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International Journal of Minerals,Metallurgy and Materials 2022年第4期29卷 836-847页

作者： Bogdan Nenchev Qing Tao Zihui dong Chinnapat Panwisawas Haiyang Li Biao Tao Hongbiao Dong NISCO UK Research Centre School of EngineeringUniversity of LeicesterLeicester LE17RHUK Nanjing Iron&Steel United Co. Ltd.Nanjing 210044China

Data-driven algorithms for predicting mechanical properties with small datasets are evaluated in a case study on gear steel hardenability.The limitations of current data-driven algorithms and empirical models are identified.Challenges in analysing small datasets are discussed,and solution is proposed to handle small datasets with multiple variables.Gaussian methods in combination with novel predictive algorithms are utilized to overcome the challenges in analysing gear steel hardenability data and to gain insight into alloying elements interaction and structure homogeneity.The gained fundamental knowledge integrated with machine learning is shown to be superior to the empirical equations in predicting hardenability.Metallurgical-property relationships between chemistry,sample size,and hardness are predicted via two optimized machine learning algorithms:neural networks(NNs)and extreme gradient boosting(XGboost).A comparison is drawn between all algorithms,evaluating their performance based on small data sets.The results reveal that XGboost has the highest potential for predicting hardenability using small datasets with class imbalance and large inhomogeneity issues.

关键词： machine learning small dataset XGboost hardenability gear steel

Generation mechanism and motion behavior of sliver defect in single crystal Ni-based superalloy

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Journal of Materials Science & Technology 2023年第6期137卷 232-246页

作者： Huxiang Xia Yanhong Yang Qiushui Feng Qingyan Xu Hongbiao Dong Baicheng Liu Key Laboratory for Advanced Materials Processing Technology(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing100084China Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang110016China School of Engineering University of LeicesterLeicesterLE17RHUnited Kingdom

Sliver is a common but easily neglected defect in single crystal Ni-based superalloy castings.To date,there is still no unified viewpoint on its formation mechanism and generation causes.In this work,the orientation discontinuity and motion behavior of sliver defects were studied through experiments and numerical simulations.The ultrathin wedge-shaped specimen containing the grain boundary of the sliver and the matrix was prepared at the initial position of the sliver defect for the observation of equal thick-ness fringes.The discontinuity of equal thickness fringes on both sides of the grain boundary was ob-served through a transmission electron microscope,which directly confirms the abrupt change in the orientation between the sliver and matrix from the nanoscale.The crystal lattices at the smooth area and the bulging area of the grain boundary were found to have unusually different arrangements.The irregular lattice arrangement at the bulging area shows that the grain boundary has experienced high-stress deformation.Statistical results of sliver orientation deviation with a further composition analysis show the micro protuberance of the mold shell has a noticeable inductive effect on the sliver generation.Furthermore,a self-developed three-dimensional phase-field simulation model coupled with the spatial topology algorithm is established to simulate the orientation deflection behavior and orientation devia-tion threshold of fractured dendrites.The simulation results indicated that there is an upper limit of the cross-section solid fraction at the fracture position for the motion of the fractured dendrites.When the cross-section solid fraction at the fracture position is higher than this upper limit,it will be difficult to produce large deviation slivers due to the structural limitation of surrounding dendrites.This upper limit does not change with the solidification temperature gradient.

关键词： Single crystal Ni-based superalloys Directional solidification Sliver defect Phase-field simulation

Seynergistic effect of Mo and Zr additions on microstructure and mechanical properties of Nb-Ti-Si-based alloys additively manufactured by laser directed energy deposition

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Journal of Materials Science & Technology 2022年第8期103卷 84-97页

作者： Yunlong Li Xin Lin Yunlong Hu Jun Yu Junguo Zhao Hongbiao Dong Weidong Huang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design MIIT ChinaNorthwestern Polytechnical UniversityXi’an 710072China School of Engineering University of LeicesterLE17RHUK

