Optimization of stir casting process parameters of aluminium silicon carbide particulate composites /
Stir casting (SC) process is a promising technique for aluminium silicon carbide particulate (Al-SiCp) composite. However, the processing of Al-SiCp composite with this technique has limited its commercial application on the industrial scale due to inconsistent distribution of the reinforced SiCp an...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Gombak, Selangor :
Kulliyyah of Engineering, International Islamic University Malaysia,
2016
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | Stir casting (SC) process is a promising technique for aluminium silicon carbide particulate (Al-SiCp) composite. However, the processing of Al-SiCp composite with this technique has limited its commercial application on the industrial scale due to inconsistent distribution of the reinforced SiCp and interface reaction which in turn influences the composite properties. Moreover, over 70% of composite industries producing Al-SiCp have interest in adopting this technique due to its flexibility and cost effectiveness. This technique is influenced by several processing parameters which has the possibility to enhance and optimize the properties of the Al-SiCp composite. In order to achieve optimum properties, the SC process is used to develop Al-SiCp composite considering reinforcement fraction (RF), stirring speed (SS), processing temperature (PTemp) and processing time (PT) as the input factors for evaluating the wear rate (wr), coefficient of friction (µ), hardness (Hr) and surface roughness (Ra) as responses. In this study, an experimental plan is designed based on four factors - five level central composite design (CCD) in order to establish the model development and optimization analysis using analysis of variance (ANOVA) and multi-objective optimization (MOO). During Al-SiCp processing, the addition of oxidized SiCp and Mg created a reactive boundary which leads to the formation of MgO and MgAl2O4. These compounds improve the interface reaction, wettability and also suppress the formation of undesired phases. The characterization of Al-SiCp composite and constituent phases was performed using SEM/EDX and XRD analyzer. The examination of surface models describes the interactions among the significant parameters on responses. Validation of the models and optimal parameters revealed that prediction accuracy is within the limit of 1.2 to 5.5% error when compared to the confirmation test. Moreover, optimal response is achieved with 13 wt% RF, 500 rpm SS, 828 °C PTemp and 150 secs PT as optimum process parameters with lower wear rate. Process parameters beyond 828 °C PTemp and 500 rpm SS increase the wear rate and also influence other properties. This is because higher PTemp translates to higher energy gained by the reinforced SiCp which in turn facilitates faster settling of particles in the melt. In addition, higher SS promotes vortex formation which entraps inclusions such as gases resulting to porosity development in the composite. Due to these conditions, further increase of the RF beyond 13 wt% of SiCp does not bring a significant change in the wear properties. The wear rate of the optimized Al-SiCp recorded a significant decrease compared to conventional cast iron material in this study. This was achieved due to the sufficient formation of a stable tribo-layers or thin film interface which plays a significant role in the wear and friction performance. The surface roughness profile attained a smooth rubbing contact with an average of 0.14 µm under optimum parameter conditions. Furthermore, the SEM morphology of the worn surface of the optimized Al-SiCp composite showed shallow grooves and mild adhesive wear mechanisms with a protective thin layer. This layer acts as a coating shield and SiCp act as a solid lubricant resulting in improved wear resistance and better friction performance (0.32-0.45) which falls within the industrial range of brake system application. |
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| Physical Description: | xxii, 250 leaves : ill. ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 219-234). |