Polyamide 6 (PA6) nanofibers were prepared via electrospinning. The electrospun PA6 nanofibers were functionalized using electroless deposition technique. Oxygen low temperature plasma treatment was applied to substitute the conventional roughening process using concentrated sulfuric acid-potassium dichromate. The deposition of copper (Cu) on the PA6 nanofibers was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDX). The observations revealed the uniform coating of the PA6 nanofibers with thin films of Cu. It was also found that the surface conductivity of the PA6 nanofibers was significantly improved by the Cu deposition. The combination of electrospinning and electroless deposition will provide a new approach to producing the functional nanofibers for various applications.

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In this study, we found that well-developed α 2 martensite was formed in a Ti-40Al-10V (atomic percent or at.%) alloy after air-cooling from a β phase field, rather than the traditional α 2 /γ lamellar colonies. The martensitic laths were produced according to the Burgers orientation relationship (OR), the same as those during quenching. Local variant selection detected that three (or six) α 2 variants sharing one (or two) common [11.0] α2 axes were predominant, while no global variant selection was observed. Subsequent to the martensitic transformation, the retained β phase was decomposed mainly via a β→γ transformation. The γ laths always nucleated at the α 2 /β interface according to a Blackburn orientation relationship. In order to stabilize the microstructure, the air-cooled samples were tempered at 800-1000 • C. During tempering, the microstructure decomposed mainly via an α 2 →γ transformation. The martensite was almost completely transformed after tempering at 1000 • C for 4 h, and hence a fine β-γ microstructure was obtained. Such a treatment resembling the quenching-tempering in steels may be a new strategy for the microstructural design of TiAl alloys, while an unexpected quenching process can be avoided.

Spin-forming of trapezoidal inner gear is a new technology of the near-net forming in gear manufacturing field. Processing parameters, such as the initial thickness of blank and radial reductions of each roller, greatly influence the forming quality of spun part. The forming quality of trapezoidal inner gear involves the filling status of gear tooth and dimensional accuracy of root circle. An approach for processing parameter optimization of the forming quality of the trapezoidal inner gear stagger spinning is proposed. The proposed approach integrates the orthogonal experiment design, gray relational analysis, and analysis of variance (ANOVA). The experiment result indicates that the proposed approach is effective in determining the optimized processing parameters for the stagger spinning of trapezoidal inner gear.

The evolution of the microstructures and properties of large direct chill (DC)-cast Al-Cu-Mn alloy ingots during homogenization was investigated. The results revealed that the Al-Cu-Mn alloy ingots had severe microsegregation and the main secondary phase was Al2Cu, with minimal Al7Cu2Fe phase. Numerous primary eutectic phases existed in the grain boundary and the main elements were segregated at the interfaces along the interdendritic region. The grain boundaries became discontinuous, residual phases were effectively dissolved into the matrix, and the segregation degree of all elements was reduced dramatically during homogenization. In addition, the homogenized alloys exhibited improved microstructures with finer grain size, higher number density of dislocation networks, higher density of uniformly distributed θ′ or θ phase (Al2Cu), and higher volume fraction of high-angle grain boundaries compared to the nonhomogenized samples. After the optimal homogenization scheme treated at 535 °C for 10 h, the tensile strength and elongation% were about 24 MPa, 20.5 MPa, and 1.3% higher than those of the specimen without homogenization treatment.