THE DECOMPOSITION OF δ-FERRITE IN A Cr-Ni-Mo-Ti STAINLESS STEEL

应用金相法研究了18/8/3/1 Cr-Ni-Mo-Ti不锈钢经1300℃固溶处理后在950℃,850℃及750℃恒温分解初期金相组织的变化,并用电解分离及X射线衍射方法鉴定在不同恒温分解阶段δ-铁素体分解的产物。观察到由于提高了固溶处理温度,高温固定下来的铁素体极为不稳定,在分解为奥氏体的同时有TiC的沉淀出现。当δ→γ的转变,由于Cr,Mo等合金元素的偏聚不能继续进行时,才发现残留的δ-铁素体转变为σ-相。过去一般认为18/8型不锈钢在550—1000℃保温后,室温冲击靭性的降低是由于σ-相的沉淀所引起的,试验结果指出在σ-相出现之前,钢的冲击靭性已显著下降,这种现象可能与δ-铁素体分解初期TiC的沉淀有关。     

SNOEK-Ke-K■STER PEAK OF INTERNAL FRICTION IN Fe-P-N ALLOYS

The internal friction and precipitate phases of the deformed Fe-P-N alloys have been investigated. It has been found that the ratio of depends on the content of P and the relation holds if the content of N is lower than 30wt.ppm and the content of P is lower than 640wt.ppm. It shows that the intercept K2 is related to the presence of the atomic pairs and clusters of P in the alloy matrix.     

SNOEK-Kê-K■STER PEAK OF INTERNAL FRICTION IN Fe-P-N ALLOYS

1.IntroductionConsiderableinterestinSnoek-Ke-Kbster(SKK)peak,asanin1portaIltinterllalfYictionphen0men0n,hasbeenheldbyphysicistsandmaterialsscientistsillthefieldofs0lidstateinternalfricti0n[1l2],andithasbeenefficientlyappliedtothestudyoftheall0yingeffectofrareearthelementsillirollandsteels[3].In0rdertogetaclearullderstandingofthecontrolmechanismoftheSKKdampiflg[4-6],Jictal.haveinvestigatedtheinterllalfiiction0fdef0rmedpureiron(99.98wt%)dopedwithasmallamountofphosphorusI7l.Ithasbeenindicate…     

THE PHASE TRANSFORMATION OF δ-FERRITE IN A STRUCTURALLY DUPLEX IRON-ALUMINIUM-MANGANESE-MOLYBDENUM ALLOY

成分为0.07％C,4.6％Al,32.5％Mn,3.1％Mo的Fe-Al-Mn-Mo合金,于1100℃固溶处理后,具有γ+δ复相组织。用金相法研究了δ铁素体于950—450℃温度范围的组织转变过程,并对转变产物进行了结构与成分的相分析。以金相法测定了等温转变的开始动力学曲线,测量了等温转变过程中δ铁素体内显微硬度的变化。 研究表明:于950—750℃有δ→γ转变,650—550℃有δ→γ+M_(23)C_6转变。此二转变分别以完全扩散型及贝茵体型方式在相应的温度范围内同时进行。750—450℃有α-Mn型晶体结构的金属化合物X相宜δ铁素体中脱溶。X相平均化学式为Fe_(26)Mn_(16)Mo_8Al_8。     

THE DECOMPOSITION OF δ-FERRITE IN A 18/8 STAINLESS STEEL CONTAINING 0.34% Ti AND 0.24% Mo

用金相方法研究了含少量钼、钛18/8 Cr-Ni不锈钢中δ-铁素体在900°—550℃恒温分解的过程。观察到在分解产物中没有σ-相。δ-铁素体分解形态及其机构随分解温度而有所不同。当分解温度高于750℃时,先析出奥氏体γ′,继之在未转变的铁素体中,才沉淀出碳化物。分解温度低于650℃时,则先析出碳化物,随后才出现有奥氏体γ′。介乎750°—650℃之间,δ-铁素体通过共析转变方式分解为碳化物及γ′。共析分解未能进行到底,在残留的铁素体中,有奥氏体γ′析出,由于合金元素分配的关系,δ→γ′的转变不久亦停止。 在试验过程中,观察到电解磨光后,在碳化物未全部溶解或δ-铁素体已发生分解的样品表面上,出现有马氏体。用同佯手续制备1300℃固溶处理(碳化物全部溶解)的样品,则没有出现马氏体。初步认为马氏体的出现是由于电解磨光过程中产生自由表面所引起的。但是这种表面马氏体的形成似亦与奥氏体的含碳量有关,其形成机构尚待进一步的研究。     

