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In this study, a typical MXene material, Ti3C2, was selected as a co-catalyst and then integrated with ZnO via a facile hydrothermal strategy. The phase composition, morphology, and photophysical properties of as-prepared samples were investigated by XRD, field emission SEM, ultraviolet–visible spectrophotometer, and fluorescence spectrophotometer, respectively. In addition, the results of the photocatalysis experiment showed that the photocatalytic activity of ZnO can be improved significantly through the hybridisation with Ti3C2, which arises from the inhibition of the photogenerated carriers recombination. Furthermore, the theoretical analysis indicated that the high-quantum efficiency arises from the appropriate Fermi level position of Ti3C2. This work demonstrated that Ti3C2 will show great potential for constructing novel and efficient photocatalysts.

The recrystallization and precipitation behaviors of an Al-4.5Cu-1.5 Mg alloy refined by Ti-supported TiC nanoparticles (NPs) (TiC/Ti refiner) were investigated in detail, and the strengthening mechanism was discussed. The results indicated that the addition of TiC/Ti refiner promoted recrystallization of the Al-Cu-Mg alloy and decreased the average grain size to 76 μm. In the aging process, a portion of the dispersed TiC NPs acted as the substrate for S′ to precipitate from the matrix along Al direction, because of the satisfactory matching relationship between the S′ (021)//Al (001)//TiC (001) planes. At the same time, the addition of TiC NPs decreased the precipitate-free zones and refined the grain boundary precipitates in the alloy. The NPs also promoted the precipitation of GPB zones and S′ phases, which reduced the cracking tendency, inhibited the dislocation motion and increased the comprehensive performance of the alloy. As a result, the yield strength, tensile strength and elongation of the TiC/Ti-refined Al-4.5Cu-1.5 Mg alloy reached 287 MPa, 421 MPa and 25.5%, indicating an increase of 22.6%, 14.7% and 109.1%, respectively, compared to the unrefined alloy.

The precipitation hardening characteristics, aging precipitation behaviors, mechanical properties and electrical conductivity of the Al-Zn-Mg-Cu alloy refined with TiN nanoparticles (well supported by Ti microparticles) are investigated, in detail. The results show that, compared with the alloy with only Ti or without any refiner, the TiN nanoparticle addition improves the solution of the alloying elements, retains the fine grains of the Al-Zn-Mg-Cu alloy during the solid solution process and enhances the Vickers hardness of the solution treated alloy. More importantly, during the aging process, the TiN nanoparticle addition promotes the diffusely uniform precipitation of the G.P. zones, η′ phase and η phase, and accelerates the evolution to the G.P. zones from the supersaturated solid solution in the matrix, but inhibits the precipitations of η′ phase and η phase. The yield stress (569.8 MPa), ultimate tensile stress (595.5 MPa) and elongation (18.1%) of the alloy refined with TiN are higher than those with only Ti or without any refiner. In addition, the electrical conductivities of the aged alloy with TiN are lower than those of the alloy with only Ti or without any refiner.

A novel grain refiner consisting of TiC nanoparticles (NPs) supported by Ti powders (abbr. TiC/Ti refiner) was prepared by high-energy milling. The addition of 0.5 wt% TiC/Ti refiner converted the structure of pure Al from coarse dendrites to fine equiaxed grains with the average grain size of 114.7 μm, and it also increased the nucleation temperature of α(Al) from 656.7 to 664.4 °C. When TiC/Ti refiner was introduced into Al melt, the heat released from the Al–Ti reaction promoted the uniform dispersion of TiC NPs. The dissolution of the reaction product TiAl3 released Ti atoms into the melt and thus formed a “Ti-rich transition region” around TiC NPs. The dispersive TiC NPs could act as the heterogeneous nuclei for α(Al) and the “Ti-rich transition region” further improved the lattice orientation relationship between Al ( $$\bar{1}1\bar{1}$$ ) and TiC ( $$11\bar{1}$$ ) planes, which eventually resulted in the refining of α(Al).

An Al–Zn–Mg–Cu–Ta alloy was successfully fabricated by laser powder bed fusion (LPBF). The effect of the added Ta on the microstructures (cracks, grain sizes, and phase constitutions), mechanical properties (tensile strength and elongation), aging behavior, and corrosion resistances (full immersion and electrochemical corrosion performances) of the LPBF-fabricated Al–Zn–Mg–Cu alloy were investigated. The results exhibited that, Ta restrained hot tearing, refined microstructures, enhanced the tensile strength and ductility, accelerated the aging processing, and improved the corrosion resistance of the LPBF-fabricated Al–Zn–Mg–Cu alloy, significantly. The reason was that Ta not only reacted with Al to form in-situ Al3Ta to refine α(Al), but also dissolved in the second phases to inhibit their coarsening.

