Fe₇₆Si₉B₁₀P₅ amorphous alloys annealed at 773~833 K with heterogeneous microstructure consisting of α-Fe, Fe₂B and Fe₃P phases, were de-alloyed in 0.05 mol/L H₂SO₄ solution. The porous structure was formed due to the preferential dissolution of α-Fe phase in the form of micro-coupling cells between α-Fe phase and cathodic residual phases. The size of nanopores increased from 150 nm to 260 nm with the temperature increasing from 773 K to 883 K. The nanoporous Fe-Si-B-P electrode showed much superior redox performance compared with Fe₇₆Si₉B₁₀P₅ amorphous alloy, which was ascribed to its large specific area and more electrochemical active sites.

7055-0.1Sc-T4 aluminum Al-alloy plates of 11 mm in thickness were firstly subjected to friction stir welding (FSW) and then the effect of post-weld heat treatment on the microstructure and mechanical properties of the FSW joints was investigated. The results show that for the as welded FSW joints, the hardness profiles distribution exhibited “W” shaped pattern with the low hardness zone (LHZ) on both the retreating (RS) and the advancing sides (AS), respectively. And the joints fractured at the LHZ on RS with the strength coefficient are 63.0%-73.8%. After the post-weld artificial aging at 120℃ for 12 h (AA), the hardness of the nugget zone (NZ) increased but the hardness of the LHZ, tensile properties and fracture location were unchanged. Solution treatment at 535℃ for 1.5 h+water quenching+artificial aging at 120℃ for 12 h (T6) did not change the grain structure of the joint under low welding speed of mm/min, but caused the abnormal grain growth at the bottom of the NZ under high welding speed of 250 mm/min. Moreover, T6 heat treatment resulted in the dissolution of the original precipitates and the re-precipitation of fine and uniform η′ and η (MgZn₂) phases, and therefore significantly improved the hardness of the joints. The T6 joint cracked along the “S” line during tension with a seriously reduced plasticity and joint efficiency of 87%.

Ferritic martensitic (F/M) steel is one of the main candidates for structural components of lead-bismuth fast reactors. Increasing the Si content can enhance the resistance of the material to Pb-Bismuth corrosion, but it also affects the precipitation behavior of precipitates and mechanical properties of the material. In this paper, four ingots of F/M steels with different Si contents (0.9%, 1.2%, 1.5% and 1.8% by mass fraction) were vacuum melted and cast, and then forged to generate blocks, afterwards, the steels were subjected to the following heat treatment process: water cooling after solution treatment at 1050℃ for 30 min, and then air cooling after tempering at 760℃ for 90 min. The effect of the Si addition on the precipitation behavior of precipitates and mechanical properties of 9Cr type F/M steel was carefully examined. The results show that the precipitated phases of 9Cr type F/M steel with different Si contents are M₂₃C₆, MX and Laves phases, and the presence of Si can promote the precipitation of Laves phase and M₂₃C₆ carbide. When the Si content is 0.9%~1.2%, the tensile strength and elongation of the steel are slightly reduced, and the impact performance remains stable; when the Si content is 1.2%~1.8%, the solid solution strengthening of Si and the precipitation strengthening of the precipitates make the strength of the steel increase, but with the increase of Si content, Laves phase and M₂₃C₆ type carbide precipitates a lot, and the impact energy decreases significantly.

