Chuanhai Jiang

Formation of Anodic Aluminum Oxide with Serrated Nanochannels

We report a simple and robust method to self-assemble porous anodic aluminum oxide membranes with serrated nanochannels by anodizing in phosphoric acid solution. Due to high field conduction and anionic incorporation, an increase of anodizing voltage leads to an increase of the impurity levels and also the field strength across barrier layer. On the basis of both experiment and simulation results, the initiation and formation of serrated channels are attributed to the evolution of oxygen gas bubbles followed by plastic deformation in the oxide film. Alternating anodization in oxalic and phosphoric acids is applied to construct multilayered membranes with smooth and serrated channels, demonstrating a unique way to design and construct a three-dimensional hierarchical system with controllable morphology and composition.

Electrodeposition of Ni matrix composite coatings containing ZrC particles

Abstract In this paper, Ni matrix composite coatings containing either micro-ZrC or nano-ZrC particles were successfully prepared by direct current electrodeposition. The microstructure of the coatings, including crystallographic texture and grain size, were studied by X-ray diffraction analysis. Energy dispersive spectrometer and scanning electron microscope were used to investigate the chemical composition and morphology of the coatings. The microhardness of the coatings was measured by a Vicker microhardness tester. Grain refinement strengthening and dispersion strengthening mechanisms were applied to interpret the evolution of the microhardness. The corrosion resistance of the Ni matrix composite coatings was investigated by corrosion polarisation method. The composite coatings exhibit better mechanical property and corrosion resistance than pure Ni coating.

Thermal performance of sputtered Cu films containing insoluble Zr and Cr for advanced barrierless Cu metallization

Abstract Pure Cu films and Cu alloy films containing insoluble substances (Zr and Cr) were deposited on Si(100) substrates, in the presence of interfacial native suboxide (SiO x ), by magnetron sputtering. Samples were vacuum annealed between 300°C and 500°C to investigate effects of Zr and Cr additions on the thermal performance of Cu films. After annealing, copper silicides were found in the Cu(Zr) films, while no detectable silicides were observed in Cu and Cu(Cr) films. Upon annealing, Zr accelerated the diffusion and reaction between the film and the substrate, and lowered the thermal stability of Cu(Zr) alloy films on Si substrates, which was ascribed to the ‘purifying effect’ of Zr on the Si substrates. Whereas, Cr prohibited the agglomeration of Cu films at 500°C and decreased the surface roughness. As a result, the diffusion of Cu in Si substrates for Cu(Cr) films was effectively inhibited. In contrast to the high resistivity of Cu(Zr) films, the final resistivity of about 2.76 μΩ·cm was achieved for the Cu(Cr) film. These results indicate that Cu(Cr) films have higher thermal stability than Cu(Zr) films on Si substrates and are preferable in the advanced barrierless Cu metallization.

Surface Modification of 304 Steel Using Triple-Step Shot Peening

This paper reports the influences of triple-step shot peening (SP) on the microstructure and residual stress evolution for the 304 stainless steel. The microstructure and residual stress were characterized by X-ray diffraction analysis methodology. After triple-step SP, the domain sizes decreased while the dislocation density and compressive residual stress increased as a result of the austenite and martensite in the peening deformed layer. With an increase in depth, the micro-strain for austenite decreased gradually while the micro-strain for martensite increased first, and then decreased.

Microstructure thermostability of shot peened duplex stainless steel surface layer

Abstract Shot peening treatment was employed to introduce deformation into the surface layer of duplex stainless steel S32205, and the microstructure thermostability during isothermal annealing was investigated using X-ray diffraction line profile analysis. Microstructure variation in shot peened layer is observed with the extension of annealing time. The domain growth activation energy and microstrain relaxation energy in both ferrite and austenite were calculated by computer regression analysis. Compared to ferrite, the shot peened austenite exhibits a higher dislocation density, a larger driving force for recrystallisation and relaxation; however, it has higher activation energy of domain growth and higher microstrain relaxation energy. The results show that the microstructure thermostability of austenite is higher than that of ferrite.

