材料期刊网

PREVENTION OF THE INTERGRANULAR FRACTURE AT ELEVATED TEMPERATURES BY ADDITION OF PHOSPHORUS TO A HIGH PURITY Fe0 002% SALLOY

C. M. Liu1) , K. Abiko2) and M. Tanino2) 1) Schoolof Materials and Metallurgy , Northeastern University , Shenyang 110006 , China 2) Institute for Materials Research , Tohoku University , Sendai980 8579 , 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 , null , null , null

RELATION BETWEEN THE INTERGRANULAR SEGREGATION OF SAND THE HOT DUCTILITY IN HIGH PURITY Fe SALLOYS

C. M. Liu1) , K. Abiko2) and M. Tanino2) 1) Schoolof Materials and Metallurgy , Northeastern University , Shenyang 110006 , China 2) Institute for Materials Research , 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 , null , null , null , null , null

Inter-conversion of M(n+1)AX(n) phases in the Ti-Al-C system

Journal of the American Ceramic Society

It is demonstrated that the M(n+1)AX(n) phase Ti3AlC2 may be readily synthesized by sintering a stoichiometric mixture of the lower order MAX phase Ti2AlC mixed with a stoichiometric amount of TiC in the temperature range 1350 degrees-1450 degrees C. High-quality Ti3AlC2 was readily produced using sintering times in the range 2-5 h. In general, < 2% of unwanted or remnant phases were found to be present and in some samples none could be detected at all.

关键词: resolved neutron-diffraction;ti3sic2 synthesis;mechanical-properties;powder diffraction;crystal-chemistry;ti3alc2;temperature;ceramics;carbide;ti2alc

MAGNETIC PROPERTIES OF Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)ALLOYS

XING Feng JIANG Chao HE Wenwang Department of Physics , Peking University , Beijing , China [Originally published in ACTA METALL SIN (CHINESEEDN) 24 (5) 1988pp B348—B352 , received 22 October 1986:in revised form 8 May 1987]

金属学报(英文版)

The magnetic properties of Nd_2(Fe_(1-x)M_x)_(14)B(M=C and Si) compounds have been investi- gated.Substituting Fe by small amount of metalloid C and Si atoms,the compounds are in tetragonal structure and have uniaxial anisotropy.The substitution of C for part of Fe de- creases the Curie temperature of the compounds and the intrinsic coercivity of bond samples at low temperature.The replacement of Fe by Si makes the Curie temperature increase with a maximum at the vicinity of x=0.15.When the range of the content of Si is 0≤x≤0.10,the coercivity distinctly increases at room temperature.from 62.7 kA/m at x=0 to 138.7kA/m at x=0.06,where the residual magnetization has a maximum:in the mean time the saturation magnetization decreases only by a small amount.

关键词: Nd-Fe-B alloy , null , null

Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)合金的磁性

邢峰 , 江潮 , 何文望

金属学报

本文研究了Nd_2(Fe_(1-x)M_x)_(14)B的磁性。少量类金属原子C和Si取代部分Fe,能形成四方结构,且具有单轴各向异性。碳取代Fe,使化合物的Curie温度降低,低温下粘结体样品的内禀矫顽力减少;而Si对Fe的取代可使Curie温度升高,并在x=0.15附近达到极大值。含Si样品在0≤x≤0.10范围内,矫顽力显著增加,室温下从x=0的62.7kA/m增加到x=0.06的138.7 kA/m,并且在x=0.06附近,剩磁有一个极值,饱和磁化强度减少不多。

关键词: Nd-Fe-B合金 , magnetic properties , Curie temperature

Eu~(2+)激活的M_7Mg_2(SiO_4)_4C1_2(M=Ca,Sr,Ba)荧光性质的研究

吴茜 , 陈永杰 , 曹发斌 , 李郎楷 , 杨英

稀有金属材料与工程

采用高温固相法合成Eu~(2+)激活的碱土金属氯硅酸盐系荧光粉M_7Mg_2(SiO_4)_4C1_2: 0.08Eu~(2+)(M=Ca,Sr,Ba),研究了它们的荧光光谱.结果表明,3种荧光粉均为宽带激发,激发带位置分别在250～500 nm、250～450 nm、250～430 nm.讨论了Eu~(2+)离子的跃迁发射随基质组成的变化规律,随着Ca、Sr、Ba离子半径的依次增大,发射波长逐渐向短波方向移动,分别产生绿(507 nm)、蓝(458、445 nm)不同颜色的发射光.

