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Ti-6Al, Ti-6Al-2Mo and Ti-6Al-3Nb alloys were prepared to investigate the toughening effects of β stabilizers Mo and Nb on impact toughness and crack resistance of titanium alloys. Instrumented Charpy impact tests showed that the total impact absorbed energy of Ti-6Al-2Mo and Ti-6Al-3Nb (∼64 J) were two times higher than that of Ti-6Al (∼30 J), indicating the higher impact toughness of Ti-6Al-2Mo and Ti-6Al-3Nb alloys. Analysis of load-displacement curves revealed the similar crack initiation energy of Ti-6Al, Ti-6Al-2Mo and Ti-6Al-3Nb (15.4 J, 16.1 J and 15.0 J, respectively). However, the higher crack propagation energy of Ti-6Al-2Mo and Ti-6Al-3Nb (46.7 J and 48.3 J, respectively) were about three times higher than that of Ti-6Al (14.4 J), indicating the stronger resistance to crack propagation in Ti-6Al-2Mo and Ti-6Al-3Nb. Post-mortem analysis of impact samples demonstrated that the increased dislocation density and deformation twinning were mainly responsible for the stronger resistance to crack propagation in Ti-6Al-2Mo and Ti-6Al-3Nb. Due to the invisibility of dislocation activation and deformation twinning during the Charpy impact process, a mathematical model has been proposed to evaluate the effects of Al, Mo and Nb elements on dislocation mobility based on the Yu Rui-huang electron theory. Addition of Mo and Nb elements significantly improved the dislocation mobility in Ti-6Al-2Mo and Ti-6Al-3Nb compared to that in Ti-6Al alloy. Therefore, more dislocations were activated in Ti-6Al-2Mo and Ti-6Al-3Nb which supplied the larger plastic deformation under impact loading. A dislocation-based model also has been proposed to interpret the nucleation and propagation of deformation twinning under the impact loading. Dislocation pileup at α/β interfaces provided potential sites for nucleation of deformation twinning in Ti-6Al-2Mo and Ti-6Al-3Nb. Furthermore, deformation twinning facilitated the dislocation motion in α grains with hard orientations. The increased dislocation mobility and deformation twinning were responsible for the stronger crack resistance as well as the higher impact toughness of Ti-6Al-2Mo and Ti-6Al-3Nb alloys.

Herein, sulfur vacancies in magnetic greigite (SVs-Fe3S4) nanosheets were synthesized by a one-step solvothermal method by adjusting the ethylene glycol: water ratio. Electron paramagnetic resonance spectroscopy (EPR) and X-ray photoelectron spectroscopy (XPS) revealed that SV-rich Fe3S4 and SV-poor Fe3S4 were acquired using 100% ethylene glycol and 100% water as solvent, respectively. A peroxidase-like activity assay demonstrated that maximum reaction rates for H2O2-mediated oxidation of 3,3',5,5'-tetramethyl-benzidine (TMB) catalyzed by the SV-rich Fe3S4 was 2.3 times higher than SV-poor Fe3S4. Density functional theory (DFT) calculations and reactive oxygen species (ROS) detection confirmed that the enhanced peroxidase-like activity by SV-rich Fe3S4 was attributed to efficient adsorption of H2O2 and subsequent decomposition to hydroxyl radicals (•OH) on the SVs sites of Fe3S4. The SV-rich Fe3S4 nanozyme was employed to develop a simple, highly sensitive and selective assay for glucose detection with a linear range of 0.5-150μM and a detection limit of 0.1μM(S/N=3). A smartphone application (App) was designed and applied to efficiently detect serum glucose with the integrated analytical system based on the SV-rich Fe3S4. These new findings highlight the important role of surface defects in nanozymes on generating peroxidase-like activity for glucose detection in point-of-care diagnosis.

Laser shock peening (LSP) is a novel surface treatment technique for strengthening metal materials. The microstructural response of lamellar Ti834 alloy was investigated after treated by LSP. Micro-hardness of LSPed specimens on the surface and along the depth direction was measured. Microstructural features of plastic deformation layer induced by LSP were identified by transmission electron microscopy (TEM). Experimental results showed that the surface micro-hardness of Ti834 alloy increases gradually with increasing impact times and the peak of the micro-hardness appear in the subsurface layer of the specimen. The depth of the strengthening layer was 200 μm and 500 μm for the one and two impacted specimens, respectively. The compressive residual stress along the depth of the specimen increases with increasing of impact times, and the maximum compressive residual stress at the depth of 100 μm from the surface of the specimen after two times impact. The microstructural evolution of Ti834 alloy with lamellar structure includes the formation of sub-grain and dislocation cell, twin–matrix (T-M) lamellae divided by the parallel MTs, MT-MT intersecting at an angle with the α-plates, the crossed arrangement of dislocation arrays (DAs-DAs) and the segmentation of DWs/DTs in the transverse direction.