INVESTIGATION OF TENSILE STRESS GENERATED BY PASSIVE FILM DURING CORROSION PROCESS FOR α-Ti

本文研究α—Ti在腐蚀过程中钝化膜所产生的内应力的大小。结果表明，一边涂有保护层的α－Ti薄条在0.1mol／LH2SO4溶液中自然腐蚀过程中，随着钝化膜的形成，薄条不断向腐蚀面弯曲（保护面鼓起），即在试样表层产生一个拉应力。这个附加拉应力不断增大，其最大值为（5个试样平均），接近或等于屈服应力。在SCC过程中这个附加应力将和外应力叠加，促进位错发射和运动，从而在低应力（或低KI）下导致SCC裂纹形核。     

IN SITU TEM STUDY OF DISLOCATION EMISSION AND MICROCRACK NUCLEATION FOR α-Ti AFTER ADSORBING Hg

用自制的恒位移加载台,在ＴＥＭ中原位观察了α－Ｔｉ在Ｈｇ蒸汽中放置前后加载裂纹前端位错组态的变化以及脆性微裂纹的形核和扩展。并和α－Ｔｉ在ＴＥＭ中原位伸的结果进行了比较。结果表明：加载裂纹吸附Ｈｇ原子后能促进位错的发射,增殖和运动;当吸附促进位错发射和运动达到临界状态时,脆性微裂纹就在原裂纹顶端或在无位错区中形核并解理扩展。     

PLASTIC DEFORMATION REGULARITY OF TAILOR-WELDED TUBE (TWT) WITH DISSIMILAR THICKNESS DURING HYDRO-BULGING

为揭示差厚拼焊管内高压胀形的变形规律, 采用有限元数值模拟和实验并结合力学分析, 研究了差厚拼焊管胀形时薄壁管、厚壁管的变形差异, 及塑性区的发生、发展过程和促进变形协调的力学和几何因素, 分析了差厚变形条件下薄壁管、厚壁管的应力、应变发展历史. 结果表明: 差厚拼焊管内高压胀形时, 厚壁管的变形始终落后于薄壁管. 薄壁管中部最先屈服, 塑性区自中部向两端逐渐扩展, 厚壁管靠近焊缝端先屈服, 随着内压升高塑性区逐渐扩展到另一端. 变形强化和长度比增大可促进两管协调变形. 无论长度比如何变化, 整个变形过程中薄壁管轴向应变始终为拉应变, 厚壁管轴向始终为压应变.     

MAGNETIC PROPERLIES AND STRUCTURE OF A MIXTURE OF α-Fe and Fe_3N DURING MECHANICAL ALLOYING PROCESS

利用X射线衍射研究了α-Fe与Fe3混合粉末机械合金化过程中结构的变化．并测量了球磨不同时间后其饱和磁化强度的变化结果表明,随着球磨时间的延长,Fe3N相迅速分解直至消失,N原子部分固溶于α-Fe中,24h后可形成稳定的α-Fe（N）过饱和固溶体,其中N的质量分数约为0．290％-0．346％．随着球磨时间的延长,α-Fe的晶粒尺寸逐渐减小,24h后趋于定值,约为8nm．球磨引起样品中Fe原子周围N原子位置的变化,使得球磨过程中混合粉末的饱和磁化强度开始时降低,5h后又有所增加,24h后达到一定值     

MATHEMATICAL MODEL AND COMPUTER SIMULATION OF MOISTURE TRANSFER PROCESS DURING SINTERING

ＭＡＴＨＥＭＡＴＩＣＡＬＭＯＤＥＬＡＮＤＣＯＭＰＵＴＥＲＳＩＭＵＬＡＴＩＯＮＯＦ　ＭＯＩＳＴＵＲＥＴＲＡＮＳＦＥＲＰＲＯＣＥＳＳＤＵＲＩＮＧＳＩＮＴＥＲＩＮＧＺｏｕ；ＺｈｉｙｉＨｕａｎｇ；ＴｉａｎｚｈｅｎｇＹａｎｇ；ＸｉａｏｓｈｅｎｇＣｈｅｎ；Ｊｉ（...     

