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Overcoming the strength-ductility trade-off by tailoring grain-boundary metastable Si-containing phase in β-type titanium alloy

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Journal of Materials Science & Technology 2021年第9期68卷 112-123页

作者： X.Luo L.H.Liu c.Yang H.z Lu H.W.Ma z.Wang D.D.Li L.c.zhang Y.Y.Li National Engineering Research center of Near-net-shape Forming for Metallic Materials South China University of TechnologyGuangzhou510640China State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan430074China Key Laboratory of Automobile Materials of MOE Department of Materials ScienceJilin UniversityChangchun130012China School of Engineering Edith Cowan University270Joondalup DriveJoondalupPerthWA 6027Australia

It is well accepted that grain-boundary phases in metallic alloys greatly deteriorate the mechanical *** our work,we report on a novel strategy to prepare high strength-ductility β-type(Ti69.71 Nb23.72zr4.83Ta1.74)97Si3(at.%)(TNzTS) alloys by tailoring grain-boundary metastable Si-containing ***,the thin shell-shaped metastable S1 phase surrounding the columnar β-Ti grain was intercepted successfully via nonequilibrium rapid solidification achieved by selective laser melting(SLM).Subsequently,the thin shell-shaped metastable(Ti,Nb,zr)5 Si3(called S1) phase was transformed into globular(Ti,Nb,zr)2 Si(called S2) phase by the solution heat ***,the globular S2 phases reinforced TNzTS alloy exhibits ultrahigh yield strength of 978 MPa,ultimate strength of 1010 MPa and large elongation of 10.4 %,overcoming the strength-ductility trade-off of TNzTS alloys by various ***,the reported yield strength herein is 55 % higher than that of conventionally forged TNzT *** analysis indicates the globularization process of the metastable S1 phase is controlled by the model of termination *** quantitative analysis on strengthening mechanism demonstrates that the increase in yield strength of the heat-treated alloys is mainly ascribed to the strengthening of the precipitated silicide and the dislocations induced by high cooling *** obtained results provide some basis guidelines for designing and fabricating β-titanium alloys with excellent mechanical properties,and pave the way for biomedical application of TNzTS alloy by SLM.

关键词： Selective laser melting βtitanium alloys Heat treatment

Numerical　Solution　of　Flow　Field　Diagnosis　Problem　in　Multistage　Axial　compressors

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Journal of Thermal Science 1995年第2期4卷 96-99页

作者： z.c.zhang J.Liu 等 DepartmentofThermalEngineering TsinghuaUniversityBeijing100084China DepartmentofThermalEngineering

A mathematical model is developed for the flow field diagnosis problem in multistage axial compressors. In view of the ill-posedness of the diagnostic problem, an effective measure is adopted to transfer the diagnostic problem into a variational problem which is solved by a regularization method. Two numerical results demonstrate the rationality of the flow field diagnosis Problem and the effectiveness of the computational method.

关键词： compressor flow field diagnosis posedness.

Strain rate sensitivity of a 1.5 GPa nanotwinned steel

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Journal of Iron and Steel Research International 2021年第11期28卷 1352-1356页

作者： R.D.Liu Y.z.Li L.Lin c.P.Huang z.H.cao M.X.Huang Iron and Steel Research Institute Ansteel GroupAnshan 114021LiaoningChina Department of Mechanical Engineering The University of Hong KongHong Kong 999077China

Two distinct regimes of strain rate sensitivity on yield strength are found in a high-strength nantwinned *** yield strength increases from 1410 to 1776 MPa when the strain rate increases from 10–3 to 1400 *** is proposed from the measured small activation volume that the yielding of the nanotwinned steel at higher strain rates is governed by the dislocation bowing out from the carbon *** lower strain rates,however,the yielding is controlled by the continuous re-pinning of dislocations due to the fast diffused carbon atoms,which leads to the relative insensitivity of yield strength to the strain rate.

