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In-situ study of damage mechanisms in Mg-6Li dual-phase alloy

Journal of Materials Science & Technology 2024年第12期179卷 114-124页

作者： Jing Li Li Jin sangbong yi Xin Zhang Jie Dong Ming Luo Key Laboratory of High Performance Manufacturing for Aero Engine(Northwestern Polytechnical University) Ministry of Industry and Information TechnologyXi'an 710072China Engineering Research Center of Advanced Manufacturing Technology for Aero Engine Ministry of EducationNorthwestern Polytechnical UniversityXi'an 710072China National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composite School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Institute of Materials and Process Design Helmholtz-Zentrum HereonGeesthacht 21502Germany

Interfaces play a crucial role in influencing the mechanical properties of Mg *** Mg-Li dual-phase alloy,the type of interfaces is complex,which includes both grain boundary and phase boundary,and the influence of such interfaces on the damage nucleation is yet to be *** this paper,in-situ scanning electron microscopy(SEM)based measurements were carried out to investigate the meso-scale damage nucleation mechanisms of the Mg-6Li dual-phase *** show that 94.8%of cracks are nucleated at the α-Mg grain boundary in the post-uniform elongation stage,while 5.2%are at phase boundary and almost no crack at the β-Li grain *** initiation of α-Mg grain boundary cracks is attributed to strain incompatibility,which induces micro-strain localization,and then causes grain boundary sliding(GBS)and crack *** compatibility analysis reveals that the geometric compatibility factor(Mk)can be used to predict the nucleation of α-Mg grain boundary *** Mk is lower than 0.075,α-Mg grain boundary cracks tend to *** cracks are generated at the phase boundary is due to the mild strain partitioning between α-Mg phase and β-Li phase and may also be partly attributed to multiple slip systems in body-centered cubic(BCC)-structured β-Li phase,which can accommodate well with the deformation of adjacent α-Mg phase.

关键词： Crack nucleation Strain localization Grain boundary sliding Phase boundary Mg–6Li dual-phase alloy

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Plastic instability and texture modification in extruded Mg-Mn-Nd alloy

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Journal of Magnesium and Alloys 2022年第1期10卷 160-174页

作者： Sang Kyu Woo Risheng Pei Talal Al-Samman Dietmar Letzig sangbong yi Magic-Magnesium Innovation Center Institute for Materials and Process DesignHelmholtz-Zentrum GeesthachtGeesthacht 21502Germany Institut für Metallkunde und Materialphysik RWTH Aachen UniversityAachen 52056Germany

Even though Mg alloys containing Mn and rare earth elements lead to higher ductility and lower yield asymmetry due to the weak texture after extrusion, plastic instability, commonly known as the Portevin–Le Chatelier(PLC) effect, causes unexpected fragility in the service environment. In the present study, the PLC phenomenon and texture development during the deformation of Mg-Mn and Mg-Mn-Nd extruded alloys were investigated under various temperatures and strain rates. The addition of Nd causes not only texture weakening but also severe PLC phenomenon. The PLC phenomenon was significantly affected by the temperatures and the strain rates, which causes a difference in mechanical properties and development of texture. In the conditions of high temperature and low strain rate, the strength increased while the elongation decreased significantly, and obvious PLC phenomenon with severe serration and negative strain rate sensitivity. The initial texture was maintained even after deformation only under severe PLC conditions, and this is due to the restriction of basal slip and suppression of lattice rotation in PLC conditions. The series of results indicate that the PLC phenomenon causes a reduction of formability even at high temperature.

关键词： Magnesium Plastic instability Portevin–Le Chatelier effect Manganese Neodymium Texture

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Solute drag-controlled grain growth in magnesium investigated by quasi in-situ orientation mapping and level-set simulations

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Journal of Magnesium and Alloys 2023年第7期11卷 2312-2325页

作者： Risheng Pei Yujun Zhao Muhammad Zubair sangbong yi Talal Al-Samman Institut für Metallkunde und Materialphysik RWTH Aachen University52056 AachenGermany Institute of Materials and Process Design Helmholtz-Zentrum Hereon21502 GeesthachtGermany Department of Metallurgical and Materials Engineering Faculty of ChemicalMetallurgical&Polymer EngineeringUniversity of Engineering&Technology(UET)LahorePakistan Institute for Materials Ruhr-Universität Bochum44801 BochumGermany

Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size *** atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion,which strongly affects the grain growth behavior during *** the current work,the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling *** quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing *** segregation at targeted grain boundaries was measured using three-dimensional atom probe ***-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute *** results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of *** longer annealing times,residual dislocation density gradients between large and smaller grains are no longer important,which leads to microstructure stability due to predominant solute *** fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates,which affects the average growth rate of large grains and their evolved shape.

关键词： Magnesium alloys Grain growth Quasi in-situ EBSD Level-set simulation Solute drag Dislocation density gradient

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Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

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Journal of Magnesium and Alloys 2023年第2期11卷 543-552页

作者： Sang Kyu Woo Risheng Pei Talal Al-Samman Dietmar Letzig sangbong yi Institute of Materials and Process Design Helmholtz-Zentrum hereon21502 GeesthachtGermany Institut für Metallkunde und Materialphysik RWTH Aachen University52056 AachenGermany

