马氏体相变的定义

对前人所下的马氏体相变定义作了总结，将马氏体相定定义为：替换原子经无扩散切变位移（均匀和不均匀的形变），由此产生形状改变和表面浮突，呈不变平面应变特征的一级，形核－长大型的相变，或简单地称马氏相变为替换原子经无扩散切变（原子沿相界面作协作运动）使其形状改变的相变。     

马氏体相变的定义

对前人所下的马氏体相变定义作了总结，将马氏体相变定义为：替换原子经无扩散切变位移（均匀的和不均匀的形变）、由此产生形状改变和表面浮突、呈不变平面应变特征的一级、形核－长大型的相变。或简单地称马氏体相变为替换原子经无扩散切变（原子沿相界面作协作运动）、使其形状改变的相变。     

纳米材料的相变

纳米纯金属常呈现与大块金属不同的晶体结构，如Co和Fe在室温呈fcc结构。不同制备方法所得的纳米Fe-Ni,其α和γ相区均较大块的扩大，并呈现奥氏体的稳定化，但逆相变近似大块合金，文章对比作了解释。测得一定晶粒大小及一定成分的Fe-Ni冷却时马氏体相变的临界温度，显示纳米材料中会发生马氏体相变。Al-Cu薄膜中，Cu在晶界偏聚量大，在饱和浓度处形成非共格Al2Cu，并无过渡相，且脱溶温度（固溶线）比大块低85K。定性地讨论了晶界包括晶界偏聚和晶界扩散对无扩散型相变和扩散型相变的作用；提出一个纳米金属相变的热力学模型，和纳米材料马氏体形核能垒的计算，用以描述纳米晶晶粒大对马氏体相变的影响。对纳米材料相变的续后研究作了展望。     

界面过程控制生长≠扩散控制

应用经典扩散理论数学模型及前人和作者测定的数据，对纯铁块状及形成等轴α相的相变动力学进行分析，结果表明，这两种相变都不属于扩散型。将动力学分析取得的相关数据代入界面过程控制相变数学模型，求得γ→α（等轴晶）的激活能为193～198kJ／mol，小于7铁的自扩散激活能（270kJ／mol），而与其相界扩散激活能相近（152～172kJ／mol）。作者认为，Christian将多形性转变、块状转变、再结晶、晶粒长大、有序化等无成分变化的非切变型相变一并划入界面过程控制类是恰当的。由于短程输送涵义易于混淆，不宜用于相变分类。界面过程控制的细节应是“半无序微位移”机制。     

块状相变

概述块状相变研究的进展，包括该相变的特征、发生条件及相界结构。块状相变可以定义为：成分不改变、通过相界扩散的形核——长大型相变；相变包括结构改变和有序化，其产物一般呈块状显微组织，但有时也呈平面边界，与其长大的母相晶粒不具完整的位向关系，与母相不具点阵对应。讨论块状相变热力学上的两种观点：上限温度为同成分两相的Gibbs自由能相等的温度T0及以α/α γ平衡相界为限制温度，本文作者倾向于前一观点。块状相变动力学及相变产物的形态决定于相界结构。阐述相界结构的研究进程。晚近研究结果已揭示相界的共格程度决定于特殊相界面的位向，从非共格到一维共格。提出对相界微观结构及其动态、定位考察以及相变产物一些性质研究的展望。总结了可能发生块状相变的相图。     

马氏体转变(十七)

正6有色金属中的马氏体相变通常,有色金属和代位型有色合金中发生的马氏体相变同样是具有表面浮突的无扩散位移型转变,但具有比较小的应变和小的热滞。马氏体的形态有片状和板条两种。马氏体的亚结构有堆垛层错、孪晶和位错。在相变中沿切变面发生孪生或滑移进行调整,以符合晶体结构的相变和形状上的改变,马氏体中亚结构的出现和相应数量取决于合金     

过冷奥氏体整合系统和转变贯序

综合分析了过冷奥氏体整合系统及其转变贯序。认为过冷奥氏体的转变复杂多变,当以系统整合的方法研究其转变体系。随着过冷度的增加,原子位移方式由扩散位移过渡到界面原子非协同跃迁,再过渡到原子集体协同共格位移。相应的转变贯序为:共析分解→贝氏体相变→马氏体相变。相结构、组织形貌、亚结构等也随之发生演化。     

