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Fabrication Of Gamma Titanium Aluminide Alloys By Gas Tungsten Arc Welding-Based Additive Layer Manufacturing, Yan Ma

University of Wollongong Thesis Collection 1954-2016

Although intermetallic titanium aluminide alloys have extensive practical industrial applications owing to their unique characteristics, their usage has been limited by the difficulties and high cost of fabrication.

This research proposes an alternative manufacturing approach to fabricating titanium aluminide alloys, which combines in-situ alloying and additive layer manufacturing (ALM) using gas tungsten arc welding (GTAW). This new fabrication process promises significant time and cost saving in comparison to traditional methods. Since the chemical composition, microstructural features and mechanical performance of the asfabricated components can be greatly influenced by the manufacturing parameters, the effect of several important variables including arc current, …

Characterisation Of Ti-6al-4v Deposits Produced By Arc-Wire Based Additive Manufacture, Nicholas Hoye

University of Wollongong Thesis Collection 1954-2016

Significant efforts have been made in recent times to reduce the relatively high cost associated with titanium alloys and hence allow for greater utilisation of the unique properties offered by these materials. One such area of interest is additive manufacturing of components through arc-wire based fusion welding processes. The present thesis details research conducted to characterise aspects of weldability of the Ti-6Al-4V titanium alloy related to this emerging manufacturing process. The resulting properties of the final deposit were also evaluated, with conclusions drawn on the suitability of the arc-wire deposition technique for the additive manufacture of large scale titanium components. …

Mechanism Of Toughening In Hydrogels, Hai Xin

University of Wollongong Thesis Collection 1954-2016

Tough hydrogel materials have recently attracted broad attentions and interests. Due to their high fracture energies, they are promising candidates for a wide range of biological and biomechanical applications. Two important categories of tough hydrogels are Double Network hydrogel (DN) and ionic-covalent PAAm-alginate hybrid gel (abbreviated as the “hybrid gel”). Both gel systems exhibit interesting network structures and remarkably enhanced mechanical toughness with respect to the conventional covalently-crosslinked hydrogels. The objective of the present PhD study is to provide a quantitative analysis on the toughening mechanism and damage process for DN and the hybrid hydrogels. The investigation for each of …

Effect Of Thermo-Mechanical Processing, Ageing And Compression On Microstructure And Mechanical Properties Of Near Β Ti Alloys Made From Powder, Mansur Ahmed

University of Wollongong Thesis Collection 1954-2016

The high cost of titanium components restricts wider utilisation of Ti materials. Blended elemental powder metallurgy (BEPM) is a promising cost-effective approach to the manufacturing of Ti products for non-fatigue critical applications. In this series of investigations three near-b Ti alloys (Ti-5Al-5Mo-5V-1Cr-1Fe, Ti-5Al-5Mo-5V-2Cr-1Fe and Ti-10V-3Fe-3Al) produced by BEPM were subjected to different thermo-mechanical processing (TMP) schedules using a Gleeble 3500 simulator. The selected TMP schedules resulted in beneficial reductions in porosity and fragmentation of grain boundary α phase. Selection of specific cooling regimes to room temperature could be used to control the extent of b phase recrystallisation, volume fraction of …

Microstructure, Crystallography And Mechanical Properties Of Low-Si Trip Steels, Fayez Alharbi

University of Wollongong Thesis Collection 1954-2016

Transformation-­‐induced plasticity (TRIP) steel has received significant research effort because its high strength to ductility ratios and high energy absorption make it eminently suitable for automotive applications. This work investigates the microstructure, crystallography, and mechanical properties of thermo-­mechanically processed (TMP) low-Si high-Al TRIP steels with and without the addition of 0.03Nb and 0.02Ti (wt%) using a combination of optical and electron microscopy, X-ray diffraction, and tensile testing.

The two TRIP steels investigated were subjected to simulated TMP and galvanising and then the results were compared with intercritically annealed–galvanised steels. After undergoing different thermo-­‐mechanical processing schedules it was found that adding …

A Study Of The Mechanical Properties And Wear Behaviour Of The Oxide Layer Formed On High Speed Steel Work Rolls, Wan Fathul Hakim Zamri

University of Wollongong Thesis Collection 1954-2016

This research is part of a larger study conducted to understand the wear of hot rolling rolls. A significant cost of hot rolling is associated with the consumption of rolls; hence a comprehensive understanding of how the roll material wears is important. As the surfaces of rolls are covered by an oxide layer it is important that the mechanical and tribological properties of these oxides be known. The mechanical properties of the oxide layer are an important aspect that leads to a better prediction of its behaviour during hot rolling operations. Due to the complex nature of the phenomena that …

Properties Of Hydrogels Prepared With Different Chain Length Distribution, Sasha Sadegholvaad

University of Wollongong Thesis Collection 1954-2016

Tough (the ability to withstand cracking under an applied stress/load) hydrogels are being developed for many applications because of their significant advantages such as fairly easy synthesis process and useful properties (such as soft and wet character) as well as their capability to bear high mechanical loads [1]. It is always essential and challenging to find a proficient method to synthesise tough hydrogels. A few types of tough hydrogels have been introduced in the last decade, namely topological gels by Okumura and Ito [2], nanocomposite hydrogels by Haraguchi and Takehisa [3] and double network hydrogels by Gong et al [4], …

Microstructure, Texture And Vacancy-Type Defects In Severe Plastic Deformed Aluminium Alloys, Lihong Su

University of Wollongong Thesis Collection 1954-2016

Severe plastic deformation (SPD) as a technique to process ultrafine grained (UFG) materials has attracted significant interest over recent years. Equal channel angular pressing (ECAP) and accumulative roll bonding (ARB) are two of the most important SPD techniques. Despite that many studies have been conducted on both techniques, some research areas have still not been explored deeply, such as the influence of low pressing temperature on ECAP, the deformation behaviour of the same material in monotonic material sheets or laminated composite sheets during ARB and the evolution of point defects during SPD. The present work investigates the microstructure, mechanical properties, …

The Development Of Electrospun Polymer Nanofibres And Measurement Of Their Individual Mechanical Properties With The Atomic Force Microscope, Adrian Gestos

University of Wollongong Thesis Collection 1954-2016

Electrospun nanofibres are being developed at an ever increasing rate for a range of applications. The intended applications vary widely, from tissue engineering inspired by natural tissue scaffolds, to energy applications as high surface area electrodes in batteries and fuel cell devices. However, the ability to routinely characterise the individual fibres themselves is still catching up with the rate and sophistication of their development.

The characterisation of individual electrospun fibres in regards to their mechanical properties is the main focus of this thesis. Understanding individual nanofibre mechanical properties is important for predicting their suitability in an intended application and can …