INFLUENCES OF EDGING ROLL SHAPE ON THE PLASTIC STRAIN DISTRIBUTION OF SLAB DURING MULTI-PASS V-H ROLLING PROCESS

Multi-pass slab vertical-horizontal （V-H） rolling process with variable edging roll shape have been simulated with explicit dynamic finite element method and updating geometric method. The distributions of plastic strain contour in slab daring rolling process with different edging roll and under different rolling stage have been obtained. The results show that there exist two thin strain assembling zones in slab when the flat edging roll is used, and there just exist one strain assembling zone in slab when the edging roll with groove is used. And compared the deformation equality between flat edging roll and edging roll with groove, the lateris better than the former, which supplies the theory prove to the slab deformation distribution during V-H rolling process and is helpful for predicting the slab texture.     

PLASTIC DEFORMATION AND DISLOCATION STRUCTURE IN γ'-PHASE OF A DIRECTIONALLY SOLIDIFIED Ni-BASE SUPERALLOY

本文利用透射电镜观察了定向凝固高温合金DS Rene80在拉伸及蠕变时的位错亚结构。试验结果表明:在低于760℃拉伸时,切割γ′粒子的是在{111}面上夹有APB的(1/2)〈110〉位错对。在不低于760℃拉伸时,切割γ′粒子的是在{111}面上夹有超点阵内禀层错(SISF)γ(1/3)〈112〉不全位错;这些不全位错在大应力的作用下于{111}面上将分解为一根(1/2)〈110〉螺位错和一根(1/6)〈112〉刃位错,并在其间夹有一个APB。在760℃,618MPa条件下蠕变时,切割γ′粒子的是在{111}面上夹有SISF的(1/3)〈112〉不全位错;这些不全位错此时不分解。与此同时,亦有(1/2)〈110〉位错对切割γ粒子。在980℃,190MPa条件下蠕变时,则无γ′粒子被切割的现象。在760℃,618MPa及980℃,190MPa条件下蠕变至第二阶段时,在γ/γ′界面上都形成了二维位错网络墙,墙上位错的攀移是合金形变的控制因素。第二阶段蠕变速率(ε)与立方γ′粒子的尺寸(α)和体积分数(V_f)的关系符合ε∝α/V_f~(2/3)     

MAGNETIC ACOUSTIC EMISSION CHARACTERISTICS OF HYDROGEN ATTACKED LOW CARBON STEEL

ＭＡＧＮＥＴＩＣＡＣＯＵＳＴＩＣＥＭＩＳＳＩＯＮＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＨＹＤＲＯＧＥＮＡＴＴＡＣＫＥＤＬＯＷＣＡＲＢＯＮＳＴＥＥＬ￥ＬＩＨｉａｏｇａｎｇ;ＭＥＮＧＱｉｎｇｈａｉ;ＣＨＥＮＨｕａ;ＣＨＥＮＪｉｎｗｅｉ;ＹＡＯＺｈｉｍｉｎｇ;...     

PLASTIC DEFORMATION AND DISLOCATION STRUCTURE IN γ'-PHASE OF A DIRECTIONALLY SOLIDIFIED Ni-BASE SUPERALLOY

The dislocation structure of directionally solidified(DS)Rene 80 superalloy during tensileand creep deformation has been studied by TEM.In tensile deformation,γ'shearing occurs byslip of APB-coupled(1/2)<110>dislocation pairs on{111}planes at temperatures below760℃.and by slip of SISF-seperated(1/3)<112>superpartials which have dissociated on{111}planes into a(1/2)<110>screw superpartial and a(1/6)<112>edgesuperpartial with an APB in between at temperatures equal to or above 760℃.In creepdeformation,γ'shearing occurs again by slip of SISF-seperated(1/3)<112>superpartialswhich have not dissociated on{111}planes and by diffusive slip of APB-coupled(1/2)<110>dislocation pairs at 760℃,618 MPa.However,no γ'shearing occurs at 980℃,190MPa.During secondary creep at 760℃,618 MPa or at 980℃,190 MPa,2-dimensional net-works have formed at γ/γ'interfaces,and the strain is mainly the result of diffusion control-led climb of dislocation networks at γ/γ'interfaces.The dependence of secondary creep rate εupon size a and volume fraction v_■ of cubic γ' has been found to be ■∝α/v_f~(2/3).     

