淬火介质对Cu－Al－Ni－Mn－Ti形状记忆合金γ1′、β1′两马氏体形成及其宏观性能的影响

对Ｃｕ－１３Ａｌ－５Ｎｉ－１Ｍｎ－１Ｔｉ形状记忆合金样品进行六种不同介质的淬火处理，然后用透射电镜对这些样品进行观察，结果表明：淬火介质对合金中γ１′、β１′马氏体的形成量、两马氏体的混合程度以及γ１′马氏体界面的完整度有明显影响。另一方面，对以上淬火样品采用自制扭转仪进行了记忆性（ＳＭＥ）和伪弹性（ＰＥ）测量，以揭示γ１′、β１′马氏体结构与合金宏观性能之间的内在联系。测量和分析表明合金中γ１′、β１′马氏体共存会降低其形状记忆性和伪弹性     

用X射线评价马氏体时效钢冷轧材的回复效应

用X射线衍射技术研究了马氏体时效钢冷轧变形和衍射峰宽化效应的关系，结果表明冷轧变形使X射线衍射峰型发生明显的变化，其中衍射峰的宽化间接证明材料塑性变形的不均匀性；510℃×3h时效使冷轧变形引起的衍射峰宽化效应大幅下降，从而证明时效析出前或析出过程中马氏体基体发生了较大程度的回复。更高温度时效后（540℃×3h），X射线衍射峰宽化已不受冷轧变形的影响，证明马氏体基体已回复到与未冷轧材料相当的程度。     

低于Ms温度变形对等温贝氏体相变动力学和组织的影响

摘要：变形和等温热处理是高强贝氏体钢主要生产工艺,已有研究表明低于马氏体相变起始温度（Ms）的等温热处理可以促进贝氏体相变动力学,低温奥氏体预变形也可以加速贝氏体相变。研究了低于Ms温度变形对后续等温贝氏体相变动力学和组织的影响,结果表明,并未出现预想的加速相变叠加效应,反而,变形温度低于Ms温度时,贝氏体相变动力学减弱,等温贝氏体相变孕育期延长。低于Ms温度等温相变时,贝氏体铁素体与母相奥氏体位向关系接近K-S关系,变形试样虽然获得了一部分先马氏体,且能提高贝氏体形核率,但并非所有的胚核都能发生长大,变形改变母相奥氏体取向,使贝氏体原本的位向关系遭受破坏,导致有效形核率降低。     

近等原子TiNi合金的电子显微镜观察

采用TEM方法对Ti-51 at％Ni合金的高温相、预马氏体转变、马氏体转变以及弥散析出第二相进行了研究。结果表明:TiNi合金高温母相具有CsCl(B_2)有序点阵,经700～900℃淬火到室温后已发生了预马氏体转变,表现出复杂的衍射效应;用母相点阵的机械失稳引起的位移波来解释预马氏体转变似乎是合理的。对温度诱发马氏体和应变诱发马氏体的观察表明它们都具有孪晶亚结构,但可以有不同的组态。采用SAD方法鉴别了弥散析出的X相,它具有f. c. c结构,点阵常数a=15.8(?)与母相具有位向关系: <111>_x∥<111>_β, {110}_x∥{321}_β。     

Fe—Mn—Si合金的形状记忆效应及工程应用

评述了近年来Ｆｅ－Ｍｎ－Ｓｉ合金形状记忆效应（ＳＭＥ）的研究及工程应用，并对Ｍｎ，Ｓｉ元素，应力诱发相变，母相强化及热－机械处理（训练）等对ＳＭＥ的影响进行讨论。     

