Advanced Materials Research Vols. 154-155

Abstract: The five-axis linkage WEDM system with the rotate-swing-swing worktable accessories was developed to machine the ruled curved surface parts, and the component, motion parameters and motion laws of this system were analyzed. According to analytic geometry of space, the forming principle of ruled curved surface was analyzed, and the accordingly mathematics models of the five-axis linkage WEDM system were established, and the common functions were illustrated with examples. At last, the typical samples were machined in accordance with the mathematics models, the ideal machining results also prove the correctness of the mathematics models established, which widen the range of processing by WEDM, solve the difficult problem of space ruled curved surface parts.

Abstract: Ceramic coatings were prepared in situ on commercial pure Ti(CP-Ti) by Plasma Electrolytic Oxidation(PEO) technology in an environmental-friendly solution. The voltage–time responses were recorded during different PEO processes. For short treatment times, the formation processes of ceramic coatings follow a linear kinetics, while for longer times the kinetics departs from the linear behavior. The surficial morphology and composition of the coatings was studies by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The acted electrochemical method was used to evaluate the corrosion of the coated samples in 1moll-1 NaOH solution. The potentiodynamic polarization curves of coated titanium samples and the untreated metal substrate show that the PEO coated titanium samples possess much higher corrosion potential and lower corrosion current than uncoated aluminum alloy. It is noticed that the passive current density of the samples decreased from 10-4A/cm2, for the titanium, to 10-7 A/cm2, for PEO coated titanium sample.

Abstract: To improve material flow of sheet metal, draw beads are used to prevent wrinkling and springback during deep drawing process. Firstly, taking BenchMark2 "S-Rail-08" of NUMSIHEET’2008 as a study case, based on the orthogonal tests of finite element simulation of stamping process, a springback prediction model which adopts response surface method (RSM) was proposed to predict the springback influenced by draw beads parameters approximately. Then, in order to reduce springback, non-dominated sorting genetic algorithm (NSGA-II), is implemented to inverse and optimize both geometry and layout parameters of draw beads cost-efficiently. Finally, the validation of optimal parameters set and the feasible of this optimize approach are confirmed by finite element simulation of S-Rail springback.

Abstract: Processing parameters of micro thixoforming, such as height-diameter ratio, die/punch temperature, billet temperature, and punch speed, have direct and complex impact on final quality of the workpiece, which is to be applied as the reaction plate of a microreactor for hydrogen production from methanol steam reforming. The micro/meso features of the workpiece, which is for catalyst loading, are micro-pin-fin arrays. Size of the surface area and uniformity of the pin-fins are quantified by average height (Ha) and relative standard deviation (RSD). An orthogonal experiment design is adopted to investigate the influence of the parameters on the semi-solid forming process. The results of the orthogonal experiment show that the optimum parameters are 150 °C for die/punch temperature, 576 °C for billet temperature, 0.14 for height-diameter ratio and 8.33 mm/s for punch speed. The experimental results validate that the optimized processing parameters can improve the quality of the reaction plate with micro-pin-fin arrays.

Abstract: For difficulties in aspheric optical parts machining, a new principle of normal equidistance methods is put forward to machine axial symmetry aspheric optical parts. Taking the quadratic revolving surface as an example, by establishing its generatrix normal equidistance line model and necessary conditions to avoid interference in machining, its theory, shaping mechanism and configuration principle of machine are studied. And then its’ advantages are clarified.

Abstract: In this paper, high quality cutting of 1 mm dense Al2O3 electronic ceramic processed by a fiber laser with spot diameter of 15 μm was reported. The narrow kerf with 30μm width was obtained with laser power of 100 W. 300 W is the laser power threshold of the kerf enlargement. Under higher laser power, the ceramics can be damage-free cut with higher cutting speed. Striation-free cutting could be achieved at 1000 W laser power with a cutting speed of 350 mm/s. The ratio of cutting speed to laser power for striation-free cutting was determined as 0.35. The black cutting surface was due to the mass tetragonal alumina induced by N2 as assist gas.

Abstract: This study investigates on the characterization and joining behavior between glass and KOVAR alloy with fiber laser. Due to the different chemic bonds and thermal expansion coefficients, the oxide layer plays an essential role in this process. First, surface treatments under different conditions have been discussed. It’s indicated that when the two textures (the square block and the strip phase) appeared on the KOVAR surface, the joinability of KOVAR alloy enhanced. Then, considering about three laser process parameters (beam scan speed, laser power and focus position) by the orthogonal experimentation, the result indicated that the possibility of this joining technology. Finally, the fractures graphs were observed by LEXT OSL 3000. By analyzing the FeO-SiO2-Fe phase diagram and XRD on the fractures, it displayed that a new chemical substances (Fe2SiO4) had formed which was considered as the key-materials for a good glass-to-KOVAR alloy joint.

Abstract: Using laser cladding technique, Ni3(Si Ti) matrix composite coatings reinforced by in-situ synthesis (Ti,W)C multi-ceramics were fabricatcd by preplacing Ni78Si13Ti9( at%)powders containing different WC contents on the nickel-matrix superalloy substrate. The phases of coatings were investigated by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and electron probe microanalysis (EPMA). Phases of the coatings mainly composed of Ni3(Si Ti), (Ti,W)C multi-ceramics A chemical reaction between WC particle and Ti powder occurs during the laser process, therefore (Ti,W)C was formed.

Abstract: According to the characteristic of the thin-walled components, through the analysis which carries on to the complex stents structure and the material, This article found the reason of the components’ distortion, and then designed the self-made jig, the self-made cutting tool, and choiced the optimized processing parameter and so on, summarized the processing technique of the stents cavity, improved the components processing quality and the processing efficiency.

Abstract: As wafer nanotechnology gate is scaling down, the fabrication technology of gate spacer for transistor becomes more critical in manufacturing processes. Because wafer fabrication technologies, sidewall spacers play an important role in the control of short channel effects by offsetting ion implantation profiles from the edge of the gate. The present study is to overcome the fabrication processes limitations and proposed modified feasible etching processes integration on the formation processing for complementary metal oxide semiconductor nanofabrication process of gate spacer technology and electrical characteristics.