The effect of C- and W-content on the microstructure and impact toughness of the weld metals for 2.25Cr1Mo steel weld via tungsten argon arc welding (TIG) technique was investigated by means of OM, SEM, EPMA, EBSD, thermal expansion- and impact-test. The results show that the microstructure of the multi-layer and multi-pass weld metal was heterogeneous, which can be divided into upper weld metal and intermediate weld metal. The upper weld metal can be divided into melting zone (MZ), coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), inter-critical heat affected zone (ICHAZ), inter-critically reheat coarse grain heat affected zone (ICCGHAZ) and sub-critical heat affected zone (SCHAZ). Intermediate weld metal composed of necklace-type microstructure which distribute along the prior austenite grain boundary and equiaxed crystal structure. The equiaxed crystal structure was tempered bainite with good toughness. Necklace-type microstructure composed of a large number of M-A constituents, which could easily cause stress concentration and promote crack initiation, whereas, deteriorate the toughness of weld metal. Increasing C content could promote the formation of lath bainite in upper weld metal and necklace-type microstructure in intermediate weld metal, which deteriorated the toughness of weld metal; However, increasing W content could promote the formation of lath bainite in upper weld metal and inhibit the formation of necklace-type microstructure in intermediate weld metal, which is beneficial to improving the toughness of weld metal.

Plate of Ni-clad 316H stainless steel was prepared via hot rolling process after pre-heating at 1200^oC for 120 minutes, then concurrently the rolling process was interrupted after rolling for 3, 5, and 7 passes respectively, while the relevant samples are taken and water-quenched for subsequent characterization in terms of the evolution of their interface-composition and -morphology, as well as the formed oxides there. Results show that until the 3rd rolling pass, the rolling plate temperature was about 1000°C, the two metals were closely bounded with equiaxed grains of slightly distorted microstructure on both sides of the interface and the inter-diffusion of elements for the two metals was not obvious; Until the 5th rolling pass, the plate temperature was about 940°C, the grains of 316H were elongated with significant lattice distortion, whereas, obvious inter-diffusion can be found near the interface; Until the 7th rolling pass, the plate temperature was about 880°C, large number of elongated and distorted grains were observed on the 316H steel side and a fine grain structure crushed by hot rolling distributed near the interface. The elements of Ni, Fe and Cr were fully inter-diffused near the interface, but the less motionable Mo enriched at the 316H side. The grains of Ni layer coarsened obviously. The interface evolution of Ni/stainless steel composite plate during the rolling process follows the so called three-stage theory and N. Bay's theory. The physical contact stage and the physical-chemical contact stage happened between the 3rd and 5th pass. Then the rolling from 5th to 7th pass was the final physical-chemical contact phase, whilst the inter-diffusion begins, that is, the "bulk" mutual phase begins. In the high-temperature and low-oxygen environment, the Mn oxides near the interface might form during the rolling process. The oxide was crushed and squeezed toward the substrate by the rolling force, therefore distributed in chains near the interface eventually.

The friction and wear properties of K417G alloy in air, vacuum, oxygen, nitrogen, carbon dioxide, hydrogen, and argon environments with different relative humidity were assessed by means of a controlled atmosphere wear tester and SEM. Meanwhile, the stress intensity factor K_I of the alloy wear surface crack is calculated based on linear elastic mechanics. The environmental sensitivity of alloying elements is also calculated based on energetics. The results show that under wear conditions, water vapor in the air with high relative humidity is the corrosive medium that causes hydrogen-induced brittle wear of K417G alloy. The water vapor reacts with γ′-Ni₃Al in the alloy to form atomic H, which causes environmental embrittlement of the alloy. The environmental brittle crack may nucleate at the interfaces of γ/γ′and carbide/alloy matrix. The cracks not only extend along the interfaces of γ/γ′ and carbide/alloy matrix, but also enter the γ′ grains. The stress intensity factor K_I of the crack on the alloy surface is smaller than the fracture toughness K_IC of the alloy. Therefore, the contact stress on the worn surface of the alloy does not cause cracks wherein. Energetics calculations show that, in air, the occurrence of surface cracks on the wearing alloy is related to the Al content in the alloy, while the critical content of Al is 5.53% (atomic fraction).

The fatigue crack initiation behavior of a single crystal superalloy DD413 was investigated under high stress amplitude at intermediate temperature. The fracture surfaces and longitudinal section morphologies of the test specimens were characterized by scanning electron microscope (SEM). It was found that fatigue cracks mostly initiate from the cracked blocky carbides on the surface as well as the cracked skeleton-like carbides at subsurface. All the carbides on the surface of testing specimen crack due to the combined effect of oxidation and cyclic loading. Besides, at the subsurface of testing specimen, the carbides located on the propagation path of a micro-crack can crack as a result of oxidation and cyclic loading. The micro-crack connected to the surface in the specimen is the transportation channel of oxygen for the oxidation of the carbides at the subsurface. Carbides cracked and the micro-crack initiated at the early stage of fatigue, which induced the final failure.