2 wt%TiN nanoparticles reinforced ultra-fined grain Al2024 composite (Al2024-2TiN) and ultra-fined grain Al2024 alloy were prepared by high-energy ball milling, spark plasma sintering (SPS), and hot compression deformation. The effect of TiN nanoparticles on aging behavior and mechanical properties of Al2024-2TiN composite was investigated. The results show that, with the introduction of TiN nanoparticles, the tensile strength of as-aged Al2024-2TiN composite increased from 568 MPa of Al2024 alloy to 783 MPa, while the yield strength and elongation decreased from 376.5 MPa and 12.7% to 359.1 MPa and 9.4%, respectively. The average grain size of as-aged Al2024-2TiN composite was 452.4 nm, smaller than 3.2 μm of Al2024 alloy. TiN nanoparticles reduced the dissolution of the second phases during solution treatment, and decreased the number of age precipitating phases which resulted in the yield strength of Al2024-2TiN composite being lower than that of Al2024 alloy. Nevertheless, TiN nanoparticles promoted the aging kinetics of Al2024-2TiN composite. The peak aging time of 6 h for Al2024-2TiN composite was 2 h earlier than that of Al2024 alloy. The thermal diffusion activation energies of phase S′ precipitated in Al2024-2TiN composite and Al2024 alloy were 78.98 kJ/mol and 82.06 kJ/mol, respectively. Phase S′ precipitation in Al2024-TiN composite became easier.

Ultra-fine grained (UFG) Al2024-TiN nanocomposite was fabricated by high energy milling (HEM) and spark plasma sintering (SPS). The effect of TiN content (1, 2, 3 and 4 wt.%) on the morphology and microstructure of as-milled powders was investigated, as well as on the microstructure and properties of as-SPSed samples. Results show that TiN can accelerate the milling process, solution of Cu atoms and deformation of Al 2 Cu during milling. Besides, Al grain size of as-milled powders was refined from ∼87 nm to 30–50 nm after TiN was added, staying steady when TiN exceeded 2 wt.%. Moreover, Al2024-2TiN nanocomposite behaved superior comprehensive properties, showing yield and ultimate strength of ∼730 MPa and ∼871 MPa, respectively, which were 185% and 35% higher than those without TiN, and still possessing ∼10% engineering strain. The Al grain sizes of as-SPSed Al2024 and Al2024-2TiN samples were 576.5 nm and 145.4 nm, respectively, exhibiting 6.6 times and 4 times those of their corresponding milled powders. It is suggested that TiN nanoparticles are helpful to refine Al grains during milling and restrain grain growth during sintering. The high strength of Al2024-TiN nanocomposite was mainly attributed to ultra-fine grains, Orowan strengthening and dislocation strengthening due to TiN nanoparticles.

A composite TiN/Ti grain refiner for aluminum and its alloys was prepared through a mixture of micro sized metal powder Ti and nanosized ceramic particles TiN by high energy ball milling. Refinement performance of the TiN/Ti refiner in pure aluminum has been examined in detail by OM, FSEM, EBSD, DSC and TEM methods. Experimental findings indicate that, after adding 0.5 wt% TiN/Ti, the solidification structure of pure aluminum can be refined and the preponderant grain size is reduced to 79.8 μm from more than 1000 μm. TiN/Ti significantly refines the aluminum grain size through not only that it makes undercooling be not measured and increase the nucleation temperature from 671 °C to 681 °C, but also the introduction of potent nuclei. Furthermore, nano TiN particles can act as the nucleus of heterogeneous nucleation of α(Al), the α(Al) grows along the {111} crystal plane from {200} surface of TiN, “Ti-rich transition region” surrounding TiN particles and the heat of reaction between Al and Ti enhances the wettability of TiN in the melt.

In this study, Al, Zn, Mg and Cu elemental metal powders were chosen as the raw powders. The nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was prepared by mechanical alloying and spark plasma sintering. The effect of milling time on the morphology and crystal structure was investigated, as well as the microstructure and mechanical properties of the sintered samples. The results show that Zn, Mg and Cu alloy elements gradually dissolved in &alpha, Al with the extension of ball milling time. The morphology of the ball-milled Al powder exhibited flaking, crushing and welding. When the ball milling time was 30 h, the powder particle size was 2&ndash, 5 &mu, m. The &alpha, Al grain size was 23.2 nm. The lattice distortion was 0.156% causing by the solid solution of the metal atoms. The grain size of ball-milled powder grew during the spark plasma sintering process. The grain size of &alpha, Al increased from 23.2 nm in the powder to 53.5 nm in the sintered sample during the sintering process after 30 h of ball milling. At the same time, the bulk alloy precipitated micron-sized Al2Cu and nano-sized MgZn2 in the &alpha, Al crystal. With the extension of ball milling time, the compression strength, yield strength and Vickers hardness of spark plasma sintering (SPS) samples increased, while the engineering strain decreased. The compression strength, engineering strain and Vickers hardness of sintered samples prepared by 30 h milled powder were ~908 MPa, ~8.1% and ~235 HV, respectively. The high strength of the nanocrystalline Al-7Zn-2.5Mg-2.5Cu bulk alloy was attributed to fine-grained strengthening, dislocation strengthening and Orowan strengthening due to the precipitated second phase particles.

