Department of Metallurgy
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Faculty of Engineering
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Iwate University
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Morioka 020
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Japan A.Chiba S.Hanada Institute for Materials Research
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Tohoku University
,
Sendai 980
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Japan
材料科学技术（英文）
This paper reviews recent research on ductility improvement of B-undoped Ni_3Al alloys.Ni_3Al binary alloys with hypostoichiometric compositions show appreciable ductility at room temperature when the samples are prepared by recrystallization annealing after cold pressing,although the alloys with stoichiometric and hyperstoichiometric compositions remain brittle.Melt-spun ribbons with hypostoichiometric compositions contain fine anti-phase domains (APDs),while no APD can be seen in melt-spun ribbons with a hyperstoichiometric composition.The ductility in hypostoichiometric Ni_3Al alloys is associated with low ordering energy of the alloys.The addition of ternary elements,which have been classified as γ formers such as Pd,Pt,Cu,Co and Ag.improves ductility of Ni_3Al alloys.Correspondingly,the microstructure of the melt-spun ribbons consists of fine APDs.The addition of γ' formers such as Si,Ti,Zr,V,Nb and Ta leads to brittle intergranular frac- ture.No APD was observed in the melt-spun ribbons of these ternary alloys.
关键词:
ductility
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null
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C. M. Liu1)
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K. Abiko2) and M. Tanino2) 1) Schoolof Materials and Metallurgy
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Northeastern University
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Shenyang 110006
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China 2) Institute for Materials Research
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Tohoku University
,
Sendai980
,
Japan
金属学报(英文版)
Effectoftheintergranularsegregationof Sonthehot ductilityof high purityiron wasquan titativelyinvestigated using high purityiron specimenscontaining < 2 ,5,10 ,20 and 60massppm Sby scanning AES,tensiletests under high vacuum and SEMof the fracturedsurface. The main resultsareasfollows: high purityironcontaininglessthan 2 massppm Sexhibitsanexcellenthotductility,thatis,reductionofareatofracturelargerthan95 % ,at alltesttemperaturesbetween673 and 1173 K. Dissolved Sof5 massppm causesanevident hot ductility dropof high purityiron at873～973 K.Increasingthedissolved Scontentfur ther decreases hot ductility and widensthetemperaturerange ofembrittlement. Theembrit tledspecimensfailinintergranular mode. Theamountoftheequilibrium intergranularseg regation of Sincreases withincreasingtheconcentration of dissolved Sand with decreasingthe annealingtemperature. Ssegregates much moreon cavitysurfacesthan atgrain boundaries.
关键词:
high purityiron
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null
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null
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null
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null
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C. M. Liu1)
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K. Abiko2) and M. Tanino2) 1) Schoolof Materials and Metallurgy
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Northeastern University
,
Shenyang 110006
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China 2) Institute for Materials Research
,
Tohoku University
,
Sendai980 8579
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Japan
金属学报(英文版)
Theeffectof phosphorusonthehotductility andthesegregation ofsulfuratgrain boundariesin high purityironcontaining 0 002 % sulfur werequantitativelyinvestigated bytensiletestat973 K, SEMobservation of fracture surface and scanning Auger electron spectroscopy.Theexperimental resultscan besum marized as follows:(1) addition of phosphorustothe iron remarkablysuppressestheintergranular fractureinduced bythesegregation of sulfur at973 Kandincreasesthe hot ductility;(2) phosphorusstrikingly decreasesthesegregation ofsulfur atgrain boundaries, whichisresponsibleforthesuppressionoftheintergranularfrac tureat973 K;(3) theremarkably decreasedsegregation ofsulfur atgrain boundariesbytheaddition of phosphoruscan beexplained bythesitecompetitioneffectandtherepulsiveinter action at grain boundariesbetweensulfuratomsand phosphorusatoms;(4) sulfurstrikinglysegregatestothevoid surfacesformed on grain boundaries, while phosphorushaslittlesegre gationtothevoid surfaces.
关键词:
high purity iron
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null
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WANG Ruikun SUN Lihong LI Dongpei YING Qiming T.Takeyama General Research Institute for Non-Ferrous Metals
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Beijing
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China [Originally published in ACTA METALL SIN (CHINESE EDN) 24 (5) 1988 pp B353—B358
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received 6 May 1987
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in revised form 6 February 1988] T.Takeyama is an emeritus professor of HOKKAIDO University
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Japan
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and now is a technical adviser of GRINFM
金属学报(英文版)
The magnetic domain structure and related magnetic properties of (NdPr)_(16)Fe_(76)B_8 permanent magnet have been studied by colloid-SEM method.In thermally demagnetized state,the ma- trix grains in the magnet generally exhibit multidomain structure,i.e.,180° plate-like indi- vidual domain and a few spike-like or maze-like domains.The average width of the domain measured was 1.5μm.Grain size of single-domain was observed to be generally about 1μm and only a few up to 3μm.The results calculated are:the domain wall energy γ=36 MJ/m~2,the exchange constant A=4.5×10~(-11)J/m,the domain wall width δ=15.7nm, and the critical grain diameter of single-domain D_c=0.5μm.The dependence of high magnet- ic field gradient at grain boundaries in different magnetization directions in the adjacent mag- netic domains located on both sides of grain boundaries and the effect of microstructure on the values of K,A and δ were discussed.
