Imperial College London

DrJunJiang

Faculty of EngineeringDepartment of Mechanical Engineering

Senior Lecturer
 
 
 
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Contact

 

jun.jiang

 
 
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Location

 

524City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

87 results found

Jiang J, Lu Q, Zhang C, Aucott L, Wang Wet al., 2022, Reveal the Viscoplastic Behaviour and Microstructure Evolution of Stainless Steel 316L, Materials, ISSN: 1996-1944

Journal article

Zhou X, Sun C, Wang B, Jiang Jet al., 2022, Investigation and prediction of central cracking in cross wedge rolling, The International Journal of Advanced Manufacturing Technology, ISSN: 0268-3768

Central cracking refers to the formation of internal cavities in cross wedge rolling (CWR) products. It occurs in various materials such as aluminium/titanium alloys, steels and plasticine at room or elevated temperatures, driven by different central cracking mechanisms. However, these mechanisms are still elusive, and a unified central cracking predictive model is absent due to the complex stress states within the workpiece, including triaxial stress states, cyclic loading and severe shear effects. In this study, the underlying fracture mechanisms were revealed, and a robust unified damage model with sound physical meanings was developed using a lab-scale CWR physical model and finite element models. The physical model with the plasticine billets was built, allowing the CWR dies with different geometries rapidly 3D printed and the billets with various ductility efficiently manufactured. The central cracking transiting from brittle to ductile fracture was experimentally observed for the first time using specifically designed plasticine/flour composite samples at varying ductility. The corresponding physics-based central cracking predictive model was proposed and validated quantitatively with 60 groups of CWR tests and compared with ten existing damage models/fracture criteria. This study effectively solves the long-lasting central cracking problem in the CWR industry and enhances the scientific understanding of fracture mechanics in complex engineering applications.

Journal article

Wang W, Politis NJ, Wang Y, Zhou X, Balint D, Jiang Jet al., 2022, Solid-state hot forge bonding of aluminium-steel bimetallic gears: Deformation mechanisms, microstructure and mechanical properties, International Journal of Machine Tools and Manufacture, Vol: 180, ISSN: 0890-6955

Solid-state dissimilar bi- or multi-metallic bonding is promising for achieving lightweight or multifunctional components in automotive, nuclear power and aerospace industries. To understand how to achieve a high-quality bonding interface between dissimilar materials, aluminium alloy (Al)–steel (Fe) bimetal gears manufactured under hot forge bonding were systematically investigated. In this work, comprehensive analyses of forge bonding mechanics, microstructure features, bonding interface behaviours and resulting mechanical properties were undertaken using ex/in-situ experiments and finite element modelling. The results revealed that the bonding behaviour and microstructure evolution were significantly affected by the mechanical property mismatch between the two dissimilar workpieces (AA6082 and E355). This mismatch could be effectively adjusted by setting different forging temperatures. The interfacial bonding strengths of AA6082 and E355, manufactured at low and high temperatures, were observed to be governed by interdiffusion and oxide particles, respectively. Balancing interdiffusion and oxide breaking appears to be key to achieving optimized interface strength for dissimilar bimetallic forge bonding technology.

Journal article

Wu Y, Tang Y, Zhang Y, Fu Y, Xing H, Zhang J, Jiang J, Sun Bet al., 2022, In situ radiographic study of the grain refining behavior of Al3Sc during the solidification of Al-10Cu alloy, Journal of Materials Science & Technology, Vol: 122, Pages: 33-43, ISSN: 1005-0302

Grain refinement of Al alloys inoculated by rare earth elements, such as Sc, has been extensively acknowledged, while the practical behavior of how inoculant Al3Sc particles affect the refinement in solidification has not been clarified due to the non-transparency of the solidification process. Here, the microstructural evolution of primary Al3Sc particles and α-Al grains in Al-10 wt.% Cu alloy solidifications with 0.2 wt.%, 0.6 wt.%, and 1.0 wt.% Sc additions was investigated by in situ synchrotron X-ray radiography. The detailed mechanisms of curve motion of grains (CMG) and melt convection were revealed. The efficient grains nucleation, uniformly scattered small initial grains, and long duration of melt convection contributed to the best refinement in the 0.6 wt.% Sc addition sample. This work provides a deep insight into grain refinement in solidification with Sc addition, which will enlighten the composition design and casting process of Al alloys inoculated by rare earth elements.

