Fabrication of ultra-high strength magnesium alloys over 540 MPa with low alloying concentration by double continuously extrusion

We prepare a new type of patented biodegradable biomedical Mg-Nd-Zn-Zr(JDBM)alloy system and impose double continuously extrusion(DCE)processing.The lowest processing temperature is 250℃for JDBM-2.1Nd and 310℃for JDBM-2.8Nd,which increases with the Nd concentration.The highest yield strength of 541 MPa is achieved in JDBM-2.1 Nd samples when extruded at 250℃and the elongation is about 3.7%.Moreover,the alloy with a lower alloying element content can reach a higher yield strength while that with a higher alloying element content can reach a larger elongation after DCE processing.However,when extruded under the same conditions,the alloy with a higher alloying contents exhibits better tensile properties.

Microstructure and Mechanical Properties of AZ31 Mg Alloy Fabricated by Pre-compression and Frustum Shearing Extrusion

The AZ31 Mg alloys were processed by 6% pre-compression and frustum shearing extrusion at various temperatures, and the microstructure, texture and mechanical properties of the resulting alloys are systematically investigated. The results show that the grain size monotonically increases from 6.4 to 12.6 lm and the texture intensity increases from 6.7 to 9.6with the increase in the extrusion temperature. The combining effect of the pre-twinning and the frustum shearing deformation is found to contribute to the development of the weak basal texture in Mg alloys. The Mg alloy sheet produced at the extrusion temperature of 563 K exhibits excellent mechanical properties. The yield strength, ultimate tensile strength and elongation for the extruded alloys are 189.6 MPa, 288.4 MPa and 24.9%, respectively. Such improved mechanical properties are comparable or even superior to those of the alloys subjected to other deformation techniques, rendering the pre-compression and frustum shearing extrusion a promising way for further tailoring properties of Mg alloys.

Polarization-dependent optical engineering of ferroelectric domains

Ferroelectric domain engineering with infrared femtosecond laser pulses has been a powerful technique to achieve a spatially modulated second-order nonlinear coefficient in three dimensions.However,studies regarding the in-fluence of laser writing conditions on the light-induced ferroelectric domain inversion remain limited.Herein,an experimental study to reveal the role of laser polarization in light-induced domain inversions is discussed.The dependence of the optical threshold and maximal writing depth of inverted domains on light polarization is ex-perimentally investigated.The results are explained by considering the second-order nonlinear optical properties and birefringence-induced focus splitting in the crystal.These findings are useful in fabricating high-quality and large-scale ferroelectric domain structures for applications in optics,electronics,and quantum technologies.

Nonlinear photonic quasi-periodic spiral

The design of nonlinear photonic Vogel's spiral based on quasi-crystal theory was demonstrated.Two main parameters of Vogel's spiral were arranged to obtain multi-reciprocal circles.Typical structure was fabricated by the near-infrared femtosecond laser poling technique,forming a nonlinear photonic structure,and multiple ring-like nonlinear Raman±Nath second-harmonic generation processes were realized and analyzed in detail.The structure for the cascaded thirdharmonic generation process was predicted.The results could help deepen the understanding of Vogel's spiral and quasi-crystal and pave the way for the combination of quasi-crystal theory with more aperiodic structures.

Second-harmonic generation in periodic fork-shaped χ^((2)) gratings at oblique incidence

Three-dimensional(3D) nonlinear photonic crystals have received intensive interest as an ideal platform to study nonlinear wave interactions and explore their applications. Periodic fork-shaped gratings are extremely important in this context because they are capable of generating second-harmonic vortex beams from a fundamental Gaussian wave, which has versatile applications in optical trapping and materials engineering. However, previous studies mainly focused on the normal incidence of the fundamental Gaussian beam, resulting in symmetric emissions of the second-harmonic vortices. Here we present an experimental study on second-harmonic vortex generation in periodic fork-shaped gratings at oblique incidence, in comparison with the case of normal incidence. More quasi-phase-matching resonant wavelengths have been observed at oblique incidence, and the second-harmonic emissions become asymmetric against the incident beam.These results agree well with theoretic explanations. The oblique incidence of the fundamental wave is also used for the generation of second-harmonic Bessel beams with uniform azimuthal intensity distributions. Our study is important for a deeper understanding of nonlinear interactions in a 3D periodic medium. It also paves the way toward achieving highquality structured beams at new frequencies, which is important for manipulation of the orbital angular momentum of light.

Synthesis of Meta Symmetric 1T'-WTe2 Using an Edge-Induced Mechanism

Lattice symmetry is vital to the properties of two-dimensional(2D)materials,yet their fixed symmetry cannot meet the increasing requirements in highly eficient and programmable electrical transport.If the structural diversity of 2D materals,as demon-strated by 1T'-WTez,is improved without any phase transition or structural reconstruction,excellent metallic 1T'-WTez would be possibly used for inte-grated devices.Here,we realized meta symmetry of 1T'-WTez by using an edge-induced mechanism,which is recognized as the combination of the intrin-sic C2v symmetry and sixfold axes.On account of the dynamically controlled growth,the meta symmetric 1T'-WTez with^94.9%purity is obtained for the first time.Meta symmetry will also keep the intrinsic electrical properties of 1T'-WTez over the node.Such meta symmetry could not only enrich the structural diversity of 1T'-WTez,but also be extended to other low-symmetry 2D materials,which would be promising for customized circuits and devices.

Metallic interface induced by electronic reconstruction in crystalline-amorphous bilayer oxide films

Extraordinary electronic properties can emerge at the interfaces between metal oxides[1-10].Interfacial behaviors have enabled a wide range of applications from electronic communication,energy conversion and storage,to data processing and memory.In recent years,unprecedented progress has been made in exploring and exploiting the emergent and/or enhanced properties of these interfaces,and it is becoming clear that interface engineering provides a new opportunity for advanced devices in the near future.The capability of using interfaces to manipulate material properties offers an effective means to achieve intriguing phenomena.