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。     

PHASE COMPOSITION AND TRANSFORMATION STRESS OF PRIMARY LAMELLAR STRUCTURE IN γ-TiAl-BASED DUPLEX ALLOY DURING ISOTHERMAL DECOMPOSITION

应用Ｘ射线衍射测定了过饱和α２单相的Ｔｉ－４５％Ａｌ合金在９５０℃等温分解过程中,初生片层形成时的γ相转变分数及２和γ相晶格参数的变化。结果表明,初生片层中α２和γ相晶格参数的变化,结果表明,初生片层中α２相是亚稳相,其成分可以由自由能成分曲线的亚稳态α２相与γ相自由能成分曲线公切线的切点稳定,该成分的确定对定量计算合金自由能及发生不连续粗化的转变驱动有十分重要的作用;     

TEM OBSERVATION OF PHASE TRANSFORMATION IN 47121 β-Ti ALLOY

用透射电镜研究了Ti-4Al-7Mo-10V-2Fe-1Zr亚稳β-Ti合金中的相变规律。结果表明,淬火态存在无热ω相(ω_a)。低于500℃时效,发生β→B+ω_(iso)→β+α转变。在400℃以下,α相均匀长大,450—500℃时效,初期由等温ω相(ω_(iso))转变的α相不再是均匀长大,在原始β相晶界和晶内局部处发生选择性长大。高于550℃时效,发生β→β+α直接转变,在多数α相的片中有内挛晶。内孪晶的量随着时效时间延长或温度升高而减少,最终消失。伴随这一过程;在α相片的边缘产生台阶和错动。低温或商温转变的α相,其与β相的晶体学取向都符合Burgers关系。本工作仅在一只试样的选区衍射花样中有弧形衍射斑,这最可能是TiH_2析出的结果。     

ISOTHERMAL PHASE TRANSFORMATION IN Au-Si AMORPHOUS ALLOY

Electric resistivity measurements and X-ray diffraction analysis were performed to study theisothermal phase transformation in amorphous Au-Si ribbons with eutectic composition pre-pared using melt-spinning technique.A series of phase transformations take placespontaneously at room temperature and accelerate at elevated temperatures.Four stages ofthe transformation from amorphous state to the equilibrium state can be distinguished.Dis-cussion on the structural character of the metastable phases indicates that Hume-Rotheryelectron compounds and size factor compounds could form during isothermal aging.     

PHASE TRANSFORMATION IN RAPIDLY SOLIDIFIED AI-Cu-Fe ALLOY

By means of rapid solidification, two Al_(65)Cu_(20)Fe_(15) powders were prepared with water and liquid N_2 as the respective cooling agent. Both powders are composed of a qnasicrystalline icosahedral phase and a crystalline hexagonal phase, with the water-cooled alloy having a higher crystalline phase content. In the isothermal an nealing process, the crystalline phase in the water-quenched alloy begins to decrease at 500℃ and then disap pears at 600～700℃. At about 800℃, new crystalline phases form, and at 900℃, the quasicrystalline phase disappears. Conversely, in the liquid N_2 quenched alloy, the quasicrystalline phase starts to decrease at about 500℃. and the hexagonal phase decomposes into new crystalline phases. At 700～800℃, the quasicrystalline phase disappears. For the water-cooled sample, the quenching at 100～200C makes the crystalline to quasicrystalline phase transformation start at a lower temperature and the crystallization of the quasicrystal occur at a higher temperature. For the liquid N_2 quenched alloy, the quenching at 100～400℃, did not affect its phase transformation at high temperature.     

CRYSTALLOGRAPHIC ANALYSIS OF THE LATH MARTENSITE TRANSFORMATION IN Fe-Ni-Mn ALLOY

1.IntroductionBased on the concept of an invariant plane strain (IPS), phenomenological theory of martensite transformation (PTMT) is established[1-3]. In this case, an invariant plane is obtained by self-accommoda-tion effect between different martensitic variants, and the formula which reveals this self-accommoda-tion effect can be written as …     

PRECIPITATION AND GROWTH OF δ''- PHASE IN 8090 Al-Li ALLOY

通过热处理，透射电镜分析、图像分析等手段，对８０９０Ａｌ－Ｌｉ合金中δ’相的析出长大行为进行了研究。结果表明，合金在１６０℃时效时，δ’相半径的３次方与时效时间不成直线关系，δ’相的析出长大存在快速和渐缓两个阶段。分析认为，随时效进行合金中过饱和空位浓度的减少造成ＬＳＷ理论模型中ｋ值的减小。     

MARTENSITE TRANSFORMATION OF A TiNiCu ALLOY

ＭＡＲＴＥＮＳＩＴＥＴＲＡＮＳＦＯＲＭＡＴＩＯＮＯＦＡＴｉＮｉＣｕＡＬＬＯＹ￥Ｚｈａｎｇ，Ｙｉ；Ｊｉｎ，Ｊｉａｌｉｎｇ；Ｊｉ，Ｚｈｉｑｉａｎｇ（ＳｈａｎｇｈａｉＩｒｏｎａｎｄＳｔｅｅｌＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，Ｓｈａｎｇｈａｉ２００９４０）...     

MECHANISMS OF α_2→α_2/γ PHASE TRANSFORMATION IN A TiAL ALLOY

ＭＥＣＨＡＮＩＳＭＳＯＦα_２→α_２／γＰＨＡＳＥＴＲＡＮＳＦＯＲＭＡＴＩＯＮＩＮＡＴｉＡＬＡＬＬＯＹＸＵＱｉａｎｇ；ＬＥＩＣｈａｎｇｈｕｉ（ＢｅｉＪｉｎｇＬａｂｏｒａｔｏｒｙｏｆＥｌｅｃｔｒｏｎＭｉｃｒｏｓｃｏｐｙ．ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆ...     

