, 650 ℃, and 840 ℃. According to the microscope analysis results, natural azurites have clearly blue angular particles with sharp edges, produced by crushing. Artificial azurite showed spherules and aggregates with tiny rounded or fibrous particles. After accelerated weathering tests, the natural azurites had no change in color, particle shape or original components, but the artificial azurites noticeably changed color and shape. The color changes of artificial azurites occurred due to the growth of calcite crystallite, a slight new product formation, and change in particle shape. Even though natural azurites are more expensive pigments, they provide superior color durability and particle shape stability compared to artificial azurites.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49247069","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.714
Tae Jin Kang, P. Narayana, S. Choi, Jae Hyuk Kim, J. Hong, Taekyung Lee
Titanium alloys are used in many fields including military, aerospace, and biomedical because of their excellent specific strength, corrosion resistance, and biocompatibility. Recently, much research has been focused on addressing the disadvantages of conventional manufacturing methods, including reducing material and energy waste when manufacturing titanium alloy parts by additive manufacturing methods. However, due to rapid cooling, during the additive manufacturing process the material develops acicular and lamellar microstructures, and despite high strength, those features are detrimental to ductility and toughness, as compared with conventionally manufactured alloys. As a result, numerous studies have sought to obtain an equiaxed microstructure through heat treatment. However, the developed heat treatment processes are quite complex, and involve several heat treatment cycles, making such processes economically unfavorable. To overcome these limitations we suggest a different approach to obtaining an equiaxed structure in 3D-printed titanium alloy, by controlling the oxygen level. The present study analyzed the globularization behavior of Direct Energy Deposited (DED) Ti-6Al-4V alloy as a function of oxygen content and a simple heat treatment. The microstructure was globularized through oxygen level control and furnace cooling to compensate the disadvantages in the mechanical properties of additive manufactured alloys.
{"title":"Effect of Oxygen Content on Microstructure and Mechanical Properties of Additive Manufactured Ti-6Al-4V","authors":"Tae Jin Kang, P. Narayana, S. Choi, Jae Hyuk Kim, J. Hong, Taekyung Lee","doi":"10.3365/kjmm.2023.61.9.714","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.714","url":null,"abstract":"Titanium alloys are used in many fields including military, aerospace, and biomedical because of their excellent specific strength, corrosion resistance, and biocompatibility. Recently, much research has been focused on addressing the disadvantages of conventional manufacturing methods, including reducing material and energy waste when manufacturing titanium alloy parts by additive manufacturing methods. However, due to rapid cooling, during the additive manufacturing process the material develops acicular and lamellar microstructures, and despite high strength, those features are detrimental to ductility and toughness, as compared with conventionally manufactured alloys. As a result, numerous studies have sought to obtain an equiaxed microstructure through heat treatment. However, the developed heat treatment processes are quite complex, and involve several heat treatment cycles, making such processes economically unfavorable. To overcome these limitations we suggest a different approach to obtaining an equiaxed structure in 3D-printed titanium alloy, by controlling the oxygen level. The present study analyzed the globularization behavior of Direct Energy Deposited (DED) Ti-6Al-4V alloy as a function of oxygen content and a simple heat treatment. The microstructure was globularized through oxygen level control and furnace cooling to compensate the disadvantages in the mechanical properties of additive manufactured alloys.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43497069","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.679
Byeong Jo Han, Y. Kim, Jong-Hyun Lee
With the increasing numbers of electric vehicles and the prevalence of high heat generating devices, recent studies have attempted to address the limitations of conventional solder materials, including their low durability at temperatures exceeding 200 ℃, insufficient mechanical properties in a joint, and low thermal conductivity. Transient liquid-phase (TLP) partial bonding using solders or Sn, and sinter bonding using Ag particles, are alternative bonding methods which involve a modification or change of the material. Advanced alternatives can significantly reduce bonding time or material cost. Various additional studies have investigated various core-cell particles that can be used to form an all-metallic bondline. This review summarizes reports of bonding studies using different core-cell particles. The particles were not only applied as a form of paste but also preform. In the TLP bonding using X(Cu, Ag, Ni)@Sn particles, the degree of voids generated in the formed bondline was dependent on the type of intermetallic compound formed. The preforms consisting of X@Sn particles provided relatively uniform microstructure and void distribution, compared to the pastes containing identical X@Sn particles, resulting in better long-term mechanical reliability. The addition of Zn@Sn particles contributed to the more practical control of microstructure and mechanical properties in the joint formed by pure Sn and Sn-58Bi solder alloys. Cu@Ag particles can be considered a promising low-cost material for compression-assisted sinter bonding, replacing pure Ag particles. The application of core-cell particles is expected to improve the processes used for forming metallic bondlines.
