冷轧对β-ZrTiAlV合金形变诱导马氏体相变的影响

对β-ZrTiAlV合金分别采用室温和液氮低温轧制变形,通过X射线衍射(XRD)、光学显微镜(OM)、背散射电子衍射(EBSD)分析技术,研究轧制温度和轧制变形量对β-ZrTiAlV合金形变诱导马氏体相变及其微观组织演变规律的影响。实验分析结果表明,在室温或低温条件下变形后合金组织中都发生了β→α＇形变诱导马氏体相变,同时在马氏体α＇中产生(102)<110>孪晶,轧制变形量的增加促进相变马氏体的形成和孪晶变体数量的增加,而低温变形则抑制了形变诱导马氏体的形成,但更有利于孪晶的产生。轧制变形量为5%时,形变诱导马氏体以板条状分布于原始β晶粒中,当变形量增至10%后,少数β晶粒完全转变为α＇相。     

304不锈钢形变诱导马氏体相变的影响因素分析

使用室温拉伸和高温拉伸实现了304奥氏体不锈钢不同应变率及不同温度下的拉伸塑性变形,使用铁素体测量仪、XRD等分析手段测试了不同应变率、不同组织状况及不同温度下的形变诱导马氏体转变量.结果表明,形变诱导马氏体的转变量与应变率、组织均匀度及变形温度三种因素有关,室温形变时,随着塑性变形率的增加,马氏体转变量逐渐上升;对于室温下周向变形率为30%的内高压成形环焊缝拼焊管而言,母材、热影响区和焊缝处的马氏体转变量依次呈上升趋势,组织均匀性越差,马氏体的转变量越高;高温拉伸时,随着环境温度的上升,马氏体的转变量呈下降趋势,在275℃时,马氏体的转变量趋近为0.     

奥氏体不锈钢弹簧丝的大变形拉拔强化

借助于光学显微镜和X射线衍射仪等研究了奥氏体不锈钢弹簧丝在经过97.7%的大变形后抗拉强度高达1980 MPa的强化现象。结果表明,钢丝的硬度和抗拉强度随着变形量的增加而升高。在大变形量时,沿拉拔方向的组织趋向纤维化,变形马氏体的体积分数在增加,拉拔钢丝的抗拉强度值升高的幅度增加。分析认为变形强化,纤维组织强化和马氏体相变强化是大变形强化的主要原因。     

异构中碳双相钢丝的微观组织与力学性能

运用异构材料理念，通过冷拉拔和临界热处理工艺制备了异构中碳双相钢丝。通过光学显微镜和扫描电镜研究了钢丝冷拉拔和热处理后的微观组织结构，并通过拉伸和硬度试验测试了力学性能，探讨了微观组织与力学性能的关系。结果表明，冷拉拔大变形处理结合短时间的临界热处理工艺，促进马氏体相变，减少铁素体再结晶，可以有效地调控组织结构，得到大量马氏体包裹细小铁素体的理想异构双相组织。随着拉拔应变量以及热处理温度的增加，马氏体体积分数增加，铁素体晶粒尺寸减小，钢丝的强度和硬度显著提高，可与高碳钢丝的强度相比。异构中碳双相钢丝的优异力学性能来源于铁素体晶粒细化、马氏体相变时在铁素体内产生的大量位错和马氏体/铁素体异质结构力学不相容性带来的非均匀变形。     

82B盘条拉拔横裂纹断裂分析

采用金相显微镜、扫描电镜、显微硬度计等对 82B盘条钢拉拔横裂纹断裂试样进行了分析。结果表明：拉拔过程中产生白亮形变马氏体是盘条出现断裂的原因。对产生形变马氏体原因进行讨论，并提出了避免形变马氏体产生的措施。     

冷拉拔珠光体钢丝中渗碳体变形与溶解研究

采用SEM、TEM和XRD研究了珠光体钢丝冷拉拔过程中的组织演变,重点在于渗碳体的变形和溶解。结果表明,渗碳体表现出了很高的变形能力,随着累积应变量的增大,片条组织逐渐转向拉拔方向;在大应变钢丝组织中渗碳体片条厚度小,部分区域只有0.5nm甚至更薄,且已很难见到渗碳体的滑移或剪切变形。在初始钢丝中铁素体含有过饱和的碳,在拉拔应变量为1.51之后,可能转变为四方结构的马氏体,且只有很少量的渗碳体溶解。在高应变量钢丝样品中,用原子探针场离子显微镜探测碳原子浓度以判定渗碳体是否溶解时,应考虑渗碳体的形变及其形貌。     

