Theses & Dissertations

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https://hdl.handle.net/20.500.14170/1590

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Browsing Theses & Dissertations by Subject "Alloys"
  • Publication
    Effect of Navo₃ concentration and hcl pre-treatment on corrosion behavior of anodized coated AZ91D magnesium alloys
    ( 2014)
    Khalid Azadi Mat Akhir
    Magnesium and its alloys have some excellent properties, such as the lowest density of industrial metals, a high strength-to-weight ratio, vibration absorbency and electromagnetic wave shield characteristics. Because of these properties, magnesium and its alloys can be applied in the manufacture of components for motor vehicles, in housing for electronics, and in the manufacture of sporting goods. In addition, magnesium and its alloys are more easily recycled than synthetic resins, which make these materials eco-friendly. The poor resistance of magnesium and its alloys to corrosion has limited the application of these materials in corrosive environments. Anodizing coating is one of the most cost effective and simple techniques for introducing a metallic coating to a substrate. This study deals with the preparation of oxide films on AZ91D magnesium alloy by anodizing coating in a solution containing La(NO₃)₃ and/or Mg(NO₃)₂, with additive NaVO₃ concentration in the solution. The anodizing coating on the AZ91D magnesium alloy has been carried out and the effect of NaVO₃ concentrations and pre-treatment was investigated. A chemical compound of AlO, MgO and VO was detected from the diffraction peaks of XRD pattern confirming the formation of an oxide layer on the surface of AZ91D magnesium alloy. The corrosion resistance of AZ91D magnesium alloy increases remarkably with corrosion rate of 0.2 mm/y was obtained. A self-healing morphology could be observed from SEM images indicated the recovery of the NaVO3 rich oxide film from the severe environment of NaCl solution. This result is remained constant for further improvement by HCl pre-treatment. A rough surface was obtained after immersing in HCl solution for 20 s and followed by anodizing, has yielded the corrosion rate up to 0.19 mm/y. Two peaks assigned for VO and MgO was detected from XRD patterns. The corrosion protection of AZ91D magnesium alloy has been increased by the following ways; the formation of selfhealing morphology to recover from the severe environment by the addition of NaVO₃, and formation of a passive oxide layer on the surface of AZ91D magnesium alloy by immersion in HCl solution. Based on the electrochemical experiments of potentiodynamics polarization and immersion test result, coating with NaVO₃ and HCl pre-treatment successfully increased the corrosion resistance of AZ91D magnesium alloy. The result demonstrated here will strongly contribute to the broad application of magnesium alloy in the field of the automotive industry.
  • Publication
    Optimization of cutting parameters for surface roughness in CNC turning machining with aluminum alloy 6061 material
    ( 2014)
    Ali Abdullah Mohammed Ahmed
    Machining process involves many process parameters. Achieving accurate dimensions, good surface quality, and maximized metal removal are of utmost importance. This research work describes the optimization of cutting parameters for the surface roughness in CNC turning machining with aluminum alloy 6061 material. Controlling the required surface quality is necessary. In this study, Taguchi method is used to find the optimal cutting parameters for surface roughness in turning. L-9 orthogonal array, signal-to-noise ratio, and analysis of variance are employed to study the performance characteristics in the turning operations of aluminum alloy 6061 using uncoated inserts. A precise knowledge of these optimum parameters would facilitate reduction of machining costs and improve product quality. The current study on turning process applies a response surface methodology on the most effective process parameters, namely, feed, cutting speed, and depth of cut, which are optimized considering the surface roughness and material removal rate. The results of the machining experiments were used to characterize the main factors affecting surface roughness by the Analysis of Variance (ANOVA) method. Feed rate and speed of cutting founds to be a most influencing parameter for the surface roughness in the shaping process whereas depth of cut is found to be significantly affecting the MRR.