A study on compressive anisotropy and nonassociated flow plasticity of the AZ31 Magnesium Alloy in hot rolling

Effect of anisotropy in compression is studied on hot rolling of AZ31 magnesium alloy with a three-dimensional constitutive model based on the quadratic Hill48 yield criterion and nonassociated flow rule (non-AFR). The constitutive model is characterized by compressive tests of AZ31 billets since plastic deformations of materials are mostly caused by compression during rolling processes. The characterized plasticity model is implemented into ABAQUS/Explicit as a user-defined material subroutine (VUMAT) based on semi-implicit backward Euler\u27s method. The subroutine is employed to simulate square-bar rolling processes. The simulation results are compared with rolled specimens and those predicted by the von Mises and the Hill48 yield function under AFR. Moreover, strip rolling is also simulated for AZ31 with the Hill48 yield function under non-AFR. The strip rolling simulation demonstrates that the lateral spread generated by the non-AFR model is in good agreement with experimental data. These comparisons between simulation and experiments validate that the proposed Hill48 yield function under non-AFR provides satisfactory description of plastic deformation behavior in hot rolling for AZ31 alloys in case that the anisotropic parameters in the Hill48 yield function and the non-associated flow rule are calibrated by the compressive experimental results

Electrochemically Inert g-C3N4 Promotes Water Oxidation Catalysis

Electrode surface wettability is critically important for heterogeneous electrochemical reactions taking place in aqueous and nonaqueous media. Herein, electrochemically inert g-C 3 N 4 (GCN) is successfully demonstrated to significantly enhance water oxidation by constructing a superhydrophilic catalyst surface and promoting substantial exposure of active sites. As a proof-of-concept application, superhydrophilic GCN/Ni(OH) 2 (GCNN) hybrids with monodispersed Ni(OH) 2 nanoplates strongly anchored on GCN are synthesized for enhanced water oxidation catalysis. Owing to the superhydrophilicity of functionalized GCN, the surface wettability of GCNN (contact angle 0°) is substantially improved as compared with bare Ni(OH) 2 (contact angle 21°). Besides, GCN nanosheets can effectively suppress Ni(OH) 2 aggregation to help expose more active sites. Benefiting from the well-defined catalyst surface, the optimal GCNN hybrid shows significantly enhanced electrochemical performance over bare Ni(OH) 2 nanosheets, although GCN is electrochemically inert. In addition, similar catalytic performance promotion resulting from wettability improvement induced by incorporation of hydrophilic GCN is also successfully demonstrated on Co(OH) 2 . The present results demonstrate that, in addition to developing new catalysts, building efficient surface chemistry is also vital to achieve extraordinary water oxidation performance

Black Phosphorus Q-Switched Large-Mode-Area Tm-Doped Fiber Laser

We report on a passively Q-switched fiber laser with black phosphorus as saturable absorber. By employing the sol-gel fabricated large-mode-area Tm-doped fiber as gain medium, a high-energy Q-switched fiber laser has been demonstrated which delivers the maximum pulse energy of 11.72 μJ with the pulse width of 660 ns at the wavelength of 1954 nm. Our experimental results indicate that BP Q-switched large-mode-area Tm-doped fiber laser is an effective and reliable approach to generate high-energy pulses at 2 μm