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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 relaxed equilibrium atomic structures of symmetric tilt grain boundaries (STGBs) in hexagonal close-packed (hcp) crystals with a given tilt axis are determined.
Abstract: Molecular dynamics simulation and interface defect theory are used to determine the relaxed equilibrium atomic structures of symmetric tilt grain boundaries (STGBs) in hexagonal close-packed (hcp) crystals with a $$ [0\bar{1}10] $$
tilt axis. STGBs of all possible rotation angles θ from 0 deg to 90 deg are found to have an ordered atomic structure. They correspond either to a coherent, defect-free boundary or to a tilt wall containing an array of distinct and discrete intrinsic grain boundary dislocations (GBDs). The STGBs adopt one of six base structures, $$ P_{B}^{(i)} $$
, i = 1, …, 6, and the Burgers vector of the GBDs is related to the interplanar spacing of the base structure on which it lies. The base structures correspond to the basal plane (θ = 0 deg, $$ P_{B}^{(1)} $$
); one of four minimum-energy, coherent boundaries, $$ (\bar{2}111),\;(\bar{2}112),\;(\bar{2}114) $$
, and $$ (\bar{2}116)\;\left( {P_{B}^{(2)} - P_{B}^{(5)} } \right) $$
; and the $$ \left( {11\bar{2}0} \right) $$
plane (θ = 90 deg, $$ P_{B}^{(6)} $$
). Based on these features, STGBs can be classified into one of six possible structural sets, wherein STGBs belonging to the same set i contain the same base boundary structure $$ P_{B}^{(i)} $$
and an array of GBDs with the same Burgers vector $$ b_{\text{GB}}^{(i)} $$
, which vary only in spacing and sign with θ. This classification is shown to apply to both Mg and Ti, two metals with different c/a ratios and employing different interatomic potentials in simulation. We use a simple model to forecast the misorientation range of each set for hcp crystals of general c/a ratio, the predictions of which are shown to agree well with the molecular dynamics (MD) simulations for Mg and Ti.
83 citations
TL;DR: In this paper, mathematical models have been developed to quantify the extent of carbon diffusion occurring in ductile cast iron during cooling from the eutectic temperature, and it has been shown that small variations in the cooling conditions may significantly alter the number density and size distribution of graphite nodules in the iron matrix, in agreement with experimental observations.
Abstract: In the present investigation, mathematical models have been developed to quantify the extent of carbon diffusion occurring in ductile cast iron during cooling from the eutectic temperature. Computer calculations show that small variations in the cooling conditions may significantly alter the number density and size distribution of graphite nodules in the iron matrix, in agreement with experimental observations. This makes it difficult to compare microstructure data from various section size materials without allowing for differences in the kinetic strength of the thermal cycles with respect to carbon diffusion.
83 citations
TL;DR: In this paper, transmission electron diffraction (TED) was used to observe extra diffraction spots in the TED patterns of molecular beam epitaxial GaAs1−y Sby layers with y=0.25, 0.50, and 0.71 grown at 520°C on (001) GaAs substrates.
Abstract: Transmission electron diffraction (TED) was used to observe extra diffraction spots in the TED patterns of molecular beam epitaxial GaAs1−y Sby layers with y=0.25, 0.50, and 0.71 grown at 520 °C on (001) GaAs substrates. Half‐order diffraction spots in the TED patterns indicated ordering on the (111) and (111) planes of the Group V sublattice, and streaks with subsidiary spots indicated a modulation in the [110] direction with a periodicity of ∼4d110 . Streaks in the [001] direction indicated monolayer disruptions of the {111} ordering and the [110] modulation in the [001] direction. As the composition parameter y varied, there were progressive changes in the {111} ordering, the [110] modulation, and the [001] disruptions, and these correlated with corresponding changes in the reconstruction of the dangling bonds at the growing layer surface, as determined by reflection high‐energy electron diffraction. A model is proposed to explain the observed effects in terms of ordered atomic arrangements of the Gr...
82 citations
TL;DR: In this paper, the influence of isothermal pre-annealing on subsequent isochronal crystallisation kinetics has been studied by means of differential scanning calorimetry, and the associated microstructural changes have been analyzed using scanning electron microscopy.
82 citations
TL;DR: In this paper, a simple model is proposed to account for the variation of lattice strain present in the crystallites, which allows the establishment of a quantitative relationship describing the dependence of the crystal lattice straining on the grain size.
Abstract: A striking feature of nanocrystalline (NC) materials prepared by different techniques is the variation of lattice strain present in the crystallites. A simple model is proposed to account for this phenomenon, which allows the establishment of a quantitative relationship describing the dependence of the crystal lattice strain on the grain size. Good agreement between theoretical and experimental data indicates that the stress field, induced by the excess volume in grain boundaries, is the dominant source of the lattice strain.
81 citations