Big-data analysis of phase-formation rules in high-entropy alloys

Big-data analysis of phase-formation rules of high-entropy alloys（HEAs）was conducted and a phase formation rule from a dynamic view was deduced.It was indicated in literatures that cooling rate has a strong influence on the phase formation of HEAs.Higher cooling rate may promote the generation of amorphous phase,and accordingly suppress the formation of intermetallics.Meanwhile,it was also shown that cooling rate had little impact on the formation of solid-solution phase.To demonstrate this rule,a series of FeCoNi（AlSiB）xHEAs ribbons were fabricated by a melt-spinning technique,and the microstructure,mechanical,and magnetic properties were also investigated.The results show that all ribbons exhibit disordered solid-solution structure.The addition of boron changes the alloy from ductility to brittleness,but without evident change of magnetic properties.The alloy in the nominal composition of FeCoNi（AlSi）0.2has the best combination of mechanical and magnetic properties.A distinct feature of HEAs in magnetization was noticed and explained.

Exploration Potential of Marine Source Rocks Oil-Gas Reservoirs in China

So far, more than 150 marine oil-gas fields have been found onshore and offshore about 350. The marine source rocks are mainly Paleozoic and Mesozoic onshore whereas Tertiary offshore. Three genetic categories of oil-gas reservoirs have been defined for the marine reservoirs in China： primary reservoirs, secondary reservoirs and hydrocarbon-regeneration reservoirs. And three exploration prospects have also been suggested： （1） Primary reservoirs prospects, which are chiefly distributed in many Tertiary basins of the South China Sea （SCS）, the Tertiary shelf basins of the East China Sea （ECS） and the Paleozoic of Tarim basin, Sichuan basin and Ordos basin. To explore large-middle-scale even giant oil-gas fields should chiefly be considered in this category reservoirs. These basins are the most hopeful areas to explore marine oil-gas fields in China, among which especially many Tertiary basins of the SCS should be strengthened to explore. （2） Secondary reservoirs prospects, which are mainly distributed in the Paleozoic and Mesozoic of the Tarim basin, Sichuan basin, Qiangtang basin and Chuxiong basin in western China, of which exploration potential is less than that of the primary reservoirs. （3） Hydrocarbon-regeneration reservoirs prospects, which are chiefly distributed in the Bohai Bay basin, North Jiangsu-South Yellow Sea basin, southern North China basin, Jianghan basin, South Poyang basin in eastern China and the Tarim basin in western China, of which source rocks are generally the Paleozoic. And the reservoirs formed by late-stage （always Cenozoic） secondary hydrocarbon generation of the Paleozoic source rocks should mainly be considered to explore, among which middle-small and small oil-gas fields are the chief exploration targets. As a result of higher thermal evolution of Paleozoic and Mesozoic source rocks, the marine reservoirs onshore are mainly gas fields, and so far marine oil fields have only been found in the Tarim basin. No other than establishing corresponding marine oil-gas exploration and development strategy and policy, sufficiently enhancing cognition to the particularity and complexity of China＇s marine petroleum geology, and applying new thoughts, new theories and new technologies, at the same time tackling some key technologies, it is possible to fast and effectually exploit and utilize the potential huge marine oil-gas resources of China.

Preternatural Hexagonal High-Entropy Alloys: A Review

Recently,various topics on high-entropy alloys have been reported and great amounts of excellent properties have been investigated,including high strength,great corrosion resistance,great thermal stability,good fatigue and fracture properties,etc.Among all these research activities,high-entropy alloys tend to form face-centered-cubic(FCC)or body-centeredcubic(BCC)solid solutions due to their high-entropy stabilization effect,while the hexagonal structures are rarely reported.Up to now,the reported hexagonal high-entropy alloys are mainly composed of rare-earth elements and transitional elements.Their phase transformation and magnetic properties have also aroused wide concern.This study summarizes the above results and provides the forecast to the future.

Entropy versus enthalpy in hexagonal-close-packed highentropy alloys

The addition of hexagonal-close-packed(hcp)non-rare-earth elements Zr,Ti and Co,to the 10-component hep rare-earth-based high-entropy alloys(HEAs)with a composition of ScYLaNdGdTbDyHoErLuX(X=Zr,Co and Ti)was investigated.The enthalpy of mixing between elements was found to have a significant effect on the formation of phases.The addition of Co combines with elements that had a strong chemical affinity to form intermetallic compounds by the effect of enthalpy.Ti was added with all elements with poor chemical affinity and exhibited rejection to form a phase alone.These were the two terminal manifestations of the role of enthalpy over entropy.Part of Zr was soluble in the matrix under the action of entropy,while the other part had a greater affinity for Sc than the other elements to form a precipitate under the action of enthalpy.This was the result of the local balance between the effect of enthalpy and entropy.The solid solution of the elements had different degrees of strengthening effect,among which Zr had the most excellent strengthening effect from 185 to 355 MPa,so the solid solution strengthening model and precipitation strengthening model were proposed to predict the strength of the alloy with the addition of Zr effectively.