Provenance of colorless and brown volcanic glass in late Pleistocene tephra layers in the Western Philippine Sea

Tephra layers in the western Philippine Sea,characterized by abundant volcanic glass shards,may provide crucial evidence on the eruption history of volcanoes and tectonic evolution of the western Pacific.A 220-ka sediment core from the Benham Rise in the western Philippine Sea offers new insights into the provenance of four intercalated tephra layers(T1–T4,in chronological order)containing either colorless or brown glass shards.Relative to primitive mantle,all glass shards are enriched in large-ion lithophile elements,such as Rb,Cs,and Pb,and depleted in high field-strength elements,such as Th,Nb,and Ta,indicating a subduction-related origin.The colorless glass shards are characterized by high SiO_(2)(>78%)and light rare earth element(LREE)contents as well as high La/Sm ratios(>9),low FeO and MgO contents(<1%),low Sr/Y(<15)and high Ba/Th ratios(>100),pointing to a rhyolitic composition and a medium-K calc-alkaline serial affinity.In contrast,the brown glass shards are characterized by lower SiO_(2)(<63%)and LREE contents,higher FeO,MgO,and CaO contents,lower La/Sm(<6)and Ba/Th(<75),and similar Sr/Y ratios(<15),indicating derivation from medium to high-K calc-alkaline andesite magma.Brown glass shards from layers T3(152 ka)and T4(172 ka)were correlated with volcanic deposits from the Taal and Laguna Caldera in the Maccolod Corridor,respectively,while the colorless glass shards from layers T1(36.5 ka)and T2(61.2 ka)were likely sourced from the Irosin Caldera in the Bicol Arc.Establishing the provenance of late Pleistocene tephra layers in the western Philippine Sea is helpful to complement a Philippine volcanic history and establish a regional tephrochronostratigraphy.

Microstructure and properties of novel Al-Ce-Sc,Al-Ce-Y,Al-Ce-Zr and Al-Ce-Sc-Y alloy conductors processed by die casting,hot extrusion and cold drawing

In order to overcome the trade-off between the strength and electrical conductivity of aluminum alloy conductors,the new Al-Ce-Sc,Al-Ce-Y,Al-Ce-Zr and Al-Ce-Sc-Y alloys were prepared by die casting,high temperature homogenization treatment,hot extrusion and cold drawing.Adding Sc and Y eliminated the dendrite segregation of the as-cast Al-0.2 Ce alloy and promoted the formation of equiaxed grains with the average grain size of 142.5μm.The Al-0.2 Ce-0.2 Sc-0.1 Y alloy inherited the great tensile properties of Al-0.2 Ce-0.2 Sc alloy and the high electrical conductivity of Al-0.2 Ce-0.1 Y alloy simultaneously.After cold drawing and annealing at 200℃for 5 h,the ultimate tensile strength of Al-0.2 Ce-0.2 Sc-0.1 Y alloy reached 200 MPa and 198 MPa,the elongation reached 6.8%and 8.5%,and the electrical conductivity reached 61.01%and 61.77%,respectively.The main second phase of Al-0.2 Ce-0.2 Sc-0.1 Y alloy after hot extrusion were Al_(13)Fe_3 Ce containing a few Y and Si atoms.The larger size and proportion of the second phase greatly reduced the concentration of solute Fe and Si atoms and the addition of Y significantly decreased the density of defects after cold drawing compared to Al-0.2 Ce-0.2 Sc alloy,which improved electrical conductivity of the alloy.Furthermore,the dispersed and coherent nano-size Al_3 Sc precipitions of Al-0.2 Ce-0.2 Sc-0.1 Y alloy greatly improved strength,elongation and heat resistance.Compared with Al-0.2 Ce-0.2 Sc alloy,the lower density of dislocation,stacking fault and subgrain boundary and the larger size of Al_3 Sc precipitions with enrichment of Y atoms enable the Al-0.2 Ce-0.2 Sc-0.1 Y alloy to maintain high strength,elongation and electrical conductivity after annealing.

Superior low cycle fatigue property from cell structures in additively manufactured 316L stainless steel

We have investigated the low cycle fatigue(LCF)properties and the extent of strengthening in a dense additively manufactured stainless steel containing different volume fractions of cell structures but having all other microstructure characteristics the same.The samples were produced by laser powder bed fusion(L-PBF),and the concentration of cell structures was varied systematically by varying the annealing treatments.Load-controlled fatigue experiments performed on samples with a high fraction of cell structures reveal an up to 23 times increase in fatigue life compared to an essentially cell-free sample of the same grain configuration.Multiscale electron microscopy characterizations reveal that the cell structures serve as the soft barriers to the dislocation propagation and the partials are the main carrier for cyclic loading.The cell structures,stabilized by the segregated atoms and misorientation between the adjacent cells,are retained during the entire plastic deformation,hence,can continuously interact with dislocations,promote the formation of nanotwins,and provide massive 3D network obstacles to the dislocation motion.The compositional micro-segregation caused by the cellular solidification features serves as another nonnegligible strengthening mechanism to dislocation motion.Specifically,the cell structures with a high density of dislocation debris also appear to act as dislocation nucleation sites,very much like coherent twin boundaries.This work indicates the potential of additive manufacturing to design energy absorbent alloys with high performance by tailoring the microstructure through the printing process.