A novel grain refiner consisting of nanoparticulate TiN suspended in a Ti metal powder (abbr. TiN/Ti refiner) was prepared by high energy ball milling. The effect of the TiN/Ti refiner addition contents on microstructures and properties of Al-Zn-Mg-Cu alloy was investigated in detail. The results show that the TiN/Ti refiner addition changes the α(Al) matrix morphology of the modified Al-Zn-Mg-Cu alloy from dendrite to equiaxed crystaline. With increasing TiN/Ti refiner addition contents from 0 wt.% to 0.5 wt.%, the average grain size of Al-Zn-Mg-Cu alloy decreases sharply from 400 μm to 78.5 μm. The SEM, EDS, XRD, and DSC results demonstrate that secondary phases of the modified Al-Zn-Mg-Cu alloy contain three kinds of intermetallic phases: σ[Mg(Zn, Cu, Al)2], θ(Al2Cu) and iron containing intermetallic of Al7Cu2Fe. With refined α(Al) grains, secondary phases are dispersed, refined and distributed uniformly. With increasing TiN/Ti addition contents from 0 wt.% to 0.5 wt.%, the yield strength, tensile strength and Vickers hardness of the modified Al-Zn-Mg-Cu alloys enhance from 36.6 MPa to 74.6 MPa, from 175 MPa to 235 MPa and from 118 HV to 152.5 HV, respectively. In addition, the yield strength σy, tensile strength σb and Vickers hardness Hv of the modified Al-Zn-Mg-Cu alloys show Hall-Peteh dependences on the grain size D. A typical interdendritic fracture is observed on the tensile fracture surface of the as-cast Al-Zn-Mg-Cu alloy. Grain boundary and secondary phase regions act as an easy path for crack propagation.

TiO2-loaded Ti3C2 with small interlayer spacing [TiO2/Ti3C2(SIS)] was successfully synthesized through hydrothermal treatment and subsequent calcination under argon atmosphere. The phase composition, morphology and photophysical properties of Ti3C2, TiO2 and TiO2/Ti3C2(SIS) were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FSEM), transmission electron microscopy (TEM), UV–Vis spectrophotometry and fluorescence spectrophotometer, respectively. Furthermore, the photocatalytic activities of Ti3C2, TiO2 and TiO2/Ti3C2(SIS) were measured through monitoring photodegradation of methylene blue (MB) under ultraviolet (UV) light irradiation. The results showed that TiO2/Ti3C2(SIS) had an interfacial heterojunction between TiO2 and Ti3C2 with small interlayer spacing, leading to obviously improved optical absorbability and light quantum efficiency. Furthermore, the results of photocatalytic experiment indicated that TiO2/Ti3C2(SIS) exhibited significantly improved photocataytic activity compared with Ti3C2 and TiO2.

The effects of Cr content and annealing temperature on abrasive wear characteristics of cast ausferrite nodular iron were investigated with Suga type abrasive wear tester. The surface morphology and Vickers hardness of the tested samples were analyzed by scanning electron microscopy (SEM), digital microscope and Vickers hardness tester. The results show that the cast ausferrite nodular iron could be obtained by alloying with Cr in the as-cast ductile cast iron and permanent mold casting, and the bainite content in the matrix increased with increasing Cr content. However, the decomposition of bainite took place during annealing at 500 °C to 800 °C; especially, at 800 °C, the bainite transformed into a mixture of fine lamellar pearlite and ferrite matrix structure. The wear loss of specimens was reduced with increasing Cr content in the cast ausferrite nodular iron. The wear loss of the sample cast ausferrite nodular iron with 0.4mass% Cr is the least. The wear loss began to increase while the Cr content is 0.6mass%. The wear loss of annealed ductile irons at different annealing temperatures was higher than that of as-cast samples. During the abrasive wear, the shear stress transformed austenite to martensite, and the hardness of specimens increased and the wear resistance of as-cast ductile cast iron was improved.

Micro arc oxidation method was utilized to prepare molybdenum doped TiO2 films through adding sodium molybdate into the electrolyte for the first time. The effect of sodium molybdate concentration on the morphology, crystal structure and photophysical properties of the films was investigated by field emission scanning electron microscopy, X-ray diffraction and UV–vis spectrophotometry. The results showed that with increasing of sodium molybdate concentration, the pores of films decreased in size and increased in number, more anatase phase transformed to rutile phase in the films and inter-plane spacing of the films increased. Furthermore, the absorption edges of the films shifted towards longer wavelength and the band gap energies of the films decreased with increasing the concentration of sodium molybdate. In addition, the photocatalytic degradation of methylene blue showed that the photocatalytic activity of the molybdenum doped TiO2 film was about 2.3 times that of pure TiO2 film.

The effect of hydrogen on the interfacial reaction between Ti–47Al alloy melt and graphite mold was studied by plasma-arc melting in hydrogen atmosphere. Especially, reduction of recarburization which is harmful to the mechanical properties of TiAl alloys has been investigated. The carbon concentration in the interface of Ti–47Al alloy, as well as the corresponding reaction distance decreases rapidly with increasing hydrogen partial pressure. Activated hydrogen atoms dissociated in high-temperature arc probably take part in the interfacial reactions, represented by [ C ] + 4 [ H ] = CH 4 .

An efficient photocatalytic ozonation system that is sensitive to visible light was designed and fabricated over Cu(II)-grafted TiO2. The results show that oxalic acid was degraded efficiently in this system under visible light. This high efficiency was attributed to the synergetic effect of photocatalysis and ozonation, which facilitated the generation of holes on TiO2 and hydroxyl radicals. Moreover, Cu(II)-grafted TiO2 proved to be very stable in the reaction without any deactivation and the Cu ions would not leach from TiO2 to aqueous solution. Therefore, this photocatalytic ozonation system is promising to purify wastewater with refractory pollutants under visible light.