Journal article

Lu Q, Wu J, Liu S, Zhang S, Cai X, Li W, Jiang J, Jin Xet al., 2022, Revealing geometrically necessary dislocation density from electron backscatter patterns via multi-modal deep learning, ULTRAMICROSCOPY, Vol: 237, ISSN: 0304-3991

Journal article

Imran SM, Li C, Lang L, Guo Y, Mirza HA, Haq F, Alexandrova S, Jiang J, Han Het al., 2022, An investigation into Arrhenius type constitutive models to predict complex hot deformation behavior of TC4 alloy having bimodal microstructure, Materials Today Communications, Vol: 31

The purpose of this study was to determine the plastic deformation behavior of TC4 alloy having bimodal microstructure at hot forming conditions and establish a suitable constitutive model. The bimodal microstructure was obtained by plate die forging at 985 °C to a deformation of 40% and then annealing at 720 °C for 1 h followed by air cooling. Quasi-static tensile tests were performed at temperatures ranging from 750 to 900 °C and strain rates of 0.0001–0.1 s−1. The experimental stress-strain curves revealed that the alloy exhibited complex deformation behavior with considerable strain hardening, dynamic recovery, and continuous dynamic recrystallization. The processing map is established to delineate the safe and unsafe thermomechanical conditions for material hot forming that revealed the existence of superplasticity at 0.0001 s−1 and 750–900 °C, DRX at 0.001 s−1 and 800–900 °C, and flow instabilities at 0.1–0.01 s−1 and 800–850 °C. Modified Arrhenius type constitutive models with strain compensated using polynomial equation (PSCAM) and exponential equation (ESCAM) were established to predict the complex deformation behavior of the alloy. Also, a novel optimization method utilizing an evolutionary algorithm (EA) and generalized reduced gradient (GRG) was employed to establish an optimized polynomial strain compensated Arrhenius type constitutive model (OPSCAM). The predictability of the three established models is evaluated and compared during strain hardening and dynamic softening of the material. The correlation coefficients of ESCAM, PSCAM, and OPSCAM were 0.98, 0.99, and 0.99, respectively, showing a good correlation for the three models. Percentage average absolute relative error for the three models is 13.76%, 9.66%, and 9.14%, respectively, during strain hardening and 12.40%, 8.41%, and 6.78%, respectively, during dynamic softening. The study showed that OPSCAM could adequately p

Journal article

Yasmeen T, Rahimi S, Hopper C, Zhao B, Jiang Jet al., 2022, Unravelling thermal-mechanical effects on microstructure evolution under superplastic forming conditions in a near alpha titanium alloy, Journal of Materials Research and Technology, Vol: 18, ISSN: 2238-7854

The superplastic formability of titanium alloys has been extensively exploited by various industries, especially for manufacturing of high value aerospace components. Material's microstructural characteristics, such as grain size and dislocations density, determine superplastic formability during manufacturing process and various constitutive relationships have been proposed to take their effects into consideration in modelling and simulation. However, most existing models do not include all these characteristics in their analyses due to the limitations in characterization techniques. This paper reports the results of a systematic study on the effects of thermal (i.e., static) and mechanical (i.e., dynamic) process parameters on the evolution of dislocations and microstructure, both independently and simultaneously, at superplastic forming regime. The evolution of microstructural phase fraction, grain size, crystallographic texture, and geometrically necessary dislocation (GND) density are investaged over a temperature range of 880–920 °C and under strain rates between 0.0005 and 0.01s−1. The results provide valuable insights into the microstructure evolution during superplastic forming on TA15 titanium alloy and form a basis for future physically based constitutive modelling.

