吴晓平
,
张立德
材料研究学报
研究了退火、淬火状态下Al-Mg 合金的晶界内耗。实验表明,随Mg 含量的增加,晶界内耗峰的峰宽和弛豫强度单调下降,峰位开始移向高温,后又移向低温;高温淬火处理能压低Al-2.4wt-%Mg的晶界峰,但对其它低Mg 含量试样不敏感,一定温度的保温能使压低的晶界峰回升。
关键词:
晶界内耗峰
,
quenching
,
annealing
,
Al-Mg alloy
,
grain boundary segregation
李长富李阁平杨义杨柯
金属学报
doi:10.3724/SP.J.1037.2010.00157
对Ti-4Al-4.5Mo合金经不同固溶温度淬火处理后的相组成进行了分析. 结果表明, 当合金在相变点以上温度淬火后, 可以获得hcp结构α´马氏体; 随固溶温度降低, 淬火后斜方α´´马氏体出现, 并在一定的温度范围内与α´马氏体共存; 在800 ℃淬火, α´´马氏体消失, 合金由 α和β相构成; α´´马氏体显著降低$\beta$转变组织的硬度. EDS分析表明, Mo含量并不是决定马氏体类型的唯一因素.
关键词:
钛合金
,
quenching
,
martensitic phase
,
microhardness
吴立新
,
陈士华
,
姚中海
物理测试
文章以5CrNiMo钢小型热锻模的开裂为例，具体分析了其化学成分、洛氏硬度、冶金质量、断口形态和显微组织等，特别针对调质后的显微组织对性能的影响进行了相关分析和讨论。最终认为：由于在调质过程中淬火冷却速度较慢，模具未完全淬成马氏体，心部存在一定量的中温转变组织，它导致了模具强度和热稳定性的下降，该模具在刚上模热锻时就发生开裂，这与热处理的目标组织存在差异有密切关系。
关键词:
5CrNiMo钢
,
fracture
,
quenching
L. Chen
,
W. Xia and X. J. Chen Department of Materials Science and Engineering
,
Nanchang Institute of Aeronautical Technology
,
Nanchang 330034
,
China
金属学报(英文版)
A computer software to simulate the phase transformation during quenching is designed based on Avrami equation and Scheil additivity principle of incubation period. The isothermal transformation diagrams of supercooled austenite are described by cubic spline functions. This software is possess of a good graphic interface of Windows style, can simulate the whole process in austenite decomposition during continuous cooling. If the cooling rate was given, the fraction of various microstructures transformed of austenite decomposition during continuous cooling at any temperature can be calculated. The simulation results are checked with the quenching experiment of 45 steel. The results indicate that the simulation results are comparatively close to the experimental results.
关键词:
quenching
,
null
,
null
,
null
J. F. Gu
,
J. S. Pan
,
M. J. Hu and F. F. Shen (School of Materials Science and Engineering
,
Shanghai Jiao Tong University
,
Shanghai 200030
,
China)
金属学报(英文版)
Complicated changns occur inside the steel parts during quenching process. The abruptly changed boundary conditions make the temperature field,micro - structure and stress field change dramatically in very short time, and these variables take a contact interactions in the whole process. In this paper, a three dimensional non - linear mathematical model for queeching process has been founded and the numerical simulation on temperature field,microstructre and stress field has been realized.In the FEM analysis, the incremental iteration method is used to deal with such complicated nonlinear as boundary nonlinear, physical property nonlinear,transformation nonlinear etc.The effect of stress on transformation kinetics has been considered in the calculation of microstructure. In the stress field anal- ysis,a thermo- elasto - plastic model has been founded, which considers such factors as transforma- tion strain,transformation plastic strain, themal strain and the effect of temperature and transforma- tion on mechanical propertier etc. The transient temperature field, microstructure distribution and stress field of the roller on any time can be displayed vividly,and the cooling curve and the changes of stress on any position can also be given.
关键词:
quenching
,
null
,
null
,
null
,
null
,
null
M. Cheng
,
J. Cheng
,
S.Q. Yuan and F. Zhao(North China Institute of Technology
,
Taiyuan 030051
,
China)
金属学报(英文版)
On the basis of experimental studies, a program dealing with the boundary condition in the quenching process has been developed. In this program the method of Beck nonlinear estimation (inverse heat conduction method) was adopted so that the problem of the heat transfer coefficient varying significantly and complicatedly in the quenching process, has been effectively solved. Calculation result shows that the heat transfer coefficient between quenching workpiece and media boundary has a peak value, and this value and the temperature interval in which the peak value occurs vary with the cross section dimensions of workpiece, the types of the quenching media, the temperature and the surface position.
关键词:
quenching
,
null
,
null
P. R. Ding
,
D. Y. Ju
,
T. Lnouc and E. de Vries( 1) MSC Japan Ltd.
,
Osaka
,
Japan 2) Saitama Institute of Technology
,
Saitama
,
Japan 3) Kyoto Universily
,
Kyoto
,
Japan 4) MacNeal - Schwendler (E. D. C. ) B. V.
,
Gouda
,
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
,
null
,
null
,
null
,
null
X.J.Xu
,
G.L.Liu
,
L.J.Shi
,
X.N.Cheng
,
L.Cai
金属学报(英文版)
The superplastic deformation characteristics, of commercial 40Cr (i.e., 5140) steel that was water-quenched only 1 times and subsequent high-temperature tempered, were investigated.The results showed that the 40Cr steel has a fine grain of 10-15μm at room temperature,and exhibits a tensile elongation of 304, a true flow stress of 89.3MPa and a strain rate sensitivity m-value of 0.227 at the initial strain rate of 1.0×10^-3s^-1 and at the temperature of 750℃. The final fracture is caused by the development of neck. The experimental result of elongation is in good agreement with the theoretically predicated value according to the analytical expression ef =(1/f )^m exp(nv +me )-1 (where ef, m, f, nv and ε is respectively elongation, average strain rate sensitivity, initial geometric defect, average strain hardening sensitivity at constant deformation velocity and average true strain). The fracture surface is intergraular, and superplastic deformation induces an equiaxed and grown grain. Decreasing strain rate increases tensile elongation and strain rate sensitivity m-value. The primary superplastic deformation mechanism is thought to be atom-diffusion-controlled grain boundary sliding.
关键词:
super plasticity
,
null
,
null
ZHANG Shaoqing TAO Chunhu Institute of Aeronautical Materials
,
Beijing
,
China.
材料科学技术（英）
The quench transfomation in a Ti-10V-2Fe-3Al near B-titanium alloy was studied by means of X-ray diffraction, transmission electron microscopy, and optical micyoscopy. The quenching temperatures were above and below the β transus temperature. The phase constitutions of specimens quenched from various solution temperatures were identified and the phase morphologies were examined. In addition, the relationship between phase lattice parameters and quenching tempera- tures was given for α, β and α ~(11) phases. This alloy has a tendency of precipitation of athermal ω phase and formation of stress induced α~(11) mar- tensite from β phase during quenching. Quenched from the temperatures above the β transus tem- perature, the alloy mainly consists of β phase, a small amount of α~(11) martensite and athemal ω phase aye also present in the alloy. After quenching from the temperatures below the β transus temperature, the α phase appeays in the alloy in addition to the phases mentioned above.
关键词:
β-titanium alloy
,
null
,
null