TRIP钢中相似结构相的区分及定量表征

为了对钢铁样品中不同相进行准确区分, 建立了一种较为直观的定量分析方法。试验以TRIP钢为例, 采用光学显微镜、X射线衍射仪及电子背散射衍射技术对试验钢的微观组织、物相及相似结构相进行了表征。结果表明:电子背散射衍射技术不仅可以区分出TRIP钢中的体心立方和面心立方结构, 而且能通过菊池带衬度图像对结构相似的铁素体、贝氏体以及马氏体3种相进行进一步细分, 并最终得出定性分布和定量结果:铁素体为45.10%, 贝氏体为47.80%, 奥氏体为5.23%, 马氏体为1.87%, 说明其在区分相似结构相方面优势显著。     

HQ130钢焊接粗晶热影响区的显微图像分析

用XQF－2000型显微图像分析仪对CO2气体保护焊的高强度钢HQ130粗晶热影响区（CGHAZ）的显微组织构成、区域宽度及晶粒度进行了测定。并用透射电镜和电子衍射技术对CG－HZA的精细组织结构作了进一步的研究。结果表明,随着焊接线能量的增加,HQ130钢CGHAZ的主体组织依次为板条马氏体→板条氏体＋下贝氏体→板条马氏体＋下贝氏体＋上贝氏体,晶粒直径逐渐变大。当焊接线能量为22．3kJ/cm时,奥氏体晶粒的直长最大达158μm。应将焊接线能量控制在16kJ/cm以下,使CGMAZ形成板条马氏体＋下贝氏体组织,避免产生上贝氏体组织,防止晶粒粗化,改善该区域的性能。     

时效和重新训练对Cu－Zn－Al合金组织与记忆性能的影响

用约束训练法对时效后的Ｃｕ－Ｚｎ－Ａｌ形状记忆合金进行了重新训练。结果表明，在未发生贝氏体转变的条件下，时效所导致的记忆衰减可以通过重新训练予以改善。透射电镜分析指出，重新训练后，发生了马氏体的再取向，因时效而导致的细条状、台阶状变体大部分消除，且变体间的结合方式变为自协作性良好的孪晶关系，从而改善了合金的记忆性能。     

MC5钢过冷奥氏体组织转变研究

本文利用磁性法、膨胀法、金相法，按照国家标准ＧＢ５０５７－８５、ＧＢ５０５８－８５技术条件测定ＭＣ５钢的过冷奥氏体等温转变曲线（ＴＴＴ图）及连续冷却转变曲线（ＣＣＴ图）。结果表明：在ＴＴＴ图中存在珠光体、贝氏体和马氏体转变，珠光体和贝氏体都呈“Ｃ”型，且有两个“鼻尖”。在ＣＣＴ图中，存在珠光体，贝氏体和马氏体转变。     

母相预变形对马氏体相变及其形态的影响

通过对ＦｅＮｉＣ系合金母相的室温预变形处理，考察了不同母相预变形量对随后冷却的马氏体形态及亚结构、相交点Ｍｓ等的影响，说明母相的屈眼强度和结构状态是影响马氏体形态及其转化的重要因素，决定着马氏体相变形状应变的协调方式：母相塑性协调或马氏作变体间的自协调。     

The effect of ordering on the yield stress of martensitic CuZnAI alloys

The structures of the martensite of four CuZnAI alloys with Al contents ranging from 9 to 20.8 at. pct were investigated using transmission electron microscopy. It was found that the structure of the martensite changed from 9R (having formed from a parent phase with B₂ order) to 18R (DO₃ parent) as the Al content was increased from 9 to 13.6 at. pct. The 0.2 pct proof stress of polycrystalline specimens initially decreased with increasing Al, corresponding to the change of order, and then increased. It is argued that the mechanism of yielding is the formation of mechanical twins which reorient the martensite, and an explanation of the change of yield stress with composition is given in terms of changes in the nature and extent of ordering affecting the twin boundary energy.     

