论文标题:γ（fcc）→α（bcc）马氏体相变的表面浮凸—形态研究及其晶体学计算
Surface Relief-morphology Study of γ(fcc)→α(bcc) Martesite Transformation and Its Crystallographic Calculation
论文作者 张勇
论文导师 林晓娉,论文学位 硕士,论文专业 材料加工工程
论文单位 河北工业大学,点击次数 166,论文页数 85页File Size8075k
2002-02-01论文网 http://www.lw23.com/lunwen_242493742/ 表面浮凸;自协作性;“不变平面”;相变切变角;原子力显微镜（AFM）;惯习面;马氏体形态
surface relief,self-accommodate,"invariant-plane",shear angle,Atomic Force Microscope (AFM),habit plane,martensite morphology
本文利用AFM、SEM、金相显微镜系统地研究了铁基合金γ(fcc)→a(bcc)马氏体相变{259}_f马氏体、板条马氏体和{225}_f马氏体形态、表面浮凸效应及其相变切变角；运用位移矢量理论预测了马氏体相变的惯习面以及相变过程中惯习面的转动；探讨了变体间自协作性与马氏体形态、表面浮凸形貌以及“不变平面”之间的关系。 研究结果表明，热处理工艺及母相预变形对Fe-23Ni-0.55C合金马氏体形态有很大的影响。随着奥氏体化温度的升高，合金的马氏体形态由细长的片状向透镜状转变，边界由平直转向弯曲，其表面浮凸由长片状向短片状变化，边界也由平整向不平整转变。母相压缩变形大于30％时，马氏体的形核和长大具有明显的方向性，马氏体片及其对应表面浮凸分别以细片状和细条状的“簇”平行排列；其马氏体形态由于母相晶格的严重畸变，不但马氏体片的边缘较为破碎，而且中脊也发生了弯曲或折断。 利用AFM对铁基合金的{259}_f马氏体、板条马氏体表面浮凸做了系统地观察与定量分析，并首次利用AFM观察、定量分析了{225}_f马氏体表面浮凸的超精细结构。试验结果表明，{259}_f马氏体基本能够实现变体间的自协作，其表面浮凸多呈“N”型或“帐篷”型，为具有不变平面应变(IPS)特征的规则表面倾动。板条马氏体其表面浮凸是通过新、母相间的塑性协调形成的，表面浮凸群由“浮凸束”构成，“浮凸束”又是由若干个近似平行排列的单根马氏体表面浮凸构成，“浮凸束”呈不规则的“N”型，单根马氏体表面浮凸呈“帐篷”型，它不是通过一次均匀切变形成的，为非IPS型表面浮凸。{225}_f马氏体表面浮凸的形成既有变体间自协作的特征，又有新、母相间塑性协调的痕迹。深冷温度较低时，{225}_f马氏体的表面浮凸虽也为“N”型，但却是不规则的，同板条马氏体“浮凸束”类似，由许多小的亚单元(或小浮凸)构成大的浮凸群，但其亚单元又不像板条马氏体中构成“浮凸束”的小浮凸那样高低起伏较大而呈台阶层状；深冷温度较高时，{225}_f马氏体先形成的“浮凸群”一侧平直，另一侧呈高低起伏；先形成的浮凸群由若干个近似平行的小浮凸台阶构成，在先形成浮凸群的侧面分布着若干个近似平行排列的单根小浮凸，并与先形成的浮凸呈近30°角，在小浮凸的侧面还存在着更小的亚单元。 建立了利用AFM测定{259}_f马氏体和板条马氏体相变切变角的计算模型与方法。结果表明，{259}_f马氏体不同变体相变切变角的AFM测定值与W-L-R晶体学表象理论的预测值符合较好，误差小于3.256°；板条马氏体相变切变角的AFM测定值与K-S关系的理论计算值符合较好，误差小于3.031°。 在深入分析了原始表象理论不适用于板条马氏体和{225}_f马氏体相变的基础上，运用位移矢量理论预测了{259}_f马氏体、板条马氏体和{225}_f马氏体相变的惯习面及其转动。 Y恤C）一 o（bC冯氏体相变的表面浮凸－形态研究及其晶体学计算结果表明，用位移矢量理论预测的惯习面与标准值相吻合。胆59＊马氏体能够基本实现变体间的自协作，惯习面转动角仅为3．52“，基本为“不变平面”；板条马氏体以新、母相间的塑性协调实现变体的长大，惯习面的转动较大为 13．5”，难以构成宏观“不变平面”；p25h马氏体片的长大既有变体间自协作的特征，又有新、母相间塑性协调的痕迹，其惯习面的转动介于胆59＊马氏体和板条马氏体之间为 7．98”，也难以构成宏观“不变平面”。 惯习面法线转动角度的大小反映母相强度的高低、相变时母相塑性协调的程度以及位错亚结构的倾向。这就将母相强度一惯习面法线转动角大小一新、母相塑性协调的程度一惯习面一亚结构从晶体学本质上有机地联系起来。显然，马氏体“不变平面”的概念有其局限性，实际上马氏体相变时惯习面都发生了不同程度的转动，只有自协作良好的p59卜马氏体通过不同变体间应变能的相互抵消，才具有宏观的“不变平面”；而板条马氏体以及 ｛225卜马氏体相变时，其惯习面都发生了较大的转动，因此难以构成宏观“不变平面”。
Morphology, surface relief effect, and transformational shear angle of (259}f martensite, lath martensite and {225}{ martensite in iron-based alloy, by means of Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and Light Optical Microscope, were intensively investigated in this paper; based on Displacement Vector Theory"s calculation, martensite"s habit plane and its rotation were predicted; the relationship between self-accommodation of different variants, martensite morphology, surface relief morphology, and "invariant plane" were also discussed.It"s shown that heat treatment processing and pre-deformation of parent phase both had quite an effect on the morphology of martensite and its surface relief in Fe-23Ni-0.55C alloy. With the increasing of austenizing temperature, martensite plate changed from thin and long shaped to lenticular shaped, as well as its boundary from flat to curved. Correspondingly, the morphology of its surface relief turned from long-plate shaped