W–Ni alloy parts were produced with selective laser melting (SLM) and the influence of the Ni content on the microstructure evolution and microhardness was investigated methodically. The resultant microstructure of the SLM specimens with a Ni content of 10 wt.%, 20 wt.% and 40 wt.% exhibited bar-shaped structures, dendrites and honeycomb structures respectively. It was found that a higher Ni content decreased the melt viscosity and increased the densities of W–Ni parts. The microhardness decreased on the other hand with increasing Ni content. The microstructure formed in the SLM process was characterized by a mixture of typical liquid phase sintering (LPS) microstructure and W dendritic structure. This revealed that the forming mechanism of the SLM process on W–Ni particles was a combination of LPS and partial melting of W particles. The microstructure showed that SLM process improved the bonding ability of the powder particles and therefore enhancing the mechanical properties.

The layer produced by Plasma electrolytic oxidation technique was used as seed layer for hydrothermal synthesis of large-area TiO2 nanotube film in this paper. The effects of hydrothermal parameters on the surface morphologies of films were investigated by field emission scanning electron microscopy (FSEM). The results showed that the surface morphologies of films can be easily changed by varying the NaOH concentration, reaction temperature and reaction time. In addition, the effect of calcination temperature on the morphologies, crystal structure, photophysical properties and photocatalytic activity of the nanotube films were also studied using field emission scanning electron microscopy (FSEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis spectrophotometry and Fluorescence spectrophotometry. Calcination resulted in crystallization of the nanotubes from amorphous state to single-crystalline anatase phase. Furthermore, the increase of calcination temperature was beneficial to the improvement of crystallization degree. However, the nanotubes completely collapsed to form short nanorods when the calcination temperature increased to 700 °C. The TiO2 nanotube film calcined at 600 °C exhibited the narrowest band gap energy, the strongest UV light absorption, the weakest band–band PL intensity and the best photocatalytic activity.

SnO2 films were prepared by plasma electrolytic oxidation technology in solution containing different concentrations. The structure and photocatalytic activity of the films were characterised by X-ray diffraction, SEM, EDX, Brunauer–Emmett–Teller (BET) and UV-vis spectrophotometer. The result shows that films consisted of pure SnO2, but the grain size increased with the increase of concentration. Porous and rough SnO2 films were formed on the substrate. The BET surface area increased with the increase of concentration and reached its maximum when the concentration of was 0·05M. The absorption edge of the films shifted from 370 to 408 nm when the concentration of increased from 0·01 to 0·03M. Degradation of rhodamine indicated that photocatalytic activity of film formed in 0·03M was highest due to its smaller grain, larger BET surface area and greater photon absorption.

In this study, hot compression tests of ultra-fine grained Al2024 alloy and Al2024-TiN nanocomposite were performed at 350–500 °C temperature and 0.01–10 s−1 strain rate on a Gleeble-3500 thermal mechanical simulator. The results show that stress increases as strain rate increases and temperature decreases in both materials. The strengthening effect of TiN appeared to be weaker than the softening effect of ultra-fine grains during hot deformation. Al2024-TiN presented lower stable flow stress than Al2024 under the same deformation conditions. Constitutive equations and processing maps were established based on the flow stress curves. The deformation activation energies of Al2024 and Al2024-TiN were determined to be 239.260 and 749.386 kJ•mol−1, respectively. The optimum deformation area of the Al2024-TiN nanocomposite has a lower temperature and higher strain rate than that of the Al2024 alloy. Microstructural analysis revealed that TiN nanoparticles restrain grain growth and promote dynamic recrystallization during hot deformation. The deformation mechanism of Al2024-TiN was found to be grain boundary sliding accompanied with dynamic recrystallization, dynamic recovery, and grain growth, that of Al2024 is intra-granular sliding accompanied with dynamic recovery and grain growth. This work may provide a workable set of guidelines to optimize the hot deformation process of ultra-fine grained Al2024-TiN nanocomposites and other similar materials.

The micro-arc oxidation process parameters of AZ91D Mg alloy and Na2WO4 concentration were optimized by orthogonal experiment. SEM, EDX, XRD, potentiodynmic polarization and immersion corrosion test were carried out to investigate the morphologies, phase composition and corrosion resistance of the MAO coatings. The results shown that the MAO coating are mainly composed of MgOMg2SiO4MgAl2O4,MgWO4 and a small amount of amorphous material as well as with a double layer structure, outer loose and inner denser, the proper parameters and additive concentration were: 300Hz,5.0A/dm2,50%/50% and 2.0g/l Na2WO4. The MAO coatings coated under the proper condition on AZ91D Mg alloy motorcycle parts provided the far batter corrosion resistance than the substrate, suggesting that MAO coatings can effectively protect the motorcycle parts against the erosion from corrosion medium. Meanwhile, it also found that the irregular part shape has some influence on the coatings formation as well as corrosion resistance.

