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A numerical analysis of machining induced residual stresses of Grade 5 titanium alloy

  • Authors: Laubscher, R.F. , Styger, G. , Oosthuizen, G.A.
  • Date: 2014-06
  • Subjects: Numerical analysis , Machining , Residual stresses , Titanium alloys
  • Type: Article
  • Identifier: uj:5055 , http://hdl.handle.net/10210/13603
  • Description: Machining induced residual stresses may have a significant effect on the mechanical performance of machined parts. AdvantEdge is an advanced finite element code dedicated to the modelling of the machining process. This paper describes a comparative evaluation of modelling results obtained with AdvantEdge with experimental results obtained during turning of Grade 5 (Ti6Al4V) titanium alloy. A two dimensional orthogonal turning process is modelled and compared with experimental data. Comparisons are made relative to residual stress, cutting force and cutting temperature for various different cutting parameters including cutting speed, feed rate and cut depth.
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A process planning framework for milling of titanium alloys

  • Authors: Dimitrov, D. , Conradie, P.J.T. , Oosthuizen, G.
  • Date: 2013
  • Subjects: Titanium alloys , Milling , High speed cutting , High performance machining
  • Type: Article
  • Identifier: uj:4949 , http://hdl.handle.net/10210/13049
  • Description: Titanium alloys are being used increasingly in new generation aircraft, creating a market for high value components. It is argued that knowledge development is the key factor for South African machining suppliers to penetrate the global aerospace supply chains. This paper discusses current results of a collaborative project aiming at systematic research towards improved and more efficient utilisation of the High Speed Cutting (HSC), and particularly the High Performance Machining (HPM) technologies for selected titanium alloys. A process planning framework for milling of titanium alloys has been developed. Using as point of departure prominent tool demands, this framework combines a tool wear map approach and cost modelling that enables process planners as well as machine operators to act towards optimised machining. In this way the targeted cost minimisation and lead time shortening could be modelled and practically achieved.
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An investigation of high speed machining of selected titanium alloys : process and thermal aspects

  • Authors: Kruger, Pieter
  • Date: 2013-11-21
  • Subjects: Titanium alloys , High-speed machining , Titanium alloys - Heat treatment
  • Type: Thesis
  • Identifier: uj:7784 , http://hdl.handle.net/10210/8679
  • Description: M.Ing. (Mechanical Engineering) , High strength alloys such as titanium are widely used within applications that require specific material properties. These include high strength, high temperature as well as low weight applications. Thus a need arises to investigate the fundamental to understand the mechanics of how these materials are machined. Titanium alloys are known for the difficulties that arise during the machining thereof. Complexities arise due to its inherent material properties, the most important property being the retention of strength at high temperatures. In addition to maintaining its strength, it becomes highly chemically reactive with other materials at increased temperatures. All these factors contribute to extreme temperatures at the tool chip interface contributing to increased tool wear and shortened tool life. The aim of the research is to investigate the effect of machining on various cutting process parameters including cutting force, temperature, tool wear and surface finish for grade 2 and grade 5 titanium alloys during high speed turning. Grade 2 titanium is a commercially grade with lower mechanical properties, while Grade 5 is titanium alloy with substantially higher mechanical properties and is the most widely used titanium alloy. In addition an experimental setup was developed and verified to conduct fundamental research on the high speed machining of titanium alloys. A literature review was concluded with focus on the machining of titanium alloys. This was followed by the development of the experimental setup, measurement and compilation of data. The data was compiled into graphs and compared with the current research available. The research found that for the cuts performed, that cutting forces are independent of cooling applied and that no substantial variation was noted between the two grades. When temperatures were evaluated, dramatic drops in temperature were noted when coolant was applied. As temperatures increased, specifically during un-cooled cutting, the inserts deteriorated having an effect on the quality of the surfaces obtained. When coolant was applied, substantial temperature drops were achieved, improving tool life and directly improving surface finishes. The best surface finish was achieved for higher cutting speeds as and lower feed rates. This phenomenon was found for both grades of titanium evaluated. The largest amount of tool wear was noted for the highest cutting speeds, with increased values noted for Grade 5 in comparison with Grade 2. This phenomenon is noted for crater as well as flank wear.
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An investigation on the effect of high speed machining on the osseointegration performance of grade 4 titanium alloy

