The machinability of rapidly solidified aluminium alloy for optical mould inserts
- Authors: Otieno, Timothy
- Date: 2018
- Subjects: Aluminum alloys , Automobiles -- Materials Materials -- Mechanical properties
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23097 , vital:30415
- Description: Ultra-high precision machining is a material removing process under the nanotechnology regime whereby the highest dimensional accuracies are attained. Critical components for optical devices and optical measuring systems are mainly produced through ultra-high precision machining. Their mass production is usually implemented by utilising optical moulds. Aluminium alloys have proven to be advantageous and very commonly used in the photonics industry for moulds. This ever-increasing use and demand within optics have led to the development of newly modified grades of aluminium alloys produced by rapid solidification in the foundry process. The newer grades are characterised by finer microstructures and improved mechanical and physical properties. The main inconvenience in their usage currently lies in their very limited machining database. This research investigates the machinability of rapidly solidified aluminium, RSA 905, under varying cutting conditions in single point diamond turning. The machining parameters varied were cutting speed, feed rate and depth of cut. The resulting surface roughness of the workpiece and wear of the diamond tool were measured at various intervals. Acoustic emissions and cutting force were also monitored during machining. The results were statistically analysed and accurate predictive models were developed. Generally, very low tool wear, within 3 to 5 μm, and very low surface roughness, within 3 to 8 nm, was obtained. Acoustic emissions recorded were in the range of 0.06 to 0.13 V and cutting forces were in the range of 0.08 to 0.94 N. The trends of the monitored acoustic emissions and cutting force showed to have a linked representation of the tool wear and surface roughness results. Contour maps were generated to identify zones where the cutting parameters produced the best results. In addition, a range of machining parameters were presented for optimum quality where surface roughness and tool wear can be minimised. As the machining is of a nanometric scale, a molecular dynamics approach was applied to investigate the underlying mechanisms at atom level. The nanomachining simulations were found to have a correlation to the actual machining results and microstructural nature of the alloy. This research proves that rapidly solidified aluminium is a superior alternative to traditional aluminium alloys and provides a good reference with room for flexibility that machinists can apply when using rapidly solidified aluminium alloys. Efficiency could be improved by reducing the required machining interruption through effective monitoring and performance could be improved by maintaining quality and extending tool life through parameter selection.
- Full Text:
- Date Issued: 2018
- Authors: Otieno, Timothy
- Date: 2018
- Subjects: Aluminum alloys , Automobiles -- Materials Materials -- Mechanical properties
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23097 , vital:30415
- Description: Ultra-high precision machining is a material removing process under the nanotechnology regime whereby the highest dimensional accuracies are attained. Critical components for optical devices and optical measuring systems are mainly produced through ultra-high precision machining. Their mass production is usually implemented by utilising optical moulds. Aluminium alloys have proven to be advantageous and very commonly used in the photonics industry for moulds. This ever-increasing use and demand within optics have led to the development of newly modified grades of aluminium alloys produced by rapid solidification in the foundry process. The newer grades are characterised by finer microstructures and improved mechanical and physical properties. The main inconvenience in their usage currently lies in their very limited machining database. This research investigates the machinability of rapidly solidified aluminium, RSA 905, under varying cutting conditions in single point diamond turning. The machining parameters varied were cutting speed, feed rate and depth of cut. The resulting surface roughness of the workpiece and wear of the diamond tool were measured at various intervals. Acoustic emissions and cutting force were also monitored during machining. The results were statistically analysed and accurate predictive models were developed. Generally, very low tool wear, within 3 to 5 μm, and very low surface roughness, within 3 to 8 nm, was obtained. Acoustic emissions recorded were in the range of 0.06 to 0.13 V and cutting forces were in the range of 0.08 to 0.94 N. The trends of the monitored acoustic emissions and cutting force showed to have a linked representation of the tool wear and surface roughness results. Contour maps were generated to identify zones where the cutting parameters produced the best results. In addition, a range of machining parameters were presented for optimum quality where surface roughness and tool wear can be minimised. As the machining is of a nanometric scale, a molecular dynamics approach was applied to investigate the underlying mechanisms at atom level. The nanomachining simulations were found to have a correlation to the actual machining results and microstructural nature of the alloy. This research proves that rapidly solidified aluminium is a superior alternative to traditional aluminium alloys and provides a good reference with room for flexibility that machinists can apply when using rapidly solidified aluminium alloys. Efficiency could be improved by reducing the required machining interruption through effective monitoring and performance could be improved by maintaining quality and extending tool life through parameter selection.