STABILIZATION OF MARTENSITE AND PARENT PHASE ORDERING IN A Cu-Zn-Al ALLOY

The reverse transformation has never occurred in a quenched and aged specimen upon heatingfrom room temperature to 320℃ at which the martensite disappears thoroughly.Both B29R and DO_318R coexist in step-quenched and short-time isothermally treated specimen.As prolonging the isothermal holding,the B29R disappears and DO_318R intensifies.B29R occurs only in specimen quenched and up-quenched immediately to 100—150℃.Rapid quenching from high temperatures will depress the B2→DO_3 ordering but not the A2→B2 one.A plenty enough concentration of vacancy is a necessary condition of occurrence ofB2→DO_3 ordering.The possible mechanism for the stabilization of martensite in aCu-Zn-Al alloy was also discussed.     

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.     

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。     

FORMATION OF QUASICRYSTALLINE PHASE IN RAPIDLY SOLIDIFIED Al-Fe-V-Si ALLOY

The icosahedral quasicrvstalline phase (i-phase)with the chemical composition of 82.4at%Al,8.8at?,3.6at%V and 5.2at%Si in melt spun Al-Fe-V-Si ribbons was found.It is suggested that the temperature and holding time of the melt prior to quenching are the important factors in the formation of the i-phase.     

MECHANISMS OF COMPATIBLE PLASTIC DEFORMATION BETWEEN THE γ-LAMELLAE IN TWO PHASE TiAl-BASE ALLOY

研究并讨论了以三类不同孪晶关系存在的γ层片间的塑性变形协调控制。结果表明，１２０°旋转孪晶层片间存在穿越和不穿越层片界面的塑性变形协调机制，两真孪晶层片间可协调的塑性变形不穿越层片界面；而两伪孪晶层片间的塑性变形则是不协调的。     

PHASE TRANSFORMATION UNIT OF BAINITIC FERRITE AND ITS SURFACE RELIEF IN LOW AND MEDIUM CARBON ALLOY STEELS

The lath-or plate-shaped bainitic ferrite of low and medium carbon alloy steels consists ofpackets of ferrite sublaths which are composed of many finer and regular ferrite blocks.Theyare uniform shear growth units of bainitic phase transformation.No carbide is precipitatedfrom them.The bainitic O-carbides are precipitated from γ-α interface or carbon-richaustenite.The mode of arrangement of the units in ferrite sublath packet is in uni-or bi-di-rection.Single surface relief is produced by the accumulation of uniform shear strains with allthe ferrite units arranged unidirectionally in a sublath packet,while tent-shaped surface reliefis formed by the integration of the uniform shear strains of two groups with ferrite units pilingup in two directions and growing face to face;whereas if they grow back to back,the integra-tion will be responsible for invert-tent-shaped surface relief.The interface trace between twogroups of ferrite units in a sublath packet is shown as“midrib”.     

A MASSIVE TRANSFORMATION MECHANISM IN Ti-48Al ALLOY

ＡＭＡＳＳＩＶＥＴＲＡＮＳＦＯＲＭＡＴＩＯＮＭＥＣＨＡＮＩＳＭＩＮＴｉ－４８ＡｌＡＬＬＯＹ￥ＷｅｎＣｕｉｅ；ＬｉｎＪｉａｎｇｕｏ；ＣｈｅｎＣｈａｎｇｑｉ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，Ｂｅｉｊｉ...     

THE FAILURE MECHANISM OF REVERSE SHAPE MEMORYEFFECT IN A Cu-BASE ALLOY

1.IntroductionItiswellknownthatthereverseshapememoryeffect(RSME)isrelatedtobainitictransf0rmati0ninCu-baseshapememoryalloys(SMA)['l'].Thusthestructure0fbainite(a1)playsanimportantroleinthiseffect.Ref.I3]indicatesfurtherthatthereverseshapememoryeffectmaybeimprovedupt00neorder0fmagnitudeunderappliedconstraintstress-ThismeansthatRSMEunderanexternalstresshaJsabroadengineeringprospect.Inordertoelucidatethemechanism0fb0threverseshapememoryeffectandbainitictransformationinCu-basealloys,thispap…     

TRANSFORMATION KINETICS AND COARSENING OF LAMELLAR STRUCTURE IN γ-TiAl ALLOY

研究了Ｔｉ－４７．８ａｔ．－％Ａｌ合金从α相区冷至室温再在双相区时效后，层状组织的转变机理及不连续粗化．层状组织转变过程与时效温度和形成过饱和α＿２单相时的冷却速度有关．建立了层状组织转变的动力学模型．层状组织的稳定性随片间距减小而降低，表现为时效时发生不连续粗化．     

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.     

AN FCC METASTABLE PHASE IN A RS Ni-Ti ALLOY

ＡＮＦＣＣＭＥＴＡＳＴＡＢＬＥＰＨＡＳＥＩＮＡＲＳＮｉ－ＴｉＡＬＬＯＹＡＮＦＣＣＭＥＴＡＳＴＡＢＬＥＰＨＡＳＥＩＮＡＲＳＮｉ－ＴｉＡＬＬＯＹ￥Ｗｕ，Ｘｉａｏｚｈｅｎ；Ｗａｎｇ，Ｓｈｉｄｏｎｇ；Ｚｈａｎｇ，Ｊｉｎｐｉｎｇ；Ｓｈｕ，Ｈｕａｑｉｎ（Ａｎａｌ...