Papers by Keyword: Metal Matrix Composite (MMC)

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Authors: Chi Fai Cheung, K.C. Chan, Wing Bun Lee, M.V. Ramesh, Suet To
375
Authors: Jiang Wen Liu, Guang Xue Chen, Tai Man Yue, Zhong Ning Guo, Zi Yao Wan
Abstract: A new concavo-convex electrode has been designed and employed and it was reported that electrical discharge machining (EDM) of particulate reinforced metal matrix composites with this kind of new electrode can accelerate the debris discharge during machining so that it has a higher material removal rate (MRR) compared to the case where a normal electrode was employed. Since there are many factors that can affect the MRR in the EDM process with the concavo-convex electrode, in order to determine which is the most important factor and to optimize the machining parameters, the relative importance of the various cutting parameters on material removal rate was established using an orthogonal experimental analysis in this study. The results of the analysis suggest that to achieve a high MRR for particulate reinforced aluminum 6061 with 10-vol% Al2O3 (10ALO) or 20vol% Al2O3 (20ALO) using a concavo-convex electrode, the duty cycle is the most influential factor among current, pulse duration and duty cycle.
890
Authors: Jiang Wen Liu, Yong Zhong Wu
Abstract: In wire electro-discharge machining with an extremely high travelling speed of wire electrode (WEDM-HS), the emulsion is used as working liquid. Because there exists a functional electrolyte, the EDM spark can operate under a relatively large spark gap size condition, and this would facilitate the removal of machined debris. An investigation has been made into the machining feasibility when WEDM-HS has been employed to process Al2O3 particle reinforced aluminum alloy 6061 with 10-vol% Al2O3 (10ALO). And the material removal rate (MRR) has been examined in this study. Since there are many factors that can influence the MRR in the WEDM-HS process, in order to determine which is the most important factor and to optimize the machining parameters, the relative importance of the various machining parameters on material removal rate was established by utilizing an orthogonal experimental analysis. The results of the analysis suggest that to achieve a high MRR for particulate reinforced aluminum 6061 with 10-vol% Al2O3, the duty cycle is the most influential factor among current, pulse duration and duty cycle. And the impact of the different factors follows the sequence of duty cycle > current > pulse duration.
61
Authors: Jiang Wen Liu, Yong Zhong Wu
Abstract: An investigation has been made into the machining feasibility when wire electro-discharge machining with an extremely high travelling speed of wire electrode (WEDM-HS) has been employed to process particle-reinforced 6061 Al matrix composites with 20-vol% Al2O3 (20ALO). And in this study, for the water based emulsion is used as working liquid, there exists an electrochemical effect. And thus, the EDM spark can operate under a relatively large spark gap size condition, and this would be helpful for the removal of the loosen particles and the machined debris. In this study, the material removal rate (MRR) has been examined. Since there are many factors that can influence the MRR during the wire electro-discharge machining process, in order to determine which factor has the most significant effect on the MRR and to obtain the optimal machining parameters, the relative importance of the various machining parameters on material removal rate was analysed by employing an orthogonal design. The results of the orthogonal analysis show that to obtain a high MRR for WEDM-HS machining of 20ALO materials, the duty cycle has the most significant effect on the MRR among current, pulse duration and duty cycle. And the impact of significance for the different factors follows the sequence of duty cycle > current > pulse duration. And under the experiment condition of this study, a duty cycle of 1:4, a current of 5A and a pulse duration of 32μs is the best arrangement for the MRR.
21
Authors: M. Shibata, Yoshito Takemoto, Ichiro Shimizu
Abstract: Aluminium alloy composites reinforced with aluminium borate whiskers (ABw), developed recently by SHIKOKU KASEI KOUGYOU Co. Ltd., Japan, were fabricated using squeeze casting. The large mismatch in the coefficients of thermal expansion (CTE) between the reinforcement material and the matrix can generate significant stress and strain in composites during thermal cycling or during fabrication of the composites when using squeeze casting. When a transmission electron microscope is used to irradiate a very small area of a thin film of the material with a convergent electron beam of several nm in diameter, High Order Laue Zone patterns (HOLZ patterns) are obtained. These HOLZ patterns can reveal fine strain fields in the reinforcement materials that are used in composites fabricated using squeeze casting. Each (001) plane in the ABw was rotated towards the [020] direction by up to 0.5 ゚. With a unit of nearly 400 nm × 400 nm, each (100) plane was rotated towards the [020] direction in a corkscrew pattern. In addition the strain and the stress generated during the fabrication of the composites were estimated by using the finite element methods taking into account the anisotropies in both the CTE and the elastic modulus of the reinforcement material.
848
Authors: Isabel Gutiérrez, S. Gutiérrez-Saiz, E.H. Bocanegra, M.L. Nó, José San Juan
881
Authors: Hong Gun Kim, H.K. Noh, Young Tae Cho, J.Y. Kim, S.K. Park, Dong Joo Lee
1219
Authors: Paolo Deodati, Riccardo Donnini, Saulius Kaciulis, Alessio Mezzi, Roberto Montanari, Claudio Testani, Nadia Ucciardello
Abstract: The composite, consisting of Ti6Al4V matrix reinforced by unidirectional SiC fibres (SCS-6), has been investigated by mechanical spectroscopy at temperatures up to 1,173 K. For comparison, the same experiments have been performed on the corresponding monolithic alloy. The internal friction (IF) spectrum of the composite exhibits a new relaxation peak superimposed to an exponentially increasing background. This peak, which is not present in the monolithic alloy, has an activation energy H = 186 kJ mol-1 and a relaxation time 0 = 2.3 x 10-15 s. The phenomenon has been attributed to a reorientation of interstitial-substitutional pairs in the  phase of Ti6Al4V matrix around the fibres. This explanation is supported by the results of micro-chemical characterization carried out by X-ray photoelectron spectroscopy (XPS) combined with Ar ion sputtering.
263
Authors: Katarzyna Gawdzińska
Abstract: Quality of metal-matrix composite castings, similarly as quality of conventional metal castings is defined by the collection of data concerning chemical constitution, properties (e.g. strength) and structure of final products. During study aimed at determining these parameters, the priority is to maintain the highest possible repeatability and automation of measurement. In case of chemical constitution or mechanical properties analysis it is considerably easy to achieve thanks to application of appropriate research procedure. Analysis of structure of studied materials is however a much bigger problem. To improve it, different tools of digital image analysis are being used, but because of only slight differences (e.g. in color) between different elements of structure, conducting such analysis without performing additional study may result in obtaining false results. In such case, identification of an object is very important: unequivocal conclusion whether a given object is a reinforcement or maybe an impurity or an inclusion foreign matter, or is it a structure of improper, unintentional chemical constitution. It is particularly important concerning composites for which on the images obtained using both optical and scanning microscopy individual phases (reinforcement, matrix and impurities) are difficult to distinguish. In such case identification of particular phases is aimed at avoiding mistakes, for example while analyzing the quantity or uniformity of spacing of reinforcement phase in given space. X-ray diffraction may be a solution for this problem. An example of identification (quantitative and qualitative description) of reinforcement phase in suspension composites is presented further in the paper. The authors present also a chemical constitution of selected elements of structure of metal-matrix composites from ex-situ group.
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