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Comparative study of extrudability, microstructure, and mechanical properties of AZ80 and BA53 alloys

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Journal of Magnesium and Alloys 2023年第1期11卷 249-258页

作者： Sang-Cheol Jin Jae won Cha jongbin Go Jun Ho Bae Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials Science and Engineering Kyoto UniversityKyoto 606-8501Japan Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

The extrudability,microstructural characteristics,and tensile properties of the Mg–5Bi–3Al(BA53)alloy are investigated herein by comparing them with those of a commercial Mg–8Al–0.5 Zn(AZ80)*** AZ80 is extruded at 400℃,severe hot cracking occurs at exit speeds of 4.5 m/min or *** contrast,BA53 is successfully extruded without any surface cracking at 400℃ and at high exit speeds of 21–40 m/*** extruded at 3 m/min(AZ80–3)and 40 m/min(BA53–40),both AZ80 and BA53 exhibited completely recrystallized microstructures with abasal ***,BA53–40 has a coarser grain structure owing to grain growth promoted by the high temperature in the deformation ***80–3 contains a continuous network of Mg_(17)Al_(12) particles along the grain boundaries,which form via static precipitation during natural air-cooling after the material exits the extrusion ***53–40 contains coarse Mg_(3)Bi_(2) particles aligned parallel to the extrusion direction along with numerous uniformly distributed fine Mg_(3)Bi_(2) ***80–3 has higher tensile strength than BA53–40 because the relatively finer grains and larger number of solute atoms in AZ80–3 result in stronger grain-boundary and solid-solution hardening effects,*** BA53 is extruded at a high temperature and extrusion speed of 400℃ and 40 m/min,respectively,the extruded material has a high tensile yield strength of 188 *** can be primarily attributed to the large particle hardening effect resulting from the numerous fine Mg_(3)Bi_(2) particles.

关键词： Mg-Bi-Al alloy Extrusion Hot cracking Second phase Tensile properties

Effects of Sn addition on the microstructure and mechanical properties of extruded Mg-Bi binary alloy

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Journal of Magnesium and Alloys 2022年第3期10卷 920-931页

作者： Sang-Cheol Jin Jong Un Lee jongbin Go Hui Yu Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566South Korea Department of Materials Science and Engineering Kyoto UniversityYoshida-honmachiSakyo-kuKyoto606-8501Japan School of Materials Science and Engineering Hebei University of TechnologyTianjin 300130China

We investigated the effects of Sn addition on the microstructural characteristics and mechanical properties of an extruded Mg-Bi binary alloy by comparing Mg-5 Bi(B5)and Mg-5 Bi-4 Sn(BT54).Both the extruded alloys exhibit a partially recrystallized grain structure with a strong extrusion fiber texture and numerous Mg3Bi2 ***,the addition of Sn significantly decreases the average grain size of the extruded alloy from 123.9 to 75.2μ*** Sn solute atoms inhibit the activity of dislocation slip,which reduces the internal strain energy accumulated in the dynamically recrystallized(DRXed)grains during ***,this reduced strain energy leads to the decrease in the DRXed grain size owing to weakened grain growth during natural *** extruded BT54 alloy exhibits higher tensile strength and ductility than the extruded B5 *** improvement in the strength by the Sn addition is attributed to the combined effects of grain refinement,Sn solute atoms,and increased dislocation *** formation of{10-11}and{10-11}-{10-12}twins during tension is suppressed by the grain refinement,thereby improving the tensile elongation considerably.

关键词： Mg±Bi alloy Extrusion Dynamic recrystallization Microstructure Mechanical properties.

Elucidating the evolution of long-period stacking ordered phase and its effect on deformation behavior in the as-cast Mg-6Gd-1Zn-0.6Zr alloy

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Journal of Magnesium and Alloys 2023年第8期11卷 2801-2810页

作者： Sangwon Lee Yejun Park jongbin Go Young Mok Kim Seok Su Sohn Jiehua Li Pyuck-Pa Choi Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon34141Republic of Korea Department of Materials Science and Engineering Kyoto UniversityKyoto606-8501Japan Department of Materials Science and Engineering Korea UniversitySeoul02841Republic of Korea Institute of Casting Research Montanuniverstät LeobenLeobenA-8700Austria

Herein,the evolution of long-period stacking ordered(LPSO)phases in the as-cast Mg-6Gd-1Zn-0.6Zr(wt.%)alloy are investigated via transmission electron microscopy(TEM)and atom probe tomography(APT).The TEM results reveal that two types of LPSO phase(a bulky interdendritic phase and a plate-like matrix LPSO phase)are formed in the as-cast *** of the LPSO phases are confirmed to be of the 14H type,with a smaller proportion being of the 18R ***,the APT results reveal that the composition of the interdendritic LPSO phase is closer to that of the ideal 14H phase compared to the matrix LPSO phase,and both the interdendritic and matrix LPSO phases exhibit a Gd/Zn ratio of 2.5,thereby indicating a deficient Zn content compared to the ideal 14H phase(i.e.,1.3).In addition,the influence of the LPSO phases on the deformation behavior is investigated at different compressive plastic strains using electron backscatter diffraction(EBSD)analysis to reveal twinning and slip behavior during *** results indicate that the LPSO phase induces additional work hardening in the late stage of deformation via the suppression of{1011}compressive twinning and the activation of non-basal slip systems.