关键词： Nanotwinned steel Strain rate sensitivity Hokinson tensile bar Twinning Twinning-induced plasticity steel

Performance of Sacrificial Anodes in Reinforced concrete

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武汉理工大学学报 2010年第17期32卷 165-169页

作者： TU L Q DONG c WANG c J zHANG G z LEI Y F SHUI z H School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China Wuhan Harbour Engineering Design & Research co. Ltd Wuhan 430071China Key Lab of Large-span Bridge construction Technology Minstry of CommunicationsWuhan 430071China zhejiang Province zhoushan Island Linking construction commanding Department Zhoushan 316032China

The electrochemical performance of the anodes was measured in the reinforced concrete test block in artificial sea water. Their chemical composition,metallographic structure and surface morphology were analyzed. It was found that concrete mix proportion and the covering layer thickness had an impact on the performance of sacrificial anodes. The thermal-sprayed zinc alloy anodes had a more negative corrosion potential and larger galvanic current than metallurgy ones in the same conditions. They had similar chemical composition. But metallographic structure showed that the structure of thermal-sprayed zinc alloy anodes was a loose porous. This structure had the catalytic effect on the andes electrochemical reactions and made the anodes the electrochemical exchange current density increase and the corrosion potential move to negative direction.

关键词： sacrificial anode reinforced concrete concrete mix proportion thermal-sprayed anodes electrochemical performance

Macro to nanoscale deformation of transformation-induced plasticity steels：Impact of aluminum on the microstructure and deformation behavior

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Journal of Materials Science & Technology 2018年第5期34卷 745-755页

作者： V.S.Y.Injeti z.c.Li B.Yu R.D.K.Misra z.H.cai H.Ding Department of Metallurgical Materials and Biomedical Engineering500 W. University Avenue USA School of Materials Science and Engineering Northeastern University Shenyang 110819 China

This work aims to elucidate the impact of aluminum-content on microstructure and deformation mechanisms of transformation-induced plasticity（TRIP） steels through macroscale and nanoscale deformation experiments combined with post-mortem electron microscopy of the deformed *** solid-state transformation-induced mechanical deformation varied with the Al contents,and influenced tensile strength-ductility *** with 2–4 wt% Al were characterized by TRIP *** contrast to 2 Al-TRIP and 4 Al-TRIP steels,twinning-induced plasticity（TWIP） was also observed in conjunction with strain-induced martensite in 6 Al-TRIP *** behavior is attributed to the increase in stacking fault energy with the increase of Al content and stability of austenite,which depends on the local chemical *** study addresses the knowledge gap with regard to the effect of Al content on austenite stability in medium-Mn TRIP *** combination is expected to potentially enable cost-effective alloy design with high strength-high ductility condition.

关键词： Medium-manganese steels Aluminum content Electron microscopy Mechanical properties Nanoscale deformation TRIP steel Twinning

The Textured Growth characteristics of Diamond Films on coSi2 (001)

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材料科学与工程学报 2000年第Z2期20卷 653-656页

作者： c.z.Gu Fraunhofer-Instiut f(u)r Schicht- und Oberfl(a)chentecbnik Bienroder Weg 54E 38108 Braunschweig Germany

Epitaxial coSi2 (001) layers, deposited on Si (001) substrate by molecular beam allotaxy (MBA), were used as substrate for diamond deposition in order to realise new applications. The results indicate that, in a microwave plasma chamber, diamond can be nucleated with a higher density on coSi2 at lower temperatures using a bias enhanced method. High quality, [001]-textured diamond films can be synthesized on coSi2 (001) using the [001] textured growth conditions. So far an epitaxial growth of diamond on coSi2 cannot be observed. Statistically, a rotating angle distribution of diamond grains around the [001] axis in an [001]-textured film shows, however, preferred in-plane orientations of 13°, 22°, 45° and 77° relative to the coSi2 [011]axis. The structural and chemical analyses show that no co and Si element diffusion from the coSi2 substrate into the diamond film can be detected.