纯铁γ—α转变机制求索

依据前人的实验数据，运用传统计算方法，对纯铁γ-α转变扩散机制进行了检验，结果表明：完成转变需用时间的理论计算值与实验值有3－4个数量级的差异。根据非切变相变大多存在非共格相界的特点，由相界原子参与相变的设想提出了存在非共格相界的非切变相变“相界与母相原子联动位移”机制。运用热力学基本原理对“联动”和新相连续长大的条件进行了简要分析。对固态相变的分类提出了质颖并建议把“扩散型相变”限定为新相与母相化学成分不同的相变。     

贝氏体相变简介

钢、有色合金和一些陶瓷材料中都存在贝氏体相变。贝氏体钢正成为有益的工程材料。总结评述切变学派和扩散学派作者们以形貌、动力学或晶体学对贝氏体相变机制所持的论点。钢中贝氏体相变以过饱和铁素体开始形成之说迄未得到支持。一些实验已发现替代（置换）型合金元素在相界面上的偏聚，并以此所呈现的拖曳效应说明相变的不完全现象，切变学者以切变机制来解释这个现象，但此现象不是钢中贝氏体相变的普遍情况。贝氏体形成时呈现帐篷形浮突，不具不变平面应变特征；有时马氏体相变晶体学表象理论能近似地应用于贝氏体相变晶体学，但不能以此来判定其相变机制为扩散或切变。溶质拖曳效应以及高分辨电镜对相界面结构实验、热力学研究、磁场和应力场对贝氏体相变影响以及一些预相变现象都确证贝氏体相变籍扩散机制进行。本文作者定义贝氏体为：在Ms温度以上，经扩散相变的产物，多呈片状，形成时会在自由表面上呈现帐篷形浮突。提出贝氏体相变机制进一步研究和应用的展望。     

时效析出对NiTi形状记忆合金阻尼特性的影响

用X射线衍射、DSC及DMA等方法研究了富Ni的NiTi记忆合金在600℃加热后经不同冷却方式处理后的组织结构及阻尼性能。结果表明，在600℃加热后缓冷的组织中有大量的马氏体型转变产物M与R相，材料的阻尼水平较高，且在对应M→R相变温度区出现明显低频阻尼峰。     

CALORIMETRY OF PARTIAL MARTENSITIC TRANSFORMATIONS

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PHASE TRANSFORMATIONS IN RAPIDLY SOLIDIFIED TiNi SHAPE MEMORY ALLOYS

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马氏体相变

对前人所下的马氏体相变定义和所作的分类进行了总结,将马氏体相定义为：替换原子经无扩散切变位移（均匀的和不均匀的形变）由此产生形状改变和表面浮突,呈不变平面应变特征的一级,形核一长大型的相变,马氏体要变按动力学分为变温相变和等温相变,按热力学和界面动态分为弹性相变,近似（半）热弹性相变和非热弹性相变,热弹性相变的判据为（１）临界项相变动动力小,热滞小;（２）相界面能往复（正,逆）运动;（３）形状应变     

Ni52Mn21+xGa27-x(x=0-5)磁性形状记忆合金的相变

研究了非化学计量成分的多晶Ni52Mn21+xGa27-x(x=0-5)系列合金的热弹性马氏体相变和磁相变.合金的马氏体相变温度Ms随Mn含量的增加而升高,当x＞4时,Ms已经升高到室温以上,而马氏体相变滞后△T随z的增大而减小;合金的磁相变温度TC随z增加而升高,但变化范围不大,在z＞2后,Tc保持在348 K左右.实验获得了一种具有实用前景的合金成分--Ni52Mn25Ga23合金,其马氏体相变温度在室温以上,相变滞后仅为5 K.     

