Martensitic transformations theories

In 1964, two competing series of slender volumes appeared one, the Macmillan Series in Materials Science , came from Northwestern Morris Fine wrote a fine account of Phase Transformations in Comlen.ted Systems, accompanied by Marvin Wayman s Introduction to the Crystallography of Martensite Transformations and by Elementary Dislocation Theory, written by Johannes and Julia Weertman. The second series, edited at MIT by John Wulff, was entitled The Structure and Properties of Materials , and included slim volumes on Structure, Thermodynamics of Structure, Mechanical Behaviour and Electronic Properties. 

Diffusionless transformations have been sometimes called military , in contrast to the more civilian diffusion controlled transformations. Considering their technical relevance, the crystallographic theory of martensite transformation has been worked out in much detail, and particularly for the habit plane selection of the given 0-0 lattice structural change. The reader is referred to the corresponding metallurgical literature (D.A. Porter, K.E. Easterling (1990) D.S. Liebermann (1970) C.M. Wayman (1983)]. 

G.B. Olson and M. Cohen. Dislocation theory of martensitic transformations. In F.R.N. Nabarro, editor, Dislocations in Solids, Vol. 7, pages 295-407. North-Holland, New York, 1986. 

J.M. Ball and R.D. James. Theory for the microstructure of martensite and applications. In Proceedings of the International Conference on Martensitic Transformations, pages 65-76, Monterey, CA, 1993. Monterey Institute for Advanced Studies. 

It was based on these uniqueness and commonalities, my colleague and I submitted a paper entitled Crystal Structure and A Unique martensitic Transition of TiNi to a Journal concerned with metals and alloys for publication in 1965. But, the paper was rejected outright by two anonymous reviewers who could not accept our observation that the Nitinol transition was unique. Obviously the reviews contend that by accepting Nitinol transition being unique, may make all other martensitic transformations garden variety. This may upset the theory of martensitic transition formulated thus far. We then, submitted the paper to the Journal of Applied Physics and was accepted for publication and eventually appeared in print [10]. A few months after the appearance of this article, the editor of the very journal that rejected my paper, asked me to review two papers on Nitinol for the journal. Suddenly, I was an undisputed expert in Nitinol Up to this point I had not really start to apply covalent-bond concept but devoting more time in collecting experimental data [14,15], which may be important in support or non-support of covalent-bond concept. 

In 1967, on April 3 and 4, under the sponsorship of ONR (Office of Naval Research) I organized the first International Conference on Nitinol called Symposium on TiNi and Associated Compounds . The conference was held at Naval Ordnance Laboratory, the birthplace of Nitinol. As the chairman of the conference I assisted in selecting the papers from this conference that were later published in block form in the Journal of Applied Physics [16]. Despite these efforts the Nitinol transition remained elusive for sometime. In fact, after more than 30 years since the discovery of memory effect and with more than 139 papers have appeared in various journals on this subject, the investigators still do not agree with one another. At the same time more than 4,000 patents worldwide have been filed on the use of the memory effect or superelasticity in Nitinol. Out of all this, the actual application of Nitinol remains only a handful. In sharp contrast other conventional alloys with martensitic transition has no controversy and in fact they are so well understood that a Crystallographic theory of martensitic transformation was formulated [27],... 

Table 1. Experimental values of latent heat of the martensitic transformation Q, the transformation temperature Tm, and the magnetization jump AM at the martensitic transformation for Nio tMrii T(ia (0 < x < 0.19) alloys. AT is the shift of the martensitic transformation temperature Tm in a field AH = 2 T calculated from the Clapeyron-Clausius relation (theory) and obtained from the magnetization measurements (experiment).

The crystalline phase follows a few independent slip systems in which classical crystal plasticity theories cannot be utilized to model them [93-95]. Similar to the metallic crystalline phases, inelastic deformation in crystalline polymeric systems follows three different mechanisms (a) crystallographic slip, (b) twining, and (c) Martensite transformations [96]. All these mechanisms leave the crystallographic axis inextensible and provide less than five independent... 

