Microstructure evolution,texture and mechanical properties of a Mg-Gd-Y-Zn-Zr alloy fabricated by cyclic expansion extrusion with an asymmetrical extrusion cavity:The influence of passes and processing route

In the present work,two processing routes(A and B)with 3 CEE-AEC passes are performed on Mg-13 Gd-4 Y-2 Zn-0.4 Zr alloys,and the resultant microstructure evolution,texture analysis and mechanical properties are investigated systematically.The core difference between the two processing routes is the orientation between the expansion and extrusion steps,i.e.,they are parallel to each other for on route A and perpendicular to each other for route B.The results show that a remarkable grain refinement is achieved via both processing routes due to dynamic recrystallization(DRX).Fine equiaxed grains are observed in the samples processed with route B with a final size of 3.6±0.4μm compared to the grain size of 4.5±0.5μm with route A.With an increasing number of CEE-AEC passes,the overall texture intensity decreases,and the basal texture gradually changes to the mixed texture components.The shear deformation introduced by the asymmetrical extrusion cavity promotes a broad angular distribution of the basal planes on routes A and B,leading to an obvious increase in the Schmid factor for the activation of the basal a slip system.The tensile test at ambient temperature reveals that the comprehensive mechanical properties are improved,and the conventional mechanical anisotropy of as-received alloys is alleviated by successive CEE-AEC processing,which is mainly derived from the competitive balance relation between the grain refinement and texture modification.

A new inclination-based method to evaluate the global geomagnetic configuration and axial dipole moment

The strength and configuration of the geomagnetic field control the average shape of the magnetosphere.The pure dipole assumption and the virtual dipole moment(VDM),determined by individual records,have been widely adopted to evaluate the strength of the geomagnetic field in geological time.However,such an assumption might not be valid during geomagnetic transitions,such as reversals and excursions.The traditional spherical harmonic modeling of the geomagnetic field could be difficult to implement because accurate global records are lacking.Here,we report that an empirical relationship exists between the ratio of the VDM to the true axial dipole moment(VDM/ADM)and the ratio of the power of the axial dipole to that of the non-axial dipole(AD/NAD)based on a new method utilizing globally distributed inclination records.The root mean square global deviation of inclination(RMSΔI)to the standard inclination distribution of the AD was fitted to the AD/NAD with a cubic polynomial by utilizing a large number of geodynamo simulations.Tests with geomagnetic field models showed that the AD/NAD derived from the RMSΔI agreed well with that calculated by using the Gauss coefficients,and the estimated ADM was consistent with the true value.Finally,the application of volcanic records during the Laschamp excursion showed the VDM might overestimate the ADM by a factor of 3.Our new method will be useful in future studies that characterize the configuration of the geomagnetic field and the strength of the axial dipole.

Eco-districts in France:What tools to ensure goals achievement?

Globally,to build cities and communities more inclusive,safe,resilient and sustainable is one of the most important sustainable development goals.Eco-districts in cities emerged as an answer to current global environmental concerns and have been developed in France since the 1990s.The objective of this work is to gather operational feedback from sustainable neighborhood projects owners to better understand the key barriers of such projects and how to overcome them.A case study of the eco-district Les Tanneries,Lingolsheim showed that the carbon footprint of each inhabitant annually amounted to 4 tons CO2 equivalent,more than half of the French average.Rooms for improvements were clearly identified regarding transports and food carbon footprint.Indicators for energy consumption,social diversity and density reached the level of the eco-districts average.A governance review pointed out some superior practices such as the formalization of a specification requirements handbook,a competition between project management teams,and the use of neighborhood sustainability assessment tools to measure and track changes in performance.The validated tools and obtained results can be useful in building sustainable cities and even China’s ecological civilization.

Correlation analysis between the occurrence of epidemic in ancient China and solar activity

As the globe has witnessed the pandemic,epidemic diseases exert a strong impact on human beings and ecosystems.Since the Sun is the primary energy source of the Earth,some scientific pioneers attempted to search for the discernible relation between solar activity and the incidence of epidemics.In this study,the periodic changes and trends of ancient Chinese epidemic data were analyzed in comparison with those of sunspot numbers,a solar activity proxy.The results show that the epidemic and solar activity changes are in good agreement to a certain extent,especially during the Gleissberg and the de Vries cycles.The wavelet coherence shows that the frequency of the epidemic data and sunspot numbers are highly associated.In addition,results from the ensemble empirical mode decomposition illustrate consistent variations in low-frequency decompositions.This study has important implications for further understanding of the potential impact of solar activity on Earth’s biosphere,the underlying mechanism of which needs further exploration.