The Fe₃O₄ coated polystyrene microsphere (PS), namely Fe₃O₄@PS_{was firstly fabricated by co-precipitation method with FeCl2·6H2O and FeCl3 as raw material, and PS microsphere as tempelate. Then Fe3O4@PS was immersed in toluene solution for removing the PS template. Next, the hollow Fe3O4 microsphere was coated with graphene oxide sheets under sonication to produce the hollow magnetic graphene oxide (HMGO). Subsequently, the absorption performance of the HMGO for methylene blue (MB) was assessed in an artificial waste MB solution. Results verified that the adsorption process reach to equilibrium at 55℃ after 60 min. The maximum adsorption capacity of MB on HMGO is 349.85 mg·g^-1. The adsorbent shows good stability and reusability, after 8 times recycling the adsorption rate is still higher than 80%. The adsorption process of MB on HMGO can be well fitted by Pseudo-second-order kinetic model and the adsorption rate is sensitive to the initial concentration. The adsorption isotherm conforms to the Langmuir isotherm model, and the adsorption process is a single-layer surface adsorption.}

The corrosion process of Q235 steel in 0.5 mol/L NaCl saturated Ca(OH)₂ solution (SCP) was investigated by electrochemical noise technology (EN) and electrochemical impedance spectroscopy (EIS), and the noise data were analyzed in time domain analysis and frequency domain analysis, and the impedance spectrum data were analyzed by way of equivalent circuit. The surface morphology and structure of the tested Q235 steel were characterized by SEM combined with EDS and XRD. The results show that the corrosion process of Q235 steel in SCP solution can be differentiated into three stages: (Ⅰ) the formation and cracking stage of passivation film, (Ⅱ) the metastable pitting corrosion stage and (Ⅲ) the Ca²⁺ deposition and corrosion product formation stage. In the stage (I), the amplitude of current noise fluctuation, the current noise standard deviation S_I and the white noise level W_I are relatively small, but the noise resistance R_n is relatively large; In the stage (Ⅱ), the amplitude of current noise fluctuation is large, S_I and W_I show a step-wise increase, and R_n decreases significantly; In the stage (Ⅲ), the amplitude of current noise fluctuation increases to 200nA, and S_I, W_I, R_n fluctuate relatively smoothly. When Q235 steel is corroded in SCP solution for 10 days, Fe₂O₃ with dispersed CaCO₃ crystallites can be observed on the surface of Q235 steel. At this time Warburg impedance appears, while the corrosion reaction is jointly controlled by the charge transfer and O₂ diffusion process.

MPP-AG resonance structure, MPP-PUFM layered structure, MPP-AG-NBR-PUFM multilayer structure material and NBR-PUFM-MPP-AG multilayer structure material were respectively prepared taking micro-perforated panel (MPP), polyurethane foam (PU), nitrile rubber (NBR) and cavity (AG) micro materials as raw materials, which were placed separately in desired structural order. The effect of MMP perforation rate, PUFM thickness, pore size of foam layer, thickness of foam and alternation order of structure on sound absorption properties of composite materials were investigated. The results show that: at lower frequency, the smaller the MPP perforation rate, and at higher frequency, the higher the MPP perforation rate, the higher the sound absorption coefficient of layered structure materials; With the increase of PUFM thickness, the resonance peak frequency of layered structure materials gradually moves toward the low frequency direction. In comparison with MPP-PUFM, the average sound absorption coefficient of MMP-AG-NBR-PUFM increases from 0.58 to 0.66 in the frequency range of 500~1600 Hz; NBR-PUFM-MPP-AG multi-layer structure material shows excellent sound absorption performance by low and medium frequencies, with the maximum absorption coefficient of 0.94 at 400 Hz and 0.85 at 2700 Hz.

Extruded sheets of 7046 aluminum alloy of 3.5 mm in thickness were subjected to friction stir welding (FSW) and then post aging treatment. The hardness profile of the FSW joint exhibits a "W" shape and the ultimate tensile strength is 406.5 MPa with a welding coefficient of 0.8. During tensile test fracture appears at the minimum hardness zone, which is the transition area between the heat affected zone (HAZ) and the thermal-mechanically affected zone (TMAZ) on the retreating side. There are a lot of dimples on the fracture surface. After aging at 120℃ for 24 h there is little change in the hardness of the base metal (BM) but the hardness of the HAZ, TMAZ and nugget zone (NZ) increase apparently, which is more or less the same as that of the BM. The ultimate tensile strength increases significantly up to about 490MPa with the welding coefficient increasing to about 0.96. Fracture appears at the NZ and there are a lot of intergranular cracks on the fracture surface. After aging, the GPI zones within grains of the FSW joint transform into η' metastable phase with better strengthening effect, leading to higher hardness and strength. η phase tends to be more continuous at grain boundaries and there is a higher volume fraction of precipitates free zones near grain boundaries in the NZ than other regions, therefore, fracture tends to occur in the NZ during tensile test.

The evolution of grain boundaries, texture types and cracks of an extruded plate of Mg-0.4%Zn alloy during deformation by different tensile strains was investigated by means of in-situ tensile test coupled with electron backscattering diffraction (EBSD) technique in Zeiss Sigma 300 field emission scanning electron microscope. The results show that by the tensile strain from 0% to 20%, the twin boundaries of material increase gradually with the strains, the twin boundaries mainly belong to the type of {10-12} extension twin. Therewith, the twinning may bring about the variation of the texture of the alloy. During the tensile process, cracks in the Mg-Zn alloy may preferentially generate at the tips of the twins and/or initial grain boundaries, simultaneously trans-granular cracks appear in some grains with the increase of strain, finally fracture happened after the propagation of cracks.