关键词： Diamond Films epitaxial growth plasma chamber diamond films in order

Fatigue Properties Improvement of Low-carbon Alloy Axle Steel by Induction Hardening and Shot Peening:A Prospective comparison

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1343-1356页

作者： G.c.chu F.z.Hu X.J.jin Y.zhang Q.Wang J.P.Hou z.F.zhang Shi-changxu Innovation center for Advanced Material Institute of Metal ResearchChinese Academy of SciencesShenyang 110016.China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China Manshan Iron and Steel co. Ltd.Maanshan 243000China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Baowu Group Masteel Rail Transit Materials Technology company Limited Maanshan 243000China

Fatigue fracture is the major threat to the railway axle, which can be avoided or delayed by surface strengthening. In this study, a low-carbon alloy axle steel with two states was treated by surface induction hardening and shot peening, respectively, to reveal the mechanism of fatigue property improvement by microstructure characterization, microhardness measurement, residual stress analysis, roughness measurement, and rotary bending fatigue tests. The results indicate that both quenching and tempering treatment can effectively improve the fatigue properties of the modified axle steel. In addition, induction hardening can create an ideal hardened layer on the sample surface by phase transformation from the microstructure of ferrite and pearlite to martensite. By comparison, shot peening can modify the microstructure in surface layer by surface severe plastic deformation introducing a large number of dislocation and even cause grain refinement. Both induction hardening and shot peening create compressive residual stress into the surface layer of axle steel sample, which can effectively reduce the stress level applied to the metal surface during the rotary bending fatigue tests. On the whole, the contribution of induction hardening to the fatigue life of axle steel sample is better than that of the shot peening, and induction hardening shows obvious advantages in improving the fatigue life of axle steel.

关键词： Surface strengthening Induction hardening Shot peening Axle steel Fatigue property improvement

coercivity Enhancement of Nd-Fe-B Thin Film Magnets through Dy Surface Diffusion Process

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Journal of Materials Science & Technology 2011年第9期27卷 826-830页

作者： c.Y. You J. zhu N. Tian z.X. Lu State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China School of Materials Science and Engineering Xi＇an University of Technology Xi＇an 710048 China

The Dy capping layer was deposited at different temperatures on the Nd-Fe-B thin films to investigate the mechanism of the coercivity enhancement through the Dy surface diffusion. The highest coercivity of 2005 kA/m （25.2 kOe） was obtained at the Dy deposition temperature of 460℃, which was significantly higher than the value of 1297 kA/m （16.3 kOe） without Dy capping layer. By performing the transmission electron microscopy （TEM） analysis, it was found that some of the grain boundaries were enriched with Nd element, which could be partly ascribed to the promotion by the Dy surface diffusion. In comparison to the evolution of the spin reorientation temperature of Nd2Fe14B phase after the deposition of the Dy capping layer, it is concluded that structural modification plays a significant role in the coercivity enhancement due to the Dy surface diffusion.

关键词： Nd-Fe-B thin film coercivity enhancement Dy layer Microstructure

Stress analysis near the tips of a transverse crack in an elastic semi-strip

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Applied Mathematics and Mechanics(English Edition) 2017年第7期38卷 935-956页

作者： z. zHURAVLOVA Institute of Mathematics Economics and Mechanics Odessa I. I. Mechnikov National University Odessa 65082 Ukraine

The plane elastic problem for a semi-strip with a transverse crack is inves- tigated. The initial problem is reduced to a one-dimensional continuous problem by use of an integral transformation method with a generalized scheme. The one-dimensional problem is first formulated as a vector boundary problem, and then reduced to a system of three singular integral equations （SIEs）. The system is solved by use of an orthogonal polynomial method and a special generalized method. The contribution of this work is the consideration of kernel fixed singularities in solving the system. The crack length and its location relative to the semi-strip＇s lateral sides are investigated to simplify the problem＇s statement. This simplification reduces the initial problem to a system of two SIEs.

关键词： semi-strip transverse crack Green's function integral transformation,fixed singularity singular integral equation (SIE)