拉拔变形量对Cu-4 mass%Ag合金线材组织和性能的影响

采用三室真空冷型竖引连铸设备制备了线径为7.821 mm的铸态Cu-4 mass%Ag合金杆，并利用多道次连续拉拔工艺制备了变形量分别为53.38%、93.14%和98.37%的线材；分别对铸态和拉拔态的Cu-4 mass%Ag合金线材进行力学性能、电学性能测试以及微观组织分析。结果表明：铸态Cu-4 mass%Ag合金杆的抗拉强度为236 MPa、导电率为88.50%IACS,当拉拔变形量达到98.37%时，抗拉强度升高到674 MPa,提升了185.59%,而导电率下降到81.00%IACS,仅下降了8.47%;铸态Cu-4 mass%Ag合金杆的横截面组织为典型的“纺布”状枝晶、纵截面为“鱼骨”状枝晶，随着拉拔变形量的增加，线材在纵截面上整体结构呈现出纤维状组织，边缘部分的变形程度要比心部剧烈；当拉拔变形量达到98.37%时，产生了形变孪晶。加工硬化和细晶强化是Cu-4 mass%Ag合金线材拉拔过程中的主要强化机制。     

冷拉珠光体钢丝的组织演变及性能变化

研究了冷拉70钢的组织演变和性能变化。结果表明，随应变量的提高，70钢的抗拉强度和硬度均提高。抗拉强度、硬度与真应变之间呈线性关系。利用场发射扫描电镜（FEM）对70钢冷拉变形过程中的组织演变进行了分析。变形过程中珠光体团发生转动，取向与拉拔轴线趋于一致，渗碳体经历了弯曲、剪切、拉伸等变形，形变量较大时渗碳体大量溶解。     

35Cr3NiMoA钢形变热处理的组织演化

研究了35Cr3NiMoA高强钢高温形变热处理后的组织和硬度.结果表明,35Cr3NiMoA钢在15％ ～ 35％形变度范围内高温形变热处理时,硬度随形变量的增大而增大.组织基本保持马氏体位相,存在少量的碳化物和铁素体,变形量相近条件下,温度越高,针片状马氏体组织越细小;形变温度相同条件下,形变量越大,针片状马氏体组织越细小.形变热处理后,再经回火处理,硬度明显下降,35Cr3NiMoA钢高温形变的最佳工艺方案为形变温度1100℃,形变量20％,回火温度280℃.     

热轧双相钢塑性变形和断裂行为的研究

文章利用SEM、TEM研究了热轧双相钢单向拉伸过程中不同变形量下的形变位错结构和断口组织特征。结果表明,双相钢中铁素体的塑性变形是由位错增殖、位错运动和交互作用、滑移带形成、位错缠结产生及其密度的增加、位错胞出现及细化等一系列演变构成;变形10%时,板条马氏体已产生塑性变形,其板条中出现形变带,并且随马氏体变形的继续,形变带不断形成和发展。变形颈缩时,双相钢中的微孔主要通过相界面结合力的丧失和马氏体断裂产生,而马氏体断裂主要出现在马氏体的尖角处。     

Crystallographic analysis of the FCC → BCC martensitic transformation in high-carbon steel

Based on the phenomenological crystallographic theory of martensitic transformations, the following crystallographic characteristics of the tetragonal martensite in high-carbon steel have been calculated: orientation relationships between the crystal lattices of the bct martensite and fcc austenite; the magnitude and direction of the macroscopic shear; the habit plane; the angle and the axis of rotation of the crystal lattice of the martensite. The calculation was performed for three variants of lattice deformation: Bain deformation; two-shear Kurdjumov-Sachs deformation; and the deformation we suggested upon the analysis of the fcc-bcc transformation. In the last variant, a minimum rotation of the crystal lattice of martensite is required; consequently, this variant is closest to the real mechanism of the martensitic transformation. An expression has been derived that describes the interrelation between the degree of tetragonality of the crystal lattice of martensite and the magnitude of the shear deformation of the lattice. It has been shown that the 12 crystal-lographically equivalent variants of shear upon the formation of the lattice of the tetragonal martensite form three groups in each of which the martensite has the same tetragonality axis. For each variant of the shear, we have two equivalent variants of deformation of the martensite with invariant lattice. This results in 24 variants of orientation relationships.     

Modified Law of Mixture to Describe the Tensile Deformation Behavior of Thermomechanically Processed Dual-Phase Steel

Low alloy steel containing 0.09 wt.% C was thermomechanically processed with various rolling reductions at intercritical temperature of 790 °C, followed by quenching in the iced brine solution. The flow of the material due to this plastic deformation increased the aspect ratio of the microstructure (α + γ) in the rolling than in the transverse directions. The strengths, both in the longitudinal and transverse directions of rolling were increased because of the development of substructure in ferrite, observed previously. The fibrous microstructure formed after rolling increased the surface area of contact of ferrite and martensite. During tensile deformation the fibrous dual-phase composite had positioned itself for better stress transfer from soft ferrite to hard martensite particles. These microstructural changes associated with hot deformation of the material were accommodated in current modifications in the law of mixture applied to dual-phase steel. A computer simulation was developed to present the deformation behavior of ferrite, martensite, and composite from the experimental tensile data (loads and strain). Different variables were introduced in the simulation for allowing the composite curves to pass through the experimental data points to demonstrate the tensile deformation behavior of ferrite and martensite. The systematic changes in these variables with degree of hot rolling in the intercritical region clearly described the deformation behaviour of ferrite and martensite individually.     

