LIU Zongchang Baotou Iron and Steel University
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China LIU Zongchang Associate Professor
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Division of Materials and Heat Treatment
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Baotou Iron and Steel University
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Baotou
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China
金属学报(英文版)
A mechanism of intergranular fracture of as-quenched martensite in high carbon steels has been proposed.When coarse grains of austenite transform to martensite,the grain plays a role of the unit of volume dilation,inhomogeneous strains necessarily produce and local microscop- ic stress concentrations create at grain boundaries.This reduces the intergration of the grains, sometimes intergranular cracks may produce.Under the action of first kind hardening stress or external force,the intergranular cracks propagated along the grain boundaries will form. This results in the candy-like fracture.
关键词:
as-quench martensite
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null
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null
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
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
新型炭材料
The influence of heat treatment on the microstructure and mechanical properties of isotropic pyrolytic carbon prepared by chemical vapor deposition was studied by TEM, SEM, XRD, polarized light metallography, laser Raman spectroscopy, microhardness and three-point bend tests. Results show that the interlayer spacing of the pyrolytic carbon decreases and the crystal size increases with increasing heat treatment temperature. At the same time, the microhardness and the elastic modulus decrease with increasing heat treatment temperature. Heat treatment below 2 400 degrees C has no effect on the flexural strength of the isotropic pyrolytic carbon, but its flexural strength. increases after graphitization at 2 600 degrees C. It is observed that the high temperature heat treatment has changed the pore structure, which consequently influences the mechanical properties.
关键词:
isotropic pyrolytic carbon;heat treatment;microstructure;mechanical;property;raman;porosity
自然科学进展﹒国际材料（英文）
Microstructural evolution and micro-hardness of a directionally solidified Ni-base superalloy subjected to shot-peening during cyclic recovery heat treatment was studied. It was found that gamma' dissolved and dislocation annihilation occurred during heating, while gamma' re-precipitated when temperature dropped. Due to the formation of a stable dislocation network at gamma/gamma' interface, full recovery and therefore complete elimination of the surface recrystallization are difficult by the present cyclic recovery heat treatment.
关键词:
recrystallization;superalloy;dislocation;recovery heat treatment;nickel-base superalloy;single-crystal;behavior
Materials Transactions
The heat treatment parameters of AZ64 magnesium alloy have been optimized using thermal analysis, scanning electron microscopy and X-ray diffraction techniques. The thermal analysis result revealed that two precipitation reactions took place during the solidification of AZ64 alloy. Therefore, a two-step solution heat treatment method, instead of traditional solution treatment whose temperature was about 10 degrees C below the solidus temperature, was developed corresponding to the dissolution of two precipitate phases. With comparison to the traditional heat treatment, the two-step treatment method could generate a complete solution effect. During the following aging process, precipitates almost uniformly dispersed throughout the matrix, thus improve the tensile strength of alloy.
关键词:
AZ64 magnesium alloy;thermal analysis;two-step solution treatment;mechanical properties;ductility;strength
P. R. Ding
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D. Y. Ju
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T. Lnouc and E. de Vries( 1) MSC Japan Ltd.
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Osaka
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Japan 2) Saitama Institute of Technology
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Saitama
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Japan 3) Kyoto Universily
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Kyoto
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Japan 4) MacNeal - Schwendler (E. D. C. ) B. V.
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Gouda
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The Netherlands)
金属学报(英文版)
A method to simulate processes of forging and subsequent heat treatment of an axial symmetric rod is formulated in eulerian description and the feasibility is investigated. This method uses finite volume mushes for troching material deformation and an automatically refined facet surface to accurately trace the free surface of the deforming material.In the method,the deforming work piece flows through fixed finite volume meshes using eulerian formulation to describe the conservation laws,Fixed finite volume meshing is particularly suitable for large three-dimensional deformation such as forging because remeshing techniques are not required, which are commonly considered to be the main bottelencek in the ssimulations of large defromation by using the finite element method,By means of this finite volume method, an approach has been developed in the framework of "metallo-thermo-mechanics" to simulate metallic structure, temperature and stress/strain coupled in the heat treatment process.In a first step of simulation, the heat treatment solver is limited in small deformation hypothesis,and un- coupled with forging. The material is considered as elastic-plastic and takes into account of strain, strain rate and temperature effects on the yield stress.Heat generation due to deformation,heat con- duction and thermal stress are considered.Temperature - dependent phase transformation,stress-in- duced phase transformation,latent heat,transformation stress and strain are included.These ap- proaches are implemented into the commerical commercial computer program MSC/SuperForge and a verification example with experimental date is given as comparison.
关键词:
finite volume method
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null
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null
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null
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null
X.G. Li
金属学报(英文版)
The specimens of 304 austenite stainless steel with the hydrogen attack bubbles orcracks were heat treated at 600℃ for 6h. The SEM and TEM observations on thespecimens before and after the heat treatment showed that the bubbles or cracks could behealed completely by heat treatment. The healing of hydrogen attack bubbles or cracksis closely related to heat diffusion of Fe and C atoms in austenite. The driving forceof crack healing results fram the plastic deforming energy Es induced by the growthof hydrogen attack bubbles or cracks. The critical condition of healing of bubbles orcracks is Es ≥ 2γ/r (where γγ is the surface tension, r is the radius of bubbles or halflength of crack). During healing of the hydrogen attack bubbles or cracks, the recovery,polygonization and recrystallization of the sub-grain also occured.
关键词:
stainless steel
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null
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null
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null
Jianlin LI
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Leao HU
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Yong ZHONG
材料科学技术（英文）
Ball milled Ti/BN composite powder was prepared by high energy ball milling for 40 h, using Ti and BN (the molar ratio of Ti/BN is 3:2) as starting materials. The as-milled composite powder consists of TiN, Ti and amorphous phase. TiN formed while the milled powder was annealed at 400℃. The heat treatment at 700℃ led to the formation of TiB2 and TiB. The nanocrystalline Ti and amorphous phase converted to TiN and TiB2 when the powder was heated to 1300℃.
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