退火温度对退火马氏体基TRIP钢显微组织和力学性能的影响

将C-Si-Mn系TRIP钢通过完全淬火和两相区退火相结合的工艺,得到一种以退火马氏体为基体的TRIP钢（简称TAM钢）,并对比分析了TAM钢在不同温度退火后的显微组织和力学性能.结果表明,TAM钢经退火后的显微组织特征为精细规整的板条退火马氏体基体、片状残余奥氏体和贝氏体/马氏体组成的混合组织.这种组织降低了基体的硬度以及基体和第二相之间的强度比,减少了基体的位错密度.随着退火温度的提高,退火马氏体基体的板条形态逐渐消失,新生马氏体/贝氏体的团状混合组织逐渐增多.当退火温度为780℃时,综合力学性能优异,抗拉强度为1130 MPa,延伸率可达20%,强塑积为22600 MPa·%.当退火温度较低时,残余奥氏体主要以片状存在于退火马氏体板条间,有利于TRIP效应的发生.      

Hot rolling texture development in CMnCrSi dual-phase steels

The amount of strain below the temperature of nonrecrystallization, T _nr , has an important influence on the phase fractions and the final crystallographic texture of a hot-rolled dual-phase ferrite+martensite CMnCrSi steel. The final texture is influenced by three main microstructural processes: the recrystallization of the austenite, the austenite deformation, and the austenite-to-ferrite transformation. The amount of strain below T _nr plays a major role in the relative amounts of deformed and recrystallized austenite after rolling. Recrystallized and deformed austenite have clearly different texture components and, due to the specific lattice correspondence relations between the parent austenite phase and its transformation products, the resulting ferrite textures are different as well. In addition, austenite deformation textures result from either dislocation glide or the combination of dislocation glide and mechanical twinning, depending on the stacking fault energy (SFE). The texture components in hot-rolled dual-phase steels were studied by means of X-ray diffraction (XRD) measurements and orientation imaging microscopy (OIM). A clear crystallographic orientation difference was observed between the ferrite phase, transformed at temperatures near A _r3 , and the ferritic bainite and martensite phases, formed at lower temperatures. The results suggest that the primary ferrite, nucleated at temperatures close to A _r3 , transformed from the deformed austenite. The low-temperature constituents, bainite and martensite, form in the recrystallized austenite.     

Ms以下温度等温淬火对中碳贝氏体钢相变和性能影响

摘要：设计了马氏体起始相变温度（Ms）以上和以下2个不同温度等温淬火试验，结合热膨胀仪、扫描电镜显微组织、X光衍射和拉伸试验等试验手段，研究了对比于Ms以上温度等温淬火试验，Ms以下等温淬火对中碳贝氏体钢相变、组织和性能的影响。结果表明，贝氏体相变可以发生在Ms温度以下，且其相变动力学被明显促进。相比于Ms以上温度等温淬火，Ms温度以下等温淬火虽然可以加速相变动力学，但导致强度和伸长率下降，因此降低了最终的力学性能。这主要是因为Ms温度以下等温淬火试样组织内部出现了大量的回火无热马氏体（AM）和少量的贝氏体和残余奥氏体（RA）。因此，Ms温度以下等温淬火热处理后的组织性能未必优于Ms温度以上等温处理后组织性能，这主要取决于具体的成分和工艺。     

Effect of microstructure on plane-strain fracture toughness of aisi 4340 steel

Commercially available AISI 4340 steel has been studied to determine the effect of transformation structures on plane-strain fracture toughness (K _IC). Martensitic and bainitic steels with wide variation in the prior austenitic grain size, and steels having two different mixed structures of martensite and bainite were investigated. Microstructures were examined by optical and transmission electron microscopy. Fracture morphologies were characterized by scanning electron microscopy. The significant conclusions are as follows: in a martensitic or lower bainitic steel in which well-defined packets were observed, the packet diameter is the primary microstructural factor controllingK _IC. The steel's property is improved with increased packet diameter. If the steel has an upper bainitic structure, the packet is composed of well-defined blocks, and the block size controls theK _IC property. When the steel has a mixed structure of martensite and bainite, the shape and distribution of the second phase bainite have a significant effect on theK _IC property. A lower bainite, which appears in acicular form and partitions prior austenite grains of the parent martensite, dramatically improves theK _IC in association with tempered martensite. If an upper bainite appearing as masses that fill prior austenite grains of the parent martensite is associated with tempered martensite, it significantly lowers the K_IC.     