关键词: 二价铕 , 氯硅酸盐 , 碱土金属

Relationship between degeneration of M7C3 and precipitation of M23C6 in a cobalt base superalloy

Materials Science and Technology

The relationship between degeneration of the primary M7C3 carbide and precipitation of the secondary M23C6 carbide has been investigated in a cobalt base superalloy after 100 h aging at 850 degrees C. The results indicated that the primary M7C3 carbide could not transform in situ into the secondary M23C6 carbide. The M23C6 formed by a direct reaction between chromium and carbon atoms. The dissolution of M7C3 provided the precipitation of M23C6 with essential carbon, which acted as a carbon reservoir. Near M7C3, the chromium content is a controlling factor of M23C6 precipitation while away from it, the carbon content dominated the reaction. The precipitate free zone around M7C3 is attributed to chromium depletion which is inherited from the as cast condition. MST/4174

关键词:

Sintered Fe08%C10%Si04%Cu P/M Steel Preform Behaviour During Cold Upsetting

A Rajeshkannan , K S Pandey , S Shanmugam , R Narayanasamy

钢铁研究学报(英文版)

Cold upsetting experiments were carried out on sintered Fe08%C10%Si04%Cu steel preforms in order to evaluate their deformation characteristics. Powder preforms of 86% of theoretical density, with two different ratios of height to diameter, were prepared using a suitable die set assembly on a 10 MN capacity hydraulic testing machine. Sintering was carried out in an electric muffle furnace for 15 h at 1 150 ℃. Each sintered compact was subjected to incremental loading of 004 MN under dry friction condition till a crack appeared at the free surfaces. The experimental results were critically analysed, the stress as a function of strain and densification was obtained, then the work hardening behaviour was analyzed. It has been found that in the process of enhancing densification, strength and strain hardening is also induced during upsetting, but the work hardening behaviour is not homogenously enhanced against strain and densification.

关键词: cold upsetting;stress;height strain;densification;work hardening behaviour

Oxidation of two three-phase Cu-30M-Cr alloys at 700-800 degrees C in 1 atm of pure oxygen

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

The oxidation of two ternary Cu-Ni-Cr alloys containing approximately 30 at.% and 40 at.% Cr, but with a similar 30 at.% Ni content, was studied at 700-800 degrees C in I atm of pure oxygen. The two alloys are composed of a mixture of three phases, where the medium gray beta phase with an intermediate chromium content forms the matrix and the lightest alpha phase with the largest copper and lowest chromium content forms large islands and has a rather large volume fraction, while dark gamma phase richest in chromium forms isolated particles dispersed in the other two phases, moreover, the gamma phase particles for the alloy containing 40 at.% Cr appear to have a precipitation of very small lighter particles. The kinetic curves for the two alloys deviate considerably from the parabolic rate law and are composed of a few of stages, where they show a large initial weight increase after which the rates decrease with time, until they become very small up to 24 h. Generally, the oxidation rates decrease by increasing the Cr content in the alloy under constant temperature and increase with temperature for a constant alloy composition. The alloy containing 30 at.% Cr produced an external scale mainly composed of a rather thick and discontinuous lighter layer of copper oxides. Beneath the external scale there is a dark and continuous layer of irregular chromia in thickness, which at some locations is followed by a thin dark layer of chromia directly in contact with the alloy. On the contrary, at other locations the scale forms deep protrusions into the alloy. The alloy containing 40 at.% Cr formed a lighter thick but discontinuous layer of copper oxides containing some nickel followed by an innermost region composed of a rather thick and continuous dark layer of regular and flat chromia. The formation of an external scale of chromia for the two alloys prevents alloys from being oxidized further. (c) 2006 Elsevier B.V. All rights reserved.

关键词: Cu-Ni-Cr alloy;three-phase;high-temperature oxidation;2-phase binary-alloys;high-temperature oxidation;high oxidant;pressures;possible scaling modes;cu-cr alloys;internal oxidation;air;oxidation;o-2;700-900-degrees-c;beneath

ON THE M_7C_3 IN Cr27 CAST IRON

LI Yuqing WANG Cirong GU Zhaofeng Research Institute of Daye Steel Works , Huangshi , China Senior Engineer , Research Institute of Daye Steel Works , Huangshi 435001 , China

金属学报(英文版)

Determination of(Fe,Cr)_7C_3 in Cr27 cast iron results about 30 v.-%.Minor Si and Mn are present.Sectional area of the M_7C_3 grains is 1—50μm~2.Combining matrix analysis of elec- tron diffraction pattern with calculated angle between plane traces,{011}twins and also {013}twins producing local environment for Ru_7B_3 are observed in the orthorhombic M_7C_3. A crystallographic model for M_7C_3 is proposed.

关键词: cast iron , null , null , null , null