关键词： Magnesium alloy Long-period stacking ordered phase Transmission electron microscopy Atom probe tomography Work hardening behavior

Stochastic structural optimization using particle swarm optimization, surrogate models and Bayesian statistics

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Chinese Journal of Aeronautics 2013年第1期26卷 112-121页

作者： jongbin Im Jungsun Park Korea Aerospace Research Institute Department of Aerospace and Mechanical Engineering Korea Aerospace University

This paper focuses on a method to solve structural optimization problems using particle swarm optimization （PSO）, surrogate models and Bayesian statistics. PSO is a random/stochastic search algorithm designed to find the global optimum. However, PSO needs many evaluations compared to gradient-based optimization. This means PSO increases the analysis costs of structural optimization. One of the methods to reduce computing costs in stochastic optimization is to use approximation techniques. In this work, surrogate models are used, including the response surface method （RSM） and Kriging. When surrogate models are used, there are some errors between exact values and approximated values. These errors decrease the reliability of the optimum values and discard the realistic approximation of using surrogate models. In this paper, Bayesian statistics is used to obtain more reliable results. To verify and confirm the efficiency of the proposed method using surrogate models and Bayesian statistics for stochastic structural optimization, two numerical examples are optimized, and the optimization of a hub sleeve is demonstrated as a practical problem.

关键词： Bayesian statistics Kriging Particle swarm optimization (PSO) Response surface method (RSM)

Investigating a Vitamin D Delivery Toothpaste Using a Penetration Enhancer Compound

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Advances in Bioscience and Biotechnology 2023年第1期14卷 1-17页

作者： Naree Lee jongbin Lee Medical and Pharmaceutical Divisions STEM Science Center Englewood Cliffs NJ USA

Expanding in the oral care business, being passionately driven by innovative and scientific products, functional toothpaste has recently become more popular for functionality, variety, and efficacy. Many new types of toothpaste are commercially manufactured with diverse fragrances, colors, probiotics, and pharmaceutical ingredients to enhance the functionalities of toothpaste. Our study attempted to create a toothpaste formulation that might facilitate the intraoral delivery of vitamin D3 into the bloodstream. Simply brushing our teeth with toothpaste should be easy to take the essential vitamin regularly. In this study, an emulsion-based toothpaste mixed with an azone compound and sodium dodecyl sulfate as penetration enhancers blended thoroughly with other ingredients and then with vitamin D. Multiple toothpaste characteristic tests were performed, such as abrasiveness, scratchiness, spreadability, pH, foaming, cleaning, and antibacterial strength with our vitamin D toothpaste, and compared with those of other commercial brand toothpaste. To confirm the intraoral delivery of vitamin D through the oral cavity, an earthworm transport study and TEER value test were conducted using L. terrestris skin. Our data demonstrated the high feasibility of intraoral delivery of vitamin D based on those two skin studies with various experimental support;our vitamin D toothpaste had comparable characteristics with other commercial toothpaste for cleaning functionality.

关键词： Azone Compound Drug Delivery System Intraoral Delivery Penetration Enhancer Toothpaste Vitamin D

Influence of Bi addition on dynamic recrystallization and precipitation behaviors during hot extrusion of pure Mg

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Journal of Materials Science & Technology 2020年第9期44卷 62-75页

作者： jongbin Go Jong Un Lee Hui Yu Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu41566Republic of Korea School of Materials Science and Engineering Hebei University of TechnologyTianjin300130China

Low material cost and high extrudability for ensuring price competitiveness with Al alloys,as well as excellent mechanical properties,are essential for expanding the application range of Mg *** is a promising alloying element for developing extruded Mg alloys that satisfy such *** is inexpensive,exhibits a high solubility limit,and forms a thermally stable Mg3Bi2 phase,which improves the commercial viability and enables the high-speed extrusion of Mg–Bi *** this study,the effects of Bi addition on the dynamic recrystallization(DRX)and dynamic precipitation behaviors during hot extrusion of a pure Mg and the resultant microstructure and mechanical properties of the extruded materials were *** addition of 6 wt%and 9 wt%Bi to a pure Mg yielded numerous fine Mg3Bi2 precipitates during the early stage of hot ***,the area fraction of dynamic recrystallized(DRXed)grains decreased because of DRX-behavior suppression by the Zener pinning ***,the DRXed grain size was substantially reduced through the grain-boundary pinning *** size and number of undissolved Mg3Bi2 particles in the homogenized billets increased when the Bi content was increased,which resulted in increased DRX fractions owing to the enhanced levels of particle stimulated *** addition yielded considerable strength improvement of the extruded pure ***,the extruded Mg–Bi binary materials were less ductile than the extruded pure Mg *** lower ductility resulted from the cracking at twins formed in the coarse unDRXed grains of the Mg-6Bi material and the cracking at large undissolved Mg3Bi2 particles in the Mg-9Bi material.

关键词： Magnesium Bi addition Extrusion Recrystallization Precipitation

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论高校图书馆知识保障体系的构建

图书馆 2010年第1期 102-103页

作者：陈钟彬河南省周口师范学院图书馆河南周口466000

高校图书馆知识服务质量的提高,需要良好的知识保障体系作为后盾。当前我国高校图书馆知识服务面临许多问题,深入分析这些问题,可以帮助我们确立明确的知识保障体系构建目标,并从信息资源存储、知识服务和队伍管理等方面建构有效的知识... 详细信息

高校图书馆知识服务质量的提高,需要良好的知识保障体系作为后盾。当前我国高校图书馆知识服务面临许多问题,深入分析这些问题,可以帮助我们确立明确的知识保障体系构建目标,并从信息资源存储、知识服务和队伍管理等方面建构有效的知识保障体系,以促进高校图书馆知识服务进一步优化。

关键词：高校图书馆知识保障