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A COLUMN RECURRENCE ALGORITHM FOR SOLVING LINEAR LEAST SQUARES PROBLEM

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journal of Computational Mathematics 1996年第4期14卷 301-310页

作者： j.x. zhao(Department of Mathematics, Nanjing University, Nanjing China) NANjING UNIV DEPT MATHNANJING 210008PEOPLES R CHINA

A new column recurrence algorithm based on the classical Greville method and modified Huang update is proposed for computing generalized inverse matrix and least squares solution. The numerical results have shown the ... 详细信息

关键词： Math A COLUMN RECURRENCE ALGORITHM FOR SOLVING LINEAR LEAST SQUARES PROBLEM ABS

ON THE A/D TYPE TWIN BOUNDARY IN 18R MARTENSITE OF A Cu-Zn-Al ALLOY

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Acta Metallurgica Sinica(English Letters) 1997年第5期10卷 425-429页

作者： Zhang, j.x. Zheng, Y.F. Cai, W. zhao, L.C. Harbin Inst of Technology Harbin China

The A/D type twin boundary in a Cu-Zn-Al shape memory alloy appears curved under TEM and shows irregularly serrated steps under HREM. Crystallographic analysis shows that the macroscopic curve results from non-self-accommodation of the boundary, the deviation from exact twin orientation and a preferential orientation for lower boundary energy.

关键词： Aluminum alloys Copper alloys Crystallography Electron microscopy Martensite Zinc alloys

Mechanical Properties and Defective Effects of 316LN Stainless Steel by First-Principles Simulations

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journal of Materials Science & Technology 2011年第11期27卷 1029-1033页

作者： x.Q. Li j.j. zhao j.C. xu x. Liu Key Laboratory of Materials Modification by Laser Ion and Electron Beams Ministry of Education Dalian University of Technology Dalian 116024 China College of Advanced Science and Technology Dalian University of Technology Dalian 116024 China School of Chemical Engineering Dalian University of Technology Dalian 116024 China

In current International Thermonuclear Experimental Reactor （ITER） design, the 316LN austenitic stainless steel （316LN SS） is used for first-wall/blanket structures. Thus, it is necessary to study the fundamental mechanical properties and irradiation effect of 316LN SS. A random solid solution model of Fe-Cr-Ni-Mn- Mo-Si alloy is used for describing 310LN S$. Using first-principles approaches, the elastic constants and ideal strength of the alloy were calculated. Such alloy exhibits good ductile behavior according to the theoretical values of Cauchy pressure and ratio of bulk modulus and shear modulus. Within the 256-atom supercell, inclusion of single vacancy defect further enhances the ductility of the alloy, and the existence of interstitial （Fe, H, He） atoms enhances the Young＇s modulus.

关键词： Stainless steel Mechanical properties Vacancy Interstitial

Machine learning guided automatic recognition of crystal boundaries in bainitic/martensitic alloy and relationship between boundary types and ductile-to-brittle transition behavior

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journal of Materials Science & Technology 2021年第25期84卷 49-58页

作者： x.C.Li j.x.zhao j.H.Cong R.D.K.Misra x.M.Wang x.L.Wang C.j.Shang Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing 100083China Department of Metallurgical Materials and Biomedical EngineeringUniversity of Texas at El Paso500 W.University AvenueEl PasoTX 79968USA

Gradient boosting decision tree(GBDT)machine learning(ML)method was adopted for the first time to automatically recognize and conduct quantitative statistical analysis of boundaries in bainitic microstructure using electron back-scatter diffraction(EBSD)*** spite of lack of large sets of EBSD data,we were successful in achieving the desired accuracy and accomplishing the objective of recognizing the *** with a low model accuracy ofxis-angle pair as characteristic features,the accuracy of the model was significantly enhanced to about 88%when the Euler angle was converted to overall misorientation angle(OMA)and specific misorientation angle(SMA)and considered as important *** this model,the recall score of prior austenite grain(PAG)boundary was~93%,high angle packet boundary(OMA>40°)was~97%,and block boundary was~96%.The derived outcomes of ML were used to obtain insights into the ductile-to-brittle transition(DBTT)***,ML modeling approach suggested that DBTT was not determined by the density of high angle grain boundaries,but significantly influenced by the density of PAG and packet *** study underscores that ML has a great potential in detailed recognition of complex multi-hierarchical microstructure such as bainite and martensite and relates to material performance.

关键词： Machine learning Feature engineering Automatic recognition Lath structure Crystallography

FORMATION OF SILICONIZED LAYER ON TiAl-BASED ALLOY AND THE OxIDATION RESISTANCE

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Acta Metallurgica Sinica(English Letters) 2003年第6期16卷 466-472页

作者： W.Liang x.x.Ma x.G.zhao j.Zhang D.x.Zou SchoolofMaterialsScienceandEngineering TaiyuanUniversityofTechnologyTaiyuan030024China CentralIron＆SteelResearchInstitute Beijing100081China

The Ti-48Al alloy was pack siliconized with 15%Si+85%Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by xRD and SEM equipped with xEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spaliation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h.

