DEFORMATION AND FRACTURE MECHANISMS OF TWO－PHASE TiAl－BASED ALLOYS WITH FULLY LAMELLAR MICROSTRUCTURE

ＤＥＦＯＲＭＡＴＩＯＮＡＮＤＦＲＡＣＴＵＲＥＭＥＣＨＡＮＩＳＭＳＯＦＴＷＯ－ＰＨＡＳＥＴｉＡｌ－ＢＡＳＥＤＡＬＬＯＹＳＷＩＴＨＦＵＬＬＹＬＡＭＥＬＬＡＲＭＩＣＲＯＳＴＲＵＣＴＵＲＥＹ．Ｇ．Ｚｈａｎｇ，Ｃ．Ｑ．Ｃｈｅｎ（ＢｅｉｊｉｎｇＵｎｉｖｅｒｓｉｔ...     

INTERFACE－RELATED DEFORMATION MECHANISMS AND DISLOCATION MOBILITIES IN TWO－PHASE TITANIUM ALUMINIDE ALLOYS

ＩＮＴＥＲＦＡＣＥ－ＲＥＬＡＴＥＤＤＥＦＯＲＭＡＴＩＯＮＭＥＣＨＡＮＩＳＭＳＡＮＤＤＩＳＬＯＣＡＴＩＯＮＭＯＢＩＬＩＴＩＥＳＩＮＴＷＯ－ＰＨＡＳＥＴＩＴＡＮＩＵＭＡＬＵＭＩＮＩＤＥＡＬＬＯＹＳＣＨＲＩＳＴＯＰＨＵｌｒｉｃｈ，ＳＰＡＲＫＡＵｌｆＡＰＰＥ...     

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.     

AN IN SITU OBSERVATION OF DEFORMATION AND FRACTURE PROCESS IN METAL PART Ⅱ CLEAVAGE PROCESS IN Nb-W-Zr

<正> 本文利用扫描电镜拉伸装置对Nb-W-Zr金属的解理过程进行了观察。 研究用的金属采用200kW电子束炉二次熔炼成合金锭,先后经挤压、锻造、热轧、温轧最后精轧成厚度为0.5mm的板材。从合金板材上截取并经机加工成动态拉伸试样,放在真空炉中经1700℃,1h退火。金相抛光腐刻,腐刻剂为氢氟酸+硝酸+乳酸,比例为1:3:2,保证晶界清晰可见。     

AN ELECTRON DIFFRACTION STUDY OF γ" PHASE IN Ni-Fe-Cr-Nb ALLOY

<正> Ni-Fe-Cr-Nb合金中γ″(Ni_3Nb) 相沿{100}_γ以三种可能的取向共格析出。γ″通常是弥散的细小析出相,选区电子衍射谱是这三种取向γ″的电子衍射谱的迭加。对于某些晶带衍射,由于两种取向的γ″电子衍射谱与基体完全相重,而被基体衍射所覆盖,其中一种取向的γ″有时又可能不形核,这样对判断这两种取向γ″的存在带来一定困难。为此,本文研究了γ″和γ基体电子衍射谱的相重规律,以选择适当晶带衍射来判定相关取向γ″成核与否,并研究了基体衍射上或其周围的条纹花样或“卫星”斑点对于判断各种取向γ″存在的作用。     

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。     

STUDY ON α/γ PHASE EQUILIBRIUM IN Ti-Al-Cr-Fe QUARTERNARY SYSTEM

设计了一种简单的扩散偶,用扩散偶－电子探针法,测定了１２００和１２５０℃Ｔｉ－Ａｌ－Ｃｅ－Ｆｅ四元系中Ｘｃｒ≤４％和ＸＦｅ≤１％范围内的α／γ相平衡关系和相平衡成分,绘出了四元系的局部等温正方形,结果表明,在Ｔｉ－Ａｌ－Ｃｒ－Ｆｅ四元系中,Ｃｒ有提高Ｆｅ在α相中的溶解度的作用,Ｆｅ亦有提高Ｃｒ在α相中的溶解度的趋势。     

STUDY ON γ/γ+NbC_x PHASE BOUNDARY IN Fe-Nb-C SYSTEM

<正> Nb是高强低合金钢的一个重要的微合金化元素。它与C,N及其它化合物在奥氏体中溶解度的大小,都直接影响钢的性能。了解γ/γ±NbC_x的平衡相边界,即溶度积〔Nb〕〔C〕~x很有必要,但目前已知的一批溶度积数据分歧很大,例如,     

INVESTIGATION ON THE INTERFACE PHASE BY TEM IN A NEWLY DEVELOPED NEAR α TITANIUM ALLOY

ＩＮＶＥＳＴＩＧＡＴＩＯＮＯＮＴＨＥＩＮＴＥＲＦＡＣＥＰＨＡＳＥＢＹＴＥＭＩＮＡＮＥＷＬＹＤＥＶＥＬＯＰＥＤＮＥＡＲαＴＩＴＡＮＩＵＭＡＬＬＯＹＭａｏＰｅｎｇｌｉｎｇ；ＸｕＪｉａｌｏｎｇ（ＳｈａｎｇｈａｉＩｒｏｎ＆ＳｔｅｅｌＲｅｓｅａｒｃｈＩｎｓｔｉ...     

AN IN-SITU STUDY ON DISLOCATION BEHAVIOR OF CRACK-TIP IN Ti_3Al-Nb ALLOY

ＡＮＩＮＳＩＴＵＳＴＵＤＹＯＮＤＩＳＬＯＣＡＴＩＯＮＢＥＨＡＶＩＯＲＯＦＣＲＡＣＫＴＩＰＩＮＴｉ３ＡｌＮｂＡＬＬＯＹ①ＷｕＹｉｎｇ，ＺｈｅｎＬｉａｎｇ，ＹａｎｇＤｅｚｈｕａｎｇＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｒ...     

