Nitrogen is well known as a beneficial alloying element which entitles stainless steels an enhanced corrosion resistance against chloride attack. The introduction of N into the surface of stainless steel can be achieved by electrochemical nitriding. The role that Nitrogen plays in pitting resistance has long been discussed focusing on the distribution and incorporation form of N as well as the modification to the local corrosive circumstance induced by the N-participated electrode reactions. For electrochemical nitriding, stainless steel surface, as the place on which involved electrode reactions occur, is expected to undergo structural evolution. This, to some extent, would influence the corrosion property of nitrided stainless steel. Detecting the structural evolution occurring in the electrochemical nitriding is of great significance for deciphering the involved electrode reactions and thus optimizing the nitriding parameters. In this work, using atomic force microscopy as well as transmission electron microscopy, we have clarified the concomitant localized reductive dissolution of passive film, anodic dissolution of metal matrix at micro-anodic sites, as well as re-deposition of the dissolved metal cations, which roughens the surface by forming the undulations at surface with undulation amplitude in the range of a few tens of nanometers. Element mapping analysis by Super EDS technique reveals that the re-deposited product is mainly comprised of iron oxide, which indicates iron is dissolved and the resultant iron cations occurs re-deposition.

Thickness modulation is an important way to improve the performance of organic light-emitting diode (OLED) device. In this paper, flexible green OLED devices were constructed by vacuum thermal evaporation, using graphene as the transparent anode and 1,1-bis[4-[N,N-bis(p-tolyl)amino]phenyl]cyclohexane (TAPC) as the hole transport layer. The effects of evaporation speed on the morphology of the TAPC layer and the thickness of TAPC layer on the device performance were studied. First, 60 nm-thick TAPC layers were fabricated by controlling the evaporation speed at 0.05, 0.1 and 0.15 nm·s^-1. It was found that the TAPC film had the lowest surface roughness of ~2.52 nm when the evaporation speed was 0.05 nm·s^-1. Subsequently, TAPC layers with thicknesses of 50, 60, 70 and 80 nm were fabricated at a evaporation speed of 0.05 nm·s^-1 and OLED devices were fabricated while keeping the thickness of other functional layers unchanged. A comparative study showed that the device with 70 nm-thick TAPC layer achieved the highest performance with a maximum brightness of 34350 cd·m^-2 and a maximum external quantum efficiency (EQE) of 21.02%. Meanwhile, the device has excellent flexibility and the CIE chromaticity coordinate is located at (0.3140, 0.6386), which is very close to the chromaticity coordinate of standard green light. This study is significant for promoting the application of flexible graphene-based OLEDs in the fields of display and lighting and for the development of wearable optoelectronic devices.

Due to the suitable degradation rate and good biocompatibility, Zn-alloys have great potential as biomedical degradable materials. However, the low mechanical properties of pure Zn limit its development as a biomedical material. In this paper, the known degradable Zn-Li-Ca-Ag alloy was further alloyed with different amount of Ca and Ag. The microstructure, mechanical properties and corrosion resistance of the prepared Zn-Li-Ca-Ag alloys were characterized by means of optical microscopy (OM), scanning electron microscopy (SEM), universal testing machine and electrochemical tests. The results showed that the microstructure of the Zn-Li-Ca-Ag alloy was composed of dendrites. The Ca addition can improve the strength of the Zn alloy by second-phase strengthening, and the Ag addition has a positive influence on the plasticity of the Zn alloy by refining the size of the dendrites. Ca has stronger influence on the enhancement of the alloy strength rather than Ag, and amoung others, the Zn-0.8Li-0.1Ca-0.2Ag alloy exhibits the highest tensile strength (186 MPa). The co-addition of Ca and Ag can also improve the corrosion resistance of Zn alloy.

Aiming at the demand of high stiffness light metal structure materials, high specific modulus Mg-alloys Mg-8Zn-4Al-0.5Cu-0.5Mn-xLi (x = 0, 3, 5, 7) (%, mass fraction) (namely ZA84-xLi) were designed and prepared, as well as and then optimized. When the Li content in the alloy is 3.14% and 5.37%, the alloy matrix is composed mainly of single-phase α-Mg, while the skeletal-like Mg₃₂(Al, Zn)₄₉ phase is precipitated near grain boundaries, and there is a granular-like Mg₅Al₂Zn₂ phase and Al₂Mn phase inside the grain; when the Li content is 7.57%, the alloy matrix is ​​mainly a dual-phase structure α-Mg + β-Li. After the addition of Li, many eutectic structures are formed near the grain boundaries, which are composed of α-Mg phase and lamellar-like AlLi phase, and with the increase of Li content, the amount of lamellar-like AlLi phase also gradually increases. The yield strength of the alloy increases gradually with the increase of Li content, while the tensile strength remains basically unchanged. The elastic modulus of the alloy increases first and then decreases with the increase of Li content. For the as-cast ZA84-5Li, the elastic modulus can reach 51.89 GPa, which is 7 GPa higher than that of pure Mg, while the mechanical properties of the alloy basically keeps unchanged. Namely, the yield strength, tensile strength and density is 141 MPa, 189 MPa and 1.71 g/cm³ respectively for the cast alloy.

