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The theory of transformations in metals and alloys
01 Jan 1965-
TL;DR: In this paper, the authors present a general introduction to the theory of transformation kinetics of real metals, including the formation and evolution of martensitic transformations, as well as a theory of dislocations.
Abstract: Part I General introduction. Formal geometry of crystal lattices. The theory of reaction rates. The thermodynamics of irreversable processes. The structure of real metals. Solids solutions. The theory of dislocations. Polycrystalline aggregates. Diffusion in the solid state. The classical theory of nucleation. Theory of thermally activated growth. Formal theory of transformation kinetics. Part II Growth from the vapour phase. Solidification and melting. Polymorphic Changes. Precipitation from supersaturated solid solution. Eutectoidal transformations. Order-disorder transformations. Recovery recrystalisation and grain growth. Deformation twinning. Characteristics of martensic transformations. Crystallography of martensitic transformations. Kinetics of martensitic transformations. Rapid solidification. Bainite steels. Shape memory alloys.
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TL;DR: In this article, the structure and energy of periodic, symmetrical tilt boundaries in b.c. bicrystals were analyzed in terms of compact polyhedral groups, called compact polyhedra, with edge lengths which vary between the first and second-nearest-neighbour separations.
Abstract: Structures and energies have been calculated for periodic, symmetrical [001] and [110] tilt boundaries in b.c.c. metals using a variety of central-force potentials. The structures were found to be independent of the potential used and in general more than one relaxed structure was found for each type of grain boundary studied. The boundary structures are analysed in terms of polyhedral groups, called compact polyhedra, with edge lengths which vary between the first- and second-nearest-neighbour separations. A smooth transition occurs between the low-angle and high-angle regimes. Relative to corresponding f.c.c. boundaries, local relaxations were found to be at least as important as rigid translations and atoms were often found to occupy coincidence sites in minimum energy b.c.c. boundaries. The symmetries of relaxed b.c.c. bicrystals were consequently found to be different, usually higher, from those for corresponding boundaries in f.c.c. bicrystals.
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TL;DR: In this paper, differential scanning calorimetric (DSC) studies were carried out on xerographic photoreceptor materials of amorphous selenium (a-Se), a-Se 1∃-xTex and a- Se: 0.5 wt% As alloys with various amounts of chlorine doping.
Abstract: Differential scanning calorimetric (DSC) studies were carried out on xerographic photoreceptor materials of amorphous selenium (a-Se), a-Se1∃-xTex and a-Se:0.5 wt% As alloys with various amounts of chlorine doping. Glass transformation kinetics of bulk and vapour-deposited film samples were essentially identical indicating a similar amorphous structure for both forms. The glass transition temperature,Tg, in the a-Se1∃-xTexsystem was found to increase monotonically with the tellurium content up to ∼13 wt% which was accompanied by a fall in the activation energy,Egl, for the structural relaxation. 0.5wt% As increasedTg, whereas chlorine doping in the amounts used (∼100 ppm) had no effect onTg. Crystallization exotherms were analysed using the Kissinger method which was shown to remain a valid analysis by integrating the fundamental Kolmogoroff equation describing crystallization transformations by nucleation and growth. The signifiance of the activation energy,EA, and the frequency factor,C0, in the Kissinger analysis is discussed and used in interpreting the different crystallization behaviour exhibited by the various alloys. The apparent activation energy,EA, of the crystallization kinetics was found to fall with the temperature range accessed in the DSC experiment. When other authors' previous crystallization studies by other methods were also considered, then 1/EA was found to fall nearly linearly with the mean reciprocal temperature, 〈1/T〉, used in the experiment. It is argued that this behaviour arises if the crystal growth rate scales with the inverse viscosity of the melt and the latter is described by a Vogel-Tammann-Fulcher type of behaviour. The additives tellurium and arsenic retard the crystallization essentially by increasing the viscosity. Chlorine doping was also found to have an inhibitory effect but due probably to a change in the nucleation kinetics, rather than a viscosity rise.
