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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

MICROSTRUCTURE AND MORPHOLOGY OF HIGH MANGANESE NON-MAGNETIC STEEL

YANG Yanqing MA Shiliang QIN Xiongpu KANG Mokuang Northwestern Polytechnical University , Xi'an , China YANG Yanqing , Graduate student , Dept.of Materials Science and Engineering , Northwestern Polytechnical University , Xi'an 710072 , China

金属学报(英文版)

Two types of lath structures and kinked ε martensite were observed in the high manganese non-magnetic steel.Both the short non-continuous lath formed by quenching and the long thin straight lath induced by plastic deformation are composed of ε martensite and fcc twin. The transformation mechanism was discussed.The crystallographic analysis indicates that the e martensite at both sides of the fcc twin boundary is of kinked morphology owing to the orientation of their matrices differing from each other.The kinked region is hcp twin.

关键词: εmartensite , null , null , null

ON THE STABILIZATION OF THERMOELASTIC MARTENSITE IN A Cu-Zn-Al ALLOY

WANG Mingpu , LIU Jinwen Central South University of Technology , Changsha , China Lecturer , Dept.of Materials Science and Engineering , Central South University of Technology , Changsha 410083 , China

金属学报(英文版)

The stabilization of thermoelastic martensite in a rapidly solidified Cu-Zn-A1 alloy is be- lieved to be the process of disordering in atomic configuration during which the structure of martensite gradually transforms into N9R(b/a=1/3~(1/2))from M18R.This is dependent upon the intrinsic decomposition tendency of the martensite.

关键词: Cu-Zn-Al alloy , null , null , null

STABILITIY OF MARTENSITE IN Cu-Zn-Al SHAPE MEMORY ALLOY AFTER DIRECT OR STEPPED QUENCHING

LU Xiaoye Central south University of Technology , Changsha , China Lecturer , Dept.of Materials Science and Engineering , Central South University of Technology , Changsha 410083 , China

金属学报(英文版)

The stability of thermoelastic martensite in a Cu-14.84 wt-%Zn-7.75 wt-%Al shape mem- ory alloy with M_s=106°C after direct quenching or stepped quenching has been investigated by using TEM,X-ray diffroctometer and double electric bridge instrument.The martensite aged for about 3 h at room temperature after either direct quenching or stepped quenching (150°C,2 rain)is the M18R structure.The martensite just directly quenched is not so stable, both its certain diffraction peaks and specific electric resistivity,change with aging at room temperature;whereas it is stable after stepped quenching(150°C.2 min),and its diffraction peaks and specific electric resistivity change no more with aging at room temperature.The above mentioned results seem to be explained by the martensite reordering.

关键词: Cu-Zn-Al alloy , null , null , null

SPALLING MECHANISM OF NITRIDED LAYER OF AUSTENITIC STEEL 4Cr14Ni14W2Mo

SUN Xudong LI Jian Northeast University of Technology , Shenyang , China Lecturer , Dept.of Materials Science and Engineering , Northeast University of Technology , Shenyang , China

金属学报(英文版)

The tendency of spalling of the nitrided layer of the hot rolled austenitic steel 4Cr14Ni14W2Mo exhibits close relation to the nitrided surface orientation relative to the rol- led steel rod.It is found that the dislocations in the imperfectly recrystalized steel align as parallel dislocation walls in macroscopic extent,and the thickness of the“white sublayer”in the nitrided layer is much larger at the surface which is parallel to the dislocation walls.On such surface the spalling of the nitrided layer happens often.

关键词: nitriding , null , null

EFFECIS OF TEMPERATURE AND OVERLOAD RETARDATION ON CORROSION FATIGUE CRACK GROWTH OF HIGH STRENGTH STEEL

QIAN Yourong HE Xiangdong Beijing University of Aeronautics and Astronautics , Beijing , China QIAN Yourong , Dept.of Materials Science and Engineering , Beijing University of Aeronautics and Astronautics , Beijing 100083 , China

金属学报(英文版)

The fatigue crack growth rate (CGR) of ultra high strength steel 30CrMnSiNi2A in distilled water at 18,35 and 55℃ were measured.It was confirmed that the temperature is strongly af- fected on the corrosion fatigue CGR of ultra high strength steel.An expression concerning the effects of Δ K and temperature on the CGR was proposed.The fact that the apparent activation energy (36.6 kJ/mol) resulted from regressive analysis of CGR data was similar to the activation energy of hydrogen diffusion in γ-Fe,strongly supporting the theory of hydrogen-assisted crack growth.The overload retardation effect was greatly reduced in cor- rosion fatigue crack growth,especially at lower frequency,e.g.,0.1 Hz.This phenomenon might be due to the increase of the SCC component of CGR after an overload.