The microstructure and notch tensile fracture morphologies at different stress concentration factors of the low alloy steel 35CrMo for the head cover bolts of the pump turbine of a storage power station were investigated by electron backscatter diffraction microscopy and scanning electron microscopy. The effects of tempering temperature on the relationship between tensile properties, damage mechanism and mechanical properties of 35CrMo steel were studied. The results show that the microstructures of tempered state at 150~200^oC and quenched state are composed of lath martensite. After tempering at 400^oC, the microstructure of tempered troostite is more uniform. The final fracture of the notched specimens is a mixture of ductile and brittle fracture. At the two stress concentration factors (K_t = 3, 5), the notch tensile strength has the same changing trend with the tempering temperature. With the tempering temperature increasing, the notch tensile strength first increases and then decreases. For K_t = 3, the highest tensile strength is 2626 MPa at tempering temperature of 150^oC; when K_t = 5, the highest tensile strength is 2450 MPa at tempering temperature of 200^oC. Notch sensitivity ratio (NSR) is greater than 1, that is, notch strengthening effect occurs after different tempering temperatures, and notch sensitivity tends to decrease with the increase of tempering temperature. With the increase of stress concentration factor, the notch strengthening effect of specimens treated at different tempering temperatures shows an increasing trend first and then a decreasing trend, and the notch strengthening efficiency was the most obvious when tempering at 400^oC. Finally, based on the relationship between hardness and notch tensile strength, a fast prediction method of notch tensile strength was proposed, and the prediction error was less than 8%.

Cold-sprayed coatings Zn (CS-Zn) and Zn15Al alloy (CS-Zn15Al) were prepared on Q235 carbon steel plates via low-pressure cold spraying technique. The corrosion behavior of the coatings in 3.5% NaCl aqueous solution was assessed by means of electrochemical measurement of open circuit potential, electrochemical impedance and potentiodynamic polarization curves, as well as SEM with EDS, XRD. The results indicate that the CS-Zn coating undergoes severe corrosion during immersion, while the CS-Zn15Al coating corrodes at a slower rate and exhibits superior corrosion resistance. XRD results reveal that the dominant corrosion product of CS-Zn is ZnO, which possesses porous structural characteristics that disrupt the compactness of the corrosion product layer. Furthermore, its semiconductor properties decrease the charge transfer resistance, thereby accelerating the process of corrosion. In the contrast, as for CS-Zn15Al, the incorporation of Al facilitates the formation of protective corrosion products, namely Zn₅(OH)₈Cl₂·H₂O and layered double hydroxides Zn₆Al₂(OH)₁₆CO₃·4H₂O. The shielding effect of CS-Zn15Al coating was significantly enhanced by this layer of corrosion products. Furthermore, electrochemical measurements demonstrate that the addition of Al reduces the corrosion potential of the coating, thereby enhancing its cathodic protection ability, and decreases the corrosion current density due to the generation of protective corrosion products. In conclusion, the addition of Al can synergistically enhance the anticorrosion performance and durability of the coating.

The open-circuit potential, electrochemical impedance spectroscopy, potentiodynamic polarization, potentiostats polarization, current-time transient measurements, Mott-Schottky analysis, X-ray photoelectron spectroscopy (XPS), Electron Back-Scattered Diffraction(EBSD)methods were used to investigate the passivation behavior of 316L stainless steel fabricated by laser selective melted (SLM 316L) in 0.05 mol/L H₂SO₄ + 0.2 mol/L NaCl solution. The results were compared with commercial rolled 316L stainless steel (R 316L). The results showed that the nucleation of passivation film follows continuous mechanism for the both stainless steel. However, the SLM 316L stainless steel has smaller grain size and higher grain boundary density than those of R 316L stainless steel. Therefore, the grow rate of passivation film is fast. The SLM 316L stainless steel took place transpassivation dissolution, while R 316L stainless steel took place pitting corrosion. The SLM 316L stainless steel has better corrosion resistance. The main reasons are the SLM 316L stainless steel has much more low angle grain boundaries without ferrite. Moreover, the passivation film of SLM 316L stainless steel has lower carrier density, lower ratio of O^2-/OH^-, lower content of NiO and higher content of Cr₂O₃ compared with R 316L stainless steel.

The tensile properties of Ti-Al-Fe alloy were assessed at 25^oC and -196^oC respectively, aiming to understand the service performance and plastic deformation mechanism of the low-cost Ti-Al-Fe alloy at extreme low temperatures, so that to ensure the service safety of the relevant engineering structures. The microstructure and fracture surface of the alloy were characterized by scanning electron microscope, transmission electron microscope and electron backscatter diffraction technology. The results show that twinning is rarely found in the microstructure of the alloy after plastic deformation at 25^oC, and the plastic deformation mechanism is mainly dislocation slipping. Ti-Al-Fe alloy exhibits better strength and plasticity at 196^oC, with clear twinning induced plastic effect. A large number of twins are produced during plastic deformation, which include{11\stackrel{-}{\mathrm{2}}2} compression twins, {10\stackrel{-}{\mathrm{1}}2} tensile twins, {11\stackrel{-}{\mathrm{2}}4} compression twins. The plastic deformation mechanism may be ascribed to the coexistence of slipping and twinning. At the initial stage of deformation, {11\stackrel{-}{\mathrm{2}}2} twins are mainly found, and the number of {10\stackrel{-}{\mathrm{1}}2} twins increase at the later stage of deformation.