Unraveling Recrystallization Mechanisms Governing Texture Development from Rare Earth Element Additions to Magnesium

The origin of texture components associated with rare-earth (RE) element additions in wrought magnesium (Mg) alloys is a long-standing problem in magnesium technology. The objective of this research is to identify the mechanisms accountable for rare-earth texture during dynamic recrystallization (DRX). Towards this end, we designed binary Mg-Cerium and Mg-Gadolinium alloys along with complex alloy compositions containing zinc, yttrium and Mischmetal. Binary alloys along with pure Mg were designed to individually investigate their effects on texture evolutions, while complex compositions are designed to develop randomized texture, and be used in automotive and aerospace applications. We selected indirect extrusion to thermomechanically process our materials. Different extrusion ratios and speeds were designed to produce partially and fully recrystallized microstructures, allowing us to analyze DRX from its early stages to completion. X-ray diffraction, electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were used to conduct microstructure and texture analyses Our analyses revealed that rare-earth elements in zinc-containing magnesium alloys promote discontinuous dynamic recrystallization at the grain boundaries. During nucleation, the effect of rare earth elements on orientation selection was explained by the concomitant actions of multiple Taylor axes in the same grain. Isotropic grain growth was observed due to rare earth elements segregating to grain boundaries, which lead to texture randomization. The nucleation in binary Mg-RE alloys took place by continuous formation of necklace structures. Stochastic relaxation of basal and non-basal dislocations into lowangle grain boundaries produced chains of embryos with nearly random orientations. Schmid factor analysis showed a lower net activation of dislocations in RE textured grains compared to ones on the other side of the stereographic triangle. Lower dislocation densities within RE grains favored their growth by setting the boundary migration direction toward grains with higher dislocation density, thereby decreasing the system energy. We investigated the influence of RE elements on extension twinning induced hardening. RE addition enhanced tensile twinning induced hardening significantly. EBSD analysis illustrated that tensile twins cross low angle grain boundaries in Mg-RE alloys, which produced large twins and facilitated transmutation of basal to prismatic dislocations. Higher activity of pyramidal II dislocations in Mg-RE alloys resulted in higher twinning induced hardening

Investigating the Effect of Renewable and Non-Renewable Energy on Air Pollution in Iran with regard to the Moderating Role of Economic Growth

Energy consumption in the world is increasing for economic growth, and as a result of the emission of greenhouse gases, especially carbon dioxide, which has destructive environmental effects, the consumption of fossil fuels has an increasing trend. Present study tries to find the effect of renewable and non-renewable energy consumption on air pollution with respect to the moderating role of economic growth, utilizing the data of time series from 1990 to 2017 in Iran and with the generalized method of moments and in terms of some control variables such as energy efficiency coefficient and urbanization, the hypotheses were tested. Findings indicate that, the effect of renewable energy consumption in reducing carbon dioxide emissions (negative coefficient at a significant level of 10%) and the effect of non-renewable energy consumption in increasing carbon dioxide emissions (positive coefficient at a significant level of 5%). Also, the role of economic growth as a moderating variable on the relationship between renewable energy consumption and carbon dioxide emissions is positive and on the relationship between non-renewable energy consumption and carbon dioxide emissions is negative and significant. Developing investment and increasing the share of the renewable energy sector in the country along with improving energy efficiency and technology level can be effective in reducing air pollution

Thermomechanical processing route to achieve ultrafine grains in low carbon microalloyed steels

.A new thermomechanical processing route is described for a microalloyed steel, with roughing deformation below the recrystallisation-stop temperature (T5%), followed by a rapid reheat to 1200 °C for 10s, and then finish deformation at the same temperature as the rough deformation. The new route focused on optimising the kinetics of strain-induced precipitation (SIP) and the formation of deformation-induced ferrite transformation (DITF). For comparative purposes, two experimental 0.06 wt% C steels were studied: one with 0.03 wt% Nb (Nb steel), and a second with both 0.03 wt% Nb and 0.02 wt% Ti ([Formula presented] steel). Two processing routes were studied. The first was a conventional route, which consisted of a simulated rough deformation schedule with the final roughing pass taking place at 850 °C, which produced fully unrecrystallised austenite grains during deformation with no strain-induced ferrite formation. The second, new, thermomechanical processing route used the same roughing step, after which the steels were reheated at 10 °C/s to a temperature of 1200 °C, isothermally held for 10s allowing for precipitate dissolution, prior to air cooling to a finishing deformation temperature of 850 °C. This route resulted in DIFT primarily on the prior-austenite grain boundaries. The precipitate solution during the reheat treatment increased the supersaturation of Nb and Ti in the austenite matrix on subsequent cooling, which therefore increased the undercooling due to the increased Ae3. The observation of nanoscale cementite in the DIFT supports the view that it formed through a massive transformation mechanism. The volume fraction of SIP after finish deformation was influenced by the supersaturation of microalloy elements in solution during heat treatment. The new process route led to a significant refinement of the final ferrite grain size