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。     

ACTIVATION ENERGY OF FeAl ALLOYS DURING SUPERPLASTIC DEFORMATION

ＡＣＴＩＶＡＴＩＯＮＥＮＥＲＧＹＯＦＦｅＡｌＡＬＬＯＹＳＤＵＲＩＮＧＳＵＰＥＲＰＬＡＳＴＩＣＤＥＦＯＲＭＡＴＩＯＮ①ＬｉＤｉｎｇｑｉａｎｇ，ＬｉｎＤｏｎｇｌｉａｎｇ（Ｔ．Ｌ．Ｌｉｎ）ＴｈｅＰｕｂｌｉｃＬａｂｏｒａｔｏｒｙｏｆＨｉｇｈＴｅｍｐｅｒａｔｕ...     

X-RAY ANALYSIS OF WORK-HARDENING PROCESS FOR POLYCRYSTALLINE α-BRASS DURING UNIAXIAL TENSILE TESTS

X-ray diffraction Fourier profile analysis has been performed for polycrystalline α-brassplate with 31.55 wt-% Zn after a series of uniaxial tensile tests with different strain rates.Dislocation density p and configuration parameter M may be presented as a function of ap-plied stress σ_a.A mechanism of alternative long-range and short-range strain hardening hasbeen proposed.     

EFFECT OF TOOL WEAR ON MICROSTRUCTURE, MECHANICAL PROPERTIES AND ACOUSTIC EMISSION OF FRICTION STIR WELDED 6061 Al ALLOY

Tool condition is one of the main concerns in friction stir welding （FSW）, because the geometrical condition of the tool pin including size and shape is strongly connected to the microstrueture and mechanical performance of the weld. Tool wear occurs during FSW, especially for welding metal matrix composites with large amounts of abrasive particles, and high melting point materials, which significantly expedite tool wear and deteriorate the mechanical performance of welds. Tools with different pin-wear levels are used to weld 6061 Al alloy, while acoustic emission （AE） sensing, metallographic sectioning, and tensile testing are employed to evaluate the weld quality in various tool wear conditions. Structural characterization shows that the tool wear interferes with the weld quality and accounts for the formation of voids in the nugget zone. Tensile test analysis of samples verifies that both the ultimate tensile strength and the yield strength are adversely affected by the formation of voids in the nugget due to the tool wear. The failure location during tensile test clearly depends on the state of the tool wear, which led to the analysis of the relationships between the structure of the nugget and tool wear. AE signatures recorded during welding reveal that the AE hits concentrate on the higher amplitudes with increasing tool wear. The results show that the AE sensing provides a potentially effective method for the on-line manitoring of tool wear.     

COUPLED THERMO-MECHANICAL FEM ANALYSIS OF TWIST COMPRESSION DEFORMATION PROCESS

ＣＯＵＰＬＥＤＴＨＥＲＭＯＭＥＣＨＡＮＩＣＡＬＦＥＭＡＮＡＬＹＳＩＳＯＦＴＷＩＳＴＣＯＭＰＲＥＳＳＩＯＮＤＥＦＯＲＭＡＴＩＯＮＰＲＯＣＥＳＳ①ＸｕｅＫｅｍｉｎ，ＺｈａｎｇＺｈｅｎｇｒｏｎｇ，ＸｉａＹｏｎｇｊｉａｎｇ，ＬｕＹａｎＭｅｔａｌＦｏｒｍｉｎ...     

PHASES AND STRUCTURE OF PREFORM DURING PREPARING PROCESS OF Al／TiCp COMPOSITES BY DIRECT REACTION SYNTHESIS

ＰＨＡＳＥＳＡＮＤＳＴＲＵＣＴＵＲＥＯＦＰＲＥＦＯＲＭＤＵＲＩＮＧＰＲＥＰＡＲＩＮＧＰＲＯＣＥＳＳＯＦＡｌ／ＴｉＣｐＣＯＭＰＯＳＩＴＥＳＢＹＤＩＲＥＣＴＲＥＡＣＴＩＯＮＳＹＮＴＨＥＳＩＳＳ．ＹＺｅｎｇ;Ｂ．ＹａｎｇａｎｄＥ．Ｌ．Ｚｈａｎｇ（Ｈａｒｂｉ...     