{"title":"A Review of Recent Research Trends of Forming of Metallic Bondlines Using Core-Shell Particles and Bonding Properties According to Particle Type","authors":"Byeong Jo Han, Y. Kim, Jong-Hyun Lee","doi":"10.3365/kjmm.2023.61.9.679","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.679","url":null,"abstract":"With the increasing numbers of electric vehicles and the prevalence of high heat generating devices, recent studies have attempted to address the limitations of conventional solder materials, including their low durability at temperatures exceeding 200 ℃, insufficient mechanical properties in a joint, and low thermal conductivity. Transient liquid-phase (TLP) partial bonding using solders or Sn, and sinter bonding using Ag particles, are alternative bonding methods which involve a modification or change of the material. Advanced alternatives can significantly reduce bonding time or material cost. Various additional studies have investigated various core-cell particles that can be used to form an all-metallic bondline. This review summarizes reports of bonding studies using different core-cell particles. The particles were not only applied as a form of paste but also preform. In the TLP bonding using X(Cu, Ag, Ni)@Sn particles, the degree of voids generated in the formed bondline was dependent on the type of intermetallic compound formed. The preforms consisting of X@Sn particles provided relatively uniform microstructure and void distribution, compared to the pastes containing identical X@Sn particles, resulting in better long-term mechanical reliability. The addition of Zn@Sn particles contributed to the more practical control of microstructure and mechanical properties in the joint formed by pure Sn and Sn-58Bi solder alloys. Cu@Ag particles can be considered a promising low-cost material for compression-assisted sinter bonding, replacing pure Ag particles. The application of core-cell particles is expected to improve the processes used for forming metallic bondlines.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43030497","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.642
Hansol Kwon, Youngjin Park, U. Nam, E. Byon
Conventional non-skid coatings for marine construction contain polymeric materials. These materials are generally susceptible to high temperature environments because of their low thermal conductivity and thermal resistance. A metal-based non-skid coating has great potential for high temperature applications, yet, there has only been limited research. In this study, twin wire arc spray (TWAS) was used to fabricate Al and Al-3%Ti coatings on a high strength low alloyed (HSLA) steel substrate. The purpose of this study is to confirm the feasibility of TWAS Al-based coating for non-skid areas on marine construction. The static coefficient friction of TWAS Al-based coatings exhibited excellent and uniform values compared with a conventional epoxy-based non-skid coating. The specific heat and thermal conductivity of TWAS Al-based coating was measured and compared with that of the substrate. The thermal property values of the TWAS Al-based coating were reported for the first time in this study. The TWAS Al-based coating had A continuous interface with the substrate and the general microstructural features of a thermal-sprayed metal coating. After exposure to 500℃ for 24 hours, the an Fe-Al intermetallic compound and oxide were formed inside of the coating and coating-substrate interface. The adhesion strength indicated that the TWAS Al-based coating sustained its strength after the isothermal exposure test. The Vickers hardness of the TWAS Al-3%Ti coating was higher than that of the Al coating. The solid solution hardening of Ti atoms in the as-deposited coating and the precipitation hardening of the TiAl3 compound in the heat-treated coating contributed to the improvement of in Vickers hardness. Thus, the TWAS Al-3%Ti coating is proven to be a promising nonskid coating for high temperature applications.
{"title":"Research on Thermal Properties and High Temperature Exposure Behavior of Non-Skid Coating Fabricated by Twin Wire Arc Spraying","authors":"Hansol Kwon, Youngjin Park, U. Nam, E. Byon","doi":"10.3365/kjmm.2023.61.9.642","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.642","url":null,"abstract":"Conventional non-skid coatings for marine construction contain polymeric materials. These materials are generally susceptible to high temperature environments because of their low thermal conductivity and thermal resistance. A metal-based non-skid coating has great potential for high temperature applications, yet, there has only been limited research. In this study, twin wire arc spray (TWAS) was used to fabricate Al and Al-3%Ti coatings on a high strength low alloyed (HSLA) steel substrate. The purpose of this study is to confirm the feasibility of TWAS Al-based coating for non-skid areas on marine construction. The static coefficient friction of TWAS Al-based coatings exhibited excellent and uniform values compared with a conventional epoxy-based non-skid coating. The specific heat and thermal conductivity of TWAS Al-based coating was measured and compared with that of the substrate. The thermal property values of the TWAS Al-based coating were reported for the first time in this study. The TWAS Al-based coating had A continuous interface with the substrate and the general microstructural features of a thermal-sprayed metal coating. After exposure to 500℃ for 24 hours, the an Fe-Al intermetallic compound and oxide were formed inside of the coating and coating-substrate interface. The adhesion strength indicated that the TWAS Al-based coating sustained its strength after the isothermal exposure test. The Vickers hardness of the TWAS Al-3%Ti coating was higher than that of the Al coating. The solid solution hardening of Ti atoms in the as-deposited coating and the precipitation hardening of the TiAl3 compound in the heat-treated coating contributed to the improvement of in Vickers hardness. Thus, the TWAS Al-3%Ti coating is proven to be a promising nonskid coating for high temperature applications.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48502238","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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