to short-plate shaped, as well as its boundary from flat to banded. When compressive deformation of parent phase was reaching 30 percent, martensite plates of Fe-23Ni-0.55C alloy were arrayed as thin "packets", parallel to each other, and the same as its surface relief. In addition, for the severe distortion of parent lattice, not only the boundary was ragged, but also its midrib was fragmental or banded.Surface reliefs AFM observation and quantitative analysis of {259}f martensite and lath martensite was performed, and surface reliefs ultra-microscopic structure of (225}f martensite, for the first time, was quantitatively analyzed. It demonstrated that self-accommodation between different variants of {259}f martensite could approximately be fulfilled, and consequently, its surface relief was regular relief, formed by Invariant Plane Strain (IPS), appearing to be "N"-shaped or tent-shaped. Incapable of self-accommodate, surface relief of lath martensite was formed through plastic-accommodation between new and parent phase i.e. surface relief cluster of lath martensite was formed by surface relief "packets", and "packet" was further formed by several single surface relives. That surface relief "packets" was irregular "N"-shaped and its single surface relief was tent-shaped indicated that surface relief of lath martensite wasn"t formed by homogeneous deformation and not to be IPS-type. Surface reliefs formation of (225}f martensite was resulted from both self-accommodation and plastic-accommodation. When deep cryogenic treated at the lower temperature, surface relief of (225}f martensite wasirregular "N"-shaped, composed of some small sub-units (or small surface relives), just like that of lath martensite. However, its small sub-units were not as fluctuating as the small surface relives in surface relief "packets" of lath martensite. Upon the higher temperature deep cryogenic treatment, the formerly formed surface relief of {225} f martensite was still irregular "N"-shaped, with one side being flat and smooth, while the other side being curved. In addition, beside the formerly formed surface relief, several small surface relives, arrayed parallel to each other, could be seen, and the angle between the formerly formed surface relief and the parallel small surface relives was about 30 . Furthermore, the even smaller surface relives were arrayed on both sides of the small surface relief, too.Calculation methods to determine (259}f martensite and lath martensite"s shear angles were established in this paper. It showed that the AFM determined shear angles of different variants of {259}f martensite were in agreement with the prediction of W-L-R theory, with the deviation being less than 3.256 ; the AFM determined shear angle of lath martensite was in agreement with the prediction of K-S model, with the deviation being less than 3.031 .The reason why PTMC was unable to predict transformation of {225}f martensite and lath martensite was intensively analyzed, and, by means of Displacement Vector Theory, habit planes and
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