Al-Li基合金中S′相透射电镜原位观察

用透射电镜双倾台围绕[220]_α作系列倾转,原位观察了Al-Li-Cu-Mg-Zr合金中S'相的形貌及其与母相的位向关系.观察结果表明,Al-Li基合金中S'相成群析出,其单体呈板条状,惯习面为{021}_α,沿<100>_α方向长大.沿同一方向生长的多个S'相单体组合成片状的板条群并躺在{110}_α面上.     

AZ91 Mg—Al合金中β—（Mg17Al12）析出相的形态及其晶体学特征

应用透射电镜研究了时效AZ91 Mg-Al合金连续析出相的显微组织形态及晶体学特征。发现四种不同形态和晶体学特征的β-（Mg17Al12)析出相,共中占绝大多数的是板条状板出相,沿基面（0001）α析出的板条析出相与基体保持Burgers位向关系,生长方向为[7,2,-/9,0];其晶体学特征与由不变线应变原理预测的完全一致,第二类析出相是其轴线与其面垂直的六棱柱体,六个棱柱面都是{1100}α{110}β与基体保持对称性好的Crawley位向关系,另有少量短棒状同相与基体保持Porter位向关系,实验中还观察到一种未见报道过的位向关系。讲座了形态不同形态和晶体学特征的机制。     

冷轧工业纯钛的退火再结晶行为

采用扫描电镜(SEM),电子背散射衍射(EBSD),取向分布函数(ODF)等测试手段和分析方法,比较系统地研究了工业纯钛的退火再结晶行为。结果表明：初次再结晶大致分为2个阶段：第1阶段为500 ℃退火的前60 min左右,约25%的材料发生了取向变化的再结晶;第2阶段为退火60~360 min,材料体积的大部分（约75%）发生了没有取向改变的再结晶。晶粒长大过程的前期,织构变化非常显著。随着晶粒的长大和退火时间的延长,织构变化越来越缓慢。增强的取向主要位于{0°,30°,30°}为中心的宽峰区域,减弱的取向主要是{0°,40°,50°}附近的取向     

电真空用冷轧钼薄板晶粒取向与力学性能分析

利用EBSD和金相分析了电真空用0.5mm厚冷轧退火钼薄板的晶粒取向及显微组织,并探讨其与力学性能的关联性。结果表明,加工性能优异的钼薄板中晶粒取向分布相对较弱、较漫散,主要包含α线和γ线织构,其中α线织构的最大组分为旋转立方{001}<110>,并含有一定量{112}<110>;晶粒多为沿RD方向且平行轧面顺序排列的“扁云片”状;有相对较少的θ＞50°大角度晶界;这使得RD、TD及45°-RD方向的屈强比和延伸率均较高,延伸率各向异性较低,强塑性匹配良好。     

��ȡ��繤�ְ�{100}��֯���ļ�㶨���ⶨ

 在探讨了无取向电工钢工业检测{100}面织构的需求和当前所面临的测量不准或测量方法过于繁杂的基础上，尝试了一种{100}面织构简便的定量测算方法。以市场上3种无取向电工钢板为实验材料，测量了{200}不完整极图。把极图中心附近10°范围内极密度分布的累积定义为{100}面织构，推导出了计算钢板{100}面织构的简便方法。其中根据{200}极图的对称性和极图的已知数据近似推导出了极图的未知部分，从而完成了定量计算过程。定量计算结果与实测极图所表现{100}面织构的强弱趋势一致。利用相似的原理也有可能发展出对其它织构简便而准确的定量测算方法。     

Zr-Sn-Nb 合金织构与性能研究

对Zr-Sn-Nb合金带材在25℃、200℃、400℃下进行拉伸试验,采用背散射电子衍射技术(EBSD)研究了织构对锆合金力学性能的影响。结果表明,带材具有较强的{0001}基面双峰织构,[0002]基轴在TD-ND平面内,并向TD方向倾斜约30°,大晶粒多为{0001}< >和{0001}< >取向,小晶粒为{0001}< >取向。织构造成带材力学性能呈现各向异性,σs在TD方向最高,在RD方向最低;σb在RD方向最高,在45°方向最低。随着温度的升高,σs与σb都有所降低,Δσs与Δσb也随之减小,且Δσs较Δσb受温度的影响更为明显。带材的延伸率随温度升高而增加,但400℃时的延伸率较200℃时的低,晶界强度的下降以及动态应变时效是造成这种现象的主要原因。     