Journal article

Mirza HA, Lang L, Tabasum MN, Meng Z, Alexandrov S, Jiang Jet al., 2022, An Investigation into the Forming of Fiber Metal Laminates with Different Thickness Metal Skins Using Hydromechanical Deep Drawing, APPLIED COMPOSITE MATERIALS, Vol: 29, Pages: 1349-1365, ISSN: 0929-189X

Journal article

Hu Y, Xi J, Jiang J, Lei M, Song M, Nikbin Ket al., 2022, Predicting virtual creep crack growth in a simulated titanium aluminide alloy microstructure containing voids, precipitates, and grain/grain boundary distortions, ENGINEERING FRACTURE MECHANICS, Vol: 262, ISSN: 0013-7944

Journal article

Wang C, Cai W, Sun C, Li X, Qian L, Jiang Jet al., 2022, Strain rate effects on mechanical behavior and microstructure evolution with the sequential strains of TWIP steel, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 835, ISSN: 0921-5093

Journal article

Wang Y, Liu Y, Zheng J-H, Lan B, Jiang Jet al., 2022, Develop a new strain rate sensitive solid-state pressure bonding model, Materials & Design, Vol: 215, Pages: 1-15, ISSN: 0264-1275

Solid-state bonding is widely involved in metal forming and joining applications. The quality of the bonded interface is the key to the final integrity of the joint or formed structure; thus, its controllability and predictivity have been the focus over decades. The interface bond quality is jointly determined by the interface oxide behaviour and microstructure evolution. In this study, a new four-stage model, considering the cohesion of different contacting pairs (oxide-oxide, oxide-metal and metal–metal) and the reduced adverse effect of remaining oxides, is proposed to describe the bonding process under hot deforming conditions. This proposed model was validated through a range of hot compression bonding tests, using Gleeble under different strains (10%, 30% and 50%), strain rates (0.001 s−1, 0.01 s−1 and 0.1 s−1) at 1150 °C with references. Scanning electron microscope (SEM) and Electron Backscatter Diffraction (EBSD) were used to characterize the oxide behaviour and microstructure evolution. Tensile tests at room temperature were conducted on bonded samples and references to reveal the interface bond ratio. 100% bonding strength, equivalent to the base metal's strength and ductility, was achieved at the large strain of 50% for all three strain rates.

Journal article

Liu Y, Wang Y, Xu X, Hopper C, Dong H, Wang X, Zhu H, Jiang Jet al., 2021, The study of hot deformation on laser cladding remanufactured 316L stainless steel, Materials and Design, Vol: 212, Pages: 1-13, ISSN: 0264-1275

Laser cladding deposition (LCD) is widely used to remanufacture/repair workpieces because of its high design freedom to rebuild areas of damage. However, the process often introduces a columnar grain structure in the cladding layer, resulting in a large variation of microstructure and hardness across the cladding layer, welding interface, and base metal. Under fatigue and tensile loading, fractures can initiate in the lower hardness cladding layer. This study explores the feasibility of a new hybrid remanufacturing method integrating the LCD with a subsequent hot deformation process to refine grain structures, reduce hardness variations, and enhance mechanical properties. The effects of deformation temperatures and imposed plastic strains were studied by examining the microstructural and stress–strain behaviour of laser cladded 316L stainless steel. After LCD, compressive deformation was imposed at temperatures of 900 and 1100 °C, with engineering strain levels of 0.1 and 0.5. A high-quality metallurgical joint was achieved, with the optimal ultimate tensile strength and yield strength under process conditions of an engineering strain level of 0.5 imposed at 900 °C (35% improvement compared to the directly laser cladding remanufacturing process). Dynamic recrystallization process was observed by the electron back scatter diffraction technique to reveal the underlying mechanism.

Journal article

Xi J, Hu Y, Xing H, Han Y, Zhang H, Jiang J, Nikbin Ket al., 2021, The Low-Cycle Fatigue Behavior, Failure Mechanism and Prediction of SLM Ti-6Al-4V Alloy with Different Heat Treatment Methods, MATERIALS, Vol: 14

Journal article

Luan Q, Wang J, Huang Y, Balint D, Jiang Jet al., 2021, How would the deformation bands affect recrystallization in pure aluminium?, Materials and Design, Vol: 209, ISSN: 0264-1275

Deformation bands (DBs), formed after plastic deformation, are known to have an impact on the recrystallization (RX) process. The exact mechanisms of how DBs influence grain nucleation and grain growth remain unclear. In this paper, deformed single and multicrystal pure aluminium samples are annealed to explore the likely effects of DBs on the grain nucleation and the subsequent grain growth. Regarding the prediction of the recrystallized (RXed) texture, it is noticeable that the orientations of nucleated grains nearby DB are originated from the orientation in DB. Regarding the nucleated positions, it is demonstrated that potential nucleation sites are more likely located in DBs in comparison with the initial grain boundary. Regarding the rate of RX, the number of nucleated grains is also predicted to have a strong positive correlation with the area fraction of DBs, which would consequently affect the kinetics of the grain growth in the deformed microstructure. All the above observations imply that the RX process is strongly controlled by the ensemble characteristics of DBs rather than the initial grain boundaries.