关键词: corrosion fatigue , null , null , null

EFFECT OF LASER MELTING PROCESSING ON MICROSTRUCTURE OF GRAY CAST IRON

SHEN Lian LI Chenglao WANG Xiuling MA Lihua ZHU Daozhen Xi'an Jiaotong University , Xi'an , China Associate Professor , Dept.of Materials Science and Engineering , Xi'an Jiaotong University , Xi'an , China

金属学报(英文版)

The microstructure of the laser hardened layer on the HT20-40 gray cast iron after laser melting processing'was examined by optical microscopy,transmission electron microscopy (TEM)and scanning electron microscopy(SEM).Experimental results showed that a struc- ture with dendritic(M+A')and interdendriticly laminal transformed ledeburite (M+A'+Fe_3C)was produced after laser melting processing.The martensite is a mixture of dis- location martensite and twin martensite.Dislocation pile-ups and twins were found in the residual austenite.Microsegregation of composition and heterogeneity of microstructure were also apparent after laser melting processing.

关键词: laser processing , null , null

SUBSTRUCTURE AND CRYSTAL MORPHOLOGY OF MARTENSITE IN MEDIUM CARBON IRON ALLOYS

LIU Yumen HE Zhirong Xi'an Jiaotong University , Xi'an , China Professor , Dept.of Materials Science and Engineering , Xi'an Jiaotong University , Xi'an , China

金属学报(英文版)

The morphologic,substructural and crystallographic characteristics of martensite in steels 60 and 60Si2Mn have been investigated by means of optical and transmission electron microscopy combined with B-M phenomenological crystallographic theory.The average hab- it plane of martensite in medium carbon iron alloys is{225}_f.Experimental data on the habit plane and the orientation relationship between the austenite and martensite are in agreement with the B-M theoretical calculation of using the Bain strain and lattice invariant shear on (100)[011]_f.

关键词: Medium carbon steel , null , null , null

INFLUENCE OF GRAIN SIZE AND ORDERING OF PARENT PHASE ON M_s IN A CuZnAl ALLOY CONTAINING BORON

WU Jianxin JIANG Bohong XU Zuyao (T.Y.Hsu) Shanghai Jiaotong University , Shanghai , China Associate Professor , Dept.of Materials Science and Engineering , Shanghai Jiaotong University , Shanghai , China

金属学报(英文版)

The effect of grain size and ordering of the parent phase on the critical points of thermoelastic martensitic transformation in Cu-25.62 Zn-3.97 Al-0.0018 B(wt-%)shape memory alloy has been investigated.Based on the thermodynamics of phase transformation,a linear rela- tionship between the starting temperature of martensitic transformation and the reciprocal of the square root of grain size is obtained,i.e.M_s temperature rises with increasing grain size. It shows a good agreement with the results of electric resistance measurement.Applying the Landau's theory,a quantitative relationship between M_s and the ordering parameter of the parent phase is set up,which is well confirmed by the results of X-ray diffraction and electric resistance measurement.The activation energy of the ordering process in the parent phase of the alloy is calculated to be 46 kJ/mol.

关键词: Cu-Zu-Al , null , null , null , null

材料期刊网

HYDROGEN INDUCED CRACKING IN FERRITICAUSTENITIC DUPLEX STAINLESS STEEL

MICROSTRUCTURE AND MORPHOLOGY OF HIGH MANGANESE NON-MAGNETIC STEEL

ON THE STABILIZATION OF THERMOELASTIC MARTENSITE IN A Cu-Zn-Al ALLOY

STABILITIY OF MARTENSITE IN Cu-Zn-Al SHAPE MEMORY ALLOY AFTER DIRECT OR STEPPED QUENCHING

SPALLING MECHANISM OF NITRIDED LAYER OF AUSTENITIC STEEL 4Cr14Ni14W2Mo

EFFECIS OF TEMPERATURE AND OVERLOAD RETARDATION ON CORROSION FATIGUE CRACK GROWTH OF HIGH STRENGTH STEEL

EFFECT OF LASER MELTING PROCESSING ON MICROSTRUCTURE OF GRAY CAST IRON

SUBSTRUCTURE AND CRYSTAL MORPHOLOGY OF MARTENSITE IN MEDIUM CARBON IRON ALLOYS

INFLUENCE OF GRAIN SIZE AND ORDERING OF PARENT PHASE ON M_s IN A CuZnAl ALLOY CONTAINING BORON

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