21-4N钢温变形拔制裂纹原因探讨

对２１－４Ｎ钢小规格材的生产采用温变形拔制的新工艺,对温变形拔制后材料出现表面裂纹的现象进行了观察和初步分析,结果表明,表面裂纹的产生与材料热处理工艺、温变形后微观组织的变化有关,经改进后,温变形拔制工艺不继优化和完善。     

餐盒用铝箔的生产工艺及盒体拉深变形特性

叙述了餐盒用铝箔的生产工艺,分析了餐盒体冲压变形的特点,并根据其变形特性,分析了提高材料拉深变形能力,保证餐盒顺利成形的主要影响因素。     

1Cr18Ni9Ti不锈钢形变诱发马氏体相变规律及其对孔蚀敏感性的影响

通过低温（－７０℃）拉伸制备不同马氏体相交量的１Ｃｒ１８Ｎｉ９Ｔｉ试样,用ＸＲＤ、ＴＥＭ及金相观察研究形变诱发马氏体相变的规律。用电化学方法研究。α’马氏体（铁磁相）含量对１Ｃｒ１８Ｎｉ９Ｔｉ钢在含Ｃｌ－溶液中孔蚀敏感性的影响。结果表明：随试样变形量加大,形变诱发马氏体中铁磁性的α’马氏体含量不断增大,而ε马氏体相的量始终较小。材料的孔蚀敏感性先随铁磁相含量的增大而增大;当铁磁相含量达到４．５８％以后,孔蚀敏感性反而渐降;当铁磁相含量超过２５．５％后,孔蚀敏感性又增加。     

低碳高强度双相钢丝的组织与性能

对20双相钢丝的组织与性能进行了研究。结果表明，随着亚温淬火温度的升高，双相组织中马氏体的亚结构由孪晶型变成位错型，两相的变形能力和拉拔性能都得到改善。变形量是影响位错数量及其在双相组织中形成位错胞的主要因素。较高温度亚温淬火钢丝经深度拉拔(79％)后，能得到好的强度、弯曲次数和扭转次数的配合。     

无模拉拔成形过程中金属氧化动力学模型

为提高无模拉拔制品的表面质量,优化无模拉拔工艺参数,并预测氧化膜厚度,通过分析变形温度、变形程度等因素对金属氧化过程的影响,针对无模拉拔成形金属锥形管,建立了无模拉拔成形时金属的氧化动力学模型,并与304不锈钢的实验结果进行对比。结果表明,无模拉拔成形过程的氧化动力学曲线呈抛物线-直线复合规律,变形程度增大,变形温度升高,金属的氧化速度加快,氧化膜厚度增加;304不锈钢锥形管无模拉拔成形时,随着拉拔的进行,变形程度逐渐增大,表面氧化膜厚度逐渐增厚,理论预测值和实测值之间的最大相对误差10%;降低感应加热温度、缩短冷热源距离,可以减小金属的氧化程度,有利于提高金属表面质量。     

Young’s Modulus of Austenite and Martensite Phases in Superelastic NiTi Wires

Young’s moduli of superelastic NiTi wires in austenite and stress-induced martensite states were evaluated by three different experimental methods (tensile tests, in situ synchrotron x-ray diffraction, and dynamic mechanical analysis) and estimated via theoretical calculation from elastic constants. The unusually low value of the Young’s modulus of the martensite phase appearing in material property tables (<40 GPa) is generally ascribed in the literature to the fact that stress-driven martensitic transformation and/or twinning processes continue even beyond the transformation range and effectively decrease the value of the tangent modulus evaluated from macroscopic stress-strain curve. In this work, we claim that this low value is real in the sense that it corresponds to the appropriate combination of elastic constants of the B19′ martensite phase forming the polycrystalline wire. However, the Young’s modulus of the martensite phase is low only for wire loaded in tension, not for compression or other deformation modes. It is shown that the low value of the martensite Young’s modulus in tension is due to the combination of the unique coincidence of elastic anisotropy of the B19′ martensite characterized by the low elastic constant C55, austenite drawing texture, and strong martensite texture due to the martensite variant selection under tensile stress.     

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 在现代的金属工艺中,为节约材料和提高材料性能,对线材或棒材等长材经常采用拉拔工艺进行加工。在这种加工艺中,会出现一种表面因拉拔而产生的白亮层,这一白亮层很薄,但硬度很高,常常引起拉拔件表面开裂,有时甚至会引起拉拔件断裂。在以往的文献记载中,常根据其硬度接近马氏体,将其归结为拉拔过程中表面异常升温而产生的马氏体。作者有幸于2010年6月接触到了一起因表面白亮层而导致的表面开裂,但分析结果是白亮层为极其破碎的渗碳体与铁素体的机械混合物,只是腐蚀剂由于表面张力无法进入,而使得其在金相显微镜下观察呈白色。