Journal article

Wang Y, Liu Y, Lan B, Jiang Jet al., 2021, A study of solid-state bonding-by-hot-deforming mechanism in Inconel 718, Journal of Materials Processing Technology, Vol: 295, ISSN: 0924-0136

Solid-state bonding shows irreplaceable advantages in joining similar and dissimilar materials with poor weldability compared with fusion welding methods. To widen its applications in manufacturing safety-critical structural parts, a sound bonding quality must be achieved under less strict conditions. In this work, the metallurgical bonding is formed by hot compressing two Inconel 718 parts to different strain levels at the temperature of 1150 °C, strain rate of 0.1s−1 under a low vacuum. Full tensile strength and ductility comparable to the parent materials have been achieved for the first time by 0.5 engineering strain. The severe plastic deformation at hot temperature rapidly bonds the two parts by effectively closing the interface micro-voids, breaking up the oxide film, and in the meantime, accelerating the grain boundary(GB) migration through the dynamic recrystallization(DRx). Based on these observations, a theoretical model is proposed to describe the bonding process under hot deforming condition and the achieved relative interface bond quality, in which the cohesion between oxide-oxide and oxide-metal is assumed, and impairing effect of remaining dispersed oxides is minimized with the attempt of introducing a strain-amplifying factor. The insights and model provide the basis for further understanding of the solid-state bonding-by-hot-deforming under practical conditions and explore its wider application with ideal joint integrity.

Journal article

Lan B, Wang Y, Liu Y, Hooper P, Hopper C, Zhang G, Zhang X, Jiang Jet al., 2021, The influence of microstructural anisotropy on the hot deformation of wire arc additive manufactured (WAAM) Inconel 718, Materials Science and Engineering A: Structural Materials: Properties, Microstructure and Processing, Vol: 823, Pages: 1-14, ISSN: 0921-5093

Hybrid additive manufacturing, incorporating additive manufacturing (AM) and other thermo-mechanical processes, has been developed to improve AM mechanical properties by modifying the as-deposited microstructure and eliminating defects. Additive manufactured parts present strong anisotropic properties, as shown by the anisotropic columnar grain morphology and texture. Samples of AM Inconel 718 were tested at high temperature and under uniaxial compression over a range of conditions. The evolution of microstructural anisotropy and the viscoplastic behaviour under these hot deformation processes was studied. The microstructure and texture evolution were characterised with optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results show that the initial anisotropic microstructure had a negligible effect on flow stress and slip system activation during the hot deformation. The shape of original grains did, however, play a predominant role in determining the final microstructure. When the compression direction was perpendicular to the longitudinal of columnar grains, a more uniform microstructure was obtained under high-flow-stress conditions. This preferred compression direction provides guidance for hot deformation in hybrid additive manufacturing practice. Furthermore, for the nickel alloy studied, controlling the deformation direction to achieve a fine grain structure at a lower temperature (950 °C, lower than δ-solvus) brings practical benefits in the form of possible further δ grain refinement and less demanding thermal conditions during subsequent deformation processes.

Journal article

Guo X, Sun C, Wang C, Jiang J, Fu MWet al., 2021, Study of dislocation-twin boundary interaction mechanisms in plastic deformation of TWIP steel by discrete dislocation dynamics and dislocation density-based modeling, INTERNATIONAL JOURNAL OF PLASTICITY, Vol: 145, ISSN: 0749-6419

Journal article

Xiong Y, Luan Q, Zheng K, Wang W, Jiang Jet al., 2021, Understanding the Strain Path Effect on the Deformed Microstructure of Single Crystal Pure Aluminum, METALS, Vol: 11

Journal article

Jing Y, Ren XY, Shang Y, Xiong H, Jiang Jet al., 2021, Develop a novel high-strength vacuum brazing technique for γ-TiAl intermetallic, International Journal of Lightweight Materials and Manufacture, Vol: 4, Pages: 237-245