Joh] Johnson, K.A., Wayman, C.M., The Crystallography of the Austenite-Martensite Transformation in an Fe-Cr-C Alloy , Acta Crystallogr., 16(6), 480-485 (1963) (Crys. Strueture, Experimental, Theory, 16)... 

Cha] Chang, H., Hsu, T.Y, Zuyao, X.U., Thermodynamic Prediction ofM and Driving Force for Martensitic Transformation in Fe-Mn-C Aalloys , Acta Metall, 34, 333-338 (1986) (Kinetics, Calculation, Theory, 23)... 

Most of the austenitic stainless steels are known to undergo a strain-induced martensitic transformation [1], Aless well-known fact is that certain commercial grades of AISI 304 and AISI 304L also undergo spontaneous transformation upon quenching to 76°K [2]. This report will be confined to the mechanical properties of alloys that undergo strain-induced transformation only. The strain-induced martensitic transformation is dependent on the temperature of deformation and the nature of the applied stress. A treatment of one theory of strain-induced martensitic transformation may be found in the work of Patel and Cohen [3]. 

Strain-induced martensite has been found to increase with decreasing temperature and increasing plastic strain in austenitic stainless steels [1]. Consequently, the reported low-temperature martensite suppression may be predictable in terms of the existing theory since the corresponding plastic strain also decreased substantially. However, there is also the possibility that the martensitic transformation is suppressed at very low temperatures in these alloys independently of the strain. 

To explain the martensitic transformation, Cohen, Machlin, and Paranjpe postulated the reaction path theory which was later revised and expanded to meet additional... 

There are more general problems of stability of materials and of phase transformations that are closely related to the tensile tests described above. Namely, the tensile test may be considered as a special case of so-called displacive phase transformation path. These paths are well known in studies of martensitic transformations. Such transformations play a major role in the theory of phase transitions. They proceed by means of cooperative displacements of atoms away from their lattice sites that alter crystal symmetry without changing the atomic order or composition. A microscopic understanding of the mechanisms of these transformations is vital since they occur prominently in many materials. 

ACAR angular correlation of annihilation BM Bowles-Mackenzie (theory of martensitic transformation)... 

Solids undergoing martensitic phase transformations are currently a subject of intense interest in mechanics. In spite of recent progress in understanding the absolute stability of elastic phases under applied loads, the presence of metastable configurations remains a major puzzle. In this overview we presented the simplest possible discussion of nucleation and growth phenomena in the framework of the dynamical theory of elastic rods. We argue that the resolution of an apparent nonuniqueness at the continuum level requires "dehomogenization" of the main system of equations and the detailed description of the processes at micro scale. 

Structures of the f.c.c. parent and b.c.t. martensite phases are shown in Fig. 24.3. The f.c.c. parent structure contains an incipient b.c.t. structure with a c/a ratio which is higher than that of the final transformed b.c.t. martensite. The final b.c.t. structure can be formed in a very simple way if the incipient b.c.t. cell in Fig. 24.3a is extended by factors of rji = 772 = 1.12 along x[ and x 2 and compressed by 773 = 0.80 along x 3 to produce the martensite cell in Fig. 24.36. This deformation, which converts the parent phase homogeneously into the martensite phase, is known in the crystallographic theory as the lattice deformation-1 Unfortunately,... 

G.B. Olson and M. Cohen. Theory of martensitic nucleation A current assessment. In Proceedings of an International Conference on Solids Solid Phase Transformations, pages 1145-1164, Warrendale, PA, 1982. The Metallurgical Society of AIME. 

Question by K. L. Clark, International Nickel One of your tables showed decreasing percentages of transformation as temperature was lowered. This appears to disagree with the generally held theory that the martensite reaction is temperature-dependent and more transformation occurs as the temperature is lowered. Please explain the discrepancy which seems to exist. 

A great scientific and atomistic step was taken by Bain (1 ) when he proposed a rather simple, albeit elegant, scheme for f.c.c. austenite to transform into b.c.t. martensite (Figure 1). The Bain distortion relates corresponding unit cells in the two structures and speciHes the upsetting strain, by means of which martensite is formed. This picture is too simple in itself but has remained an integral part of the more sophisticated theories that have ensued. 

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