The mechanism and kinetics of synergetic effect in TiO2/O3/UV process on H-acid degradation were investigated. The experimental results showed that H-acid removal rate of TiO2/O3/UV process was the highest among TiO2/UV, O3/UV and TiO2/O3/UV processes. The investigation of reactions with suitable active species scavengers confirmed that H-acid was mainly oxidised by ozone and holes on TiO2 in the TiO2/O3/UV process. The recombination between holes and electrons in TiO2 reduced in the presence of ozone, as indicated by fluorescence emission spectra. Moreover, the intermediates generated during H-acid oxidation in various processes were analysed by LC/MSD trap. It is proposed that H-acid was oxidised to polyhydroxy aromatics, benzene carboxylic acids and quinoids in the first step. Then, saturated aliphatics carboxylic acids were formed and mineralised to inorganic compounds through the Photo-Kolbe reaction. Finally, a kinetic study on TiO2/UV, O3/UV and TiO2/O3/UV processes was conducted and it was confirmed that both ozonation and photocatalytic activity were improved in TiO2/O3/UV process because of the synergetic effect.

ZrO2/TiO2 composite photocatalytic film was produced on the pure titanium substrate using in-situ Zr(OH)4 colloidal particle by the micro-arc oxidation technique and characterized by scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and ultraviolet-visible (UV-Vis) spectrophotometer. The composite film shows a lamellar and porous structure which consists of anatase, rutile and ZrO2 phases. The optical absorption edge of film is shifted to longer wavelength when ZrO2 is introduced to TiO2. Furthermore, the photocatalytic reaction rate constants of degradation of rhodamine B solution with ZrO2/TiO2 composite film and pure TiO2 film under ultraviolet irradiation are measured as 0.0442 and 0.0186 h−1, respectively.

Amorphous oxide film was prepared on the titanium substrate by plasma electrolytic oxidation (PEO) technology in acidic electrolyte consisting of tungstate and then subject to calcination in air. Films were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and UV-Vis DRS before and after calcination, respectively. Calcined film consisted of anatase and WO3, showing more open structure compared with uncalcined film. Furthermore, the absorption edge of calcined film was shifted to visible light region and the recombination of photo-induced carriers was inhibited effectively, resulting that WO3/TiO2 composite film produced by PEO technology and calcination should be effective as a visible-light-responsive photocatalyst.

As cast AZ91D and AZ91D+1·0 wt-%Y magnesium alloy were prepared by the lost foam casting process and then treated by solution and aging treatment. The effects of Y on the microstructure and mechanical properties of heat treated AZ91D magnesium alloy were investigated. The results show that the addition of Y to AZ91D alloy formed the Al2Y phase, which still existed after solution treatment. During the aging treatment process, the rate of β-Mg17Al12 phase precipitating in AZ91D+1·0 wt-%Y alloy was much slower than in AZ91D alloy because the formation of Al2Y phase led to the depletion of Al atoms. The addition of Y was thus claimed to play a key role in delaying the age hardening peak on AZ91D alloy.

W–Ni–Cu alloy (90 wt% W, 7.5 wt% Ni, and 2.5 wt% Cu) parts were successfully fabricated via selective laser melting method. Phases, microstructure, compositions, and laser forming parameters of laser melted samples were investigated. It was found that the W–Ni–Cu powder system was based on the mechanism of liquid solidification. This process was realized through full melting of W, Ni, and Cu particles under high laser energy input. However, using relatively lower energy input, particle bonding was realized through liquid phase sintering with complete melting of Ni–Cu acting as binder and nonmelting of W acting as structure. Due to the Ni–Cu solid solution phase that appeared in a wide range from 1,084 to 1,455 °C, a coherent matrix interface can be observed after solidification. The microhardness of laser-fabricated specimens varied with different powder layer thicknesses, resulting from the laser-treated condition and ability of trapped air in the loose powder bed to escape. The metallurgical mechanisms were also addressed.

V2O5/TiO2 composite films were prepared on pure titanium substrates via micro-arc oxidation (MAO) in electrolytes consisting of NaVO3. Their morphology and elements were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. Phase composition and valence states of species in the films were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS) were also employed to evaluate the photophysical property of the films. The V2O5/TiO2 composite films show a sheet-like morphology. Not only V2O5 phase appears in the films when the NaVO3 concentration of the electrolyte is higher than 6.10 g/L and is loaded at the surface of anatase, but also V4+ is incorporated into the crystal lattice of anatase. In comparison with pure TiO2 films the V2O5/TiO2 composite films exhibit significantly narrow band gap energy. The film prepared in an electrolyte consisting of NaVO3 with a concentration of 8.54 g/L exhibits the narrowest band gap energy, which is approximately 1.89 eV. The V2O5/TiO2 composite films also have the significantly enhanced visible light photocatalytic activity. The film prepared in an electrolyte consisting of NaVO3 with a concentration of 8.54 g/L exhibits the best photocatalytic activity and about 93% of rhodamine is degraded after 14 h visible light radiation.

