Strengthening Mechanism and Carbide Precipitation Behavior of Nb-Mo Microalloy Medium Mn Steel

This study investigates the strengthening mechanism and carbide precipitation behavior of medium Mn steel with Nb-Mo microalloy after cyclic quenching and austenite reverse transformation treatment. The results show that the Nb/Mo element not only precipitates (Nb,Mo)C in the grains, hindering the movement of dislocations and increases the strength, but also segregates at the austenite/ferrite grain boundary, thus delaying the transformation from austenite to ferrite. In addition, a large amount of nano-scale cementite is retained after cyclic quenching and austenite reverse transformation, which has a positive effect on the proportion of retained austenite in medium Mn steel. Moreover, the carbides with small size and low Mn content are dissolved, and the decomposed C and Mn content are beneficial to the nucleation of austenite during the intercritical annealing process at a temperature of 690 °C.

Cognitive Mechanisms of Nominating Plants in English

The article deals with cognitive models underlying the process of plant categorization by the speakers. Having analyzed 200 names of herbs and flowers in English, the authors differentiated three cognitive models, which the phytonyms categorization is based on: metaphoric, metonymic and propositional. It is shown that "the codes of culture", or in other words, well-known realia, are used as sources for nomination; on their basis typical cognitive models are formed. Since the names of flowers and herbs in the English language are mostly compound words, the identified cognitive models are described taking into account the action of the cognitive word-formation mechanisms of proverse and reverse. The first mechanism structure of a phytonym presupposes the direct order of compound-word components as a result of the initial word-combination integration. This word building mechanism is typical of the compound structures "adjective / verb + noun". The reversive mechanism represents the inner structure of a phytonym as a result of reverse transformation of the word-combination initial components. This type of mechanism is characteristic of the phytonyms created on the basis of the structures "noun + noun", "noun + ' + noun". The article describes the models of proverse and reverse structuring, which are typical of English phytonyms. The prospects of the research are to study the cognitive models and mechanisms underlying plant nomination in a comparative aspect based on the material of several languages.

Имитационная модель оценки артефактов немоноэнергетичности и рассеяния в компьютерной томографии

A simulation model for estimating the beam-hardening and scattering in computed tomography in the geometry of a parallel beam is proposed on the example of inhomogeneous objects with axial symmetry. The modeling algorithm consists of a block of formation of projections and a block of reconstruction of images of object cross sections based on the Abel reverse transformation. The developed algorithm is implemented as a MathCad program. The efficiency of the algorithm and program is demonstrated by the example of a multilayer ball. Estimates of the beam hardening artifacts and scattering of the simulation model are compared with experimental estimates for the radial distributions of the linear attenuation coefficient.

Modelling the structural variation of quartz and germanium dioxide with temperature by means of transformed crystallographic data

The pseudocubic (PC) parameterization of O4 tetrahedra [Reifenberg & Thomas (2018). Acta Cryst. B74, 165–181] is applied to quartz (SiO2) and its structural analogue germanium dioxide (GeO2). In α-quartz and GeO2, the pseudocubes are defined by three length parameters, a PC, b PC and c PC, together with an angle parameter αPC. In β-quartz, αPC has a fixed value of 90°. For quartz, the temperature evolution of parameters for the pseudocubes and the silicon ion network is established by reference to the structural refinements of Antao [Acta Cryst. (2016), B72, 249–262]. In α-quartz, the curve-fitting employed to express the non-linear temperature dependence of pseudocubic length and Si parameters exploits the model of a first-order Landau phase transition utilized by Grimm & Dorner [J. Phys. Chem. Solids (1975), 36, 407–413]. Since values of tetrahedral tilt angles about 〈100〉 axes also result from the pseudocubic transformation, a curve for the observed non-monotonic variation of αPC with temperature can also be fitted. Reverse transformation of curve-derived values of [Si+PC] parameters to crystallographic parameters a, c, x Si, x O, y O and z O at interpolated or extrapolated temperatures is demonstrated for α-quartz. A reverse transformation to crystallographic parameters a, c, x O is likewise carried out for β-quartz. This capability corresponds to a method of structure prediction. Support for the applicability of the approach to GeO2 is provided by analysing the structural refinements of Haines et al. [J. Solid State Chem. (2002), 166, 434–441]. An analysis of trends in tetrahedral distortion and tilt angle in α-quartz and GeO2 supports the view that GeO2 is a good model for quartz at high pressure.

Effects of Peening Direction on Reverse Transformation Induced by Shot-Peening for Fe-33%Ni Alloy

Effects of peening direction on the reverse transformation induced by the shot-peening for the Fe-33 mass%Ni alloy with large amount of martensite (α’) are investigated. When the angle between the peened surface and the peening direction (Hereafter, peening angle) is 90 o, the reverse transformation occurs and subsequently martensitic transformation is induced by the shot-peening. On the other hand, in case of the peening angle of 30 o, only reverse transformation occurs. Furthermore, the volume fraction of austenite (γ) in the specimen after the shot-peening increases as the peening angle decreases. This means that the reverse transformation induced by the shot-peening is enhanced by decreasing the peening angle. Moreover, residual compressive stress around the peened surface increases as the peening angle decreases. Since the hydrostatic compressive stress decreases phase transformation temperature, the phase transformation temperature around the peened surface would be decreased by the shot-peening. Therefore, the reverse transformation behavior depending on the peening angle can be explained by the residual compressive stress due to the shot-peening.

Effect of Starting Microstructures on the Reverse Transformation Kinetics in Low-Carbon Steel

The effect of the initial starting microstructures on the austenite reverse transformation kinetics is thoroughly studied in low-carbon steel. The different initial starting microstructures including the ferrite + pearlite, bainite, and martensite are obtained through varied forward transformation. It is found that the bainite phase demonstrates highest reverse transformation rate while the ferrite + pearlite shows the lowest transformation rate. The above observation can be explained through the different grain size of the initial starting microstructures as the grain boundaries could act as the nucleation sites for austenite reverse transformation. The explanation is further substantiated based on the consideration of the reverse transformation kinetics from the martensite microstructure with different grain size.

Diseño de una actividad didáctica con base en un diálogo entre TAD y APOEDesign of a didactic activity based on a dialogue between ATD and APOE

We present the design of a modelling activity based on the dialogue between anthropological theory of the didactic (ATD) and the Action-Process-Object-Schema (APOS) theory. We focus in illustrating the potentiality of this dialogue for the design and analysis of research experiences.Palabras-clave: TAD, APOE, Modelación, Álgebra lineal; Transformación inversa.ResumenSe presenta el diseño de una actividad de modelación a partir del diálogo entre la teoría antropológica de lo didáctico (TAD) y la teoría Acción-Proceso-Objeto-Esquema (APOE). Nos centramos en ilustrar la potencialidad de dicho diálogo para el diseño y análisis de experiencias de investigación.Keywords: TAD, APOS, Modeling, Linear algebra; Reverse transformation.