Martensitic transformations kinetics

Such transformations have been extensively studied in quenched steels, but they can also be found in nonferrous alloys, ceramics, minerals, and polymers. They have been studied mainly for technical reasons, since the transformed material often has useful mechanical properties (hard, stiff, high damping (internal friction), shape memory). Martensitic transformations can occur at rather low temperature ( 100 K) where diffusional jumps of atoms are definitely frozen, but also at much higher temperature. Since they occur without transport of matter, they are not of central interest to solid state kinetics. However, in view of the crystallographic as well as the elastic and even plastic implications, diffusionless transformations may inform us about the principles involved in the structural part of heterogeneous solid state reactions, and for this reason we will discuss them. 

We have mentioned above the tendency of atoms to preserve their coordination in solid state processes. This suggests that the diffusionless transformation tries to preserve close-packed planes and close-packed directions in both the parent and the martensite structure. For the example of the Bain-transformation this then means that 111) -> 011). (J = martensite) and <111> -. Obviously, the main question in this context is how to conduct the transformation (= advancement of the p/P boundary) and ensure that on a macroscopic scale the growth (habit) plane is undistorted (invariant). In addition, once nucleation has occurred, the observed high transformation velocity (nearly sound velocity) has to be explained. Isothermal martensitic transformations may well need a long time before significant volume fractions of P are transformed into / . This does not contradict the high interface velocity, but merely stresses the sluggish nucleation kinetics. The interface velocity is essentially temperature-independent since no thermal activation is necessary. 

Schultzlam S, Beveridge TJ (1994) Physicochemical characteristics of mineral-forming S-layer from the cyanobacterium Synechococcus strain GL24. Canadian J Microbiol 40 216-223 Shannon RD, Pask JA (1965) Kinetics of the anatase-ratile transformation. J Am Ceram Soc 48 391-398 Shen P, Lee WH (2001) (11 l)-specific coalescence twinning and martensitic transformation of tetragonal Z1O2 condensates. Nanoletters (in press) (web release)... 

By assuming that the rate of crack growth is controlled by the rate of tetragonal-to-monochnic phase transformation, a kinetic model was proposed as an analogue to that for martensitic transformation. Only the final form of the model is given here specific details of its formulation may be found in [9]. In this model, the rate... 

Toda and coworkers applied temperature-modulated DSC to measure the kinetics of the martensitic transformation in Ti-Ni alloy [22]. By analyzing the temperature dependence of the relaxation time, they foimd that the process has two characteristic relaxation times, apparently related to different processes. 

Kak] Kakeshita, T., Sato, Y, Saburi, T., Shimizu, K., Matsuoka, Y, Kindo, K., Effects of Magnetic Field on Athermal and Isothermal Martensitic Transformations in Fe-Ni-Cr Alloys , Mater. Trans., JIM, 40(2), 100-106 (1999) (Experimental, Kinetics, Phase Relations, 13)... 

Shi] Shimizu, K., Tanaka, Y., The 7-e-a Martensitic Transformations in an Fe-Mn-C Alloy , Trans. Jpn. Inst. Met., 19, 685-693 (1978) (Phase Relations, Kinetics, Morphology, Crys. Structure, Experimental, 22)... 

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)... 

Gho] Ghosh, G., Olson, G.B., Computational Thermodynamics and the Kinetics of Martensitic Transformation , J. Phase Equilib., 22, 199-207 (2001) (Calculation, Phase Relations, Thermodyn., 65)... 

More on the t-Zr02 m-Zr02 Martensitic transformation in TZP ceramics is found in the work of Yin in his discussions on the thermodynamics, crystallography and kinetics of this transformation. The solid transformation in pure zirconia is ... 

The diffusion-dependent transformations of austenite (to ferrite, pearlite, and bainite) compete with the martensitic transformation such that the volume fraction available for the latter will decrease as the volume transformed by the former increases. This transformation kinetics of the diffusional phase transformations is strongly dependent on alloy composition. 

Behind the shock front various relaxation processes occur in the potential and the kinetic energies. The potential energy relaxation is associated both with thermal relaxation (see below) and with structural rearrangement within the system. Structural relaxation generally occurs at a speed considerably lower than that of the shock front (e.g., plastic flow), but it may be as fast as the shock front (e.g., martensitic transformation). It is accompanied by stress relaxation which occurs at the appropriate speed of first sound. 

A martensitic transformation is a lattice-distortive, virtually diffusionless structural change having a dominant deviatoric component and associated shape change such that strain energy dominates the kinetics and morphology during the transformation. 

Mittemeijer E J, Cheng L, der Schaaf P J V, Brakman C M and Korevaar B M 1988 Analysis of nonisothermal transformation kinetics tempering of iron-carbon and iron-nitrogen martensites Metall. Trans. A 19 925... 

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