Key Engineering Materials Vols. 315-316

Abstract: To solve the problems caused by high temperature in the cutting zone during high-speed milling of Titanium alloys, some cooling methods are employed, such as cold air cooling, high pressure coolant jet impinging, MQL, etc. But all have their shortfalls, both in cooling efficiency and environmental pollution. Here a new high efficiency cooling technology-cryogenic pneumatic mist jet impinging (CPMJI) cooling technology is offered. In this technology, a little quantity of coolant is carried by high pressure cryogenic air (-20
) and reaches the machining zone in the form of mist jet. This paper mainly focuses on the cooling effects of CPMJI in high-speed milling of Titanium alloy Ti-6Al-4V, as compared with dry, cold air cooling and MQL conditions. CPMJI greatly reduced the temperature in cutting zone and flank wear of tool.

Abstract: The mechanism responsible for scanning probe field-induced oxidation in ambient air is attributed to an electrochemical process, i.e., anodic oxidation or anodization,after the analyses is given of a surface of a sample exposed to air. The effects of biases, tip speeds on morphology of field-induced oxidation, are introduced and deduced in the form of kinetics formula of oxidation growth. The field-induced oxidation of hydrogen-passivated Si (Si:H)using contact-mode AFM in air at room temperature is investigated. The result achieved from the experiment and that drawn from theoretical analysis are identical, which indicates the accuracy of the experimental operation.This experiment suggested that it may be used for further investigation of field-induced oxidation technology.

Abstract: In this paper, ceramic coatings prepared on 2024 Al alloy surface in electrolyte by micro-arc oxidation are studied. The parameter of discharge and rate of ceramic coating formation are investigated. We analyzed microstructure and phase composition of the coatings by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), and studied the tribological performance of the coatings. The reactions on the electrode surface are deduced and the mechanism of coating formation has been analyzed. The results show that the relation between the thickness and reaction time is not linear. The ceramic coatings contain phase γ-Al2O3 andα-Al2O3; there is a big difference in contents of phase composition between inner coating and outer coating due to the different cooling rates of them. In MAO process, the coating undergoes a course of melting, solidifying and cooling. The coating can be divided into three layers, namely, transition layer, compact layer, and loose layer. The coating and substrate adheres firmly by a metallurgical process. Not only the elements of electrolyte (K, Si) and substrate (Cu) are found in the coatings but also the element of cathode (Fe). The Si-Al-O complex compound is formed in the discharge channels under high energy density condition.

Abstract: For the characteristics of soft X-ray stress testing technology, a formula to resolve main residual stress is deduced based on analyzing the relationship between main residual stress and normal stress of different sections. The distribution of main stress of laser shock forming TA2 metal sheet is studied combined with the experimental study on the determining residual stress with soft X ray diffraction analyzer. The result shows that testing and calculating main residual stress is an important approach to study the deformation law of sheet metal material.

Abstract: The present study was undertaken to examine the effects of rare earth (RE) in hot pressing of Cu-Sn-TiH2-bonded diamond composites. Two kinds of composite specimens – with RE and without RE – were fabricated. As an additive to the Cu-Sn-TiH2 bond matrix, the RE was used in the form of misch-metal. The hardness and transverse rupture strength (TRS) of the specimens were measured. SEM and EDS were used to analyze the fracture surfaces of the specimens. Both hardness and TRS of the specimens with RE were found to be higher than the specimens without RE. SEM observations indicated that the pop-outs of diamonds on the fracture surface of the segments without RE are more than the specimens with RE. But more diamonds were fractured on the fracture surface of the segments with RE.

Abstract: This paper systematically presents the relationship between cutting forced-induced errors and the spindle motor current basing on kinematic chain of NC machine tools. Constructs the model of cutting force-induced errors with BP Neural network, and develops the real-time error compensation system. The compensation effect of this system is verified through the experiment and the compensation system is of a great importance to precision manufacturing industry.

Abstract: Chemical mechanical polishing has emerged recently as an indispensable processing technique in large scale integration. In chemical and mechanical polishing process, chemical and mechanical principle is the vital factor in the removal process. Little is known about what is occurring beneath a wafer during Chemical Mechanical Polishing (CMP) processes. The paper provides a LIF technology to visualize the fluid flow between the wafer and pad. In this paper, the experiment setup is built. And then, the images of fluorescence intensity excited by LIF have been obtained from CCD. Finally, the relationships between pH, temperature, laser power, film thickness and fluorescence intensity excited by LIF (Laser induced Fluorescence) are studied.

Abstract: The ultra-precision lapping processes to obtain the damage-free surfaces at Å level surface roughness of Potassium titanyl phosphate (KTiOPO4, KTP) crystal is studied in this paper. The influence of the lapping parameters on the stoke removal rate and surface roughness and material removal mechanism in the process of ultra-precision lapping process is discussed, and the evolution of the lapped surface is also observed with electric telescope. A super-smooth surface of quartz crystal with roughness Ra 0.8667 Å has been obtained by adopting the fine SiO2 abrasive powders and the elastic polyurethane pad in this study.

Abstract: The pad is one of the key factors in the chemical-mechanical planarization (CMP) process. To ensure the machining capability and the quality of workpieces, the pad must be conditioned in the process. It will cause the pad thiner, and be replaced by a new one for losing the machining capability finally. For this reason, a new method of CMP by using the continuous composite electroplating on the polishing disc is introduced. In this process, the machining ability of the pad can be ensured due to the continuous Sn-SiO2 composite electroplating. The effect of cathode current density and time of plating on the characteristics of composite coating and silica wafer are investigated. The experiment indicates that the continuous composite electroplating polishing (CCEP) is an efficiency method for polishing silicon wafer, and the surface roughness of the silicon wafer is 0.005μm