影响钢的磁感应强度的面织构分析

分析了主要晶面上的取向特点。测定了Nb-V和Nb-Ti微合金钢不同条件下冷轧退火后的主要面织构密度和磁感应强度B50和B100,分析了两者间的关系。分析结果表明,对磁感应强度而言,{100}面织构是有利的;{111}、{211}面织构是不利的;{110}面织构是中性的。{111}与{211}面织构密度有显著的相关关系。     

Zr—4合金双轴疲劳行为及其微观变形机理Ⅱ.双轴循环变形亚结构及其？…

用透射电镜分别观察了Zr-4合金比例和非比例双轴疲劳变形亚结构.结果表明等效应变幅为0.8%,不同主应变比下,Zr-4合金比例双轴疲劳后典型的位错组态是{1010}柱面滑移产生的平行位错线.随着等效应变幅提高,从平面状向波纹状滑移转化,有形成位错胞的趋势.非比例加载过程中,随着相位角从30°增大到90°,位错组态从平行位错墙变化成位错胞.相位角为90°时,随着等效应变幅提高,位错保持位错胞结构,但位错密度增高.非比例变形前后织构分析表明随着相位角提高,{1010}极点密度减弱,{1011}锥面极点密度增强,表明合金塑性变形从以{1010}柱面滑移为主向柱面滑移加锥面滑移多系滑移转化.Zr-4合金非比例附加强化一方面是由于部分柱面滑移被锥面滑移取代后,滑移系本身临界分切应力提高;另一方面由于多滑移导致〈a/a〉和〈c+a〉/〈a〉位错与位错之间交互作用力提高.     

用金相法研究马氏体的惯析面

本文提出了用双面金相法研究马氏体惯析面的二种方法。首先通过高温加热,在奥氏体中引入大量{111}_A 孪晶,淬火以后,使这种带有孪晶面的奥氏体转变为马氏体。通过测定孪晶面和板条马氏体的惯析面的截距,可计算出它们之间的夹角和马氏体惯析面的品面指数。从而确定40Cr钢马氏体的惯析面不可能是{111}_A而应该是{557}_A,这种方法实验误差小,费用低,简便,有一定的实用价值。     

相邻板条马氏体间位向关系的TEM研究

研究了1Cr21NiSTi双相不锈钢γ相在0℃以下的马氏体相变，着重测试和分析了相邻板条马氏体间位向关系。结果表明：马氏体与母相奥氏体之间的位向关系(K—S或N—W关系)决定了相邻板条马氏体间的位向关系，K—S或N—W关系条件下板条马氏体变态使得相邻板条马氏体间呈多种位向关系。交替排列的互为孪晶的马氏体板条间不存在残留奥氏体，这是马氏体自协调形成的结果，这一孪晶位向关系与K-S关系马氏体变态的孪晶关系不同。     

REVERSIBLE TRANSFORMATION BETWEEN MATRIX AND MARTENSITE IN Ni-Ti SHAPE MEMORY ALLOYS

The reversible transformation between matrix and martensite in Ni-Ti shape memory alloyshas been dynamically observed under TEM.The orientation relation between martensite andaustenite as well as the structural change near the transition temperature has been also studiedwith the help of HREM SADP.The results show that the orientation relation betweenmartensite and austenite is[(?)11]_A//[(?)10]_M,[110]_A//[001]_M,(110)_A//(001)_M and theangle between((?)110)_A and(010)_M is about 6.5°.The crystal defects of martensite are foundto be twin and stacking fault,and the twin plane as(100).     

Ni-Ti形状记忆合金中母相(?)马氏体可逆转变过程的研究SCIEI

用透射电镜对Ni-Ti形状记忆合金中母相?马氏体可逆转变进行了动态观察。利用高分辨电子显微术研究了该合金相变温度上下的结构变化。结果表明,马氏体与奥氏体的取向关系为:[111]_A∥[110]_M,[110]_A∥[001]_M,(110)_A∥(001)_M,(110)_A与(010)_M间夹角为6.5°左右;马氏体的晶体缺陷多为孪晶和层错,新发现有孪晶而为(100)的孪晶。     

Maraging behavior of an Fe-19.5Ni-5Mn alloy II: Evolution of reverse-transformed austenite during overaging

