The strain-hardening behavior of a cold-rolled dual phase steel of 780MPa grade after different heat treatments was analyzed by a modified Crussard-Jaoul ( C-J ) method, and the deformation behavior of which was simulated with representative volume element (RVE) model. The results show that dual phase steels of different states all exhibit higher initial strain-hardening rate. The steel containing island- and needle-like martensite showed two-stage strain-hardening characteristics which related to the plastic deformation of ferrite and coordination plastic deformation of ferrite and martensite respectively, while the steel containing coarse block-like martensite exhibited three-stage strain-hardening characteristics and of which, the strain hardening capacity of the third stage decreases significantly due to the plastic deformation. The finite element method (FEM) simulation result showed that the strain concentration of the dual phase steel containing coarse block- and needle-like martensite mainly distributed in the interface of ferrite and martensite, while that containing island-like martensite distributed in junctions of martensite grains.

The effect of annealing temperature on microstructure and mechanical properties of TWIP steel (Fe-0.5C-18.6Mn-1.5Al-0.5Si) is investigated, while the steel was produced aforehand by severe symmetric and asymmetric rolling at room temperature. The results show that the grain size is significantly refined after severe asymmetric and symmetric rolling, and the ultimate tensile strength (UTS) increased from 593 MPa to 2021 MPa. The severely rolled TWIP steel shows no recrystallization when annealed below 500℃, partial recrystallization when annealed between 500-600℃, and full recrystallization when annealed above 700℃. With the increasing annealing temperature, the strength decreases while the elongation increases. Specifically, the UFG (Ultrafine-grained) TWIP steel with an average grain size of 500nm and excellent mechanical properties can be obtained when annealed at 700℃, i.e. the UTS, elongation and product of strength and elongation of the steel are 1114 MPa,59.4 % and 66.2 GPa·%, respectively. Moreover, when annealed between 500-600℃, there existed many dispersive fine-grained intermetallic compounds with DO₃-type crystallographic structure in the produced steel, which can significantly enhance the strength of the steel

Composites of 8-hydroxyquinoline/nano-SiO₂ were prepared with nano-SiO₂ as carrier and 8-hydroxyquinoline as modifier. Then the composistes were blended with epoxy resin to form the nanocomposite epoxy coating. The corrosion performance of the prepared composite coating was investigated by means of salt spray test and electrochemical impedance spectroscopy. Results show that composites of 8-hydroxyquinoline/nano-SiO₂ can improve the corrosion resistance of the epoxy coatings, among others the coating with 5% (mass fraction) 8-hydroxyquinoline/nano-SiO₂ was the optimal. The relevant mechanism may be ascribed to the fact that 8-hydroxyquinoline could release from pores of nano-SiO₂ and then penetrate to the interface coating/steel substrate forming Fe-containing complex, thus improving the corrosion resistance of the steel substrate.

The warm laser shock peening (WLSP) of heat resistant martensite stainless steel ЭП866 was carried out by Nd glass pulse laser, and the microstructure and properties of the impacted layer were assessed by transmission electron microscopy and X-ray stress analyzer. The results show that WLSP has obvious strengthening effect compared to LSP at room temperature. Through dynamic strain aging (DSA) and dynamic precipitation (DP), the WLSP generates higher compressive residual stress, higher density dislocation structures and nano-scale precipitates on the impacted layer of the treated steel ЭП866.

The relationship between the dry sliding tribological performance of T10 steel disc against polyester pin in surface contact and the austenite grain size of the steel was investigated using a MM-W1 universal tester. The results show that the austenite grain size of T10 steel after five cycle-quenching is only 5 μm, which is much smaller than 32 μm of the one after one cycle-quenching. Grain refinement efficiently improves the strength and toughness of the steel,while slightly decreases its strain-hardening index. Although the grain refinement does not enhance the hardness of the steel but decrease the friction coefficient of friction couples of polyester/T10 steel, therewith the wear resistance of the steel increases remarkably. It is thought that the wear resistance improvement of T10 steel with fine grain and lower strain-hardening capability is benefited from the strong friction-induced hardening of the worn surface layer. The wear mechanism is mainly plough wear with accompanying slight contact fatigue wear.

The rate and quantity of heat release during hydration of magnesium potassium phosphate cement (MKPC) containing 0、5%、10%、15%、20% and 25% fly ash respectively were measured at 20℃ via isothermal calorimetry. The effect of fly ash content on the hydration process of MKPC was investigated in terms of the relevant kinetics parameters, as well as the final heat release Q_∞、hydration resistance N and reaction constant K were calculated by the Knudsen and Kondo hydration kinetics formula. The results show that Knudsen and Kondo hydration kinetics formula presented a good applicability for calculation of the final heat release and kinetics parameters of MKPC, with very high relevance fitting. Hydration process of MKPC can be divided into 6 stages, and hydration reaction started from the second stage. At the fourth stage of hydration, MKPC changed from nucleation and crystal growth process to diffusion process directly. The content of reaction components of MgO and KH₂PO₄ decrease with the increasing fly ash content varied from 0~15%,resulting in decrease of hydration heat of MKPC. Fly ash participanted hydration as physical fitter and showed little influence on the hydration process of of MKPC. When the incorporation amount of fly ash content varied from 15% to 25%, an increase of hydration heat was matched and both content N and K for each hydration stage of MKPC presented huge variation due to the decrease of borax content and the pozzolanic effect of fly ash.