AN INVESTIGATION OF INTERNAL CRACKS IN THE CONTINUOUS CASTING BILLETS AND ROLLING PRODUCTS OF A 0.45％ C STEEL

在工艺条件不适当时,45钢连铸坯在高温下会产生内部裂纹,当压延比近于4时,裂纹即可焊合。而富集在裂纹上的夹杂物和偏析元素,则被变形并沿轧制方向分散。当这种分散程度不太大时,酸洗后会在那里腐蚀出和裂纹形状相似的沟槽。这种缺陷对纵向力学性能没有影响,但使横向的塑性下降。     

AN ELECTRON DIFFRACTION ANALYSIS OF δ-PHASE IN A Ni-Fe-Cr-Nb ALLOY

根据电子衍射花样的矩阵分析和对有序结构δ相的结构振幅的分析计算,确认了Ni-Fe-Cr-Nb合金晶内魏氏体状δ相具有Kirman等人所指出的取向关系和形成机理,某些晶界胞状δ相不具有那种取向关系,而且具有不完全固定的某些取向关系,发现某些胞状δ相中的Ni,Nb原子可能不完全有序分布。     

ELECTRON MICROSCOPE STUDY ON δ-EUTECTOID IN HIGH SPEED STEEL

The morphology and structure of δ-eutectoid and the transformation of δ-eutectoidicaustenite in high speed steel have been studied under SEM and TEM.The δ-eutectoid inas-cast high speed steel is rod-shaped eutectoidic units with different orientations and ismarkedly surrounded by carbide shell.The eutectoidic carbide is rod-shaped M_6C of squareeross section.The eutectoidic austenite may transform into pearlite structure during cooling.     

EFFECT OF HEAT TREATMENT ON INTERNAL FRICTION OF GRAIN BOUNDARY IN 2091 Al-Li ALLOY

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MECHANICAL PROPERTIES IN AN INTERCRITICALLY HEAT-TREATED BAINITE-TRANSFORMED 2%Si STEEL

A significant amount of austenite can be retained by rapid cooling following intercritical annealing and holding at the bainite transformation range in steel with comparatively low carbon and silicon contents. Retained austenite is blocky and very fine and moderately stabilized due to C enrichment. The elongation and the strength-ductility balance of the steel can be enhanced considerably due to strain-induced martensite transformation and transformation-induced plasticity (TRIP) of retained austenite.     

SUBSTRUCTURE OF BONDING ZONE IN AN EXPLOSIVE CLADDED TITANIUM-MILD STEEL SYSTEM

ＳＵＢＳＴＲＵＣＴＵＲＥＯＦＢＯＮＤＩＮＧＺＯＮＥＩＮＡＮＥＸＰＬＯＳＩＶＥＣＬＡＤＤＥＤＴＩＴＡＮＩＵＭ－ＭＩＬＤＳＴＥＥＬＳＹＳＴＥＭ￥ＹａｎｇＹａｎｇ；ＺｈａｎｇＸｉｎｍｉｎｇ（ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇ...     

CHARACTERISTICS OF INTERNAL FRICTION AND MODULUS ASSOCIATED WITH NON-EQUILIBRIUM DIFFUSION-TYPE PHASE TRANSFORMATION IN EUTECTOID Al-Zn ALLOY

The characteristics of the low frequency internal friction and the modulus effect associatedwith the non-equilibrium spinodal pretransformation and the following discontinuous trans-formation was investigated in an as-quenched eutectiod Al-Zn alloy.It was observed that theloss of the stability in the lattice,which corresponded to the large-amplitude long-wavelengthstatic concentration wave in the non-equilibrium spinodal pretransformation,did not induceany effect of localized soft modulus.Although there are two aging internal friction peaks inphase transformation which correspond to the appearance and disappearance of the coherencyin spinodal pretransformation and the maximum of the interface area in the discontinuoustransformation respectively,the effect of localized soft modulus did not take place yet.     

