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Abstract: Effects of firing temperature and soaking time on phase transformations of a Chloritic-illitic raw clay were investigated at 900–1075 °C and 0–64 h, by using X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and following the change of the main ceramic properties. The Mg-spinel phase developed at lower temperature, essentially from the breakdowns of chlorite, and the activation energy of its growth was about 124.6 kJ/mol. A glassy phase was formed from the decomposition products of dehydroxylated micaceous species, especially from pseudo-tetrahedral sheets and potassium. The required activation energy for the latter decomposition process was around 166.7 kJ/mol. The ceramic properties were controlled by the development of the glassy phase. Intensive melt formation, manifesting at higher temperatures or times, favored the nucleation of olivine. The formation processes of the main phases are discussed basing on SiO2–Al2O3–MgO and SiO2–Al2O3–K2O equilibrium diagrams. [Copyright &y& Elsevier]

Abstract: The paper offers a variant of the generalized TTT-diagram (temperature–time–transition) for the α→β transformation of unalloyed plutonium under isothermal conditions. The authors constructed it using published information on plutonium phase transformation kinetics under isothermal conditions and α→β transformation parameters under the conditions of pulsed electric heating. The authors also present their results—parameters of the beginning of the α→β transformation in isothermal conditions and in linear-through-volume heating by neutrons from pulsed nuclear reactors exploited at RFNC-VNIITF. Using a number of typical TTT-diagrams as examples, the authors demonstrate characteristic features in the dependence of the phase transformation incubation time on plutonium temperature in isothermal conditions (for example, in samples hold in oil) and in electric heating conditions. They identify segments where, in the authors’ view, phase transformation conditions were not isothermal and justify the use of the most authentic experimental data including those obtained by the authors for isothermal conditions for the construction of the generalized TTT-diagram. To justify the use of their own results obtained for the uniform-through-volume heating of samples by neutrons, the authors used known theoretical results for non-isothermal first-kind transition kinetics. Theoretical results suggest that for certain conditions of the first-kind transition, it is possible to relate the temperature dependences of the incubation time for non-isothermal and isothermal transformations. So, the authors propose a generalized TTT-diagram for a range of plutonium temperatures corresponding to the incubation times of unalloyed plutonium phase transformation between 10−5 and 105 s. [Copyright &y& Elsevier]

The curing of a thermoreactive alkyd-melamine-formaldehyde resin system was investigated by rheologycal, TG and TMA-analysis, in order to construct the time-temperature-transformation diagram. The points of the gelation curve were determined by measuring the increase in viscosity during isothermal curing at different temperatures. A power-function could be fitted to the gelation curve, which is suitable to estimate gelation at any curing conditions, as well as to establish storage conditions. The reaction in the resin matrix was followed by monitoring the loss of mass during iso- thermal curing at different temperatures. The final section of the resulted iso-curing temperature (iso-Tcure) diagrams could be fitted with logarithmic functions, which may be used for estimating the conditions needed to a given, desirable mass loss, i.e. conversion. The steepness of the curves increases with temperature suggesting the forthcoming of degradation during cure with increasing temperature. From these data the iso-mass loss curves of the TTT-diagram were constructed. For determining the iso-Tg curves of the TTT-diagram isothermal curing was carried out in a drying oven at different temperatures, followed by TMA measurements. The iso-Tcure diagrams served to determine Tg∞, and to construct the iso-Tg curves of the TTT diagram. Vitrification curve is far beyond conditions of storage, curing and degradation, meaning that the resin matrix is in rubbery physical state before, during and after the cure. Curing conditions resulting degradation can also be estimated from the TTT-diagram. [ABSTRACT FROM AUTHOR]

During diffusional phase transformations at high temperatures (e.g. γ–α transformation in low-alloy steels) the interface migrates due to a chemical and/or mechanical driving force. A low solubility in the product phase forces the solute atoms (C in α) to move by diffusion, and, therefore, the mole fraction of the solute depends on time and spatial position. In order to evaluate the transformation kinetics numerically, carbon diffusion and interface migration, coupled by appropriate boundary conditions, are simulated. The grain size, the mobility, and the diffusion coefficient determine the growth kinetics. A micromechanical study has been performed in order to investigate the influence of an external uniaxially applied load on the transformation kinetics. [Copyright &y& Elsevier]

• The effect of iron on electrical and mechanical properties in aluminium AA1370 is investigated. • Precipitation kinetic of supersaturated iron in aluminium is fastest at 450 °C. • Metal screw extrusion is proven viable of producing aluminium wire conductors. • Screw extruded aluminium shows high electrical conductivity and intermediate strength. • Investigated materials are compared to numerous pure and diluted aluminium alloys in terms of strength and conductivity. In order to develop well-performing aluminium electrical conductors, the role of iron and processing method on electrical and mechanical properties was studied for an AA1370 alloy. Firstly, Ø3 mm cold drawn wires were subjected to a solid solution heat treatment (640 °C/1 h) followed by artificial aging at various temperatures in order to reveal the representative time-temperature-transformation (TTT)-diagram for Fe-rich precipitates. The highest precipitation rate occurred at 450 °C. Secondly, an identical AA1370 alloy was produced by the novel metal continuous screw extruder (MCSE) process into a new Ø3 mm wire. The as produced wire had a recrystallised outer layer and an elongated fibrous structure having a typical 〈0 0 1〉 texture in the center region. TEM investigations revealed Fe-rich precipitates at grain boundaries thus impeding grain growth to some extent. The screw extruded wire processed at 450 °C had a high conductivity (64.2%IACS) while being softer (UTS ~ 65 MPa) than the cold drawn wire (UTS ~ 164 MPa, 61.9%IACS). The correspondence between strength and electrical conductivity for cold drawn and screw extruded wires was compared to literature data for pure and dilute alloys. The screw extruded wire outperformed other alloys as to electrical conductivity, while being among the materials having lowest strength. [ABSTRACT FROM AUTHOR]