The evolution of reverse-transformed austenite in a maraging Fe-19.5Ni-5Mn alloy was examined using transmission electron microscopy. The types of reversed austenite observed were determined by the aging temperature and time. It was found that matrix austenite appeared first, followed by lath-like austenite and then by recrystallized austenite, the latter after prolonged aging at higher temperatures. Each evolved at different preferential sites. The first two types of reversed austenite contained dense dislocations that probably contributed to the subsequent recrystallization. The lath austenite was twin-related, and its orientation relationship with the residual martensite films obeyed either Nishiyama (N) or Kurdjumov-Sachs (K-S) relations, depending on the aging temperature. Each individual austenite lath nucleated independently with a habit plane close to {111}_f, and constituted a lamellar structure with the residual martensite. Its formation possibly involved a shear mechanism accompanied by element redistribution. The matrix austenite and the lath-like austenite eventually recrystallized to form fine grains of austenite. Part of the recrystallized austenite transformed to martensite after cooling so that the resultant microstructure was a mixture of a few newly formed martensite laths and oval/spherical ferrite particles distributed in the recrystallized austenite matrix. The recrystallized austenite and ferrite particles, rather than the lamellar structure of lath-like austenite, are thought to be the equilibrium phases at 550°C.     

SUBSTRUCTURE AND CRYSTAL MORPHOLOGY OF MARTENSITE IN MEDIUM CARBON IRON ALLOYS

The morphologic,substructural and crystallographic characteristics of martensite in steels 60and 60Si2Mn have been investigated by means of optical and transmission electronmicroscopy combined with B-M phenomenological crystallographic theory.The average hab-it plane of martensite in medium carbon iron alloys is{225}_f.Experimental data on the habitplane and the orientation relationship between the austenite and martensite are in agreementwith the B-M theoretical calculation of using the Bain strain and lattice invariant shear on(100)[011]_f.     

Crystallographic analysis of the martensitic transformation in medium-carbon steel with packet martensite

Based on X-ray diffraction studies of the martensite texture in a single martensite packet, exact orientation relationships between the orientations of martensite crystallites and the original austenite single crystal in medium-carbon steel 37KhN3A have been determined to be as follows: (011)_α||(1; 0.990; 1.009)_γ to an accuracy of \( \pm 0.15^\circ ,{\left[ {01\overline 1 } \right]_\alpha }||{\left[ {1;1.163; - 2.133} \right]_\gamma }\) to an accuracy of ±0.15°. It has been shown that the orientation relationships proved to be almost the same as in the Fe–31% Ni alloy with a twinned martensite with close lattice parameters. Therefore, the conclusion has been drawn that the mechanism of the lattice deformation upon the martensitic transformation is the same in both alloys. It is described as follows. The lattice deformation occurs by shear on the (111) plane in the \({\left[ {11\overline 2 } \right]_{_\gamma }}\) direction and is accompanied by an additional change in the dimensions in the mutually perpendicular directions \({\left[ {11\overline 2 } \right]_{_\gamma }},\left[ {111} \right],\;and{\left[ {1\overline 1 0} \right]_{_\gamma }}\). The invariantlattice deformation is implemented by slip in martensite on the planes of the (112)_α type in the direction \({\left[ {\overline 1 \overline 1 1} \right]_\alpha }\). One of the 24 crystallographically equivalent variants of the transformation mechanism has been considered. Apart from this type of deformation, an additional deformation of martensite is possible that does not change its orientation. It has been shown that the orientation of the martensite crystallite calculated via the phenomenological theory of the martensitic transformations (PTMT) differs by approximately 1° from the experimentally determined orientation. This refers to both the lath and twinned martensite. In the twinned martensite, the invariant plane obtained in the PTMT calculations and the habit plane coincide. In lath martensite of 37KhN3A steel, the invariant plane of the martensite crystal obtained in PTMT calculations deviates by ~25° from the orientation of the surface of the martensite plate (habit plane), which is close to the (111)_γ plane. An explanation of this phenomenon is given.     

Crystallography and structural evolution during reverse transformation in an Fe–17Cr–0.5C tempered martensite

