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Journal of Magnesium and Alloys 2020年第2期8卷 537-545页

作者： sang Won Lee sang-Hoon Kim Sung hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

This study investigates the microstructural characteristics of AZ31 Mg alloys rolled at room temperature(RT)and cryogenic temperature(CT)and the variation in their microstructure and hardness during subsequent *** induces the formation of more side cracks than does RT rolling,because of the reduction in the ability of the material to accommodate deformation at ***{10-11}contraction and{10-11}-{10-12}double twins are formed in both the material rolled at RT and that rolled at CT,because the grains of the initial material are favorably oriented for{10-11}twinning under *** RT-rolled material has a higher dislocation density than the cryorolled material,and more twins are uniformly distributed throughout the former *** a result,static recrystallization during subsequent annealing is more pronounced in the RT-rolled material,which results in the formation of a highly recrystallized homogeneous microstructure after *** contrast,the formed twins are predominantly present along the shear bands in the cryorolled material,as a result of which this material has an inhomogeneous bi modal structure containing a large amount of coarse unrecrystallized grains after *** hardness of the annealed RT-rolled material is higher than that of the annealed cryorolled material owing to the finer grain structure of the former.

关键词： Magnesium Rolling Cryogenic temperature Annealing Microstructure

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Journal of Central South University 2012年第4期19卷 1032-1039页

作者： park Wook-je LEE sang-min LEE sang-hyuk Institute for Information and Electronics Research Inha University Department of Electrical and Electronic Engineering Xi'an Jiaotong-Liverpool University

Similarity measure construction has been proposed as fault detection of flight test method in order to obtain the primary control surface stuck and the combination stuck of primary *** measures were obtained through analyzing the certainty and uncertainty of fuzzy membership functions,which were designed based on well-known Hamming *** was applied to the fault detection of primary control surface stuck of uninhabited aerial vehicle(UAV).At post-failure control surface,if the UAV is controllable and trimmable using other control surfaces,the UAV is able to fly or return to the safety region through reconfiguration of flight control *** detect the fault,similarity measure computations were carried *** result could be applicable with the real-time parameter estimation *** monitoring the value of coefficients due to the control surface deviation,it becomes aware that the control surface fault occurs or *** control surface stuck position and value were separated by comparing the trim value with the reference *** is the advantage of increasing in reliability without adding sensors or with additional low cost.

关键词： similarity measure fault detection and isolation real-time parameter estimation control surface stuck

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Journal of Central South University 2013年第8期20卷 2233-2238页

作者： park Jean-Ho HWANG Jai-hyuk park Wook-Je 魏荷 LEE sang-hyuk Advanced Convergent Technology R&D Group Korea Institute of Industrial Technology School of Aerospace & Mechanical Engineering Korea Aerospace University Institute for Information and Electronics Research Inha University Department of Electrical and Electronic Engineering Xi'an Jiaotong-Liverpool University

Study of fuzzy entropy and similarity measure on intuitionistic fuzzy sets (IFSs) was proposed and analyzed. Unlike fuzzy set, IFSs contain uncertainty named hesitance, which is contained in fuzzy membership function itself. Hence, designing fuzzy entropy is not easy because of many entropy definitions. By considering different fuzzy entropy definitions, fuzzy entropy on IFSs is designed and discussed. Similarity measure was also presented and its usefulness was verified to evaluate degree of similarity.

关键词： similarity measure multi-dimension discrete data relative degree power interconnected system

Effects of initial texture on deformation behavior during cold rolling and static recrystallization during subsequent annealing of AZ31 alloy

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Journal of Materials Science & Technology 2021年第7期66卷 139-149页

作者： sang Won Lee Gukin Han Tea-Sung Jun Sung hyuk park School of Materials Science and Engineering.Kyungpook National University Daegu 41566Republic of Korea Department of Mechanical Engineering Incheon National UniversityIncheon 22012Republic of Korea

This study demonstrates that the initial texture of Mg alloy significantly affects the microstructure developed during cold rolling and the recrystallization behavior during subsequent annealing. In a sample with a texture oriented toward the normal direction(ND sample), thick and large-sized shear bands are intensively formed during cold rolling and the deformation is strongly localized along these bands. In contrast,in a sample with a texture oriented toward the transverse direction(TD sample), many {10-12} twins are formed at the early stage of cold rolling, and then, numerous small-sized shear bands are formed in these twins. Results of nanoindentation tests reveal that the cold-rolled ND sample has internal strain energy that is substantially concentrated along the shear bands, whereas the cold-rolled TD sample has a large amount of internal strain energy that is homogeneously distributed throughout the material;this latter behavior is strongly related to the extensive {10-12} twinning and the resultant microstructural variations in the TD sample. During subsequent annealing, recrystallization occurs locally along the shear bands in the ND sample, which leads to the formation of a bimodal grain structure comprising fine recrystallized grains and coarse unrecrystallized grains. In contrast, during subsequent annealing of the TD sample, static recrystallization occurs homogeneously throughout the material, which results in the formation of a uniform grain structure that mostly comprises equiaxed recrystallized grains.

