Global Techniques for Characterizing Phase Transformations – A Tutorial Review

Abstract

To characterize phase transformations, it is necessary to get both local and global information. No experimental technique alone is capable of providing these two types of information. Local techniques are very useful to get information on morphology and chemistry but fail to deal with global information like phase fraction and size distribution since the analyzed volume is very limited. This is why, it is important to use, in parallel, global experimental techniques, that investigate the response of the whole sample to a stimulus (electrical, thermal, mechanical…). The aim of this paper is not to give an exhaustive list of all global experimental techniques, but to focus on a few examples of recent studies dealing with the characterization of phase transformations, namely (i) the measurement of the solubility limit of copper in iron, (ii) the tempering of martensite, (iii) the control of the crystallinity degree of a ultra high molecular weight polyethylene and (iii) a precipitation sequence in aluminum alloys. Along these examples, it will be emphasized that any global technique requires a calibration stage and some modeling to connect the measured signal with the investigated information.

The effect of silicon on the nanoprecipitation of cementite

“…This observation would imply that ε-and θnucleation is a two-step process. However Perez and Deschamps [23] based their work on the postulate that both carbides nucleate at the same time, independent of each other, but due to competitive precipitation kinetics, the metastable ε-carbide grows first. Once it loses stability, it would dissolve to allow θ grow.…”

Strain-Rate-Dependent Phase Transition Mechanism in Polybutene-1 during Uniaxial Stretching: From Quasi-Static to Dynamic Loading Conditions

“…The stretching-induced phase transition of semicrystalline polymers has drawn great attention due to its close relation with industrial processing and further modification. − Due to the complicated hierarchical structure and polymorphism, the phase transition of these polymers is even more complex compared to that in other condensed matters. − With respect to the crystalline domain, after decades of investigation, two mainstream mechanisms are proposed, namely, stretching-induced solid–solid transition and melt-recrystallization. − Debates still exist due to the coexistence of experimental evidence supporting different or even opposite opinions.…”

Recrystallization Microstructure Character of Annealing Strip Steel Based on the Compact Strip Production

“…It would show a very effective pinning in ferrite matrix [7,8] . In addition, a few dislocation density was revealed, the dislocation/precipitation interaction in ferrite matrix should highly likely be one of the dominant reasons for strengthening [9] .…”