The synergistic effect of Mo and Zr additions on microstructure evolution,room-temperature fracture toughness and microhardness of Nb-22Ti-15Si-xMo-yZr(x=4,8,y=3,6)alloys manufactured by laser directed energy deposited(L-DED)have been investigated.The major phases in as-deposited 4Mo-3Zr alloy are Nb solid solution(Nbss),Nb_(3)Si andγ-Nb_(5)Si_(3).The Nb_(3)Si phases disappear with increasing Mo content to 8 at.%or increasing Zr content to 6%.γ-Nb_(5)Si_(3) precipitates formed in the Nbss of as-deposited xMo-yZr alloys due to the cyclic re-heating,and theγ-Nb_(5)Si_(3) precipitates and Nbss matrix exhibits orientation relationship(OR)of[001]Nbss//[1112]γand(110)Nbss//(0110)γin as-deposited 4Mo-6Zr alloy.The microstructure of xMo-yZr alloys became relative homogeneity and the Nbss matrix showed the better continuity after the heat treatment(1400°C/30 h).The Nb_(3)Si phase has transformed into Nbss andαNb_(5)Si_(3) with the OR have been determined as{100}Nbss//{100}αand{111}Nbss//{111}αin the heat-treated 4Mo-3Zr alloy.When Mo content increase to 8at.%,a part ofγ-Nb_(5)Si_(3) phase also transformed into theα-Nb_(5)Si_(3) phase with the OR have been determined as{1120}γ//{110}αand{1010}γ//{111}αafter heat treatment.Among the as-deposited alloys,the 4Mo-6Zr alloy has the highest fracture toughness KQ with the lowest hardness.The average KQ of 4Mo-6Zr and 8Mo-6Zr alloys increased by 28%and 30%after the heat treatment,and reached 13.61 and 11.43 MPa·m^(1/2),respectively.The hardness of Nb-22Ti-15Si-xMoyZr alloys is significantly decreased after the heat treatment.

关键词： alloys microstructure toughness

Reduced Annealing Time and Enhanced Magnetocaloric Effect of La(Fe,Al)13 Alloy by La-nonstoichiometry and Si-doping

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Acta Metallurgica Sinica(English Letters) 2020年第11期33卷 1535-1542页

作者： Liang Yang Jun Li Defang Tu Joel C.J.Strickland Qiaodan Hu Hongbiao Dong Jianguo Li School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Engineering University of LeicesterLeicester LE17RHUK Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong UniversityShanghai 200240China

LaFe13-x Mx(M=Si,Al)alloys are promising for use in magnetic refrigeration.However,they require long annealing time(30 days)in order to optimize the magnetocaloric properties.Research has shown that the addition of extra La in off-stoichiometric alloys can greatly shorten the annealing time.Therefore,the purpose of this study is to investigate the influence of the extra addition of La on the annealing properties of a new off-stoichiometric La1.7Fe11.6Al1.4-xSix(x=0,0.1,0.4)alloys.It was demonstrated that after a 36 h annealing time,a large volume fraction of 1:13 magnetocaloric phase was obtained for all alloys.Further microstructural analysis of the off-stoichiometric La1.7Fe11.6Al1.4-xSix alloys revealed a facet-like grain morphology.The La1.7Fe11.6Al1.4 and La1.7Fe11.6Al1Si0.4 alloys were shown to contain large 1:13 phase precipitates separated in a La-rich matrix,while the La1.7Fe11.6Al1.3Si0.1 alloy had a continuous 1:13 phase matrix with a fine dispersion of La-rich precipitates throughout.When the magnetic field varied between 0 and 2 T,the corresponding magnetic entropy change and relative cooling capacity for the La1.7Fe11.6Al1.3Si0.1 specimen were determined as 4.58 J/kg K and 173.6 J/kg,respectively.More importantly,the La1.7Fe11.6Al1.3Si0.1 alloy displayed only a slight volume change when the meta-magnetic phase transition occurred,which is promising for cyclic use.

关键词： Solidifi cation Magnetic properties Heat treatment Microstructure Functional alloys

Deformation Mechanism and Hot Workability of Extruded Magnesium Alloy AZ31

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Acta Metallurgica Sinica(English Letters) 2018年第1期31卷 71-81页

作者： Zhao-Yang Jin Nan-Nan Li Kai Yan Jian Wang Jing Bai Hongbiao Dong School of Mechanical Engineering Yangzhou University School of Physics and Optoelectronic Engineering Nanjing University of Information Science and Technology School of Materials Science and Engineering Southeast University Department of Engineering University of Leicester