Plasma electrolytic oxidation (PEO) ceramic coatings were prepared on 6061 aluminum alloy substrate in silicate based electrolyte with and without Na2WO4additive with different pulse frequency. The composition, surface morphology and corrosion resistance of PEO coatings were investigated by means of SEM, XRD, potentiodynamic polarization and EIS measurement in a 3.5% NaCl solution. These results show that Na2WO4can contributing to the transition from the metastable γ-Al2O3to a better thermal stability α-Al2O3, while has certain inhibitory effect on the deposition of SiO32-anion on the surface during the plasma discharge process. After adding Na2WO4in the electrolyte, the surface layer of PEO coatings are more smoother and less distinctly discharge holes appear which leads to the PEO coatings have better corrosion resistance than those of samples coated in the electrolyte without Na2WO4additive.

A composite ceramic coating containing Y 2 O 3 –ZrO 2 –MgO (YSZ–MgO) was prepared on AZ91D magnesium alloy, which was immersed in Y(NO 3 ) 3 aqueous solution as pretreatment, by micro-arc oxidation (MAO) process. The morphology, elemental and phase compositions, corrosion behavior and thermal stability of the coatings were studied by SEM, EDX, XRD, electrochemical corrosion test, high temperature oxidation and thermal shock test. The results show that the coating mainly consists of ZrO 2 , Y 2 O 3 , MgO, Mg 2 SiO 4 , and MgF 2 . Among these compounds, Y 2 O 3 accounts for 26.7% of (Y 2 O 3 + ZrO 2 ). The thickness of YSZ–MgO coating is smaller than that of ZrO 2 –MgO coating, but its compactness and surface roughness are better than those of ZrO 2 –MgO coating. YSZ–MgO coating has a good corrosion resistance, and its corrosion rate in 5% NaCl aqueous solution is lower than that of ZrO 2 –MgO and only about 8.5% of that of AZ91D magnesium alloy. After oxidation at 410 °C, the mass gain of AZ91D magnesium alloy presents a linear increase with the oxidation time. The YSZ–MgO coating and ZrO 2 –MgO coating can remarkably decrease the oxidation mass gain. The oxidation mass gain of YSZ–MgO coating is lower than that of ZrO 2 –MgO coating, especially during a long oxidation period. The thermal shock resistance of YSZ–MgO coating is superior to ZrO 2 –MgO coating.

WO 3 /TiO 2 composite films were prepared by plasma electrolytic oxidation in electrolytes containing different tungstate concentration. The morphology, topography, compositions, crystal structure and photophysical properties of films were characterized by SEM, AFM, EDX, XRD, XPS, UV–vis DRS and PL, the surface acidity of films was investigated by ATR-IR. The results showed porous films formed on the titanium substrate, consisted of Ti, O and W, and presented mixed crystal of anatase and rutile. Tungsten species were well-dispersed for WO 3 /TiO 2 film formed in lower tungstate concentration, but were in crystalline WO 3 in higher concentration. For WO 3 /TiO 2 film prepared in optimal tungstate concentration, the highest content of anatase and the maximum surface acidity were obtained, and the recombination of holes and electrons was effectively inhibited. However, coupled-WO 3 did not shift the optical absorption to the visible region. The improvement of photocatalytic activity was attributed to the increased surface acidity, better separation between photo-induced carriers and higher content of anatase.

A ZrO2-Y2O3-containing composite ceramic coating was firstly in situ prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in an alkaline silicate-containing electrolyte. The morphology, chemical composition and corrosion resistance of the PEO coating were investigated by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive X-ray (EDX) spectrometer, dropping corrosion and electrochemical corrosion test. The results showed that the ceramic coating consisted of two distinct structural layers: an outer loose layer and an inner dense layer; it was composed of t-ZrO2, Y2O3, SiO2and some magnesium compounds, such as MgO,MgF2and Mg2SiO4. In addition, the ceramic coating also showed excellent dropping and electrochemical corrosion resistance, which was mainly attributed to its special phase composition and microstructure.

A new kind of V–Ti–N high strength microalloyed medium carbon steel has been developed, which is used for fracture splitting connecting rod. In this article, the characteristics of this carbon steel and its production process were studied. The microstructure, precipitated phases and their effects on mechanical properties were investigated by optical microscope, SEM, and TEM. The results showed that the steel was constituted of ferrite and pearlite. By reducing the finish rolling temperature and accelerating the cooling rate after rolling, microstructure with fine grain ferrite and narrow lamellar space pearlite could be obtained in V–Ti–N microalloyed medium carbon, and a large number of precipitated phases distributed over ferrite. These led the tensile strength to be more than 1000 MPa, yield strength (YS) more than 750 MPa. The impact fractograph showed typically brittle fracture characteristic.

The fracture splitting method is being increasingly used for manufacturing connecting rods that are made of the powder forging material, high-carbon steel, etc., which are comparatively easy to fracture, in order to improve the accuracy and productivity. In this paper, a microalloyed high carbon steel used for fracture splitting connecting rod is developed by the process “EAF-EBT-LF-CC-CR”. The steel microstructure, nonmetallic inclusions, precipitated phases, mechanical property and fracture surfaces are investigated by microscope, SEM and TEM. The results show that the steel is constituted of pearlite and a small mount of ferrite, the nonmetallic inclusions in the steel include MnS, Al-rich (taken to be Al2O3) and Al-Ca-rich (taken to be CaO-Al2O3) particles. The precipitations mainly are VC, VN, (Mn, Cu)S, etc. these precipitations are beneficial to fine the pearlite group, short lamellar spacing of pearlite and improve the strengthening of the microalloyed high carbon steel. The tensile tests indicate that the microalloyed high carbon steel has high yield strength, ultimate tensile strength (UTS), but low elongation and contraction of area. It is required for heavier loads, higher performance of automobile engine and less distortion on fracture splitting. The fracture surface of connecting rod shows distinct brittle fracture character and it is beneficial to improve fracture splitting performance.