3-D RIGID PLASTIC FEM SIMULATION OF EXTRUDING-BULGING PROCESS OF TEE TUBES

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｅｅｔｕｂｅｓａｒｅｗｉｄｅｌｙａｐｐｌｉｅｄａｓｉｍｐｏｒｔａｎｔｐｉｐｅｊｕｎｃｔｉｏｎｓｉｎｐｉｐａｇｅｉｎａｌｋｉｎｄｓｏｆｉｎｄｕｓｔｒｙｄｅｐａｒｔｍｅｎｔｓ．Ｗｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｉｎｄｕｓ...     

EFFECT OF α-PHASE MORPHOLOGY ON STRENGTHENING AND FRACTURE BEHAVIOUR OF 47121 β-Ti ALLOY

用TEM,SEM,X射线衍射及拉伸试验等研究了47121β-Ti合金的拉伸性能与α相形貌及其断裂行为的关系。结果表明,低温时效由ω相转变成的弥散α相质点,随其体积分数增加,质点间共格应力场发生交叠,产生较强的内应力,在负荷作用下,导致宏观脆断,而微观断裂机制仍属于韧窝,因此可以把局部的内应力区认为是形成精细韧窝的核心。魏氏组织的α相具有强的加工硬化效应,位错切割α相是主要强化机制,但以孪生形变的α相片阻止位错切过。晶界两侧形成的无析出带,以及随后形成的羽毛状α相群,都使晶界区弱化,导致形成类似沿晶型断口。     

PLASTIC DEFORMATION BEHAVIOR OF ELECTROFORMED COPPER LINER OF SHAPED CHARGE AT DIFFERENT STRAIN RATES

The paper deals with different plastic deformation behavior of electroformed copper liner of shaped charge, deformed at high strain rate (about 1×107s-1) and normal strain rate (4×10-4s-1). The crystallographic orientation distribution of grains in recovered slugs which had undergone high-strain-rate plastic deformation during explosive detonation was investigated by electron backscattering Kikuchi pattern technique. Cellular structures formed by tangled dislocations and sub-grain boundaries consisting of dislocation arrays were detected in the recovered slugs. Some twins and slip dislocations were observed in specimen deformed at normal strain rate. It was found that dynamic recovery and recrystallization take place during high-strain-rate deformation due to the temperature rising, whereas the conventional slip mechanism operates during deformation at normal strain rate.     

DEFORMATION AND WORK HARDENING OF HADFIELD MANGANESE STEEL

The work hardening of Hadfield manganese steel arises mainly form two causes;1)a largeamount of twinning makes perfect dislocations or Shockley dislocations to be blocked at thecoherent twin boundaries.2)the deformation leads to strong unsymmetrical distortion due tothe occurrence of a large number gf Mn-C pairs or Mn-vacancy carbon-carbon cluster.Ithas been demonstrated by TEM observation and internal friction tests.As deformation pro-ceeds,the slip constantly accomodates twinning shear giving rise to stress relaxation.Thus,the Hadfield steel exhibits both rapid work hardening and good ductility.     

BAUSCHINGER EFFECT AND DISLOCATION STRUCTURE IN STAINLESS STEEL DURING CYCLIC DEFORMATION

Cyclic deformation in symmetrical push-pull mode was carried out at room temperature in airusing a Schenck hydropuls machine.The total strain amplitude which was kept constant dur-ing the test ranged from ±0.004 to±0.012.The 0.2% offset yield stress σ_(0.2f) in tensionand σ_(0.2r) in compression and peak stress σ were measured from the stress-strain hysteresisloop at various cycles.The Bauschinger strenghth differential factor(BSDF)was then calcu-lated from σ_(0.2f) and σ_(0.2r).The energy loss △E of each cycle was determined fromhysteresis loop areas.These parameters,BSDF,σ and △E,appear to have two distinctivelydifferent stages.The dislocation structures were observed using TEM in specimens deformed cyclically,forvarious cycles.The observation shows that the dislocations pile-up mainly against grainboundaries and there exist large amount of deformation twins.The addition of 0.25 wt-% ni-trogen reduced the stacking fault energy of the alloy significantly.Cross-slip and climb aretherefore rather difficult to occur during the cyclic deformation at room temperature,andwell-defined dislocation cells and walls can only be seen at the final stage of fatigue.