In order to solve the imbalance between strength and toughness in different cross sections of a large size piston for hydraulic crushing hammer, the influence of heat treatment and microstructural adjustmen/control on the microstructure and mechanical properties of 9CrV steel near-real shaped piston with a diameter of 190 mm was studied. The results show that when the piston were austenitized at 850℃ for 5 h and quenched at 230℃ for 4 h, then tempered at 230℃ for 4 h, the microstructure of a piston consists of bainite, bainite + troostite + residual austenite and pearlite respectively, from the surface to the core. The tensile strength of the piston surface layer is 1442 MPa, the impact absorbed energy is 11 J, the impact toughness in the piston core part is poor, and the impact toughness is the lowest at 2/3 R of the piston. When the austenitizing temperature is decreased to 800℃ and tempering temperature is increased to 400℃, the tensile strength of the piston surface layer increased to 1610 MPa, and the impact absorbed energy decreased to 7.4 J. The impact toughness of the piston core shows an increasing tendency, while the strength will decrease. When the piston is austenitized at 800℃ for 5 h and followed by quenching at 230℃ for 4 h, then tempering first at 230℃ for 4 h and then at 400℃ for 4 h, the tensile strength of the piston surface layer becomes 1672 MPa, the impact absorbed energy becomes 9.8 J. The impact toughness of piston core part has been improved, and the combination of strength and toughness of the piston tend to balance. It is found that with the lower austenitizing temperature a large number of undissolved carbide particles will be retained, it will hinder austenite growing, but refine grains. With the increasing tempering temperature, the dislocation tangles to pearlite ferrite will be restored, and the toughness of piston core can be improved. The carbon-rich residual austenite film in the bainite of piston surface layer is stable. When it is tempered at 400℃, the carbide thin film will precipitate during the decomposition of residual austenite, which is easy to become a rapid crack propagation path and reduce the impact toughness. The residual austenite was transformed into lower bainite by tempering at 230℃ to prevent the formation of thin-film carbides by tempered at 400℃ to improve the impact resistance of piston core, so that the toughness becomes balance in the different cross section parts of a piston. Based on the combination of optimizing and controlling of piston microstructure and heat treatment process, the strength and toughness of the piston are balanced.

The microstructure and tensile deformation behavior of different zones (base metal, heat affected zone and weld zone) of joints of P91 steel pipe before after 136000 hours of service as steam pipeline were comparatively studied by means of hardness tester, tensile tests at 25 and 545℃, metalloscopy, SEM and TEM+EDS etc. The results show that the hardness test results can reflect the degradation behavior of tensile properties and the aging process of P91 steel joints. Compared with non-service steel pipes, the martensite decomposition and carbide coarsening behavior in each zone of welded joints of long-term serviced steel pipes obviously weaken the effect of martensite strengthening, precipitation strengthening and solution strengthening, and finally lead to the degradation of hardness, tensile properties at room temperature and high temperature in each zone. Among others, the hardness of weld zone and the relevant room temperature- and high temperature-tensile properties are most significantly degraded due to long-term service. The synergistic effect of the thermal cycling induced severe tempering during welding process with the long-term high temperature service may be an important cause for the significant degradation of the mechanical properties of P91 steel pipe welds.

The creep behavior at 130~240 MPa /973~1023 K of Sanicro25 steel for ultra-supercritical power plants were investigated by OM, SEM and TEM. The results showed that the minimum creep rate increases with the increasing temperature and applied stress. Based on the characteristics of the minimum creep rate, the stress exponents of 7.6~8.2 and the apparent activation energy of 496.7~531.8 kJ/mol can be acquired for the creep process. Nano-scale Cu-rich phase and MX phase precipitated in the matrix imped the dislocation motion, thus resulted in the emerging of creep threshold stress. The creep threshold stresses can be estimated by the linear extrapolation method, and which decrease with the increase in temperature. By invoking the concept of the threshold stresses to modify the constitutive equation, $\dot{\varepsilon}_{\min }=A_{2}\left[\left(\sigma-\sigma_{\mathrm{th}}\right) / G\right]^{n} \exp (-Q / R T)$, the normalization of the minimum creep rate can be acquired at various temperatures; Meanwhile, the true stress exponent (n=5) and the true apparent activation energy (Q=286.6kJ/mol approximately equal to the γ-Fe self-diffusion activation energy) can be identified. The creep rate-controlling mechanism was determined to be dislocation climbing mechanism assisted by lattice self-diffusion.