Limited strength and ductile joints for bonding γ-TiAl intermetallics are one of the main concerns on γ-TiAl applications in the aerospace industry. In this study, a new ductile brazing filler with TiZrCuNi system was developed by an established model for calculating the electrons distribution of the unit cell for the filler. Three kinds of fillers with fixed amount of Cu and Ni as 25 wt.%, but different Zr level (25, 18, 10 wt.%) were designed. It was found that the filler diffusion was affected by the filler composition, which was insufficient with high Zr content up to 37.5 wt.%. And the defects such as the voids and the cracks were observed with medium Zr level as 25 wt.% and brazing temperature as 1000 °C. The sound joints by Zr as 18 wt.% and 10 wt.% filler at 950 °C and 980 °C respectively were achieved with tensile strength as 520 MPa–570 MPa at room temperature. This tensile strength was remained as 495 MPa in average at 600 °C. The strong joints were attributed to the fine, randomly oriented Ti3Al grains and evenly distributed elements at the interfaces.

Journal article

Guo L, Yuan J, Pei J, Zhao Y, Zhang K, Jiang Jet al., 2021, Study of the microstructure, bonding evolution and mechanical properties of continuously extruded magnesium AZ31 sheet, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 819, ISSN: 0921-5093

Journal article

Pruncu CI, Jiang J, 2021, Modeling and Optimization in Manufacturing Toward Greener Production by Integrating Computer Simulation, Publisher: John Wiley & Sons, ISBN: 9783527346943

The book elaborates on the foundations and applications of computational modeling and optimization processes, as well as recent developments in the field.

Book

Zheng J-H, Pruncu C, Zhang K, Zheng K, Jiang Jet al., 2021, Quantifying geometrically necessary dislocation density during hot deformation in AA6082 Al alloy, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 814, ISSN: 0921-5093

Journal article

Hopper C, Pruncu CI, Hooper PA, Tan Z, Yang S-T, Liu Y, Jiang Jet al., 2021, The effects of hot forging on the preform additive manufactured 316 stainless steel parts, Micron, Vol: 143, Pages: 103026-103026, ISSN: 0968-4328

Additive Manufacture (AM) offers great potential for creating metallic parts for high end products used in critical application i.e. aerospace and biomedical engineering. General acceptance of AM within these fields has been held back by a lack of confidence in the consistency of the mechanical properties of AMed parts associated by the occurrence of porosity, large columnar grains and texture. In this research, to counters this problem we have combined hot forging and subsequent heat treatment. Although, perhaps not best suited to components featuring fine detail, this technique should be well suited to the manufacture of forged components such as fan blades. Here, AM is able to create a near net-shape blank which is then hot forged to size, eliminating intermediate production stages and generating good mechanical properties in the final component. The material used in the current study is AM 316 L Stainless Steel. By altering the printing parameters of the AM machine, two batches of samples were built, each displaying a different porosity content. This allowed the influence of initial build quality to be illustrated. By comparing the two sample batches, it was possible to gain an insight into the possibilities of controlling porosity and material microstructure. The success of the proposed hot forging and heat treatment technique was validated by mechanical testing (i.e. tensile and hardness experiments) and microstructure evolution characterization (i.e. optical microscopy observation and electron backscatter diffraction (EBSD) techniques). The results revealed that the post processing strategy reduced material porosity and enabled the creation of a more robust microstructure, resulting in improved mechanical properties of the AM material.

Journal article

Zhang K, Zheng J-H, Hopper C, Sun C, Jiang Jet al., 2021, Enhanced plasticity at cryogenic temperature in a magnesium alloy, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 811, ISSN: 0921-5093

Journal article

Wang CH, Sun CY, Qian LY, Cai W, Jiang J, Xiao Yet al., 2021, Dynamic mechanical behaviour induced by adiabatic temperature rise of Fe-Mn-Al-C steel, MATERIALS SCIENCE AND TECHNOLOGY, Vol: 37, Pages: 280-291, ISSN: 0267-0836

Journal article

Zhang K, Shao Z, Daniel CS, Turski M, Pruncu C, Lang L, Robson J, Jiang Jet al., 2021, A comparative study of plastic deformation mechanisms in room-temperature and cryogenically deformed magnesium alloy AZ31, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, Vol: 807, ISSN: 0921-5093

