XIA Lifang YAN Mufu Harbin Institute of Technology
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Harbin
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China Laboratory of Metal Materials and Heat treatment
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Harbin Institute of Technology
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Harbin
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China
金属学报(英文版)
The mathematical models of the kinetics of the layer growth at different ion nitriding condi- tions of armco iron.steels 45,40Cr,42CrMo and 38CrMoAl have been established.Based on these models the expression of nitrogen concentration profile of ion nitrided layers have been deduced with profile simulating method.They are C_=C_(min)~+(P_4)/(ξ_1-x)+(P_5)/(ξ_(10)~2)(ξ_1-x)~2 C_(γ′)=C_(min)~(γ′)+(P_1)/(ξ_(21))(ξ_2-x)+(P_2)/(ξ_(21)~2)(ξ_2-x)~2 C_α=C_(min)~α+(C_(33))/(C_(33))/(ξ_(32))(ξ_3-x)~3 Using these models,the kinetics of layer growth and the nitrogen concentration profile of ion nitrided layers were sinulated on Apple-Ⅱ computer.Results show that the simulated curves coincide quite well with the experimental data.
关键词:
computer simulation
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null
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null
Journal of Materials Science
The mechanical properties and microstructure were evaluated and analyzed by optical microscopy (OM) and transmission electron microscopy (TEM) for micro-alloy carbon steel weld metal with and without Nb addition, respectively, under different heat treatment processes including stress relief annealing, normalizing, and no treatment after welding. The strength and elongation of the weld metal without treatment after welding were improved with the addition of Nb element, and the impact toughness was not affected obviously with the Nb addition. After stress relief annealing, the strength decreased for the Nb-free weld metal, while the elongation and impact toughness increased. However, for the Nb-bearing weld metal, stress relief annealing improved the strength of the weld metal significantly, and deteriorated the elongation and impact toughness. In the case of normalizing treatment to the weld metal, it was shown that with the increase of the holding time at the normalizing temperature of 920 A degrees C, for both the weld metals with and without Nb addition, the microstructure of the columnar grain zone (CGZ) was transformed from one of columnar grain into one of equiaxed grain. The grain size of the equiaxed grain zone (EGZ) increased initially, then remained almost unchanged with the prolonging of the holding time. The mechanical properties of the weld metal with and without Nb addition showed no obvious change with the increasing holding time. With the increase of the normalizing temperature, the strength of the Nb-bearing weld metal increased, while the elongation and impact toughness decreased significantly. OM and TEM analysis found that the fine NbC particles were precipitated at the normalizing temperature of 920 A degrees C, which refined the grains of the weld metal and increased the impact toughness. With the increase of the normalizing temperature, the content of widmanstatten ferrite (WF) in the Nb-bearing weld metal increased, whereas the quantity of the NbC particles decreased, which improved the strength and lowered the impact toughness.
关键词:
nb-microalloyed steels;continuous cooling transformation;similar yield;strength;pipeline steel;impact toughness;mn;behavior;precipitation;kinetics;vanadium
Journal of Materials Science-Materials in Medicine
Titanium and its alloys have been widely used for orthopedic implants because of their good biocompatibility. We have previously shown that the crystalline titania layers formed on the surface of titanium metal via anodic oxidation can induce apatite formation in simulated body fluid, whereas amorphous titania layers do not possess apatite-forming ability. In this study, hot water and heat treatments were applied to transform the titania layers from an amorphous structure into a crystalline structure after titanium metal had been anodized in acetic acid solution. The apatite-forming ability of titania layers subjected to the above treatments in simulated body fluid was investigated. The XRD and SEM results indicated hot water and/or heat treatment could greatly transform the crystal structure of titania layers from an amorphous structure into anatase, or a mixture of anatase and rutile. The abundance of Ti-OH groups formed by hot water treatment could contribute to apatite formation on the surface of titanium metals, and subsequent heat treatment would enhance the bond strength between the apatite layers and the titanium substrates. Thus, bioactive titanium metals could be prepared via anodic oxidation and subsequent hot water and heat treatment that would be suitable for applications under load-bearing conditions.
关键词:
simulated body-fluid;treated titanium;low-temperature;mechanical-properties;direct deposition;aqueous-solutions;oxide-films;hydroxylapatite;anatase;glass
Qian CONG
金属学报(英文版)
Five-layered Al/Al-Cu functionally graded material (FGM) was prepared by powder metallurgy technology, and the subsequent heat treatment was carried out for the graded material. The microstructures and distribution of Cu element under pressure sintering (F), solution treatment (T4) and artificial aging treatment (T6) were investigated, and the Vickers hardness and flexural properties of different states were tested. The results showed that sintered compact with dense structure and compositional continuous change was obtained. The second-phase CuAl2 was dispersively distributed along grain boundary of Al matrix. After solution treatment at 503℃ for 3 h, CuAl2 phase obviously decreased and dissolved into the Al matrix, and the flexural strength was thereupon enhanced to 228.5~MPa. With the subsequent aging treatment at 150℃ for 15 h, the majority of flake shaped precipitates Θ" phases were uniformly distributed in the matrix. And the distribution of Cu element became gradual continuous compared to sintered compact. Meanwhile, the flexural strength increased further, which accompanied with the decline of plasticity.
