Microstructure transformation

Figures 11.2-11.6 show how the room temperature microstructure of carbon steels depends on the carbon content. The limiting case of pure iron (Fig. 11.2) is straightforward when yiron cools below 914°C a grains nucleate at y grain boundaries and the microstructure transforms to a. If we cool a steel of eutectoid composition (0.80 wt% C) below 723°C pearlite nodules nucleate at grain boundaries (Fig. 11.3) and the microstructure transforms to pearlite. If the steel contains less than 0.80% C (a hypoeutectoid steel) then the ystarts to transform as soon as the alloy enters the a+ yfield (Fig. 11.4). "Primary" a nucleates at y grain boundaries and grows as the steel is cooled from A3...

Electrical conductivity is an easily measured transport property, and percolation in electrical conductivity appears a sensitive probe for characterizing microstructural transformations. A variety of field (intensive) variables have been found to drive percolation in reverse microemulsions. Disperse phase volume fraction has been often reported as a driver of percolation in electrical conductivity in such microemulsions [17-20]. 

Muller, J. Joubert, J.C. (1974) Synthese en milieu hydrothermal et caracterisation de Voxyhydroxyde de vanadium V OOH et d une nouvelle variete allotropic du dioxide VO2. J. Solid State Chem. 11 79—87 Muller, J.P. Bocquier, G. (1986) Dissolution of kaolinites and accumulation of iron oxides in lateritic-ferruginous nodules Mineralogical and microstructural transformations. Geoderma 37 113-136... 

This loop is, however, affected by the availability of the reactant oxygen, which in surplus destroys the precursor VPO. Further, oxygen is positively needed to activate and re-oxidize the VxOy sites but leads also to more water formation that in turn hydrothermally deactivates the active mass. Likewise, water is needed to separate, via hydrolysis, the vanadium phosphate into VxOy and mobile phosphate. The multiplicity of the feedback loops is at first puzzling but explains the apparent stable steady state that can be reached with a catalyst undergoing so many chemical and microstructural transformations the multiplicity of controls prevents one single factor becoming dominant and thus potentially destabilizing the whole process. 

Qiao ZJ, Li JJ, Zhao NQ, Shi CS et al (2006) Graphitization and microstructure transformation of nanodiamond to onion-like carbon. Scripta Materialia 54(2) 225-229... 

Understanding the microstructural transformation mechanism which takes place during the activation of vanadium phosphorus oxide catalysts... 

Glasson, S., Espinat, D. and Palermo, T. Study of Microstructural Transformation of Overbased Calcium Sulphonates During Eriction , Lubrication Science 1993, 5, 91-109. 

At macroscopic scale initial deformation and microstructure transformation occurs in the macro shear band. However, formation of the shear bands is retarded at subsequent deformation since development of globularization in the central area of a sample leads to superplastic flow realization. This accompanied with steady flow stage appearance on the S-Xe curve and increasing of value of the strain-rate-sensitivity m from 0.17 for e = 0.4 to 0.35 for Xc = 0.9. Consequently successive rotations lead to accumulation of strain primarily in the center of the workpiece, and to the formation of a homogeneous microstructure with globular grains of the a- and (3-phases with a mean size of 0.4 pm is formed (Fig. 5c). 

Furthermore, 5 depends on material properties in addition to a. 5 may not achieve its minimum value. The thinning of a shear band is driven by the slope of the strain-softening curve. This varies widely between metals. Microstructural transformations, for example, dynamic... 

Y. Hu. Preparation process and microstructure transformation of cermets-based Ti(C,N). PhD thesis. Library of Huazhong University of Science and Technology. 38.. Wirhan, 2002.1. 

For the boron-nitrogen system, because the high gas pressure is required for the synthesis, it is difficult to apply any dynamic method for investigation of the microstructural transformations, which occur in the combustion front. Thus, the static quenching technique was used [26, 23, 27]. The idea of this method is to extinguish the combustion wave and quickly cool the sample it is necessary to freeze all zones with the characteristic microstructure, chemical and phase structure of the reactants, intermediates, and final products. For quenching to take place, the heat loss from the reaction front at some point must exceed the critical... 

The effect of microstructural transformations in clay soils on clay properties was studied... 

The type of microstructure transformation upon deformation depends on the stress state. For example, the clay compaction upon triaxial isotropic compression leads to system strengthening whereas the uniaxial compression in odometer is accompanied by a certain direction of structural elements in the plane normal to the compressing stress. Therefore, soils with the similar density and moisture but compacted under different conditions manifest different properties. 

Some intriguing morphological details of doped -Glu-Bis-3 assemblies captured by TEM (Fig. 6B,C) provided an opportunity to examine intermediate states of microstructural transformation between ribbons and vesicles. These micrographs clearly suggest that ribbons (relatively rigid) and vesicles (relatively fluid) were physically interrelated during the formation of different microstructures in these multi-component systems. 

P. B. Messersmith and S. I. Stupp, High-temperature chemical and microstructural transformations of a nanocomposite organoceramic. Chemistry of Materials, 1 (1995), 454-60. 

G Sell C, Dahoun A, Favier V, Hiver J M, Philippe M J and Canova G R (1997) Microstructure transformation and stress-strain behavior of isotactic polypropylene under large plastic deformation, Polym Eng Sd 37 1702-1711. 

In Refs. [168,169], it was shown that, properly used, FIR spectroscopy can be appli l, for example, to follow the microstructural transformation of poly(vinylidene fluoride) (PVFj) in a static electric field at various temperatures. At 65 °C, the transformation from a to phase can be easily accomplished by a low field at a high rate and characterized by the bands of crystallinity at 70 cm (the librational mode of lattice) and 176 cm (the torsional mode CH-CF-CH-CF). 

Danino D, Talmon Y and Zana R. 2000. Cryo-TEM of thread-like micelles on-the-grid microstructural transformations induced during specimen preparation. Colloids and Surfaces A -Physicochemical and Engineering Aspects 67-73. 

Chemical and microstructural transformations resulting from the thermal treatments... 

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