Using the flow stress curves obtained by Gleeble thermo-mechanical testing, the processing map of extruded magnesium alloy AZ31 was established to analyze the hot workability. Stress exponent and activation energy were calculated to characterize the deformation mechanism. Then, the effects of hot deformation parameters on deformation mechanism, microstructure evolution and hot workability of AZ31 alloy were discussed. With increasing deformation temperature, the operation of non-basal slip systems and full development of dynamic recrystallization （DRX） contribute to effective improvement in hot workability of AZ31 alloy. The influences of strain rate and strain are complex. When temperature exceeds 350 ℃, the deformation mechanism is slightly dependent of the strain rate or strain. The dominant mechanism is dislocation cross-slip, which favors DRX nucleation and grain growth and thus leads to good plasticity. At low temperature （below 350 ℃）, the deformation mechanism is sensitive to strain and strain rate. Both the dominant deformation mechanism and inadequate development of DRX deteriorate the ductility of AZ31 alloy. The flow instability mainly occurs in the vicinity of 250 ℃ and 1 s^-1.

关键词： Hot workability. Deformation mechanism Dynamic recrystallization Activation energy Magnesium alloy

Effect of electropulsing treatment on static recrystallization behavior of cold-rolled magnesium alloy ZK60 with different reductions

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Journal of Materials Science & Technology 2019年第6期35卷 1113-1120页

作者： Huijun Guo Xun Zeng Jianfeng Fan Hua Zhang Qiang Zhang Weiguo Li Hongbiao Dong Bingshe Xu Key Laboratory of Interface Science and Engineering in Advanced Materials. Ministry of Education Taiyuan University of Technology Taiyuan 030024China Shanxi Key Laboratory of Advanced Magnesium-Based Materials Taiyuan 030024 China Shanxi Research Center of Advanced Materials Science and Technology Taiyuan 030024 China Department of Engineering University of Leicester Leicester LEI 7RH UK

Effect of electropulsing treatment(EPT) on recrystallization behavior of cold-rolled Mg alloy ZK60 strips was investigated. It was found that EPT significantly improved nucleation rate and migration ability of grain boundaries, leading to accelerated recrystallization of the deformed metals at relatively low temperature. After the recrystallization induced by EPT, the average grain size of 20% rolling reduction samples decreased from 113 um to around 10 um, meanwhile the typical basal-type texture of the coldrolled sample was weakened. EPT was normally accompanied with a thermal and an athermal effects. The athermal effect played a dominated role in increasing nucleation rate, while the thermal effect promoted grain growth. A fewer recrystallized grains originated along the grain boundaries in the 10% reduction samples, while most of the recrystallization took place inside the twins in the 20% reduction samples.

关键词： Mg alloys Recrystallization Athermal effect Twins

Extraordinary mechanical properties of AZ61 alloy processed by ECAP with 160° channel angle and EPT

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Journal of Magnesium and Alloys 2021年第2期9卷 548-559页

作者： Zhaohui Shan Jie Yang Jianfeng Fan Hua Zhang Qiang Zhang Yucheng Wu Weiguo Li Hongbiao Dong Bingshe Xu Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024P.R.China Shanxi Key Laboratory of Advanced Magnesium-based Materials Taiyuan 030024P.R.China Department of Engineering University of LeicesterLeicester LE17RHUK

AZ61 Mg alloy with homogeneous refined microstructure and exceptional mechanical properties was obtained by the combined technology of equal-channel angular pressing(ECAP)and electropulsing treatment(EPT)in this paper.Based on an ECAP die with an intersection angle of 160,the lower temperature is particularly adapted for AZ61 alloy to be deformed,in which accompanied by high accumulated defects density.The recrystallization of EPTed samples during different stages indicated that the recrystallization behavior of the deformed Mg alloy was mainly affected by the processing time and duration of EPT.Compared to those of the as-received samples,the average grain size of the EPTed samples was refined from 89μm to 1.0μm,accordingly the yields stress(YS)and ultimate tensile strength(UTS)were increased from 100 MPa and 260 MPa to 330 MPa and 448 MPa,respectively.The mechanisms of microstructure transformation and the reinforced mechanical properties were analyzed based on the strain of single ECAP,cumulative storage energy and the athermal effect of EPT.