关键词:
Al/Al-Cu graded material
C. Jiang
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Y.B. Chen
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B.S. Wu
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Q.L. Jin
金属学报(英文版)
Temperature field numerical simulation about he heat treatment process curve of large turbine rotor is presented. With simulation software Deform3D in according to the heat treatment processing of China First Heavy Machinery, the details of temperature change at the different location of the rotor is to be found. Once knowing the temperature field change, the duplex grain defect long time existed in large forgings can be solved with a quantitative analysis instead of only the qualitative one. Precondition for small metal samples is brought to simulate microstructure and grain size change of large rotor according to the numerical simulation result. Also, consistent feature with real manufacture is showed from the physical experiment, so that the simulation can be used to not only improve the products process but also prevent wasting unnecessary energy and shorten process periods. The rotor quality is controlled thoroughly with plenty of experiments data.
关键词:
temperature field
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null
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null
Shaoxiong ZHOU
材料科学技术（英文）
The discovery of the first Fe-based ferromagnetic amorphous alloy in 1966 had made an impact on conventional magnetic materials because of its unique properties. Since then, a number of amorphous magnetic materials have been successfully developed and used in a wide variety of applications. A brief review of R & D activities on amorphous soft magnetic materials in China is given from the beginning to the present in a somewhat chronological order, followed by a brief introduction to their applications on electric and electronic industries. An analysis and a prospect of Chinese market of such amorphous materials are also presented.
关键词:
Z.D. Qian
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B.W. Li
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E.G. Wang
金属学报(英文版)
A new treatment for interface of metal and dielectric in finite-difference time domain(FDTD) method was presented, further how and why this treatment should be as itis was explained. The FDTD method was developed to compute the low-frequencyelectromagnetic fields in the metal instead of the traditional high-frequency ones as itwas originally proposed. The computational results agreed well with the experimentalones.
关键词:
FDTD method
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null
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null
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null
Lixing HUO
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Furong CHEN
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Yufeng ZHANG
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Li ZHANG
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Fangjun LIU
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Gang CHEN
材料科学技术（英文）
The electron beam local post-weld heat treatment (EBLPWHT) is a rather new method that provides the advantages of high precision, flexibility and efficiency, energy saving and higher productivity. This paper studies the effect of two post-weld heat treatment processes on the microstructure, mechanical properties and fracture toughness of an electron beam welded joints in 30CrMnSiNi2A steel. EBLPWHT, in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were compared. The experimental results show that, after EBLPWHT treatment, the main microstructure of weld was changed from coarse acicular martensite into lath martensite, HAZ was changed from lath martensite, bainite into lower bainite, and base metal was changed from ferrite and pearlite into upper bainite and residual austenite. The microstructures of different zones of joints in FWPWHT condition were tempered sorbite. The properties of welded joints can be improved by the EBLPWHT in some extent, and especially largely for the fracture toughness of welded joints. However the value of fracture toughness of base metal is comparatively low, so appropriate heat treatment parameters should be explored in the future.
关键词:
Post-weld heat treatment
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null
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null
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null
Journal of Applied Physics
High coercivity Nd-Fe-B films with c-axis texture perpendicular to the film plane have been prepared by dc magnetron sputtering and subsequent heat treatment. The influences of heat treatment and buffer layer materials (Mo and Ti) on the microstructure and magnetic properties of the Nd-Fe-B films are investigated. For the film with Mo buffer layer, when the substrate temperatures (T-s) are below the crystallization temperature (T-cr), the as-deposited films are identified to be soft magnetic with a mazelike stripe magnetic domain structure. After subsequent heat treatment, Nd2Fe14B phase forms with c-axis texture perpendicular to the film plane, and the domain structure is not mazelike anymore. The coercivity of the annealed films increases with decreasing T-s and the highest coercivity of about 22.8 kOe has been achieved. For the film with Ti buffer layer, the heat treatment also results in changing the magnetic domain structures from a mazelike pattern to a disordered pattern. Atomic force microscopic observation shows that some ridgelike areas exist in the annealed film with Ti buffer layer.
关键词:
ndfeb thin-films;nd2fe14b films;domains
Applied Surface Science
Anodic oxidation could be employed to produce crystalline titania films on Ti6Al4 V surfaces for inducing apatite formation in simulated body fluid (SBF). In this work, the effect of further heat treatment on the bioactivity of anodic titania films was researched. The surface constitution, morphology, crystal structure and apatite-forming ability of titania films were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated the apatite formation on the Ti6Al4 V surfaces could be attributed to abundance of Ti-OH groups formed via anodic oxidation, but subsequent heat treatment would decrease the amount of surface hydroxyl (OH) groups and result in the loss of the apatite-forming ability. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Heat treatment;OH;Anodic oxidation;Bioactivity;apatite-forming ability;metal;oxidation;surface;water