Plastic instability, called Portevin-Le-Chatelier(PLC) effect, manifests itself as an unstable plastic flow during tensile tests of structural materials. This phenomenon has a strong influence on diverse properties, leading to unexpected vulnerabilities in the service *** various magnesium-based alloys, PLC phenomenon is most prominently observed in the Mg-Mn-Nd alloy under elevated temperature and low strain rate conditions. An important aim of the study is to clarify and compare the significance of the RE and Ca addition, which are known to cause a formation of a largely weakened non-basal type texture, in the occurrence of plastic instability. Due to the PLC phenomenon, there is a risk of weakening texture and formability improvement by the addition of RE and Ca elements in Mg alloys. Based on the understanding of the role of Nd to the PLC phenomenon in Mg-Mn alloy identified in previous studies, the PLC characteristics according to alloying elements and deformation conditions were compared and analyzed. To identify the micromechanical mechanisms of the PLC phenomenon, varies in the microstructure and mechanical properties during deformation of Mg-Mn binary and Ca or Nd-containing Mg-Mn-based ternary alloys in various conditions were systemically analyzed. The addition of Ca did not show a marked PLC effect due to the formation of low number density Mn-Ca and Ca-Ca solute clusters and an unbalanced Mn:Ca ratio. In contrast, the addition of Nd leads to the formation of a higher number density of Nd-Nd and Mn-Nd solute clusters than that of Ca-Ca and Mn-Ca solute clusters of the Mg-Mn-Ca alloy, resulting in a stable solute-dislocation interaction atmosphere under specific ranges of deformation temperature and strain rate. The deformation in the regime of PLC phenomenon, results in a decrease in ductility and an increase in strength, despite deformation at elevated temperatures with maintaining the weakened texture.

关键词： Magnesium Plastic instability Portevin-Le Chatelier effect Solute cluster Neodymium Calcium

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Influence of Ca addition on the dynamic and static recrystallization behavior of direct extruded flat profiles of Mg-Y-Zn alloy

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Journal of Magnesium and Alloys 2023年第10期11卷 3736-3748页

作者： Maria Nienaber Jan Bohlen sangbong yi Gerrit Kurz Karl Ulrich Kainer Dietmar Letzig Institute of Material and Process Design Helmholtz-Zentrum Hereon GmbHMax-Planck-Str.1Geesthacht 21502Germany Agnes-Miegel Str.11Bad Essen 49152Germany

This paper investigates the influence of addition of Ca in a Y-Zn-containing magnesium alloy on the dynamic and static recrystallization behaviors and reveals the formation mechanism of the quadrupole texture during thermomechanical processing. Direct extrusion of flat bands has been conducted at various process conditions to study the difference between the two alloys WZ10 and WZX100 in terms of microstructure and texture development. It can be shown that, Ca addition promotes the DRX of WZ10 alloy. During additional heat treatment,the absence of Y segregation at the grain boundaries and the associated lack of solute drag to the boundary mobility leads to a pronounced grain growth during SRX in WZX100 alloy. Furthermore, it is shown that the addition of Ca to Y-Zn is not beneficial in terms of *** is demonstrated that alloying elements can have different effects depending on the recrystallization mechanisms. Partially recrystallized microstructure is a prerequisite at the as-extruded status to form the quadrupole texture and during subsequent annealing, which stands for high formability.

关键词： Extrusion Recrystallization Magnesium alloy Mg-Y-Zn-Ca alloy Formability quadrupole texture

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Assessing the microstructure and in vitro degradation behavior of Mg-xGd screw implants using μCT

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Journal of Magnesium and Alloys 2021年第6期9卷 2208-2223页

作者： Diana Krüger Berit Zeller-Plumhoff Björn Wiese sangbong yi Marcus Zuber D.C.Florian Wieland Julian Moosmann Regine Willumeit-Römer Institute of Metallic Biomaterials Helmholtz-Zentrum HereonMax-Planck-Str.1Geesthacht 21502Germany Institute of Material and Process Design Helmholtz-Zentrum HereonMax-Planck-Str.1Geesthacht 21502Germany Institute for Photon Science and Synchrotron Radiation Karlsruhe Institute of TechnologyHerrmann-von-Helmholtz-Platz 1Eggenstein-Leopoldshafen 76344Germany Laboratory for Applications of Synchrotron Radiation Karlsruhe Institute of TechnologyKaiserstr.12KarlsruheGermany Institute of Materials Physics Helmholtz-Zentrum HereonMax-Planck-Str.1Geesthacht 21502Germany

Biodegradable implants are taking an increasingly important role in the area of orthopedic implants with the aim to replace permanent implants for temporary bone healing *** the implant preparation process,the material’s surface and microstructure are being changed by stresses induced by *** degradable metal implants need to be fully characterized in terms of the influence of machining on the resulting microstructure and corrosion *** this study,micro-computed tomography(μCT)is used for the quantification of the degradation rate of biodegradable *** our best knowledge,for the first time quantitative measures are introduced to describe the degradation homogeneity in *** information enables a prediction in terms of implant stability during the degradation in the *** magnesium gadolinium alloys,Mg-5Gd and Mg-10 Gd(all alloy compositions are given in weight%unless otherwise stated),in the shape of M2 headless screws have been investigated for their microstructure and their degradation performance up to 56 *** the microstructure investigations particular attention was paid to the localized deformation of the alloys,due to the machining *** vitro immersion testing was performed to assess the degradation performance quantified by subsequent weight loss and volume loss(usingμCT)*** differences were observed in the degree of screw’s near surface microstructure being influenced from machining,the degradation rates of both materials appeared to be suitable for application in orthopedic *** the degradation homogeneity point of view no obvious contrast was detected between both ***,the higher degradation depth ratios between the crests and roots of Mg-5Gd ratios may indicated a less homogeneous degradation of the screws of these alloys on contract to the ones made of Mg-10Gd *** to its lower degradation rates,its more homogeneous microstructure,its weaker texture

关键词： Magnesium alloys Biodegradable implant Degradation rate Degradation homogeneity Micro-comptued tomography

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