75 citations
TL;DR: This paper reported the discovery of oriented needles of rutile and ilmenite in garnet crystals from granulite facies metapelitic rocks of the Merrimack synclinorium, Connecticut, and presented a precipitation model for their origin.
Abstract: We report the discovery of oriented needles of rutile and ilmenite in garnet crystals from granulite facies metapelitic rocks of the Merrimack synclinorium, Connecticut, and present a precipitation model for their origin. The rocks were strongly metamorphosed and deformed during the Devonian Acadian orogeny. The needles are primarily elongated parallel to in garnet. Rutile has anomalous extinction angles as great as ~35° (cf. Griffin et al. 1971). Rutile and ilmenite needles are typically a few hundred nanometers to several micrometers in diameter and are several tens of micrometers to nearly a millimeter long. Other oxide inclusions that may be present include submicrometer- to micrometer-scale twinned rutile bicrystals, as well as srilankite and a crichtonite group mineral. Some garnet cores have unusual, box-shaped quartz inclusions, which coexist with Ti±Fe oxide needles and commonly contain micrometer-scale rods of F-OH-Cl apatite. Negative garnet crystal “pores” are also widespread. Ti±Fe oxide needles are restricted to garnet core regions; rims have a distinctly different inclusion population dominated by granulite facies minerals including sillimanite, spinel, cordierite, and K-feldspar. Consequently, the garnet core regions represent an earlier, distinct period of growth relative to the rims. Garnet cores contain ~25–35% pyrope, and a host of minor and trace constituents including TiO2 (0.07–0.6 wt%), Cr2O3 (0.01–0.10 wt%), Na2O (0.01–0.03 wt%), P2O5 (0.01–0.09 wt%), and ZrO2 (up to ~150 ppm). Na2O and ZrO2 correlate positively with TiO2. Titanium zoning is preserved in some garnets; zoning profiles and two-dimensional chemical mapping show that Ti and, to a lesser degree, Cr are depleted around Ti±Fe oxide inclusions. Therefore, we conclude that the needles are precipitates that formed from Ti-bearing garnet during exhumation and cooling. Garnet contained sufficient Ti to form precipitates; no Ti source external to garnet was necessary. Titanium-bearing garnets that contain oriented Ti±Fe oxide needles are known primarily from ultrahigh-pressure metamorphic rocks, mantle peridotites and pyroxenites, and high-pressure granulites. Thus, the presence of needle-bearing garnets in Connecticut strongly suggests that a previously unrecognized domain of extreme pressure and/or temperature metamorphism exists in the Acadian orogen.
75 citations
TL;DR: In this article, the kinetics of laser and furnace-induced solid phase epitaxial crystallization of amorphous layers (∼0.16 μm) on Si (100) substrates was studied using a time-resolved optical reflectivity technique.
Abstract: The kinetics of laser and furnace‐induced solid phase epitaxial crystallization of As‐implanted amorphous layers (∼0.16 μm) on Si (100) substrates was studied using a time‐resolved optical reflectivity technique. Epitaxial rates from 10−10 to 0.2 cm/sec were measured over a temperature range from 750 to 1550 °K at two different As concentrations, ∼2×1019 cm−3 and ∼4×1019 cm−3. Temperatures achieved during cw‐laser heating were calculated using a three‐dimensional steady‐state thermal analysis. The crystal growth rates are accurately described by the Arrhenius equation v = v0e−Ea/kT , with Ea dependent on the dopant concentration; Ea = 2.62 and 2.52 eV for the lower and the higher concentrations, respectively. Additionally, the rate measurements at high temperatures imply that the melt temperature of amorphous Si is greater than 1550 °K.
75 citations
TL;DR: In this article, the effect of hydride nucleation rate on the hydrogen capacity of pure magnesium powders was analyzed using the Johnson-Mehl-Avrami (JMA) equation.
75 citations