Direct Observation that Bainite can Grow Below MS

In situ simultaneous synchrotron X-ray diffraction and laser scanning confocal microscopy have confirmed that bainite in steels can grow below the martensite start temperature. This observation suggests that the formation curves for bainite in time-temperature-transformation diagrams should be extended below the martensite start temperature. Furthermore, the implication of this observation on the growth mechanism of bainitic ferrite is discussed.     

Effect of Cooling Rate and Deformation on Microstructures and Critical Phase-Transformation Temperature of Boron-Nickel Added HSLA H-Beams

 Microstructures and critical phase-transformation temperature of boron-nickel added Nb-treated high strength low alloy (HSLA) H-beams cooled at different cooling rate, with different deformation were investigated. Continuous cooling transformation (CCT) diagram of this new type of steel was obtained by using Gleeble 1500 thermomechanical simulator. Microstructures and hardness, especially micro-hardness of the experimental steel were investigated by optical microscopy (OM), scanning electron microscope (SEM), Rockwell and Vickers hardness tests. Phase analysis was also studied by X-ray diffraction (XRD). The results indicated that with increase of cooling rate, microstructures of continuous cooled specimens gradually transformed from polygonal ferrite and pearlite, grain boundary ferrite and bainite, bainite and martensite to single martensite. The CCT diagram revealed that slow cooling was needed to avoid austenite-bainite transformation to ensure toughness of this steel. By plastic deformation of 40%, austenite-ferrite transformation temperature increased by 46 ℃, due to deformation induced ferrite transformation during continuous cooling, but Rockwell hardness has little change.     

Aging effects in a Cu-12Al-5Ni-2Mn-1Ti shape memory alloy

The isothermal aging effects in an as-quenched Cu-11.88Al-5.06Ni-1.65Mn-0.96Ti (wt pct) shape memory alloy at temperatures in the range 250 °C to 400 °C were investigated. The changes in the state of atomic order and microstructural evolutions were traced by means of in situ X-ray diffraction and electrical resistivity measurements, as well as transmission electron microscopy (TEM) and optical observations. The kinetics of the aging process, i.e., the temperature and time dependence of the properties including hardness, resistivity, martensitic transformation temperatures, and shape memory capacity were characterized, and at least three temperature-dependent aging stages were distinguished: (1) D0₃ or L2₁ atomic reordering, which causes the martensitic transformation temperatures to shift upward and leads the M18R martensite to tend to be a N18R type structure; (2) formation of solute-depleted bainite which results in a drastic depression in martensitic transformation temperatures and loss of the shape memory capacity, accompanied by the atomic disordering in both the remaining parent phase and bainite; and (3) precipitation of the equilibrium α and γ ₂ phases and destruction of the shape memory capacity.     

热处理工艺对冷轧热镀锌双相钢组织与性能的影响

在实验室试制了热镀锌冷轧DP590双相钢,分析了临界区退火温度对双相钢组织性能的影响,并将同种成分的实验室试制双相钢与工业生产双相钢的组织性能作对比,结果表明:热镀锌双相钢在镀锌段易出现贝氏体组织,且随临界区温度的上升,贝氏体组织含量增多,双相钢的强度上升,而塑性下降;工业试制双相钢,贝氏体和马氏体交互附着在铁素体晶界上,它们的体积分数约占29%,抗拉强度为610MPa,伸长率为31.5%,各项性能符合要求。研究得出,通过控制第二相(马氏体+贝氏体)体积分数和分布形态,能够充分改善热镀锌双相钢的力学性能。