材料期刊网

RELATIONSHIP BETWEEN M-A CONSTITUENT AND CLEAVAGE FRACTURE BEHAVIOUR OF GRANULAR BAINITIC WELD METAL

XU Xiangxing SU Yi ZHOU Wei Tsinghua University , Beijing , ChinaCAI Qigong Central Iron and Steel Research Institute , Ministry of Metallurgical Industry , Beijing , China XU Xiangxing , Dept.of Mechanical Engineering , Tsinghua University , Beijing , 100084 , China

金属学报(英文版)

The cleavage fracture mechanism of granular bainitie weld metal in 15MnVN steel has been investigated.SEM observation of a special specimen for revealing simultaneously fracture sur- face and microstructure shows that the cleavage of the weld is initiated by M-A constituent. The 95th percentile equivalent diameter of M-A constituent controls the cleavage fracture stress of the weld metal.

关键词: granular bainite , null , null , null

IN-SITU OBSERVATION OF CRACK TIP DEFORMATION IN A DUPLEX STAINLESS STEEL

YAO Kefu TANG Naiyong CHEN Nanping Tsinghua University , Beijing , China [Originally published in ACTA METALL SIN(CHINESE EDN)25(3)1989 pp A213—A218 , Ph.D.Student , Dept.of Materials Sci.and Eng. , Tsinghua University , Beijing , China

金属学报(英文版)

The development of dislocation structures in the plastic zone ahead of a crack tip has been in- vestigated in a duplex stainless steel during in-situ deformation experiments in a scanning transmission electron microscope.It was found that the dislocation distribution was significantly different in the ferrite and in the austenite.In the ferrite grains,the dislocations emitted by the crack tip may cross-slip out of the original slip planes and form a broad plastic zone.However,in the austenite,the dislocation free zone is small and the dislocations emitted by the crack pile up in its slip plane.The selection of slip systems at the crack tip depends on the crack tip Schmid factors in both phases.But after large deformation,the selection of the second slip systems at the craek tip in austenite does not depend on the Schmid factors.

关键词: crack tip , null , null , null

HIGH TEMPERATURE OXIDATION AND STRUCTURE OF SCALE AND WHISKERS FOR Fe-Ni-Cr SEALING ALLOYS

DONG Zhili , MA Jusheng , TANG Xiangyun , YOU Liang Tsinghua University , Beijing , China lecturer Department of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The oxidation rate,the growth,morphology and structure of oxide scale and whiskers for Fe-Ni-Cr sealing alloys in H_2-H_2O atmosphere at high temperatures have been studied. The growth rate of scale is controlled by diffusion.The scale is composed of Cr_2O_3 and spinel(Fe,Mn)O·Cr_2O_3 and the oxide whisker,are spinel(Fe,Mn)O·Cr_2O_3.

关键词: oxidation , null , null , null

HYDROGEN INDUCED CRACKING IN FERRITICAUSTENITIC DUPLEX STAINLESS STEEL

HE Jianhong TANG Xiangyun CHEN Nanping Tsinghua University , Beijing , China Professor , Division of Metallic Materials , Dept.of Materials Science and Engineering , Tsinghua University , Beijing , China

金属学报(英文版)

Hydrogen induced cracking in a ferritic-austenitic duplex stainless steel has been investigated using compact tension tests.The stress intensity threshold K_H of the steel rises with increasing austenite content and decreases with increasing current density during hydrogen charging.The hydrogen induced cracking initiates and propagates on {100} planes of the ferrite grains.The austenite grains play a “fibre-toughened” role during obstructing crack propagation.

关键词: duplex stainless steel , null , null

AGING PRECIPITATION OF Cu-Zr AND Cu-Zr-Si ALLOYS AND AFFECTED BY COLD WORKING

DONG Zhili TANG Xiangyun Tsinghua University , Beijing , ChinaHORI Sgigenori FUJITANI Wataru Faculty of Engineering , Osaka University , Japan DONG Zhili Dept.of Material Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

The hardness and electrical conductivity of Cu-Zr and Cu-Zr-Si alloys varying with differ- ent aging regimes were measured and the factors influencing the electrical conductivity were analysed.It is believed that a little Si can refine the precipitates and improve the resistance to softening.The improvement of materials properties by aging and the effect of cold work were also discussed.

关键词: aging , null , null

DIFFUSION OF HYDROGEN IN(α+γ)DUPLEX STAINLESS STEEL

HE Jianhong TANG Xiangyun CHEN Nanping Tsinghua University , Beijing , China Professor , Division of Metallic Meterials , Department of Materials Science and Engineering , Tsinghua University , Beijing , China

金属学报(英文版)

The permeation curves of hydrogen in ferritic-austenitic duplex stainless steel have been electrochemically determined.The apparent diffusivity of hydrogen depends on the austenite content(f_γ)at room temperature,D=(0.27+0.9/f_γ~2)(10~(-10)cm~2/s).It is simply verified that hydrogen in ferritic-austenitic duplex stainless steel diffuses in “series-connection” form through both ferrite grain and austenite grain.The apparent diffusivity is D=D_αD_γ/(f_α~2D_γ+f_γ~2D_α),where D_α,D_γ are diffusivity of hydrogen in ferrite grain and austenite grain respectively,f_α,f_γ are volume fraction,in turn,of ferrite grain and austenite grain.

关键词: hydrogen , null , null

RF deflecting cavity design for bunch length measurement of photoinjector at Tsinghua University

中国物理C

关键词:

Design of an MeV ultra-fast electron diffraction experiment at Tsinghua university

中国物理C

关键词:

SIMULATON ON WELDING PROCESS OF T - JOINTS

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

PREPARATION OF B-N FILMS BY ION BEAM ASSISTED DEPOSITION

JIANG Hai TAO Kun LI Hengde Tsinghua University , Beijing , China lecturer , Department of Materials Science and Engineering , Tsinghua University , Beijing 100084 , China

金属学报(英文版)

BN films,synthesized by ion beam assisted deposition,were analysed by RBS,AES, IR spectra and TEM.Formatiom of c-BN phase was shown not only by IR spectra at absorption peak of 1100 cm~(-1),but also by electron diffraction pattern.The results of AES demonstrate an effect of N~+ implantation near the film surface.The deposited films consist of three layers,i.e.,ion implantation layer,film layer and mixed intermediatelayer, according to the difference of concentration.The micro-Knoop hardness of the film is 25—35 GPa.

关键词: ion beam assisted deposition , null