IN-SITU OBSERVATION OF δ→γ PHASE TRANSFORMATION OF AN AISI304 STAINLESS STEEL

利用共焦激光扫描显微镜原位观察了AISl304不锈钢冷却过程中高温铁素体(δ)→奥氏体(γ)相变的过程及其特征.结果表明,γ相优先在δ晶界处形成;冷却速率影响γ相的生长形态,典型形态分为块状、圆形、树枝状等;"游离"γ枝晶发生粗化,并和周围的γ枝晶聚合;相同冷却条件下,δ晶界处的γ枝晶聚合程度明显高于δ晶粒内部;二次枝晶在冷却过程中粗化,并竞争生长.利用ThermoCalc计算C元素在δ→γ相变过程中的偏析系数,以此求解δ→γ相变数学模型.     

INTRAGRANULAR FERRITE FORMED IN ASSOCIATION WITH INCLUSIONS IN A VANADIUM MICROALLOYED STEEL

lntragranular ferrite was formed at inclusions in a vanadium microalloyed steel with excess amount of sulfur. The chemical composition of inclusions in the steel was analyzed by SEM-EDS. The inclusions were mainly composed of MnS and aluminum oxides. The precipitation of MnS at aluminum oxides might result in Mn depletion, which, in turn, promotes the formation of intragranular ferrite. Optical and SEM observations and threedimensional (3D) reconstruction demonstrated that intragranular ferrite was formed at inclusions. The morphology of intragranular ferrite changed with undercooling. At higher temperatures intragranular ferrite was nearly equiaxed whereas it was plate-like or lath-like at lower temperatures.     

EXPERT CONTROL SYSTEM FOR COAL BLENDING PROCESS IN AN IRON AND STEEL CORPORATION

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BEHAVIOUR OF BUFFER LAYER IN JOINING OF SIALON CERAMICS TO STEEL 40Cr

The buffer layer material itself may be influential to the bond strength between active brazingfiller and ceramics.For Ag_(57)Cu_(38)Ti_5 filler metal,Cu or Ta is excellent buffer layer material,but Kovar or Ni-15Cr-15Co is worse.It was important to design a layer of soft buffer,suchas Cu,to relax interfacial stress rather than hard buffer layer,such as Mo,to avoid stress.There is an optimum thickness range of soft buffer layer,saying h/L=0.02—0.1. It was agood solution to the interfacial stress problem to use soft/hard buffer layer to increasemetal/ceramics joint strength.Finally,an idea of designing gradual materials as buffer layerbetween metal and ceramics was suggested.     

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

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 scanningtransmission electron microscope.It was found that the dislocation distribution wassignificantly different in the ferrite and in the austenite.In the ferrite grains,the dislocationsemitted by the crack tip may cross-slip out of the original slip planes and form a broad plasticzone.However,in the austenite,the dislocation free zone is small and the dislocations emittedby the crack pile up in its slip plane.The selection of slip systems at the crack tip depends onthe crack tip Schmid factors in both phases.But after large deformation,the selection of thesecond slip systems at the craek tip in austenite does not depend on the Schmid factors.     

PHOSPHORUS SEGREGATION AND ANNEALING TEXTURE IN A LOW CARBON STEEL SHEETS

The present work is to study the effect of phosphorus on the annealing texture of a low carbonsteel at different cold rolling and annealing condition by means of pole-figure,inverse-polefigure and orientation distribution function(ODF)method.The microstructure and distribu-tion of phosphorus in steel sheet are studied by means of metallography,scanning electron mi-croscope(SEM)and electron probe microanalysis(EPMA).The results show that phos-phorus promotes the formation of the fiber texture of〈011〉parallel to the rolling direc-tion and〈111〉normal to the sheet surface.The texture was found to be affected mainlyby preannealing temperatures,promoted at 390 or 590℃,and retarded at 490℃.At thepreannealing temperature promoting the formation of texture,phosphorus segregation to theinterior of grains was observed.It seems that the formation of the fiber texture may be associ-ated with the segregation of phosphorus.     

EFFECT OF SLIP ORIENTATION ON STRESS RESPONSE,INTERNAL FRICTION AND ULTRASONIC ATTENUATION DURING CYCLIC DEFORMATION IN Al SINGLE CRYSTALS

The variation of cyclic stress,internal friction and ultrasonic attenuation during cyclicdeformation and relations among them have been investigated with different slip orientationAl single crystals.The results indicate that the value of cyclic stress σ,internal frictionQ~(-1)and ultrasonic attenuation △α depend obviously on the slip orientation.There are largedifferences in above three parameters for different slip orientation Al crystals.In early stageof fatigue life,σ and △α increase and Q~(-1)decreases with cycles N,and △α reached maxi-mum before σ,while Q~(-1)and σ get the valley and the peak,respectively,at same cycles.