Residual stress and micro-structure of GCr15 steel after multistep shot peening

Abstract Experiments were conducted to investigate the effects of different shot peening (SP) techniques on the residual stress and micro-structure of GCr15 steel by X-ray diffraction (XRD) profile analysis. The results showed that SP induced the martensitic phase transformation, compressive residual stress (CRS) and micro-structure modification within the deformed layer. Under the optimum SP intensity of 0·52+0·25+0·16 mmA, the maximum compressive residual stress (MCRS) for martensite attains 745 MPa at the depth of 35 μm while the MCRS for austenite attains 869 MPa at the depth of 50 μm; and the domain size of GCr15 steel attains the minimum value of 9 nm at the top surface; The micro-strain and dislocation density attain the maximum values of 0·0042 and 2·29×1015 m−2 at the top surface respectively.

Investigation of the shear slag model for the SiCw/Al composite by X-ray diffraction

Abstract The shearing stress of the matrix in the whisker-reinforced composite under uniaxial tensile loading was theoretically analyzed by utilizing the shear slag model, and the actual shearing stress subjected in the matrix in the as-extruded 20 vol.% SiCw/6061Al composite was measured by X-ray diffraction. Then, the effect of stress transfer across the whisker ends was investigated. The results have shown that the actual shearing stress of the matrix is 61.5% of the applied stress for the composite, and the whisker end stress equals the average shearing stress of the matrix times 2.38. Therefore, the effect of stress transfer across the whisker ends cannot be neglected for the composite, which is mainly due to the lower whisker aspect ratio in the composite.

Investigation for Different Peening Techniques on Residual Stress Field of SiCw/Al Composite

In order to improve the residual stress field of SiCw/Al composite after conventional shot peening, modified warm peening, stress peening, and compound peening were carried out on SiCw/Al composite specimens and residual stress fields of those specimens were investigated via x-ray measurement. Results show conventional peening can improve residual stress field of SiCw/Al composite but the improvement has a limit. Compared with conventional peening, modified warm peening can increase the maximum residual stress, the depth of compressive residual stress layer and improve stability of residual stress field whereas stress peening can increase all characteristic parameters of residual stress field efficiently. Compound peening combines the positive effects of modified warm peening and stress peening, and has the most strengthening effects.

Residual Stress Relaxation of Shot-Peened Deformation Surface Layer on Duplex Stainless Steel Under Applied Loading

The relaxation of residual stress in shot-peened surface layer of duplex stainless steel S32205 under static and cyclic loading was investigated. The results reveal that the compressive residual stress is relaxed under applied tensile stress. The relaxation of residual stress in longitudinal direction is more obvious than that in transverse direction in both austenite and ferrite. When the applied stress is beyond the yield strength of the materials, the relaxation of the residual stress becomes drastic. Under cyclic loading, the residual stress relaxation occurs fast in the first few cycles, it then becomes stable gradually. A model was used to quantitatively calculate the residual stress under cyclic loading with different applied tensile stresses. The relaxation behavior is determined by the applied loading, the number of cycles, dislocation density, and the residual stress gradient. The relaxation behavior difference under cyclic loading between ferrite and austenite is discussed.

Thermostability of S30432 shot peened surface layer

Abstract The recrystallisation behaviour of S30432 shot peened deformation surface layer during isothermal annealing has been investigated by X-ray diffraction line profile analysis method. The results revealed that annealing time and temperature were two key parameters for isothermal annealing process of S30432 steel. With higher annealing temperature, the recrystallisation behaviour in the shot peened deformed layer was more obvious. Based on the results of line profile analysis, the recrystallisation activation energy and microstrain relaxation energy were calculated. In addition, after isothermal annealing, the depth distribution of domain size in the deformed layer was also investigated and discussed in details. According to the analysis, the results showed that the thermostability of S30432 shot peened surface layer was relatively stable when the annealing temperature was below 650°C.