关键词： Magnesium alloy Cold rolling Initial texture Twinning Static recrystallization

Variation in dynamic deformation behavior and resultant yield asymmetry of AZ80 alloy with extrusion temperature

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Journal of Materials Science & Technology 2020年第11期42卷 225-236页

作者： sang-Hoon Kim sang Won Lee Byoung Gi Moon Ha Sik Kim Sung hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu702701South Korea Implementation Research Division Korea Institute of Materials ScienceChangwon51508South Korea

In this work,variation in the dynamic recrystallization(DRX)and dynamic precipitation behavior of AZ80 alloy during extrusion due to changes in extrusion temperature was investigated,and the resultant microstructure and yield asymmetry were *** the extrusion temperature increases from 250℃to 350℃,the primary DRX mechanism changes from twin-induced DRX to discontinuous DRX,resulting in an increase in the DRX area fraction and un DRXed grain *** addition,as the extrusion temperature rises,Mg17Al12 precipitation during extrusion decreases sharply throughout the extruded *** reduction in the compressive yield strength(CYS)with increasing extrusion temperature is more pronounced than it is for the tensile yield strength(TYS),which ultimately increases the yield asymmetry of the extruded *** higher extrusion temperature has less of an influence on the TYS due to the promotion of certain hardening *** the other hand,the greater reduction in the CYS is attributed to the increased fraction and size of regions in which{1012}twins predominantly form and the lower amount of precipitates,which effectively facilitates{1012}twinning.

关键词： Magnesium alloys Extrusion Recrystallization Precipitation Yield asymmetry

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Journal of Central South University 2011年第5期18卷 1602-1608页

作者： LEE sang-hyuk park Wook-Je JUNG Dong-yean Department of Electrical and Electronic Engineering Xi'an Jiaotong-Liverpool University Institute for Information and Electronics Research Inha University253 Yonghyun-dongNam-GuIncheon402-751Korea Daeho Technology Korea Co. LtdChangwonGyeongnam641-773Korea

The similarity computations for fuzzy membership function pairs were carried *** number related knowledge was introduced,and conventional similarity was compared with distance based similarity *** usefulness of the proposed similarity measure was *** results show that the proposed similarity measure could be applied to ordinary fuzzy membership functions,though it was not easy to *** conventional results on the calculation of similarity for fuzzy membership pair,fuzzy membership-crisp pair and crisp-crisp pair were carried *** proposed distance based similarity measure represented rational performance with the heuristic point of ***,troublesome in fuzzy number based similarity measure for abnormal universe of discourse case was ***,the similarity measure computation for various membership function pairs was discussed with other conventional results.

关键词： similarity measure fuzzy number distance similarity evaluation fuzzy membership function

Influence of undissolved second-phase particles on dynamic recrystallization behavior of Mg–7Sn–1Al–1Zn alloy during low-and high-temperature extrusions

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Journal of Materials Science & Technology 2021年第12期71卷 87-97页

作者： Hyun Ji Kim sang-Cheol Jin Jae-Gil Jung Sung hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChangwon51508Republic of Korea

This study investigates the effects of fine and coarse undissolved particles in a billet of the Mg–7 Sn–1 Al–1 Zn(TAZ711)alloy on the dynamic recrystallization(DRX)behavior during hot extrusion at low and high temperatures and the resultant microstructure and mechanical properties of the *** this end,partially homogenized(PH)and fully homogenized(FH)billets are extruded at temperatures of250 and 450°*** PH billet contains fine and coarse undissolved Mg_(2) Sn particles in the interdendritic region and along the grain boundaries,*** fine particles(<1μm in size)retard DRX during extrusion at 250°C via the Zener pinning effect,and this retardation causes a decrease in the area fraction of dynamically recrystallized(DRXed)grains of the extruded *** addition,the inhomogeneous distribution of fine particles in the PH billet leads to the formation of a bimodal DRXed grain structure with excessively grown grains in particle-scarce *** contrast,in the FH billet,numerous nanosized Mg_(2) Sn precipitates are formed throughout the material during extrusion at 250°C,which,in turn,leads to the formation of small,uniform DRXed grains by the grain-boundary pinning effect of the *** the PH billet is extruded at the high temperature of 450°C,the retardation effect of the fine particles on DRX is weakened by their dissolution in theα-Mg matrix and the increased extent of thermally activated grain-boundary *** contrast,the coarse Mg_(2) Sn particles in the billet promote DRX during extrusion through the particle-stimulated nucleation phenomenon,which results in an increase in the area fraction of DRXed *** both low and high extrusion temperatures,the extruded material fabricated using the PH billet,which contains both fine and coarse undissolved particles,has a lower tensile strength than that fabricated using the FH billet,which is virtually devoid of second-phase *** lower strength of the former is attributed mai