W-Ni-Fe alloys are important materials for many practical applications; however, at present, they are usually fabricated by conventional powder metallurgy techniques, which is difficult in fabrication with complex shapes. In this work, a selective laser melting (SLM) processing method was developed for fabricating W-Ni-Fe alloys parts. A process map was obtained for selection of proper laser parameters by optimizing processing conditions. Microstructures of laser fabricated samples in different laser energy inputs were investigated. There are two coexisting forming mechanisms in the SLM process: (i) liquid phase sintering (LPS) with full melting of Ni and Fe powders but non-melting of W powders and (ii) melting/solidification with full melting of W powders. Moreover, with increasing laser energy, a transition trend of forming mechanism from LPS to full melting/solidification can be observed.

Using W, Ni, and Fe powders as raw materials, selective laser melting (SLM) technology was considered for fabrication of 90W–7Ni–3Fe parts in one step. The investigation into simulation of temperature field of SLM W–Ni–Fe powder system was highlighted. Effects of processing parameters of scan velocity, laser power, scan interval, and preheating process on temperature field distribution were studied through establishing a 3D model based on finite element analysis theory. The simulation results show that a lower thickness, narrower scan interval, and a slower scan velocity tend to improve the temperature in powder bed. Moreover, the parameter range in which the maximum temperature in powder bed could reach up to the melting point of W (about 3,420°C) was obtained. Experiments on different processing parameters were carried out, and a good agreement with the simulation results could be found.

Shrinkage tends to generate when loose metal powder melted in each processing layer along the direction of layer growing during selective laser melting process, resulting in an increased real layer thickness. The shrinkage model for layer shrinkage in SLM process is established. The variation of real layer thickness and the relevant mathematical explanations are discussed in this paper. The results show that the total shrinkage of metal powder layer sharply increases in the initial layers, and then reaches to a plateau value with the increased processing layers. This value is defined by the ratio of sliced layer thickness (h) to relative density (k) during selective laser melting process.

WO3/TiO2 composite film was prepared by microarc oxidation technique and characterized by SEM, XRD, UV-vis spectra and Zeta-potential. The photocatalytic activity of WO3/TiO2 composite film was evaluated by examining the degradation of methyl orange. The influence of solution pH and inorganic anions on removal ratio of methyl orange was investigated. Removal ratio of methyl orange decreased with an increase of pH value in acidic solution, while it increased with the pH value in alkaline solution. The influence of added anions on the removal ratio is divided into two aspects. Addition of Cl− and SO42− resulted in a decrease in photocatalytic removal ratio of methyl orange, while it was facilitated by PO43−, HCO3− and NO3−.

TiO2 films were prepared on pure titanium substrate via micro-arc oxidation (MAO) technique in tungstate-electrolyte. The influence of fluorine ion concentration in electrolyte on the microstructure and photocatalytic activity of TiO2 films was investigated. The results showed that the porosity, element content and phase composition of TiO2 films were affected by fluorine ion concentration in electrolyte. The number of pores, the content of tungsten and the content of anatase phase all increased when appropriate fluorine ion was added into the electrolyte. Thus, the photocatalytic activity of TiO2 films could be promoted by adding appropriate fluorine ion into the electrolyte. The addition of fluorine ion did not alter the iso-electric points of TiO2 films. It was confirmed by UV–Vis spectrophotometer that the photocatalytic activity of the film prepared in electrolyte containing 2 g/L NaF was higher than that of the films prepared in other electrolytes during the degradation of methyl orange.

ZrO 2 -containing ceramic coatings were prepared on AZ91D magnesium alloy by plasma electrolytic oxidation (PEO) technique in three different zirconate electrolytes. The morphology and phase composition of the ceramic coatings were characterized by environmental scanning electron microscopy (ESEM) and X-ray diffractometer (XRD). The corrosion properties of the coatings were examined by immersion test and electrochemical corrosion test in 3.5 wt.% NaCl solution at 20 °C and 60 °C. The results show that the corrosion resistance of the coatings is related to their thickness, microstructure and phase composition. The better results are obtained for the coating formed in K 2 ZrF 6 –Na 2 SiO 3 –KOH electrolyte because it has a uniform surface, a compact inner layer, the maximum thickness and more corrosion resistant phases relative to those formed in Zr(NO 3 ) 4 –KOH and ZrOCl 2 –KOH electrolytes. Compared to the bare AZ91D magnesium alloy, the corrosion resistance of the same coating in the NaCl solution at 60 °C is higher than that in the NaCl solution at 20 °C, which might be attributed to ZrO 2 in the coating being propitious to improve the corrosion resistance of the specimens, especially the relatively high temperature corrosion resistance of those.