Isothermal and athermal martensitic transformations in Ni–Ti shape memory alloys

Ni–Ti shape memory alloys are known to demonstrate three possible transformation paths between B2 and B19′ phases, B2–R–B19′, B2–B19′ and B2–B19–B19′, depending on their composition and thermo-mechanical treatment. In this work the isothermal kinetics of accumulation of martensite/austenite for all types of martensitic transformations in Ni–Ti and Ni–Ti–X (X = Fe or Cu) has been studied by means of resistance measurements during interruption of cooling/heating scans. Experimental results show that all transformations to the B19′ phase (B2–B19′, R–B19′, B19–B19′) demonstrate a substantial isothermal accumulation of martensite during isothermal dwelling between the martensitic transformation start and finish temperatures. The reverse transformations B19′–R and B19′–B19 are also classified as isothermal. The isothermal accumulation of austenite detected during the reverse B19′–B2 transformation is much less intense, at least partially due to the low sensitivity of resistance to the martensite fraction variation during the reverse transformation, and remains comparable with the resolution of the experimental set-up. The transformations between the B2 and R as well as between the B2 and B19 phases are athermal. Analysis of the entire set of possible transformations in β Ni–Ti systems allows one to conclude that isothermal transformations possess a much broader hysteresis and transformation range compared with athermal ones. Since the hysteresis of the transformation is related to the friction forces acting on interfaces this fact, and also observation of the isothermal effects during reverse martensitic and intermartensitic transformations, strongly support the interpretation of the observed isothermal effects in Ni–Ti as due to the diffusionless but thermally activated motion of interfaces during transformation. The difference between the transformation to B19′ martensite (isothermal) and all others (athermal) is attributed to a distinction in strain accommodation.     

近几年马氏体相变研究的进展

综合整理了近年来马氏体相变试验研究的新成果.认为马氏体相变切变过程缺乏热力学可能性.指出马氏体在晶界、相界面、位错等缺陷处形核,并非共格切变过程.发现板条状马氏体、片状马氏体中均存在堆垛层错亚结构；高密度位错、孪晶、堆垛层错亚结构的形成并非切变所致；马氏体形貌的演化系应变能起主导作用,与切变无关；马氏体表面浮凸是相变比...     

Premartensitic phenomena and other phase transformations in Ni–Mn–Ga alloys studied by dynamical mechanical analysis and electron diffraction

Ni–Mn–Ga ferromagnetic ordered shape memory alloys are known to exhibit phonon softening and soft mode condensation into a premartensitic phase prior to the martensitic transformation itself. In the present work, this unique behaviour of Ni–Mn–Ga system has been studied as a function of electron concentration (i.e., alloy composition) and a region on the phase transformations diagram which corresponds to the stability of the intermediate phase has been determined, being completely in the ferromagnetic zone. The results were mainly obtained by means of dynamical mechanical analysis and transmission electron microscopy. The two types of lattice instability which might occur in the parent phase driving it to either the soft mode condensed intermediate phase or to the martensitic phase are discussed in this work, together with precursor phenomena and the intermartensitic transformation observed in alloys with the highest electron concentration.     

A comparison of the phenomenological theory of martensitic transformations with a model based on interfacial defects

Structural models of martensitic interfaces are those where the habit plane (HP) is comprised of coherent terraces reticulated by arrays of interfacial defects. Such interfaces are shown explicitly to exhibit no long-range displacements and to move in a glissile manner by lateral motion of disconnections along the interface. We quantify predictions of HP and orientation relationship (OR) between the parent and product crystals for such models in terms of a reference lattice in an approach called a topological model (TM). These crystallographic quantities for the TM are compared with those of the phenomenological theory of martensite crystallography (PTMC). For the case of transformations resembling α to β in Ti, but where lattice invariant deformation is suppressed, the two models agree when the interplanar spacings of the terraces in the two crystals are the same. However, although the OR’s according to the two approaches are very similar, the predicted HP’s differ systematically when the terrace plane spacings are varied. The differences arise because the PTMC interfaces are unrelaxed configurations that are invariant planes of the geometrical shape transformation, whereas TM interfaces are physically invariant planes as a transformation progresses.     

Orientation relationship,shape change and their traces in electron diffraction patterns and high-resolution transmission electron microscopy images

This paper outlines a straightforward method that can be used to predict the total number of orientation relationships between a pair of lattices that can be related by an invariant plane strain transformation and the shape change associated with each of the orientation relationships. This paper also provides a simple technique for calculating the shape strain and crystallography directly from electron diffraction patterns or Fourier-transformed digital patterns of high-resolution transmission electron microscopy images. It demonstrates that many of those diffusional phase transformations that are traditionally classified as non-displacive exhibit in fact a remarkable shape change and that the shape change can even be a simple shear.