关键词： TiAl-based alloy microstructure composite coating high tem-perature oxidation

DESIGN AND PROPERTIES OF A FUNCTIONALLY GRADIENT CERAMIC TOOL MATERIAL

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Acta Metallurgica Sinica(English Letters) 1999年第5期12卷 1054-1058页

作者： j. zhao,x. Ai, j.H. Zhang, j.x. Deng and C.Z. Huang Department of Mechanical Engineering, Shandong University of Technology, jinan 250061,China

Based on the analyses of the severity of cutting process as well as the failure mechanisms of ceramic tools, a model for designing functionally gradient ceramic tool materials with symmetrical distribution is presented, by which a Al 2O 3/(W,Ti)C ceramic tool material FG 2 was developed. Multi objective optimization method was employed in designing the compositional distribution of this ceramic tool material. The results of both continuous and intermittent cutting tests are indicative of the much better cutting behavior of the functionally gradient ceramic tool FG 2 than that of the common ceramic tool SG 4.

关键词： functionally gradient materials materials design compositional distribution ceramic tool

ExPERIMENTAL INVESTIGATION AND THERMODYNAMIC CALCULATION ON PHASE PRECIPITATION OF INCONEL 740

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Acta Metallurgica Sinica(English Letters) 2006年第6期19卷 425-431页

作者： S.Q.zhao Y.jiang j.x.Dong x.S.xie Department of Physics Ningxia UniversityYinchuan 750021China Department of Materials Science The Northwest Second Nationalities InstituteYinchuan 750021China High Temperature Materials Research Laboratories University of Science and Technology BeijingBeijing 100083China

A novel nickel-based superalloy INCONEL 740 was under development for application in ultra-supercritical superheater tubers above 750℃. The precipitation behaviors of η phase and γ' particles of the alloy were investigated through experimental study and phase computation. Experimental results showed that η phase formed a Widmanst?tten pattern structure following long-term exposure at elevated temperatures and that the coarsening of γ' particle follows a cube rate law:r-3 ∝ t. Thermodynamic calculation results showed that Al and Ti had an important effect on the precipitation behavior of γ' andη phases. Two suggested novel modified alloys, wherein the Al and Ti contents were modified, were designed and melted for the experimental study. The preliminary results indicated that the modified alloys exhibited higher structural stability following long-term exposure at 750℃ till 5000h.

关键词： superalloy INCONEL 740 precipitate thermodynamic calculation

Photoluminescence from Silicon Nanocrystals in Encapsulating Materials

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journal of Materials Science & Technology 2013年第3期29卷 221-224页

作者： Z.Deng x.D.Pi j.j.zhao D.Yang State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering Zhejiang University

Naturally oxidized freestanding silicon nanocrystals （Si NCs） are incorporated in commonly used encapsulating materials to explore the photoluminescent application of Si NCs in device structures such as solid-state lighting light-emitting diodes （LEDs） and solar cells. The quantum yield of Si NCs before the incorporation has reached about 45% at the excitation wavelength of 370 nm without any special surface modification. It is found that medium Ioadings, e.g., 5 wt% of Si NCs in encapsulating materials help to obtain high external quantum efficiency （EQE） of the mixtures of Si NCs and encapsulating materials. The curing of encapsulating materials significantly reduces EQE. Among all the encapsulating materials investigated in this work, silicone- OE6551 enables the highest EQE （21% at excitation wavelength λex = 370 nm） after curing. Based on current findings, we have discussed the continuous efforts to advance the photoluminescent application of Si NCs.

关键词： Photoluminescence Silicon nanocrystals Epoxy Silicone Quantum yield External quantum efficiency

EFFECT OF SILICON ADDITION ON RECRYSTALLIZATION AND PHASE TRANSFORMATION BEHAVIOR OF HIGH-STRENGTH HOT-ROLLED TRIP STEEL

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Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 163-168页

作者： L.j. Zhu D. Wu x.M. zhao College of Materials Science and Engineering Jilin University Changchun 130025 China The State Key Laboratory of Rolling Technology and Automation Northeastern University Shenyang110004 China

Because Si is a noncarbide forming element, a multiphase microstructure consisting of ferrite, bainite, and retained austenite, at room temperature, can be formed by controlling the thermomechanical process strictly. The cooling schedules must be restricted by the formation of pearlite and cementite. In the present article, a new integrated mathematical model for prediction of microstructure evolution during controlled rolling and controlled cooling is developed for a typical kind of low carbon Si-Mn TRIP steel, which consists of temperature simulation, recrystallization, and transformation models. The influence of Si contents has been thoroughly investigated. The calculated results indicate that Si retards recrystallization, restrains austenite grain growth as well as accelerates polygonal ferrite transformation.

关键词： TRIP steel Recrystallization Ferrite transformation Bainite transformation Silicon