Rate-dependent inhomogeneous creep behavior in metallic glasses

Creep deformation can be classified as homogeneous flow and inhomogeneous flow in bulk metallic glass(BMG).In order to understand the conversion conditions of the two types of creep deformation,the effect of loading rate on the creep behavior of a Ti_(40)Zr_(10)Cu_(47)Sn_(3)(at.%)BMG at ambient temperature was investigated using nanoindentation and molecular dynamic simulation.Results indicate that at low loading rates,many serrations appear in loading stage,leading to inhomogeneous serrated flow in the creep stage.When the loading rate is high enough,the creep deformation tends to be homogeneous.The related mechanism responsible for the rate-dependent creep behavior is attributed to the number of pre-existing major shear bands which is influenced significantly by the loading rate.

Development characteristics and controlling factor analysis of the Neogene Minghuazhen Formation shallow water delta in Huanghekou area, Bohai offshore basin

Based on a combination of high resolution 3-D seismic, drilling and well logging and core data, this study focuses on describing the depositional features of the Neogene Minghuazhen Formation shallow water delta in Huanghekou area(HHKA), Bohai offshore basin and discussing the evolution and controlling factors of shallow water delta sandbody. An obvious meandering fluvial delta system developed in sequence 1(SQ1) of the Neogene in HHKA with thinner sandbody of distributary channels and poor development of mouth bar. The sequence texture obviously influences the vertical development and stacking pattern of sandbodies and controls the distribution of sandbodies in plain view as well. In shallow water lacustrine basins, relative topographic height difference leads to change of distribution of accommodation space, and sandbodies of distributary channels usually develop well in local low-lying areas where accommodation space increases. The delta is dominated by distributary channel sandbodies during the early period of base level rising. Sandbodies contact with each other in a lateral stacking pattern and are characterized by a fan shape in plain view. Distributary channels gradually narrow and tend to shift during the mid-late-period of base level rising, while the sandbodies are characterized by a net shape in plain view. During the period of base level slow falling, the multistory/multilateral channel sandbodies dominated the inner front of shallow-water delta and the delta sand dispersal distributes as a lobe shape.

Genesis and mechanisms of organic matter enrichment of the Hongshuizhuang Formation in the Zhoukoudian area of Jingxi sag,North China

The Hongshuizhuang Formation is a Meso-Neoproterozoic high-quality source rock in the North China Craton(NCC),comprising abundant organic matter.The present study focuses on the analysis of the Hongshuizhuang Formation in the Zhoukoudian area of the Jingxi sag,discussing its genesis and mechanisms of organic matter enrichment through geological and geochemical methods.The Hongshuizhuang Formation is divided into three members from bottom to top respectively as the lower,middle and upper member.Trace elements analysis indicate that the Hongshuizhuang Formation developed restricted neritic facies in an extensional environment within a continental island arc under a post-orogenic background.The lower and upper members were deposited in a relatively shallow,strongly retained water mass within a suboxic and saline environment influenced by subhumid climate,while the middle member was deposited in an anoxic deep-water environment with relatively low salinity and weak restrictions.The PAAS-normalized rare earth element distributions of the middle and upper members show an enrichment of LREEs and a depletion of HREEs,and a low mean Y/Ho ratio with a positive Eu anomaly,indicating that the regional deposition has been affected by hydrothermal fluids.The negativeδ13 C andδ18 O values and the positive87 Sr/86 Sr values confirm that the deposition of the middle and upper members was accompanied by crustal hydrothermal activities.Accumulation of organic matter and enrichment of Baxsand P indicate that productivity is the basis of organic matter enrichment in the Hongshuizhuang Formation,where high-quality source rocks are concentrated in the middle member.In addition,reduced water mass controls the preservation of organic matter.Hydrothermal activity,humid climate,and salinity support a higher primary productivity and the formation of reduced water masses.However,due to limitations in depth,the high-quality source rocks in the Jingxi sag are thinner than the Jibei sag.