Microstructural characterization of friction stir lap welds of aluminium incorporated with titanium carbide
- Authors: Abegunde, O. O. , Akinlabi, Esther Titilayo , Madyira, D. M.
- Date: 2015-07-01
- Subjects: Aluminium , Friction stir welding , Titanium carbide , Aluminum
- Type: Article
- Identifier: uj:5123 , ISBN 9789881404701 , http://hdl.handle.net/10210/14085
- Description: In this research study, the characterization of the microstructure evolution of friction stir lap welds (FSLW) of Aluminium incorporated with Titanium Carbide powder to form Aluminium based composites is presented. The Titanium Carbide powder was infused at the weld interface to produce a composite. The FSLW were conducted on an Intelligent Stir Welding for Industry and Research (I-STIR) Process Development System (PDS). Different welding parameters were used for the welding process. Rotational speeds of 1600 rpm and 2000 rpm and transverse speeds of 100 mm/min, 200 mm/min and 300 mm/min were employed. The process parameters were carefully selected to represent a low, medium and high setting for the feed rates. The microstructural evolution of the samples were studied. Optical microscope and scanning electron microscopy (SEM) techniques were used to investigate the particle distribution of the welded samples. The results obtained revealed the influence of the welding parameters on the particle distribution of the welded samples. A homogenous mixture of the materials was observed at higher rotational speed of 2000 rpm.
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Characterization of functionally graded commercially pure titanium (CPTI) and titanium carbide (TiC) powders
- Authors: Akinlabi, Esther Titilayo , Akinlabi, Stephen A.
- Date: 2015-07-01
- Subjects: Functional graded materials , Laser metal deposition , Titanium , Titanium carbide
- Type: Article
- Identifier: uj:5136 , ISBN 9789881404701 , http://hdl.handle.net/10210/14102
- Description: Functionally Graded Materials (FGM) are advanced materials fabricated using additive manufacturing techniques. It belongs to a class of advanced material characterization in which the properties of the material composition is varied. The resulting property of the composite is always different from the properties of the individual material employed in the formation of the composite. They are known to also exhibit good mechanical and chemical properties and as such, are used for different industrial applications. One of the techniques employed in the fabrication of FGMs is called Laser Metal Deposition (LMD) technique. It uses laser beam to melt powder material on a substrate forming a melt pool that solidifies upon cooling. This paper reports on the material characterization of functionally graded Titanium and Titanium Carbide (TiC) powders deposited on Titanium substrate by laser metal deposition approach. The formed deposits were fabricated by varying the processing parameters such as laser power, scanning speed and the powder flow rate. From the result obtained, the microstructures showed that the laser power has much influence on the grain growth of the material. In addition, with the SEM analysis of the microstructure since the percentages of the titanium and titanium carbide were varied, it was observed that the sharp boundaries of the Titanium Carbide were reduced greatly and this resulting effect can be attributed to the thermal effect of the laser. The microstructures further revealed that as the percentage of TiC decreases, it becomes more difficult to see the TiC as a different material in the composite, emphasizing this as one of the best characteristics of functionally graded materials, which is the elimination of sharp interfaces and layers. Furthermore, it was observed that the laser power has great influence on the evolving hardness of the material compared to the TiC content.
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Influence of scanning speed and energy density on the evolving properties of laser deposited Ti6Al4V/Cu composites
- Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo , Pityana, Sisa
- Date: 2015-07-01
- Subjects: Laser metal deposition , Microhardness , Titanium composites , Copper composites
- Type: Article
- Identifier: uj:5131 , ISBN 9789881404701 , http://hdl.handle.net/10210/14094
- Description: Titanium is a light metal and finds application majorly in the aerospace and bio medicals. This paper presents the influence of scanning speed and energy density on the evolving microstructure and microhardness of laser deposited Ti6Al4V/Cu composites. The laser power, powder flow rates and gas flow rates were kept constant while varying the scanning speed. From the microscopic analysis, α acicular structures were found growing from the top of the cross section of the composite and broke into the β-phase and the grain boundary of the (α+β) phase, and found to disappear gradually as the scanning speed increases. Widmanstettan was also found in all the samples. Sample S21 of energy density 240 J/mm2 deposited with a laser power of 1200 W and a scanning speed of 5 mm/secs shows the highest hardness value of 541±20 HV0.5 while Sample S27 of energy density of 48 J/mm2 deposited with a laser power of 1200 W and a scanning speed of 25 mm/secs shows the lowest hardness value of 405±12 HV0.5. This was attributed to the Cu content added and plays a vital role in stabilizing and strengthening the β-phase.