Journal article

Zhou X, Shao Z, Zhang C, Sun F, Zhou W, Hua L, Jiang J, Wang Let al., 2020, The study of central cracking mechanism and criterion in cross wedge rolling, International Journal of Machine Tools and Manufacture, Vol: 159, ISSN: 0890-6955

Cross wedge rolling (CWR) is an innovative metal forming process to manufacture axisymmetric stepped shafts used in the transport industry. Central cracking, also called the Mannesmann Effect, consistently occurs in the central region of the CWR workpiece. This results in reduced product quality and increased costs due to rejected and failed parts. However, the understanding of central cracking mechanism and criterion is limited due to the complex stress states in CWR and the experimental limitations. A large number of CWR tests and different die geometries are required in the identification of the potential mechanistic factors such as the axial tensile stress, secondary tensile stress, shear stress and cyclic loading. Also, there is as yet no efficient method of determining the material constants associated with the central cracking fracture criteria. These problems are addressed in the present study. A physical model was built to reproduce the industrial CWR process. A newly designed model material (plasticine/flour composite) was used to mimic the material flows and internal fracture behaviours found in commercial CWR workpieces. This allowed a variety of die shapes to be rapidly and cost-effectively 3D printed, thereby enabling specific stress states to be achieved within the workpiece. Via experimental observations and the corresponding finite element modelling under different die geometries, the maximum shear stress was identified as the dominant factor for central cracking. The fracture criterion involving the maximum shear stress was quantitatively verified to be accurate and robust in predicting central cracking moments and locations. A novel approach using simplified die geometries to determine the associated material constants was proposed and validated. The high accuracy and cost/time efficiency of this new approach will be a significant benefit to fundamental research and also in industrial applications.

Journal article

Sun F, Pruncu CI, Penchev P, Jiang J, Dimov S, Blackman BRKet al., 2020, Influence of surface micropatterns on the mode I fracture toughness of adhesively bonded joints, International Journal of Adhesion and Adhesives, Vol: 103, Pages: 1-11, ISSN: 0143-7496

Surface patterning has been used to enhance the fracture toughness of adhesive joints. In this study, the effect of the variable bondline thickness introduced by the patterns and the effect of pattern geometry on the fracture behaviour of adhesive joints were analysed. Surface patterns including longitudinal grooves, transverse grooves, dimples and grids were fabricated by means of laser texturing. The patterned surfaces were bonded using a tough structural adhesive and the mode I fracture toughness was measured using the J-integral method. The toughness of the patterned joints was compared with the results from bonding with control surfaces and with grit blasted in combination with chromic acid etched (GB-CAE) surfaces. It was shown that both longitudinal and transverse grooves led to the highest value of toughness. Grids patterns yielded a toughness close to the GB-CAE treatment, both of which were higher than the dimple patterns. It was also shown that the variable bondline thickness due to the existence of surface patterns, which influences the size of the plastic zone, reduced rather than increased the fracture toughness.

Journal article

Jiang Y, Offer GJ, Jiang J, Marinescu M, Wang Het al., 2020, Voltage hysteresis model for silicon electrodes for lithium ion batteries, including multi-step phase transformations, crystallization and amorphization, Journal of the Electrochemical Society, Vol: 167, Pages: 1-9, ISSN: 0013-4651

Silicon has been an attractive alternative to graphite as an anode material in lithium-ion batteries (LIBs). The development of better silicon electrodes and the optimization of their operating conditions for longer cycle life require a quantitative understanding of the lithiation/delithiation mechanisms of silicon and how they are linked to the electrode behaviors. Herein we present a zero-dimensional mechanistic model of silicon anodes in LIBs. The model, for the first time, quantitatively accounts for the multi-step phase transformations, crystallization and amorphization of different lithium-silicon phases during cycling while being able to capture the electrode behaviors under different lithiation depths. Based on the model, a linkage between the underlying reaction processes and electrochemical performance is established. In particular, the two sloping voltage plateaus at low lithiation depth are correlated with two electrochemical phase transformations and the emergence of the single broad plateau at high lithiation depth is correlated with the amorphization of c-Li15Si4. The model is then used to study the effects of crystallization rate and surface energy barriers, which clarifies the role of surface energy and particle size in determining the performance behaviors of silicon. The model is a necessary tool for future design and development of high-energy-density, longer-life silicon-based LIBs.

Journal article

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