Thermal barrier coatings are widely used in the protection of engine turbine blade, in this paper, Ln₂(Zr_0.7Ce_0.3)₂O₇ (Ln=La, Nd, Sm, Gd) nanomaterials for the applications of thermal barrier coatings were synthesized by hydrothermal method, the crystallographic structures, morphologies and related thermophysical properties of powders and their bulk materials were comparatively assessed via various techniques. The analysis results of XRD and Raman spectra indicate that La₂(Zr_0.7Ce_0.3)₂O₇, Nd₂(Zr_0.7Ce_0.3)₂O₇ and Sm₂(Zr_0.7Ce_0.3)₂O₇ are pyrochlore structures, while Gd₂(Zr_0.7Ce_0.3)₂O₇ belongs to fluorite type. The lattice parameters, average particle sizes and specific surface areas were also characterized. The volume shrinkage / relative density, the sintering-resistance properties of the four bulk materials were evaluated by SEM observation. Additionally, their thermophysical properties (such as the activation energy of crystal growth, thermal expansion coefficient, and thermal conductivity) were investigated in detail. As the ionic radii of Ln decreasing, the activation energy of crystal growth and thermal expansion coefficient of Ln₂(Zr_0.7Ce_0.3)₂O₇ (Ln=La, Nd, Sm, Gd) increased, however the thermal conductivity is just the opposite.

The coarse-grained and fine-grained CuCr50 electrical contact materials were prepared by combining high-energy ball milling and spark plasma sintering (SPS) technology, and their composition, density, microhardness and conductivity, the distribution of cathode spots on the surface of the contact during discharge, the speed of movement and the morphology of contact surface erosion were characterized, and the arc erosion characteristics of coarse-grained and fine-grained CuCr materials were studied. The results show that the hardness of fine-grained CuCr50 contacts (160.29HV) is higher than that of coarse-grained CuCr50 contacts (104.15HV), and the movement speed of cathode spots of fine-grained contacts is 16.9 m/s under 50 Hz power frequency conditions, which is 4.9% lower than that of coarse-grained contacts of 17.78 m/s. This suggests that the cathode spot on the surface of the coarse-grained contact moves slightly faster to the edge of the contact than the fine-grained contact. Compared with coarse-grained contacts, the cathode spots produced on the surface of the fine-grained contacts during arc burning are small in size, large in number, low in brightness and more uniform. Under the same current amplitude, the arc voltage drop of fine-grained CuCr contacts is lower than that of coarse-grained contacts. After arc ablation, the overall morphology of the fine-grained CuCr contact is flat, and there is no obvious large ablation pit and droplet splash. The comprehensive results show that the refinement of the second phase Cr phase can significantly improve the overall electrical contact performance of CuCr50 contacts, and the arc ablation resistance of fine-grained CuCr50 contacts is higher than that of coarse-grained contacts.

A composite of Z-scheme Ag₃PO₄/MIL-125(Ti) heterojunction was synthesized by loading Ag₃PO₄ nano particles on the surface of round-shaped MIL-125(Ti). The Ag₃PO₄/MIL-125(Ti) composite can effectively improve the utilization of light and charge separation efficiency. The crystal-structure, morphology, optical absorption, valence band structure and charge separation efficiency of the prepared Ag₃PO₄/MIL-125(Ti) composite were characterized by XRD、SEM、EDS、UV-vis、FTIR、EIS and PL testing methods. Under a simulated solar irradiation, the performance of Cr(VI) reduction by Ag₃PO₄/MIL125(Ti) composite with different deposition amounts of Ag₃PO₄ was studied. Furthermore, the effect of solution pH and catalyst dosage in the photocatalytic reduction process was also discussed. The photocatalytic test results indicated that the deposition of Ag₃PO₄ effectively improved the photocatalytic reduction performance of MIL-125(Ti). When the concentration of Cr(VI) solution was 10mg/L and pH was 2, the reduction rate of Cr(VI) by Ag₃PO₄/MIL-125(Ti)-2 could reach to 96.9%. The results of bandgap structure calculation and free radical trapping experiments show that photon-generated carriers in Ag₃PO₄/MIL-125(Ti) are conformed to Z-scheme mechanism.