双相不锈钢中裂纹尖端塑性变形行为的透射电镜原位观察

在透射电子显微镜下对铁素体-奥氏体双相不锈钢薄膜试样进行了动态拉伸试验,原位观察了裂纹尖端塑性变形过程和位错分布,发现在铁素体相和奥氏体相中,裂尖位错组态有明显差异。在铁素体相中,裂尖无位错区较大,且让错易发生交滑移,在裂纹前端形成较大的塑性区。在奥氏体相中,裂尖无位错区较小,发射的位错在其滑移面内逆塞积。两相中裂尖滑移系的选择都与裂尖Schmid因子有关。但当形变较大时,奥氏体相中裂尖二次滑移系的选择不再为裂尖Schmid因子所支配。     

阳极电流对纯铜裂尖表面形变和总体形变影响的对比

采用微机控制激光散斑干涉技术，对多晶纯铜平板预裂纹试样在空气及在３．５％ＮａＣｌ溶液中外加阳极电流条件下的裂纹张开位移进行了原位测量，并对比了这两种条件下，裂尖表面应变场的变化，研究了阳极溶解对裂尖材料总体形变和表面形变的影响。结果表明：加阳极电流后，裂尖表面应变量和应变范围都明显增大，而反映裂尖总体形变的张开位移变化很小。阳极溶解对金属内部材料的形变没有直接的影响，只能缓解金属表面的变形硬化，促进金属的表面变形．     

裂纹尖端局部形变带的TEM观察SCIEI

在透射电子显微镜(TEM)下对铁素体-奥氏体双相不锈钢薄膜拉伸试样进行了动态拉伸实验,发现在铁素体相和奥氏作相中在裂纹尖端有与裂纹扩展方向接近一致的局部形变带生成,其形成与裂尖Schmid因子、位借的屏蔽效应、潜在硬化和硬化系数的变化规律有关.当裂纹尖端优先在纯II型应力分量作用下开动与裂纹共面的滑移系、并且有合适的硬化系数下降速率时,裂尖易形成局部形变带。     

循环载荷下裂尖形变规律的实验研究

应用散斑干涉技术，在常幅载荷下对疲劳裂纹扩展过程中的一个循环周期内，不同加载阶段的裂尖应变、裂纹张开位移进行了原位测量，给出了裂纹闭合对裂纹张开位移及裂尖形变的影响规律。结果表明：由于裂纹闭合和残余压应力的存在，疲劳裂尖应变与外加载荷的平方并不成正比，在加载初期，裂纹处于闭合状态，裂尖应变无明显变化，随着载荷的增加，裂纹逐渐由远离裂尖处张开并向裂尖发展，一旦裂纹完全张开，裂尖应变迅速增加，对裂尖应力-应变状态的分析表明，裂尖材料的应力-应变关系类似于光滑试样低周拉压疲劳应力-应变滞后关系。     

TEM OBSERVATION OF LOCAL DEFORMATION BAND AT CRACK TIP

The thin foil specimen of a ferrite-austenite duplex stainless steel was tensiled under transmis-sion electron microscope(TEM).It was found that both in ferrite and austenite the localdeformation band at crack tip was formed near to the crack propagating direction.Its forma-tion was related with the crack tip Schmid factor,dislocation shielding,latent hardening andhardening coefficient.When the crack tip emitted dislocations to a slip system by the action ofpure mode Ⅱ stress resolute,and the decreasing rate of hardening coefficient was suitable,lo-cal deformation band was easy to form.     

大型饼类锻件变形规律及夹杂性裂纹产生过程研究（续）

大型饼类锻件变形规律及夹杂性裂纹产生过程研究（续）（清华大学１０００８４）马庆贤，曹起骧，谢冰（第一重型机械集团公司１６１０４２）谢云岫，宋士丹，吴书勤４夹杂性裂纹产生过程的模拟研究４．１实验条件大型钢锭的解剖实验表明：低熔点非金属夹杂物（如硫化物、...     

氢在面心立方金属裂纹尖端变形过程中的作用SCIEI

选用高纯度Ni单晶体,利用扫描电镜原位拉伸,观察了充氢后Ni单晶裂纹尖端的变形过程。发现氢的存在不改变在混合型载荷作用下,裂纹尖端的塑性变形特征。用网格法加计算机处理系统,测出氢显著促进裂纹尖端区域内的局部塑性变形。     

裂纹在珠光体钢中的近门槛区扩展

在不同应力比(R)条件下研究珠光体片层距(d)对疲劳裂纹近门槛区扩展的影响,测定了材料闭合应力强度因子(K_(cl))和门槛值(ΔK_(th))以及在门槛区扩展时裂纹尖端张开位移范围(ΔCOD)。     

AN APPLICATION OF SPI TECHNIQUE FOR STUDING STRA DISTRIBUTION AT CRACK TIP

A computerized digital speckle-interferometry(SPI)system has been set up to determinethe in-plane distribution of displacement and strain at crack tip of CF specimens.Theprinciple and the experimental method of this technique are described in detail.Theeffect of corrosion factors on plastic deformation at crack tip in CF process has beenexamined by comparing the near-tip strain fields of steel A537 before and after hydrogencharging,and of pure copper before and after applying an anodic current in 3.5% NaCl.The results shows that the clasic finite element mathematical models are not suitable todescribe the near-tip deformation under the experimental conditions.Hydrogen chargingmade the crack tip plasticity decreased for steel A537 and the anodic dissolution enhancethe near tip deformation of pure copper specimen.