关键词： Mg–Sn alloy Second-phase particle Extrusion Homogenization Dynamic recrystallization

Effects of homogenization temperature on microstructure and mechanical properties of high-speed-extruded Mg–5Bi–3Al alloy

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Journal of Magnesium and Alloys 2022年第10期10卷 2833-2846页

作者： Jae Won Cha sang-Cheol Jin Jae-Gil Jung Sung hyuk park School of Materials Science and Engineering Kyungpook National University80 DaehakroDaegu 41566Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effects of billet homogenization temperature on the dynamic recrystallization behavior during high-speed extrusion and resultant microstructure and tensile properties of the Mg–5Bi–3Al(BA53,wt%)*** billets homogenized at 350 and450℃(350H and 450H billets)are extruded at a high speed of 69 m/*** 350H billet has a relatively smaller grain size and a higher abundance of fine Mg3Bi2particles compared to the 450H *** extrusion of the 350H billet,enhanced dynamic recrystallization occurs as a result of its finer grains and abundance of particles,while the growth of recrystallized grains is suppressed by the grain-boundary pinning effect of ***,the extruded 350H material is characterized by smaller grains,relatively greater number of Mg3Bi2particles,and a higher internal strain energy than the extruded 450H *** tensile strength of the extruded 350H material is higher than that of the extruded 450H material owing to stronger grain-boundary hardening,particle hardening,and strain hardening *** extruded 350H material also exhibits a higher tensile elongation as its smaller grains inhibit the formation of crack-inducing undesirable twins during *** results from this study demonstrate that a decrease in the homogenization temperature from 450 to 350℃leads to improved strength and ductility in the high-speed-extruded BA53 material.

关键词： Mg–Bi–Al alloy High-speed extrusion Homogenization Dynamic recrystallization 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.

Improvement in tensile strength of extruded Mg-5Bi alloy through addition of Sn and its underlying strengthening mechanisms

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Journal of Magnesium and Alloys 2022年第11期10卷 3100-3112页

作者： sang-Cheol Jin Jae Won Cha Jeong Hun Lee Taekyung Lee sang-Ho Han Sung hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Ulsan Regional Division Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea Department of Materials Analysis Korea Institute of Materials ScienceChangwon 51508Republic of Korea

Through an investigation of the microstructure and mechanical properties of extruded Mg–5Bi–x Sn(BT5x, x = 0, 2, 4, and 6 wt%) alloys,this study demonstrates that the addition of Sn to an Mg–5Bi binary alloy significantly improves the tensile strength of the extruded *** the extruded alloys exhibit a typical basal fiber texture and a partially dynamically recrystallized(DRXed) microstructure consisting of fine DRXed grains and coarse un DRXed grains. As the Sn content increases from 0 wt% to 6 wt%, the average size of the DRXed grains decreases from 4.2 to 2.8 μm owing to the increase in the amount of precipitates via their grain-boundary pinning effect. The extruded B5 and BT52 alloys contain numerous Mg_(3)Bi_(2) precipitates, but their size and number density are smaller and higher, respectively, in the latter *** Mg_(2)Sn precipitates as well as Mg_(3)Bi_(2)precipitates are present in the extruded BT54 and BT56 alloys, and the number density of the Mg_(2)Sn precipitates is higher in the latter alloy because of its higher Sn content. The addition of 2 wt% Sn to the B5 alloy significantly improves the yield strength(YS) and ultimate tensile strength(UTS) of the extruded alloy—by 76 and 57 MPa, respectively. This drastic improvement is the combined outcome of enhanced grain-boundary hardening, precipitation hardening, and solid-solution hardening effects induced by the refined DRXed grains, numerous precipitates, and Sn solute atoms, respectively. The further addition of 2 wt% or 4 wt% Sn to the BT52 alloy leads to moderate increments in the YS and UTS of the extruded alloy. Specifically, each addition of 2 wt% Sn increases the YS and UTS by ~26 and ~20 MPa, respectively, which is attributed mainly to the additional precipitation hardening effect induced by the Mg_(2)Sn precipitates.

关键词： Mg-Bi-Sn alloy Extrusion Precipitation Microstructure Tensile property