Uniform complex particles of polytetrafluoroethylene (PTFE)/carbon black (CB) were firstly hetero-coagulated without additives of non-ionic surfactant by mechanical stirring. Then composites of PTFE/CB with better properties were successfully prepared via cold pressing and sintering method with complex particles of PTFE/CB as raw material. The effect of sintering temperature and the CB amount on properties of composites PTFE/CB was investigated. Results show that the optimum sintering temperature was 390^oC, and the mechanical properties of composite PTFE/CB sintered at 390^oC exhibited significantly better mechanical properties due to the formation of good micro-fibrous structure. Among others, with the CB addition of 2 mass%, the composite exhibited the best mechanical properties, i.e. its tensile strength increased from 19.1 MPa to 27.3 MPa and the elongation at break increased from 420% to 525%. Importantly, the electrical conductivity could reach the percolation threshold for the composite with 3 mass % CB due to the formation of a conductive network in the PTFE/CB matrix. Therefore, it follows that the composite of PTFE with 3 mass % CB can possess high degree of crystallinity with appropriate antistatic performance.

The microstructure evolution, and the dissolution and precipitation of the main phase of the homogenized superalloy GH3625 during melting and solidifying process were investigated by means of differential scanning calorimetry (DSC), confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the twostep homogenization process is effective for eliminating the laves phase of low-melting point and the segregation in micro-scale for alloying elements of the superalloy GH3625; The initial melting temperature of the homogenized superalloy GH3625 is obviously improved, and the melting occurs firstly in the regions such as grain boundary, surface, shrinkage cavity and carbide (NbC) etc.. The solidification process of the alloy GH3625 can be divided into three stages, and which correspond to mainly the crystallization reactions such as L→γ, L→γ+MC and L→γ+laves. The nucleation of γ phase belong to heterogeneous nucleation, so that solute atoms easily segregate at grain boundaries, which in the dendrites inevitably formed elemental segregation and phase segregation. The precipitation type of the low melting point laves phase is mainly related to the cooling rates.

The in-situ TiC/FeAl composite coating was fabricated by laser cladding technology in this paper. The microstructure of the coating was characterized by metallographic microscope (OM), scanning electron microscopy(SEM).The phases in the coating were examined by energy dispersive spectrometry (EDS) and X-ray diffraction (XRD), microhardness and wear resistance of the coating were also investigated. The results show that from the bottom to the surface of the melt pool along the depth the coarse dendrite grain is changed into fine quiaxed rosette grain. Some TiC particles going across the interface exist in the surface layer of the substrate. Most of TiC particles existing in the grains are nucleation centers during FeAl matrix solidification. The content of TiC particles in the top of the coating is much higher than that in other zone of the coating. Meanwhile, the microhardness and wear resistance of in-situ laser cladding are 5 times and 52 higher than those of substrate, respectively. And the wear mechanism of the composite coating is abrasive wear.

Effect of the addition of modified sepiolite on the thermal oxidative stability of the surface modified sepiolite reinforced ethylene propylene diene monomer rubber (OSP/EPDM) was investigated via the orthogonal experiment L₉(3⁴). The peak temperature variation for the oxidation process of OSP/EPDM is determined by thermogravimetric and differential thermal analysis (TG-DTA). The apparent activation energy (ΔE) and reaction rate constant (K_T) were acquired via oxidation reaction test of the vulcanized rubber and oxidation reaction kinetics calculation, while the oxidation induction time (OIT) was calculated according to Doyle formula, which was compared with the experimental resultsof rubber aging test. The results show that the oxidation induction time (t₇₀) are in good agreement with the reaction rate constant K₇₀, and the calculated results are consistent to the experimental ones, indicating that the t₇₀ could be applied to evaluate thermal oxidative stability of OSP/EPDM.

Composites of GO-g-PVA/TPU were prepared by using polyvinyl alcohol (PVA) grafted graphene oxide as filler and thermoplastic polyurethane (TPU) as matrix by melt blending method. The structure and properties of the resultant composites were characterized by means of FTIR, DSC, DMA and tensile tests. DSC tests show that the addition of GO-g-PVA increased the crystallization temperature of the composites. When the content (mass fraction%) of GO-g-PVA was 4%, the crystallization temperature of GO-g-PVA/TPU increased by 28.8℃ in contrast to that of the plain TPU. Tensile tests show that the modulus of GO-g-PVA/TPU composites increased with the increasing filler content when the content of GO-g-PVA was higher than 1%. DMA analysis indicated that GO-g-PVA enhanced the storage modulus and loss modulus of GO-g-PVA/TPU composites. Shape memory properties results show that the addition of GO-g-PVA significantly improved the shape fixed rate (R_f) of the composites. When the content of GO-g-PVA was 4%, the R_f of the composite was 87.5%, which increased by 20% compared with that of pure TPU. However, with the increasing amount of GO-g-PVA the shape recovery ratio (R_r) of the composite decreased generally at 50℃, and the composites showed higher R_r value at high temperature rather than at low temperature.