- Full Text:
- Date Issued: 2018
Characterisation of dissimilar friction stir welds between 5754 Aluminium alloy and C11000 copper
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
- Authors: Akinlabi, Esther Titilayo
- Date: 2010
- Subjects: Friction stir welding , Aluminum alloys , Copper alloys
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9629 , http://hdl.handle.net/10948/1536 , Friction stir welding , Aluminum alloys , Copper alloys
- Description: Friction Stir Welding (FSW) is a solid state welding process invented and patented by The Welding Institute (TWI) in 1991, for joining ferrous and non-ferrous materials1. The FSW of Aluminium and its alloys has been commercialised; and recent interest is focused on joining dissimilar materials. However, in order to commercialise the process, research studies are required to characterise and establish process windows. This research work through material characterisation of the welded joints establishes a process window for the Friction Stir welding of 5754 Aluminium Alloy and C11000 Copper. Furthermore, preliminary studies83,85 on the FSW of aluminium and copper have revealed the presence of intermetallic compounds which are detrimental to the weld qualities. This research work is also aimed at establishing process parameters that will result in limited or no intermetallic formation in the weld. The joint integrity of the resulting welds will also be correlated with the input process parameters. Based on the preliminary investigations conducted, a final weld matrix consisting of twenty seven welds was produced by varying the rotational speed between 600 and 1200 rpm, and the feed rate between 50 and 300 mm/min using three different shoulder diameter tools – 15, 18 and 25 mm to compare the heat input into the welds and to achieve the best results. The welds were characterised through microstructural evaluation, tensile testing, microhardness profiling, X-Ray Diffraction analysis, electrical resistivity and statistical analysis – in order to establish the interrelationship between the process parameters and the weld qualities. viii Microstructural evaluation of the weld samples revealed that the interfacial regions are characterised by mixture layers of aluminium and copper; while 33 percent of the tensile samples are within the acceptable range (> 75 percent joint efficiency). High Vickers microhardness values were measured at the joint interfaces, which corresponded with the intermetallic compounds. The Energy Dispersive Spectroscopy analysis revealed the presence of thin layers of intermetallics in nanoscale at the interfacial regions. The diffractograms of the X-Ray Diffraction analysis showed small peaks for intermetallics in some of the welds. Low electrical resistivities were measured at the joint interfaces. The statistical analysis showed that the downward vertical force, (Fz) can significantly influence the resulting weld qualities. An overall summary of the analysis of the weld qualities - with respect to the shoulder diameter tools employed showed that the 18 mm shoulder diameter tool is most appropriate among the three shoulder diameters considered, and a process window of medium spindle speed of 950 rpm and low-to-medium feed rate between 50 and 150 mm/min is established for FSW of Aluminium and Copper. Welds produced at 1200 rpm and 300 mm/min with low heat input did not have intermetallics formed at the joint interface.
- Full Text:
- Date Issued: 2010
Optimisation of cold rolling process parameters to improve surface quality of the AA 3003-H22 treadbright coils
- Authors: Makhanya, Lehlohonolo
- Subjects: Aluminum alloys
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9611 , http://hdl.handle.net/10948/554 , Aluminum alloys
- Description: The main objective of this dissertation was to investigate how cold rolling process parameters could be optimised to improve surface quality of the AA 3003 H22 treadbright coils. This treadbright product is one of Hulett Aluminium’s main products and is exported mainly to the North American market. One of its critical requirements is a defect-free bright surface. The literature review was conducted with particular focus on the effects of selected parameters or settings with respect to surface quality and a chapter outlining these aspects has been included. It was clear from the literature review that selected parameters do affect the surface quality and if adjusted accordingly can improve surface quality on treadbright coils. Subsequent chapters after the literature review outline how the tests were conducted, procedures followed and equipments used from the cold rolling machine to laboratories. Surface appearance results after each parameter was adjusted, showed that the surface quality did improve and even got better when other parameters like the colouring roll angle and percentage reduction were adjusted. Correct working limits within which each parameter would yield acceptable surface quality were also established. All experiments conducted had no influence on the microstructure of the metal as it remained the same throughout each experiment. The same has been found with the mechanical properties as percentage reductions experiments led to no change in tensile strength, proof strength and percentage elongation. In conclusion, this research has proved that cold rolling process parameters selected did affect the product surface quality. If controlled they can be used to optimise the surface quality on the treadbright product as required by Hulett Aluminium and its customers.
- Full Text:
- Authors: Makhanya, Lehlohonolo
- Subjects: Aluminum alloys
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9611 , http://hdl.handle.net/10948/554 , Aluminum alloys
- Description: The main objective of this dissertation was to investigate how cold rolling process parameters could be optimised to improve surface quality of the AA 3003 H22 treadbright coils. This treadbright product is one of Hulett Aluminium’s main products and is exported mainly to the North American market. One of its critical requirements is a defect-free bright surface. The literature review was conducted with particular focus on the effects of selected parameters or settings with respect to surface quality and a chapter outlining these aspects has been included. It was clear from the literature review that selected parameters do affect the surface quality and if adjusted accordingly can improve surface quality on treadbright coils. Subsequent chapters after the literature review outline how the tests were conducted, procedures followed and equipments used from the cold rolling machine to laboratories. Surface appearance results after each parameter was adjusted, showed that the surface quality did improve and even got better when other parameters like the colouring roll angle and percentage reduction were adjusted. Correct working limits within which each parameter would yield acceptable surface quality were also established. All experiments conducted had no influence on the microstructure of the metal as it remained the same throughout each experiment. The same has been found with the mechanical properties as percentage reductions experiments led to no change in tensile strength, proof strength and percentage elongation. In conclusion, this research has proved that cold rolling process parameters selected did affect the product surface quality. If controlled they can be used to optimise the surface quality on the treadbright product as required by Hulett Aluminium and its customers.
- Full Text:
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