C.C. Liu
,
Z. Liu and G.X. Chen (Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)(Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)(Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)
金属学报(英文版)
ZBainitic transformation is analyzed in detail according to the factors such as morphology,crystallography,mechanical property of bainite and transformation kinetics,and conclusion is drawn that bainitic transformation is controlled by displacive mechanism and self-fempering of displacive microstructure.That is to say,bainite is the product of such procedure during which undercooled austemite first transforms into one certain displacive microstructure by displacive mechanism and then this microstructure experiences self-fempering.With this idea,several questions,which cannot be illustrated only by displacive transformation mechanism,can be explained successfully.
关键词:
bainitic transformation
,
null
,
null
Yali TANG
,
Ningfu SHEN
,
Xiaofang LIU(Research Center for Materials
,
ZhengZhou University of Technology
,
Zhengzhou 450002
,
China)Zhiping LUO(Institute of Aeronautical Materials
,
Beijng 100095
,
China)Baicheng LIU(Tsinghua University
,
Beijing 100084
,
China)
材料科学技术（英文）
Zn-Mg-Y and Mg-Zn-Y-Zr ingots with different chemical compositions were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The icosahedral phases were found in all alloys studied in present work under the as-cast conditions. There are nearly all quasicrystal phases with some MgZn2 Laves phase in a Zn-28.31Mg-13.80Y alloy (wt pct).After annealing at 400℃ for 8 h, the quasicrystal phases transformed to an fcc "W" phase in an Mg-5.57Zn-1.08Y-0.60Zr alloy (wt pct).
关键词:
Author H.J. Shi1)
,
S.L. Liu2)
,
Y.H. He1) and Z.X. Duan2) 1) Department of Engineering Mechanics
,
Tsinghua University
,
Beijing 100084
,
China2) Laboratory of Material Mechanical Properties
,
Beijing Institute of Aeronautical Materials
,
Beijing 100095
,
ChinaManuscript received 18 October 1998
金属学报(英文版)
A series of low cycle fatigue and creepfatigue tests on smooth specimens and notched specimens were performed with a high temperature alloy used in the manufacture of aeroengine turbine discs. The cyclic stressstrain behavior and fracture characteristics of the notched specimens were emphatically investigated. A comparison of fatigue behavior between smooth and notched specimens was done and lifetime of notched specimens was evaluated. At the same temperature, the fatiguecreep lives of the smooth specimens are far greater than that of the notched specimens.
关键词:
low cycle fatigue
,
null
,
null
,
null
Z.S. Zhu
,
N.P.Chen
,
J.L. Gu and M.G. Yan(1)Institute of Aeronautical Materials
,
P.O. Box 8115
,
Beijing 100095
,
China 2)Department of Materials Science and Engineering
,
Tsinghua University
,
Beijing 100084
,
China Manuscript received 26 August 1996)
金属学报(英文版)
By means of crystallite orientation distribution function (ODF) analysis, the influence on orientation variant selection of cold rolling reductions, recrystallization annealing and cooling rates during α→β→α cyclic phase transformation treatments in cold rolled titanium sheet has been investigated. The results show that, cold rolling reduction and annealing treatment both have a great effect on the formation of phase transformation textures.No variant selection occurs in cold rolled and recrystallization annealed titanium sheet which resulte in a more randomly distributed texture.The phase transformation texture formed α→β→α transformation is inherited after 3 cycles of α→β→α phase transformation. The cooling rates during phase transformation have little effect on orientation variant selection.
关键词:
:texture
,
null
,
null
,
null
,
null
Z.K. Fan
,
Y.Q. Wang
,
S.H. Liangand HS. Huang(School of Materials Science and Engineering
,
Xi'an University of Technology
,
Xi'an 710048
,
China)(Mechanical Engineering Department
,
Tsinghua University
,
Beijing 100084
,
China)
金属学报(英文版)
The combinational use of alloying elements with positive and negative segmpation hasbeen shown to be very thective in strengthening the matrix of cast iron. Negativesegmpation alloying elements, Cu and Si, make the inner parts of dendritic austenitesand eutectic cells get good handenability. On the contrury, positive segmpation alloyingelements Cr and Mn make the outer parts of dendrites have higher microhaofness.Appropriate combination of the above two tyPes Of alloying elements can produce auniform microharkness and high strength in grny cast irons.
关键词:
cast iron
,
null
,
null
H. Y. Zhao
,
A. L. Lu
,
Q. Y. Shi and F. Yan (Welding Division
,
Department of Mechanical Engineering
,
Tsinghua University
,
Beijing 100084
,
China)
金属学报(英文版)
T-joints are widely used in ship manufacturing and other welding structures.The welding residual stress and deformation hare significant influence on failure and service life in welding structures.By us- ing of 3D thermal elasto - plastic FEM, the temperature fields,stress fields and deformation of weld- ing processes on T - joints are analyzed in this paper.The moving heat source is considered in the com- putation. Moreover, weld metal filling and multiple - pass welding are simulated using activate/deac- tivate ability.For avoiding "locking" in full integration elements of welding computation,the re- duced intergration elements are used in weld area.The nonlinear FEM analysis program MARC is used to complete the computations, as well as its user subroutines that are programmed to develop the special techniques needed in the simulation of welding process.Some different welding procedures are com- pared, and the welding residual stress and deformation are discussed in details.
关键词:
welding
,
null
,
null
,
null
,
null
Zhigang YANG
,
Hongsheng FANG
,
Jiajun WANG
,
Yankang ZHENG and Chunming LI(Dept. of Materials Science and Engineering
,
Tsinghua University
,
Beijing 100084
,
China)
材料科学技术（英文）
Scanning tunneling microscopy (STM ) has been first employed to study the surface relief accompanying bainite transformation in a Fe-2.17C-12.18Cr-0.31Si-0.26Mn (wt pct) steel. With the exclusive vertical resolution of STM, we observed that the surface relief associated with bainite is a group of surface reliefs related to subplates, subunits and sub-subunits. As a whole, the relief group is in a tent shape, not of invariant plane strain (IPS) type, which is obviously different from that of martensite, and implying that bainite is not formed by shear mechanism. The fine structure of bainite in Fe-1.0C-4Cr-2.0Si (wt pct) alloy has also been studied with STM and TEM. It is found that the bainite plate is composed of subplates, subunits and sub-subunits. On the basis of the fine structure inside a bainitic ferrite plate observed under STM, a sympathetic-ledgewise mechanism of bainite formation is proposed
关键词:
X. J. Sun
,
J. L. Gu
,
B. Z. Bai
,
B. Dai and N. P. Chen (Department of Materials Science and Engineering
,
Tsinghua University
,
Beijing 100084
,
China
金属学报(英文版)
This paper reviews various fabrication methods of ultrafine grained materials and their limitations briefly, and examines the possibility to produce ultrafine grained titanium alloy by compressive deformation preliminarily. It has been shown that submicrongrained TC11 alloy can be obtained by compressive deformation below 725°C. During microstructure refinement, dynamic recrystallization occurs only in α phases, and β phases undergo a process of precipitation and growth. Compared with the situation of static annealing, deformation can not only enhance the precipitation and growth of β phases but also change the morphology of βprecipitates.
关键词:
TC11 alloy
,
null
,
null
,
null
