Tensile deformation behavior and mechanical properties of a bulk cast Al0.9 CoFeNi2 eutectic high-entropy alloy

In this study,a new Al0.9CoFeNi2 eutectic high entropy alloy(EHEA) was designed,and the microstructures as well as the deformation behavior were investigated.The bulk cast Al0.9CoFeNi2 EHEA exhibited an order face-centered cubic FCC(L12) and an order body-centered cubic(B2) dual-phase lamellar eutectic microstructure.The volume fractions of FCC(L12) and B2 phases are measured to be 60 % and 40 %,respectively.The combination of the soft and ductile FCC(L12) phase together with the hard B2 phase resulted in superior strength of 1005 MPa and ductility as high as 6.2 % in tension at room temperature.The Al0.9CoFeNi2 EHEA exhibited obvious three-stage work hardening characteristics and high workhardening ability.The evolving dislocation substructure s during uniaxial tensile deformation found that planar slip dominates in both FCC(L12) and B2 phases,and the FCC(L12) phase is easier to deform than the B2 phase.The post-deformation transmission electron microscopy revealed that the sub-structural evolution of the FCC(L12) phase is from planar dislocations to bending dislocations,high-density dislocations,dislocation network,and then to dislocation walls,and Taylor lattices,while the sub-structural evolution of the B2 phase is from a very small number of short dislocations to a number of planar dislocations.Moreover,obvious ductile fracture in the FCC(L12) phase and a brittle-like fracture in the B2 phase were observed on the fracture surface of the Al0.9CoFeNi2 EHEA.The re search results provide some insight into the microstructure-property relationship.

Effects of Chromium on the Microstructures and Mechanical Properties of AlCoCrxFeNi2.1 Eutectic High Entropy Alloys

In the present study,a series of AlCoCrxFeNi2.1(x=0,0.25,0.5,0.75,1.0)eutectic high entropy alloys(EHEAs)have been designed and prepared.And the effect of Cr content on the microstructures and mechanical properties of the AlCoCrxFeNi2.1 alloys was systematically investigated.The results indicate that the AlCoCrxFeNi2.1(x>0)alloys exhibit almost complete lamellar eutectic microstructures with a mixture structure of FCC and B2 phases.And the AlCoFeNi2.1 alloy without Cr element exhibited a hypoeutectic microstructure with a primary B2 phase.In addition,the eutectic microstructures for AlCoCrxFeNi2.1 eutectic alloys do not change significantly.The room temperature compressive tests results show that with an increase in Cr content(from x=0 to x=1.0),the yield strength will first decrease,and thereafter increase.The trend is the opposite with the fracture strength and plastic strain.They show an increase trend at first,and then decrease.The AlCoCr0.5 FeNi2.1(Cr0.5)alloy shows the best comprehensive mechanical properties.The tensile yield strength,fracture strength,and elongation are 536.5 MPa,1062 MPa,and 13.8%,respectively.Furthermore,the Cr0.5 alloy also displays a high strength with a yield strength of 362 MPa at 700℃.In summary,by changing the Cr content,AlCoCrxFeNi2.1 eutectic high entropy alloys with excellent comprehensive mechanical properties were obtained and prepared.

A Facile Construction of Bisheterocyclic Methane Scaffolds through Palladium-Catalyzed Domino Cyclization

Main observation and conclusion A convenient palladium-catalyzed domino cyclization reaction for the construction of bis(benzofuranyl)methane scaffolds bearing an all-carbon quaternary center has been described.In the cascade process,one C(sp2)—O bond,two C(sp2)—C(sp3)bonds as well as two benzofuran rings are formed in a single synthetic sequence.The approach shows wide scope of substrates and good functional-group tolerance.Moreover,this methodology is successfully extended to the synthesis of benzofuranyl methyl chromane derivatives.

Construction of Alkenyl-Functionalized Spirocarbocyclic Scaffolds from Alkyne-Containing Phenol-Based Biaryls via Sequential lodine-Induced Cyclization/Dearomatization and Pd-Catalyzed Coupling of N-Tosylhydrazones

of main obse rvation and conclusion An efficient strategy for the formation of alkenyl-functionalized spirocarbocyclic scaffolds from alkyne-containing phenol-based biaryls via sequential iodine-induced cyclization/dearomatization and Pd-catalyzed coupling of N-tosylhydrazones is developed.The approach provides various spirocarbocyclic compounds in moderate to excellent yields with good functional tolerance.The results also demonstrate the feasibility for the direct cross-couplings of N-tosyl hydrazones with sterically congested tetrasubstituted alkenyl halides.