This study investigated the impact of topography and vegetation on distribution of rare earth elements(REEs)in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the stud...This study investigated the impact of topography and vegetation on distribution of rare earth elements(REEs)in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the study were to set a basis for further research on the biogeochemical REE cycle and to provide references for soil–water conservation and REE-containing fertilizer amendments. The results show a generally flat Post-Archean Average Australian Shale—normalized REE pattern for the studied calcareous soils. REE enrichment varied widely. The proportion of acidsoluble phases of heavy REEs was higher than that of light REEs. From top to bottom of the studied hills, dominant REE sources transitioned from limestone in-situ weathering to input from REE-containing phases(e.g., clay minerals,amorphous iron, REE-containing fluids). Our results indicate that the REE content of calcareous soils is mainly controlled by slope aspect, while the enrichment degree of REEs is related to geomorphological position and vegetation type.Furthermore, the proportion of acid-soluble phases of REEs is mainly controlled by geomorphological position.展开更多
High entropy alloy(HEA)-based alloy design is experiencing a conceptual broadening from equiatomic alloys to non-equiatomic alloys.To provide experimental basis for designing Cu-rich non-equiatomic HEAs,in the current...High entropy alloy(HEA)-based alloy design is experiencing a conceptual broadening from equiatomic alloys to non-equiatomic alloys.To provide experimental basis for designing Cu-rich non-equiatomic HEAs,in the current study,a dual phase(Cu-rich and CoCrFeNi-rich phases) face-centered cubic CoCrFeNiCu_(4) alloy was systematically investigated.We provided initial and experiment-based understanding of the behavioral change of the alloy during a variety of thermal cycles and thermomechanical processing.The current results indicate that,during heating,preferred precipitation of Cu-rich particles occurs,leading to more pronounced compositional differences between the two constituent FCC phases and increased relative volume fraction of the Cu-rich phase.The Alloy exhibits a continuous melting and discontinuous solidification of the Cu-rich and CoCrFeNi-rich phases.After being cold-rolled to ~90 % thickness reduction,the alloy exhibits a recrystallization temperature higher than 800℃.Annealing at 300 and 500℃ led to strength reduction and/or ductility decrease;further increasing annealing temperature monotonically caused softening and ductilization due to decreased density of pre-existing dislocations.The yield-drop phenomena observed for the 900℃-and 1000℃-annealed specimens are associated with the locking of pre-existing dislocations by some "atmosphere",the nature of which warrants further elucidation.展开更多
基金supported jointly by the National Natural Science Foundation of China(41571130042,41522207,41325010)the State’s Key Project of Research and Development Plan of China(2016YFA0601002)
文摘This study investigated the impact of topography and vegetation on distribution of rare earth elements(REEs)in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the study were to set a basis for further research on the biogeochemical REE cycle and to provide references for soil–water conservation and REE-containing fertilizer amendments. The results show a generally flat Post-Archean Average Australian Shale—normalized REE pattern for the studied calcareous soils. REE enrichment varied widely. The proportion of acidsoluble phases of heavy REEs was higher than that of light REEs. From top to bottom of the studied hills, dominant REE sources transitioned from limestone in-situ weathering to input from REE-containing phases(e.g., clay minerals,amorphous iron, REE-containing fluids). Our results indicate that the REE content of calcareous soils is mainly controlled by slope aspect, while the enrichment degree of REEs is related to geomorphological position and vegetation type.Furthermore, the proportion of acid-soluble phases of REEs is mainly controlled by geomorphological position.
基金supported financially by the National Natural Science Foundation of China(No.51901077)the Science and Technology Innovation Platform and Talent Plan of Hunan Province(No.2019RS1020)the open Foundation of State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body(No.71865003),Hunan University,Changsha,China。
文摘High entropy alloy(HEA)-based alloy design is experiencing a conceptual broadening from equiatomic alloys to non-equiatomic alloys.To provide experimental basis for designing Cu-rich non-equiatomic HEAs,in the current study,a dual phase(Cu-rich and CoCrFeNi-rich phases) face-centered cubic CoCrFeNiCu_(4) alloy was systematically investigated.We provided initial and experiment-based understanding of the behavioral change of the alloy during a variety of thermal cycles and thermomechanical processing.The current results indicate that,during heating,preferred precipitation of Cu-rich particles occurs,leading to more pronounced compositional differences between the two constituent FCC phases and increased relative volume fraction of the Cu-rich phase.The Alloy exhibits a continuous melting and discontinuous solidification of the Cu-rich and CoCrFeNi-rich phases.After being cold-rolled to ~90 % thickness reduction,the alloy exhibits a recrystallization temperature higher than 800℃.Annealing at 300 and 500℃ led to strength reduction and/or ductility decrease;further increasing annealing temperature monotonically caused softening and ductilization due to decreased density of pre-existing dislocations.The yield-drop phenomena observed for the 900℃-and 1000℃-annealed specimens are associated with the locking of pre-existing dislocations by some "atmosphere",the nature of which warrants further elucidation.