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Biodiesel production over ZnO/TiO₂ catalyst : effect of co-solvent, temperature and reaction time
- Authors: Mahangani, Ndanganeni , Vunain, Ephraim , Meijboom, Reinout , Jalama, Kalala
- Date: 2015-07-01
- Subjects: Biodiesel , Hexane , Waste vegetable oils
- Type: Article
- Identifier: uj:5127 , ISBN 9789881404701 , http://hdl.handle.net/10210/14090
- Description: The aim of this work was to produce biodiesel from waste vegetable oil over ZnO/TiO2 catalysts as well as investigating the effect of co-solvent (hexane), reaction temperature and time on waste vegetable oil conversion to biodiesel. Production of biodiesel from virgin oil is still a downfall in commercial processes due to high cost. Thus, the process of producing biodiesel from waste vegetable oil over a TiO2-supported ZnO catalyst was studied in the absence and the presence of hexane as co-solvent respectively. The conversion of waste vegetable oil was found to increase with temperature and reaction time. The highest conversion that has been achieved was 99.1% at a temperature of 200 °C after 15 min of reaction for the reaction using hexane as co-solvent. The use of hexane as co-solvent was found to increase the oil conversion at lower reaction temperature and no effect was observed at higher temperatures.
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Modeling of the mechanical responses of nanocrystalline metals and alloys
- Authors: Sanusi, K. O. , Afolabi, A. S. , Muzenda, E. , Akinlabi, Esther Titilayo
- Date: 2015-07-01
- Subjects: Nanocrystalline materials , Hall-Petch relations , Nanocrystalline alloys
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/390253 , uj:5122 , ISBN 9789881404701 , http://hdl.handle.net/10210/14083
- Description: This paper reports the proposed model of the flow behaviors of nanocrystalline metals and alloys deformed at different strains, strain rates and temperatures. It incorporated the effect of grain size, high internal stresses and lattice distortions existing near boundaries to the Hall-Petch relations. The developed model was compared to that of Khan-Huang-Liang and found to be more reliable in clarifying the inverse Hall-Petch relation. Using the new proposed constitutive model, the mechanical behaviour of materials at different grain sizes for ultrafine grained to nanostructure materials at different temperatures and strain rates can be obtained. The model is also useful in predicting the response of nanocrystalline metals and alloys during the forming process.
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Waste vegetable oils to biodiesel over Al₂O₃ –supported SnO₂ catalyst : effect of support pore size
- Authors: Zulu, Vusumuzi C. , Vunain, Ephraim , Meijboom, Reinout , Jalama, Kalala
- Date: 2015-07-01
- Subjects: Biodiesel , Waste vegetable oils
- Type: Article
- Identifier: uj:5132 , ISBN 9789881404701 , http://hdl.handle.net/10210/14098
- Description: The main aim of this study was to investigate the catalytic properties of Al₂O₃-supported SnO₂ for the conversion of waste vegetable oil into biodiesel. The effect of support pore size on waste oil conversion was investigated at 100 and 200 °C by using α-alumina (with larger pore size) and γ-alumina (with smaller pore size) respectively as support for SnO₂. The effect of pore-size on conversion was found to depend on the operating temperature. At low temperature, i.e. 100 °C, higher conversion for waste vegetable oil was measured on SnO₂ catalyst supported on α-Al₂O₃ than the catalyst supported by γ-Al₂O₃. This effect became less significant at 200 °C. It was also observed that the oil conversion increased with an increase in reaction temperature and reaction time.
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