Individual effect of recrystallisation nucleation sites on texture weakening in a magnesium alloy: Part 1- double twins

Recrystallised grain nucleation, grain growth and corresponding texture evolution in a cold-rolled rare earth containing WE43 Mg alloy during annealing at 490 �C was fully tracked using a quasi-in-situ electron backscatter diffraction method. The results show nucleation sites, such as double twins, can weaken the deformed texture and for the first time provide direct evidence that recrystallised grains originating from double twins can form the rare earth texture during annealing. Precipitation and recrystallisation occurred concurrently during most of the annealing period, with precipitates forming preferentially along prior grain and twin boundaries. These precipitates effectively retard the recrystallisation due to particle pinning leading to an excessively long time for the completion of recrystallisation. A large portion of recrystallised grains were observed to have 〈0001〉 poles tilted 20e45� away from the normal direction. The RE texture emerges during the nucleation of recrystallised grains and is maintained during subsequent uniform grain growth, which results in a stable RE texture being developed as recrystallisation progresses. The uniform grain growth could be attributed to solute drag suppressing the grain boundary mobility of those grains that had recrystallised with a basal texture and precipitate pinning restricting potential orientated grain growth

Prioritising ecosystem services in Chinese rural and urban communities

Identifying ecosystem services that are important to society can help decision-makers to prioritize specific services for protection. However, ecosystem services may be valued differently by different sections of society. This study sets out an approach for assessing the use and prioritization of freshwater ecosystem services by people in rural and urban areas in China. Face-to-face interviews were conducted with 30 rural and 30 urban respondents in the same region of Shandong province. Respondents were asked about how they used their local river and to prioritize ecosystem services provided by the river. In addition, respondents were asked to state whether they would be prepared to pay to protect their local river. The rural community used more ecosystem services and prioritized them more highly than the urban community; probably because they interacted with them more frequently. The results of this study raise the question of whether there should be different ecosystem services protection goals for rural and urban regions, as well as highlighting potential trade-offs between ecosystem services prioritized by different sections of society

Twin nucleation and variant selection in Mg alloys: An integrated crystal plasticity modelling and experimental approach

Extension twin nucleation and variant selection in magnesium alloy WE43 is investigated in experimentally characterised and deformed microstructures replicated in crystal plasticity models. Total stored (dislocation) energy density is found to identify the experimentally observed locations of twins which are not otherwise explained by global Schmid factors or local resolved shear stress criteria. A critical total stored energy of the order 0.015 Jm-2 is determined below which twin nucleation does not occur. The total stored energy density explains the locations of the observed twins and the absence of twins in parent grains anticipated to be favourable for twin nucleation. Twin variant selection has been shown to be driven by minimising locally stored shear energy density, while the geometric compatibility and strain compatibility factors only aid in partial prediction. All experimentally observed variants were correctly determined

Relationship between education and social capital

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Are people willing to pay for river water quality, contingent valuation

Now a day's water pollution has caused incoveriences for people whom live near the Pavana river in Pune city, India. The river water quality has deteriorated by major water quality parameters like dissolved oxygen (DO), biological oxygen demand (BOD) and phosphates level. In present study it is tried to find people's willingness to pay (WTP) for improvement of river water quality. Contingent valuation method (CVM) was utilized for valuation of river water quality in Pavana river. Five categories of users have been chosen and then interviewed: households, farmers, fishermen, washing clothes women, bath taking people. One kilometer from each side of river was covered by researchers for sampling. Mean of willingness to pay was estimated at Rs 17.6 (45 Indian Rupees=$ 1) per family per month. This research shows CVM applicablity and the importance of river quality for Pune city and can effectively be used in developing countries