关键词:
Nd-Fe-B permanent magnet
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null
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null
J
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H
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Wang
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H. Lu and H. Murakawa 1) Shanghai Jiao Tong University
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Shanghai 200030.China 2) Osaka University
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Japan
金属学报(英文版)
Local postweld heat treatment (PWHT)is usually performed when it is impractical to heat treat the whole vessel in a furnace, Many factors have an influence on PWHT procedures, such as size of the pipe,heated widths, insulation conditions, heating rates soak temperatures and hold times, material composition etc,. However up to now the influences these factors have on PWHT are not very clearly understood and different criteria for sizing the parameters can be found in different codes. This study provides a direct method to assess the effectiveness of local PWHT.An axisymmetrical model was used based on the thermal-visco-elastic-plastic Finite Element Method with the consideration of creep phenomena. By using this method both temperature and stress distributions can be simulated during whole local PWHT history. The computation results of temperature distributions and the strain histaries during local PWHT are compared with the experiments, and good agreements are obtained, Investigations show that the thermal stresses induced by local PWHT are much affected by creep behavior and the changes of Young's Modulus. The study of stress relief history shows that the stresses decrease quickly in the heating stage, then decrease slowly according to creep law in the hold stage and then studdenly increase when the cooling stage starts. The study shows the possibility that through a series of computations the effects of many factors can be assessed and the optimum parnmeters can be found. Compared with the heated widths based apon some applicable codes, it is found that a heated area of 2.5 on either side of the weld seems more reasonable.
关键词:
postweld heat treatment
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null
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LIU Shicheng Dalian Railway Institute
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Dalian
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ChinaHAMAGOCHI Yoshikazu KUWANO Hisashi Muroran Institute of Technology
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Muroran
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Japan
金属学报(英文版)
The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transformed into stable μ-phase,Laves-phase,X-phase or σ-phase in the later stages.The crystallographic structure of metastable R-phase is rhombohedral with lattice parameters of a=0.9075 nm and α=74.45°.The chemical compo- sition of R-phase is Fe-(27.5—34.9)Mo-(0—25.5)Cr and Fe-(28.9—33.0)W-(9.36— 21.0)Cr in at.-% in Fe-Cr-Mo and Fe-Cr-W system,respectively.
关键词:
Fe-Cr-Mo alloy
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null
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LIU Xingyang Northeast University of Technology
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Shenyang
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China FUJITA Toshio The University of Tokyo
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Tokyo
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Japan
金属学报(英文版)
The effect of W on mechanical properties of 12% Cr-W-V-Nb heat resistant steel at high temperatures and room temperature is reported.The experimental results indicated that if the W content was about 2.2—3.0 wt-%,there was no obviously change of R.T.tensile strength, but impact toughness decreased with the rise of W content.On the other hand,the increase of W content enhanced the short time stress rupture strength,but did not for the long time one. The increase of W have two effects on the precipitation behavior,promoting Laves formation of type Fe_2W,increasing the precipitated phase amount and speeding up the coarsening pro- cess of precipitated phase at high temperatures.The effect of W on the mechanical properties is closely associated with precipitation behaviors.When the rupture life is short,there has no enough time to coarsen the precipitated phases,so the increase of precipitated phases results in strengthening effect,i.e.the W increases the high temperature strength.After prolonged expo- sure,the evident coarsening took plaee,that decreased the effect of precipitation.
关键词:
12%Cr-W-V-Nb steel
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null
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null
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YAN Shichun Institute of Solid State Physics
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Academia Sinica
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Hefei
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ChinaOKUDA Shigeo MIZUBA YASHI Haka Institute of Materials Science
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University of Tsukuba
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Japan
金属学报(英文版)
The softening of stainless steel 316 of non-detectable difference in magnitude induced by thermal pulse was found during fatigue with strain amplitude of 1.17×10~(-4) in temperature range of 333—573K.And it occurred if the measurements of fatigue with thermal pulse were performed in range of 333—503K.However,it will become of the hardening in range of 503 —573K.The temperature,at which hardening of the steel induced by thermal pulse emerges in fatigue process,increases with the increasing in strain amplitudes.
关键词:
fatigue
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null
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LI Yan WU Yigui Luoyang Institute of Technology
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Luoyang
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ChinaHASHIMOTO Hatsujiro Okayama University of Science
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Japan
金属学报(英文版)
The reversible transformation between matrix and martensite in Ni-Ti shape memory alloys has been dynamically observed under TEM.The orientation relation between martensite and austenite as well as the structural change near the transition temperature has been also studied with the help of HREM SADP.The results show that the orientation relation between martensite and austenite is[11]_A//[10]_M,[110]_A//[001]_M,(110)_A//(001)_M and the angle between(110)_A and(010)_M is about 6.5°.The crystal defects of martensite are found to be twin and stacking fault,and the twin plane as(100).
关键词:
Ni-Ti alloy
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null
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