Improving Fatigue Properties of 316L Stainless Steel Welded Joints by Surface Spinning Strengthening

The surface spinning strengthening(3S)mechanism and fatigue life extension mechanism of 316L stainless steel welded joint were systematically elucidated by microstructural analyses and mechanical tests.Results indicate that surface gradient hardening layer of approximately 1 mm is formed in the base material through grain fragmentation and deformation twin strengthening,as well as in the welding zone composed of deformedδ-phases and nanotwins.The fatigue strength of welded joint after 3S significantly rises by 32%(from 190 to 250 MPa),which is attributed to the effective elimination of surface geometric defects,discrete refinement ofδ-Fe phases and the appropriate improvement in the surface strength,collectively mitigating strain localization and surface fatigue damage within the gradient strengthening layer.The redistributed fineδ-Fe phases benefited by strong stress transfer of 3S reduce the risk of surface weak phase cracking,causing the fatigue fracture to transition from microstructure defects to crystal defects dominated by slip,further suppressing the initiation and early propagation of fatigue cracks.

A Novel Method for Achieving Gradient Microstructure in a Cu-Al Alloy:Surface Spinning Strengthening (3S)

A new designed surface strengthening method, surface spinning strengthening （3S）, was applied to achieve gradient microstructure in the surface layer of a Cu-11 at.%A1 alloy. According to the level of grain refinement, the gradient microstructure can be divided into four zones, including nanoscale grain zone, ultra-fine grain zone, fine grain zone and coarse grain zone from the surface to the matrix. Meanwhile, a plenty of grain boundaries and twin boundaries were introduced to inhibit the dislocation motion in the surface layer during the plastic deformation process. Consequently, the hardened layer with a microhardness gradient and high residual compressive stress was produced on the samples, and the yield strength of the Cu-11 at.%A1 alloy was effectively improved after 3S processing due to the strengthening effect caused by the gradient microstructurc.

Magnetically tunable Airy-like beam of magnetostatic surface spin waves

In this Letter,we report an Airy-like beam of magnetostatic surface spin wave(Ai BMSSW)supported on the ferromagnetic film,which is transferred from the optical field.The propagation properties of Ai BMSSW were verified with micromagnetic simulation.From simulation results,the typical parabolic trajectory of the Airy-type beam was observed with an exciting source encoding 3/2 phase pattern.The simulation results coincide well with design parameters.Furthermore,simulated results showed that the trajectories of the Ai BMSSW could be tuned readily with varied external magnetic fields.This work can extend the application scenario of spin waves.

Enhanced spin Hall effect of reflected light with guided-wave surface plasmon resonance

The photonic spin Hall effect(SHE) has been intensively studied and widely applied, especially in spin photonics.However, the SHE is weak and is difficult to detect directly. In this paper, we propose a method to enhance SHE with the guided-wave surface-plasmon resonance(SPR). By covering a dielectric with high refractive index on the surface of silver film, the photonic SHE can be greatly enhanced, and a giant transverse shift of horizontal polarization state is observed due to the evanescent field enhancement near the interface at the top dielectric layer and air. The maximum transverse shift of the horizontal polarization state with 11.5 μm is obtained when the thickness of Si film is optimum. There is at least an order of magnitude enhancement in contrast with the transverse shift in the conventional SPR configuration. Our research is important for providing an effective way to improve the photonic SHE and may offer the opportunity to characterize the parameters of the dielectric layer with the help of weak measurements and development of sensors based on the photonic SHE.

Spin-flop transition and Zeeman effect of defect-localized bound states in the antiferromagnetic topological insulator MnBi_(2)Te_(4)

The correlation of surface impurity states with the antiferromagnetic ground states is crucial for understanding the formation of the topological surface state in the antiferromagnetic topological insulators MnBi_(2)Te_(4).By using low-temperature scanning tunneling microscopy and spectroscopy,we observed a localized bound state around the Mn-Bi antisite defect at the Teterminated surface of the antiferromagnetic topological insulator MnBi_(2)Te_(4).When applying a magnetic field perpendicular to the surface(Bz)from–1.5 to 3.0 T,the bound state shifts linearly to a lower energy with increasing Bz,which is attributed to the Zeeman effect.Remarkably,when applying a large range of Bz from–8.0 to 8.0 T,the magnetic field induced reorientation of surface magnetic moments results in an abrupt jump in the local density of states(LDOS),which is characterized by LDOSchange-ratio■quantitatively.Interestingly,two asymmetric critical field,–2.0 and 4.0 T determined by the two peaks in■are observed,which is consistent with simulated results according to a Mills-model,describing a surface spin flop transition(SSF).Our results provide a new flatform for studying the interplay between magnetic order and topological phases in magnetic topological materials.