Different plasma electrolytic oxidation (PEO) coatings were prepared on AZ91D magnesium alloy in electrolytes containing various concentrations of (NaPO 3 ) 6 . The morphologies, chemical compositions and corrosion resistance of the PEO coatings were characterized by environmental scanning electron microscopy (ESEM), X-ray diffractometer (XRD), energy dispersive analysis of X-rays (EDAX), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) test. The results showed that the PEO coatings were mainly composed of MgO, Mg 2 SiO 4 , MgAl 2 O 4 and amorphous compounds. As the (NaPO 3 ) 6 concentrations increased from 0 to 10 g/l, the thickness and surface roughness of the coatings approximately linearly increased; the MgO and Mg 2 SiO 4 phase increased within the concentration range of 0–3 and 0–5 g/l, and then decreased within the range of 3–10 and 5–10 g/l, respectively, while the MgAl 2 O 4 phase gradually decreased. Moreover, the corrosion resistance of the coatings increased within the range of 0–5 g/l and then decreased within the range of 5–10 g/l. The best corrosion resistance coating was obtained in electrolyte containing 5 g/l (NaPO 3 ) 6 , it had the most compact microstructure. Besides, a reasonable equivalent circuit was established, and the fitting results were consistent with the results of the EIS test.

Spark anodizing (SA) has been developed as a novel technique for corrosion protection by forming a ceramic layer on magnesium alloys, in which the fluoride in the electrolyte recipes plays a key role during coating. In the present work, the SA ceramic layer produced on AZ91D magnesium alloy was characterized by using SEM, TEM and EDS. The results showed that: 1) there was a fluoride enriched zone around 1-2μm in thickness at the coating/substrate interface, which was composed of the amorphous substrate, nanocrystal MgO particles sized in 20-60nm and sealed cavities; 2) the oxygen content in the inner layer was higher than that in the outer layer, while the fluorine content was relative even in both layers, which suggested that the barrier layer was included in this fluoride zone, and that the fluorine may be only a retained marker during the formation of new coating materials.

This paper reports the heat-resistance of plasma electrolytic oxidation (PEO) coatings formed on AZ91D alloy in phosphate electrolytes (P-film) and silicate electrolytes (Si-film). The results showed that the P-film was mainly composed of MgAl2O4, MgO and the Si-film was composed of Mg2SiO4, MgO. Thermoanalysis results verified that all these phases contained in the two type coatings had excellent thermal stability below 800oC. Meanwhile, the total area of heat erosion formed on the surface of samples tended to be increased with the exposure time prolonged in high temperature (410 oC and air atmosphere).

This paper studied the appearance transition of microdischarges, the phase composition and the morphology evolution of the oxide film formed by microarc oxidation on AZ91D magnesium alloy. The appearance of microdischarges population experienced apparent changes in size, spatial density and color, which was related with the changes of the type and quantity of the disintegrated gas bubbles generated at the interface between the electrolyte and substrate. Correspondingly, the diameter of micropores together with net-like fine microcracks increased when a higher voltage was employed. The coating was composed of MgO, MgAl2O4 and there existed a fluoride-enriched zone of about 3–5 μm at the film/substrate interface.

The failure of the trial impeller of slurry pump used in zinc hydrometallurgy process occurred only after a service of about a month, the expected service life was more than 3 months. The failure impeller was subjected to serious corrosive wear. This paper deals with failure analysis of the impeller (mainly including composition analysis of the slurry, corrosive wear surface characteristics by visual inspection and optical microscopes as well as scanning electron microscope (SEM), composition analysis of the impeller material by spectrum analyser and SEM–EDX, microstructure analysis by optical microscopes) and an improved method. Failure analysis revealed that an improper austenite/ferrite ratio of duplex stainless steel (DSS) material resulting from a too high nitrogen content was primarily responsible for the rapid failure of the impeller. In addition, a melting test in a vacuum furnace verified again that nitrogen content had a significant effect on austenite/ferrite ratio of duplex stainless steel, a comparing corrosive wear test revealed further that DSS consisting of equal austenite/ferrite volume showed better corrosive wear resistance.

The effect of aging temperature on erosion-corrosion (E-C) behavior of 17-4PH stainless steels in dilute sulphuric acid slurry containing solid particles was studied by using self-made rotating E-C apparatus. The effect of impact velocity on E-C behavior of 17-4PH steels at different aging temperatures was analyzed. Surface micrographs of the specimens after E-C test were observed by using scanning electron microscope (SEM). The results showed that under the condition of the same solution heat treatment, when aging temperature ranged from 400 °C to 610 °C, the hardness reached the highest value near the temperature 460 °C. The characteristics of E-C for 17-4PH stainless steels at different aging temperatures were as follows: pure erosion (wear) was dominant, corrosion was subordinate and at the same time corrosion promoted erosion. The effect of aging temperature on E-C rate of 17-4PH steels was not significant at low impact velocity, but it was found that E-C resistance of 17-4PH steels aged near 460 °C was the most excellent due to the best precipitation strengthening effect of fine and dispersed ɛ-Cu phase. With a prerequisite of appropriate corrosion resistance, the precipitation hardening could significantly improve the E-C resistance of the materials.