The mechanism and the crystallography of austenite and δ-ferrite formation from tempered martensite at temperatures of 900–1200°C have been studied by means of transmission electron microscopy in an Fe–17Cr–0.55C alloy. It was found that austenite nucleates within ferrite at low angle, high angle and twin-related lath boundaries as well as at high angle equiaxed grain boundaries in contact with M₂₃C₆ grain/lath boundary carbides. The austenite grains are in a cube–cube relationship with the M₂₃C₆ carbide particles and bear the Kurdjumov–Sachs orientation relationship with at least one of the adjacent ferrite grains. They are often in the Kurdjumov–Sachs relationship with both ferrite laths separated by a high angle boundary as far as the laths had formed from the same austenite. The {111}_A close packed plane of γ precipitate is parallel to the {110}_F plane most parallel to the grain boundary. The close packed planes of some austenite grains nucleating at the high angle lath boundaries are parallel to the close packed planes of both ferrite laths. These crystallographic features often result in a single variant of austenite orientation at a grain boundary. After nucleation, the austenite grains grow by the migration of both semicoherent and incoherent interfaces. These results demonstrate that a specific orientation relationship is preferred for the austenite nucleation, but is not necessary for the subsequent growth. The kinetics of austenite growth are controlled by chromium diffusion. The δ-ferrite particles precipitate at high temperatures as a non-equilibrium phase. No rational orientation relationship between δ-ferrite and retained austenite was found. The experimental results are discussed qualitatively in terms of the thermodynamic predictions using the software ThermoCalc, assuming local equilibrium at the moving interfaces.     

Effect of heat treatment on formability in 0.15C−1.5Si−1.5Mn multiphase cold-rolled steel sheet

The effects of volume fraction and the stability of retained austenite on the formability of a 0.15C−1.5Si−1.5Mn (hereafter all in wt.%) TRIP-aided multiphase cold-rolled steel sheet were investigated after various heat treatments. The steel sheets were intercritically annealed at 800°C, and isothermally treated at 400°C and 430°C. Microstructural observation, tensile tests and limiting dome height (LDH) tests were conducted on the heat-treated sheet specimens, and the changes in retained austenite volume fraction as a function of tensile strain were measured using an X-ray diffractometer. The results showed a plausible relationship between formability and retained austenite stability. Although the same amount of retained austenite was obtained after isothermal holding at different temperatures, better formability was obtained in the specimens with the higher stability of retained austenite. If the stability of the retained austenite is high, the strain-induced transformation of retained austenite to martensite can be stably progressed, resulting in a delay of necking to the high strain region and improvement in formability.     

Effect of nitrogen on microstructure and corrosion resistance of Cr15 super martensitic stainless steel

ABSTRACT

To investigate the influence of nitrogen on structure and corrosion resistance of Cr15 super martensitic stainless steels (SMSS), two types (N-free and N-0.12%) of specimens were quenched at 1050°C and tempered at different temperatures, and then, optical microscope, transmission electron microscopy, X-ray diffraction, potentiodynamic polarisation, immersion experiments and Kelvin Probe Force Microscope were used to characterize its microstructures and corrosion properties. The experimental results show that the microstructure in the N-free Cr15 super martensitic stainless steel is a biphasic tissue with alternating martensite and austenite distribution while quenched at 1050°C and tempered between 600 and 700°C. The nitrogen addition increases the content of austenite, and changes the austenite morphology significantly into the coarse block and strip distribution. What’s more, micro-galvanic corrosion is formed between austenite and martensite, which deteriorates the corrosion resistance of the SMSS.     

INHERITANCE OF PRECIPITATED V_4C_3 IN MARTENSITIC TRANSFORMATION

The inheritance phenomenon of precipitated V_4C_3 in martensitic transformation has been in-vestigated by means of electron diffraction and matrix analysis.A crystallographic orientationrelation among austenite,martensite and V_4C_3 carbide was found to be.(010)_A∥( 10)_M∥(010)_(v_4c_3),[10 ]∥[11 ]_M [10 ]_(v_4c_3)The V_4C_3 first precipitated in austenite,and then was inherited to martensite.Although cer-tain orientation relation was kept between V_4C_3 and martensite,the interfacial structural ana-lysis pointed out that the biphase interfacial energy is higher than that determined byBaker-Nutting relation,thus it is metastable.Because the V_4C_3 precipitated along thecrystalline defects in austenite,they could be inherited to martensite.     

析出V4C3在马氏体相变中的遗传

本文利用电子衍射和矩阵分析方法探讨了析出V_4C_3在马氏体相变中的遗传现象。结果表明,奥氏体、马氏体和V_4C_3三相间的晶体学取向关系为: (010)_A∥(110)_M∥(010)_(V_4C_3) [101]_A∥[111]_M∥[101]_(V_4C_3)V_4C_3首先在奥氏体中析出,遗传至马氏体中后,虽能与马氏体保持一定的取向关系,但界面结构理论分析指出,两相间的界面结合能高于Baker-Nutting关系所规定的结合能,因而是一五稳态。由于V_4C_3沿奥氏体的晶体缺陷析出,故这些缺陷将遗传至马氏体中。