Evolution of microstructure and mechanical properties of A356 aluminium alloy processed by hot spinning process

The evolution of microstructure and mechanical properties of A356 aluminum alloy subjected to hot spinning process has been investigated. The results indicated that the deformation process homogenized microstructure and improved mechanical properties of the A356 aluminum alloy. During the hot spinning process, eutectic Si particles and Fe-rich phases were fragmented, and porosities were eliminated. In addition, recrystallization of Al matrix and precipitation of Al Si Ti phases occurred. The mechanical property testing results indicated that there was a significant increase of ductility and a decrease of average microhardness in deformed alloy over die-cast alloy. This is attributed to uniform distribution of finer spherical eutectic Si particles, the elimination of casting defects and to the recrystallized finer grain structure.

Effect of Strontium Substitution on Microstructure and Magnetic Properties of Electrospinning BaFe12O19 Nanofibers

Barium ferrite micro/nano fibers were successfully prepared via the electrostatic spinning by using dimethyl formamide（DMF） as the solvent, and poly vinyl pyrrolidone（PVP） as the spinning auxiliaries. Effects of strontium substitution on the structure, morphology, and magnetic properties were investigated by scanning electron microscope（SEM）, X-ray diffraction analysis（XRD）, and vibration sample magnetometer（VSM）. XRD patterns of the samples confirm that pure barium ferrite fibers form, and the Sr substitution makes the main peaks（110）,（107）, and（114） move to right slightly. Also, the FE-SEM images show that the Sr substituted fibers can keep complete fibrous morphology. Moreover, the VSM results demonstrate that the saturation magnetization can reach 56.7 emu/g when the fibers are calcined at 800℃.

Investigations of mechanical, electronic, and magnetic properties of non-magnetic MgTe and ferro-magnetic Mg_(0.75)T M_(0.25)Te (TM = Fe, Co, Ni): An ab-initio calculation

The mechanical, electronic and magnetic properties of non-magnetic MgTe and ferro-magnetic （FM） Mgo.75 TM025 Te （TM = Fe, Co, Ni） in the zinc-blende phase are studied by ab-initio calculations for the first time. We use the generalized gradient approximation functional for computing the structural stability, and mechanical properties, while the modified Becke and Johnson local （spin） density approximation （mBJLDA） is utilized for determining the electronic and magnetic properties. By comparing the energies of non-magnetic and FM calculations, we find that the compounds are stable in the FM phase, which is confirmed by their structural stabilities in terms of enthalpy of formation. Detailed descriptions of elastic properties of Mgo.75TMo.25Te alloys in the FM phase are also presented. For electronic properties, the spin- polarized electronic band structures and density of states are computed, showing that these compounds are direct bandgap materials with strong hybridizations of TM 3d states and Te p states. Further, the ferromagnetism is discussed in terms of the Zener free electron model, RKKY model and double exchange model. The charge density contours in the （110） plane are calculated to study bonding properties. The spin exchange splitting and crystal field splitting energies are also calculated. The distribution of electron spin density is employed in computing the magnetic moments appearing at the magnetic sites （Fe, Co, Ni）, as well as at the non-magnetic sites （Mg, Te）. It is found that the p-d hybridization causes not only magnetic moments on the magnetic sites but also induces negligibly small magnetic moments at the non-magnetic sites.

Spin transport properties of a Dresselhaus-polygonal quantum ring

We propose a theoretical method to investigate the effect of the Dresselhaus spin–orbit coupling（DSOC） on the spin transport properties of a regular polygonal quantum ring with an arbitrary number of segments. We find that the DSOC can break the time reversal symmetry of the spin conductance in a polygonal ring and that this property can be used to reverse the spin direction of electrons in the polygon with the result that a pure spin up or pure spin down conductance can be obtained by exchanging the source and the drain. When the DSOC is considered in a polygonal ring with Rashba spin–orbit coupling（RSOC） with symmetric attachment of the leads, the total conductance is independent of the number of segments when both of the two types of spin–orbit coupling（SOC） have the same value. However, the interaction of the two types of SOC results in an anisotropic and shape-dependent conductance in a polygonal ring with asymmetric attachment of the leads. The method we proposed to solve for the spin conductance of a polygon can be generalized to the circular model.

First-Principles Calculation on Geometric,Electronic and Optical Properties of Fully Fluorinated Stanene:a Large-Gap Quantum Spin Hall Insulator

The searches for large-gap quantum spin Hall insulators are important for both practical and fundamental inter- ests. In this work, we present a theoretical observation of the two-dimensional fully fluorinated stanene （SnF） by means of density functional theory. Remarkably, a significant spin-orbit coupling is observed for the SnF monolayer in the valence band at the F point, with a considerable indirect band gap of 278 meV. The direct gap of the SnF monolayer is at the F point, which is slightly larger by as much as 381 meV. In addition, the elastic modulus of the SnF monolayer is about 20J/m^2, which is comparable with the in-plane stiffness of black phos- phorus monolayer along the x-direction （~28.94 J/m^2）. Finally, the optical properties of stanene, SnF monolayer and stanene/SnF bilayer are calculated, in which the stanene/SnF bilayer is supposed to be an attractive sunlight absorber.

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.