关键词： AZ61 Mg alloy Equal channel angular pressing Electropulsing treatment Recrystallization Mechanical properties

Exceptional mechanical properties of AZ31 alloy wire by combination of cold drawing and EPT

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Journal of Materials Science & Technology 2020年第16期47卷 111-118页

作者： Zhaohui Shan Jing Bai Jianfeng Fan Hongfei Wu Hua Zhang Qiang Zhang Yucheng Wu Weiguo Li Hongbiao Dong Bingshe Xu Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024China School of Materials Science and Engineering Southeast UniversityNanjing 211189China Shanxi Key Laboratory of Advanced Magnesium-based Materials Taiyuan 030024China Department of Engineering University of LeicesterLeicester LEI 7RHUK

A 0.66 mm-diameter AZ31 alloy wire with ultimate tensile strength of 400 MPa and elongation of 28.5%was successfully prepared via the combination of cold-drawing and electropulsing treatment processing(EPT).Microstructure observation showed that the grain size of EPTed samples was refined to about 1μm and the basal texture strength with maxima texture index was weakened to 7.18.EPT can significantly accelerate recrystallization by enhancing the mobility of dislocation and atomic diffusion due to the coupling of the thermal and athermal effects.Finally,uniform ultrafine-grained structure was obtained in the EPTed samples by static recrystallization completed in a very short time(30 s)at relatively low temperature(433 K).

关键词： AZ31 alloy wire Electropulsing treatment Dislocation Atomic diffusion Microstructure Mechanical properties

A general and transferable deep learning framework for predicting phase formation in materials

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npj Computational Materials 2021年第1期7卷 89-98页

作者： Shuo Feng Huadong Fu Huiyu Zhou Yuan Wu Zhaoping Lu Hongbiao Dong School of Engineering University of LeicesterLeicester LE17RHUK Beijing Advanced Innovation Center of Materials Genome Engineering University of Science and Technology Beijing100083 BeijingChina School of Informatics University of LeicesterLeicester LE17RHUK State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing100083 BeijingChina

Machine learning has been widely exploited in developing new materials.However,challenges still exist:small dataset is common for most tasks;new datasets,special descriptors and specific models need to be built from scratch when facing a new task;knowledge cannot be readily transferred between independent models.In this paper we propose a general and transferable deep learning(GTDL)framework for predicting phase formation in materials.The proposed GTDL framework maps raw data to pseudoimages with some special 2-D structure,e.g.,periodic table,automatically extracts features and gains knowledge through convolutional neural network,and then transfers knowledge by sharing features extractors between models.Application of the GTDL framework in case studies on glass-forming ability and high-entropy alloys show that the GTDL framework for glass-forming ability outperformed previous models and can correctly predicted the newly reported amorphous alloy systems;for high-entropy alloys the GTDL framework can discriminate five types phases(BCC,FCC,HCP,amorphous,mixture)with accuracy and recall above 94%in fivefold cross-validation.In addition,periodic table knowledge embedded in data representations and knowledge shared between models is beneficial for tasks with small dataset.This method can be easily applied to new materials development with small dataset by reusing well-trained models for related materials.

关键词： materials alloys alloy

On the Fully Implicit Solution of a Phase-Field Model for Binary Alloy Solidification in Three Dimensions

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Advances in Applied Mathematics and Mechanics 2012年第6期4卷 665-684页

作者： Christopher E.Goodyer Peter K.Jimack Andrew M.Mullis Hongbiao Dong Yu Xie School of Computing University of LeedsWoodhouse LaneLeedsLS29JTUK School of Process Environmental and Materials EngineeringUniversity of LeedsWoodhouse LaneLeedsLS29JTUK Department of Engineering University of LeicesterUniversity RoadLeicesterLE17RHUK

A fully implicit numerical method,based upon a combination of adaptively refined hierarchical meshes and geometric multigrid,is presented for the simulation of binary alloy solidification in three space dimensions.The computational techniques are presented for a particular mathematical model,based upon the phase-field approach,however their applicability is of greater generality than for the specific phase-field model used here.In particular,an implicit second order time discretization is combined with the use of second order spatial differences to yield a large nonlinear system of algebraic equations as each time step.It is demonstrated that these equations may be solved reliably and efficiently through the use of a nonlinear multigrid scheme for locally refined grids.In effect this paper presents an extension of earlier research in two space dimensions(J.Comput.Phys.,225(2007),pp.1271–1287)to fully three-dimensional problems.This extension is validated against earlier two-dimensional results and against some of the limited results available in three dimensions,obtained using an explicit scheme.The efficiency of the implicit approach and the multigrid solver are then demonstrated and some sample computational results for the simulation of the growth of dendrite structures are presented.

关键词： Phase-field simulations binary alloys mesh adaptivity implicit methods nonlinear multigrid