Sintering and Smelting Property Investigations of Ludwigite

In this paper, orthogonal experiments are designed to study the sintering and smelting characteristics of the ludwigite ore. The predominant influencing factors of the optimal ratio, basicity and carbon content on different single sintering indexes, including the vertical sintering speed, yield rate, drum strength and low-temperature reduction pulverization index, are firstly explored by the range analysis method, and the main influencing factors on comprehensive indexes are obtained by a weighted scoring method based on different single index investigation. Considering the sintering characteristics, the primary and secondary influencing factors are: ordinary ore ratio, carbon content and basicity, and the optimal ore blending scheme is: basicity 1.7, ordinary ore blending ratio 60% and carbon content 5%. In terms of the smelting characteristics, the research obtains the order of the influencing factors on the softening start temperature, softening end temperature, softening zone, smelting start temperature, dripping temperature, smelting-dripping zone, maximum pressure difference and gas permeability index of the ludwigite sinters by simply considering various single smelting indexes. On this basis, considering the comprehensive softening-melting-dripping characteristics, the primary and secondary influencing factors are: carbon content, ordinary ore ratio and basicity, and the optimal ore blending scheme is: basicity 1.9, ordinary ore blending ratio 60% and a carbon content of 5.5%. Comprehensively, considering the sintering and smelting property of the ludwigite ore, the primary and secondary influencing factors are: carbon content, ordinary ore ratio and basicity, and the optimal ore blending scheme is: basicity 1.9, ordinary ore blending ratio 60% and a carbon content of 5.5%.

Investigating the utility of a high-temperature Thellier-style paleointensity experimental protocol

High-quality data are vital to the research field of paleointensity, which has long suffered from poor-quality and/or sparse data. Previous paleointensity work has established that repeatedly heating specimens increases the opportunity for thermochemical alteration to decrease the reliability of paleointensity data. In addition, recent work has shown that repeatedly heating specimens in paleointensity experiments can also exaggerate the effects of non-ideal, non-single domain grains. Arai plots resulting from paleointensity experiments containing such grains are often curvilinear (two-slope) across most of the specimen’s unblocking temperature spectrum, except in the temperature range nearest to the grains’ Curie temperature. This study tests the following strategy to mitigate these effects: that of performing a Thellier paleointensity experiment using fewer temperature steps that are also concentrated at higher temperatures. For this purpose, we use natural specimens with well-constrained rock magnetic data from the Hawaiian Scientific Observation Hole 1 (SOH1) drill core in paleointensity experiments with starting temperatures ranging from 200 °C to 500+ °C. Those experiments that focused in on the portion of the unblocking temperature spectrum nearest the Curie temperature of the specimen (HiTeCT) had an exceptionally low success rate, whereas those with initial temperatures at comparatively moderate temperatures (200–400 °C) had high success rates (~ 70%). Thermochemical alteration was minimized with a start temperature of 400 °C, but the curvature of the Arai plots had no clear dependance on start temperature. We conclude herein that increasing the start temperature can help avoid the effects of low-temperature alterations. Additionally, we found that the approach of focusing in on the highest temperature range is not a feasible one to apply in paleointensity experiments, in general, and consider this likely to be a result of a lack of intermediate-temperature checks for alteration and insufficient independence of temperature steps. Graphical abstract

Features of High-Temperature Synthesis in Clad Mechanocomposites of Ti-Al System

The influence of mechanoactivated reagents cladding on the structural-phase state of the SHS-products was investigated. Titanium and aluminum powders were used as reagents. Mechanical activation was performed on the AGO-2 planetary ball mill. The coating on Ti+Al mechanocomposite was carried out using magnetron installation “VSE-PVD-Power”. At deposition time of 40 minutes, the reaction start temperature increases from 525 °C to 648 °C (compared to reagents without cladding). It can be assumed that an increase in the thickness of the deposited SiO2 film serves as a barrier to the reaction start, thereby increasing ignition temperature. Apart from pretreatment, the phase composition of the final product contains intermetallic compounds TiAl, TiAl3, Ti3Al5, as well as the small amount of residual Ti. The main phase is TiAl.

Microstructural Changes During Short-Term Heat Treatment of Martensitic Stainless Steel—Simulation and Experimental Verification

Short-term heat treatments of steels are used for tools and cutlery but also for the surface treatment of a variety of other workpieces. If corrosion resistance is required, martensitic stainless steels like AISI 420L or AISI 420MoV are typically used. The influence of short-term heat treatment on the different metastable states of the AISI 420L steel was examined and reported in this article. Starting from a defined microstructural state, the influence of a short-term heat treatment is investigated experimentally with the help of a quenching dilatometer and computer assisted simulations are carried out. With the results obtained, a simulation model is built up which allows to compute the microstructural changes during a short-term heat treatment to be evaluated without the need for an experiment. As an indicator, the value of the martensite start temperature is calculated as a function of different holding times at austenitizing temperature. The martensite start temperature is measured by dilatometry and compared to calculated values. Validation of simulated results reveals the potential of optimizing steel heat treatment processes and provides a reliable approach to save time, resources and energy.

Dehydration Alters Behavioral Thermoregulation and the Geography of Climatic Vulnerability in Amazonian Lizards

Since high temperatures and low water availability often strike organisms in parallel, observing how they behaviorally thermohydroregulate may help us to better understand their climatic vulnerability. This understanding is especially important for tropical lizards, purportedly under greater climatic risk. We observed the influence of hydration level on the Voluntary Thermal Maximum (VTM) of two small amazonian lizard species: Loxopholis ferreirai (semiaquatic and scansorial) and Loxopholis percarinatum (leaf litter parthenogenetic dweller), accounting for several sources of variation (turn, body weight, start temperature and heating rate). Then, we used two modelling approaches (simple mapping of thermal margins and NicheMapR), to examine the effects of dehydration, decrease in rainfall, ability to burrow, and tree cover availability, on the geography of climatic vulnerability. Dehydration decreased the VTM in both species, which also reacted to start temperature and heating rates. Our two modelling approaches show that dehydration, changes the intensity, extent and duration of thermal risk across the Amazon basin. Based on our results and previous studies, we identify new evidence needed to better understand thermohydroregulation and model the geography of climatic risk, more realistically.

Microstructure of the Heat Treated Advanced Low Carbon Steel

The microstructure of the advanced low carbon steel with a superior hardenability was studied. The steel contained the following main alloying elements, wt. %: C – 0.20; Cr – 2.0; Mn – 2.0; Si – 1.04 Ni – 1.0; Mo – 0.3. The dilatometer investigation of the steel under consideration revealed the only phase transformation occurring during continuous cooling (0.1...30 °C/s), which started at the martensite start temperature Ms. It was shown that the isothermal treatment of the studied steel led to the bainite formation above and below Ms. The temperature of the bainite morphology shift was determined.