  • Authors: Reddy, Andrish
  • Date: 2015-02-12
  • Subjects: Titanium alloys , Titanium alloys - Testing , High-speed machining
  • Type: Thesis
  • Identifier: uj:13323 , http://hdl.handle.net/10210/13339
  • Description: M.Eng. (Mechanical Engineering) , High speed machining (HSM) has the potential to greatly increase productivity and to lower manufacturing costs if workpiece surface integrity can be controlled. The surface fmish of a biomaterial is vitally important for proper implant functioning, and is the focus of this study. Grade 4 titanium was turned on a lathe with cutting speeds increasing from the conventional to the high speed range. The surface finish was assessed using profilometry, atomic force microscopy, and contact angle measurement. The ability of the material to bond directly with bone was predicted by cell adhesion studies. Results indicate that there is a general relationship between cutting speed, surface roughness, contact angle, and cell adhesion. Turning grade 4 titanium at cutting speeds between 150m/min and 200m/min may provide an optimal surface for osseointegration.
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An investigation on the effects of high speed machining on the surface integrity of grade 4 titanium alloy

  • Authors: Mawanga, Philip
  • Date: 2012-08-01
  • Subjects: Titanium alloys , High-speed machining , Titanium alloys - Testing
  • Type: Thesis
  • Identifier: uj:8924 , http://hdl.handle.net/10210/5394
  • Description: M.Ing. , Grade 4 titanium is a commercially pure grade titanium alloy extensively used in various industries including the chemical industry and more recently in the biomedical industry. Grade 4 has found a niche as a biomedical material for production of components such as orthopaedic and dental implants. Its physical properties such as high corrosion resistance, low thermal conductivity and high strength make it suitable for these applications. These properties also make it hard-to-machine similar to the other grades of titanium alloys and other metals such as nickel based alloys. During machining of titanium, elevated temperatures are generated at the tool-workpiece interface due to its low thermal conductivity. Its high strength is also maintained at these high temperatures. These tend to impair the cutting tool affecting its machinability. Various investigations on other grades of titanium and other hard-to-machine materials have shown that machining at high cutting speeds may improve certain aspects of their machinability. High speed machining (HSM) is used to improve productivity in the machining process and to therefore lower manufacturing costs. HSM may, however, change the surface integrity of the machined material. Surface integrity refers to the properties of the surface and sub-surface of a machined component which may be quite different from the substrate. The properties of the surface and sub-surface of a component may have a marked effect on the functional behaviour of a machined component. Fatigue life and wear are examples of properties that may be significantly influenced by a change in the surface integrity. Surface integrity may include the topography, the metallurgy and various other mechanical properties. It is evaluated by examination of surface integrity indicators. In this investigation the three main surface integrity indicators are examined. These are surface roughness, sub-surface hardness and residual stress. White layer thickness and chip morphology were also observed as results of the machining process used. The effect of HSM on the surface integrity of grade 4 is largely unknown. This investigation therefore aims to address this limitation by conducting an experimental investigation on the effect of HSM on selected surface integrity indicators for grade 4. Two forged bars of grade 4 alloy were machined using a CNC lathe at two depths of cut, 0.2mm and 1mm. Each bar was machined at varying cutting speeds ranging from 70m/min to 290m/min at intervals of approximately 20m/min. Machined samples were prepared from these cutting speeds and depths of cut. The three surface integrity indicators were then evaluated with respect to the cutting speed and depth of cut (DoC). iv Results show that a combination of intermediate cutting speeds and low DoC may have desirable effects on the surface integrity of grade 4. Highest compressive stresses were obtained when machining with these conditions. High compressive stresses are favourable in cases where the fatigue life of a material is an important factor in the functionality of a component. Subsurface hardening was noticed at 0.2mm DoC, with no subsurface softening at all cutting speeds. Surface hardness higher than the bulk hardness tends to improve the wear resistance of the machined material. Though surface roughness values for all depths of cut were below the standard fine finish of 1.6μm, roughness values of samples machined at 0.2mm DoC continued to decrease with increase in cutting speed. Low surface roughness values may also influence the improvement of fatigue life of the machined components. These machining conditions, (intermediate cutting speeds and low DoC), seem to have promoted mechanically dominated deformation during machining rather than thermal dominated deformation. Thermal dominated deformation was prominent on titanium machined at DoC of 1mm.
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Characterising the effect of laser metal deposited Ti6Al4V/Cu composites in simulated body fluid for biomedical application

  • Authors: Erinosho, M. F. , Akinlabi, Esther Titilayo , Pityana, S.
  • Date: 2015-01-15
  • Subjects: Hank’s solution , Laser metal deposition , Surface morphologies , Titanium alloys
  • Type: Article
  • Identifier: uj:5120 , ISBN 9789384935108 , http://hdl.handle.net/10210/14078
  • Description: Ti6Al4V alloy has been known to have very excellent corrosion resistance due to the oxide layer formed on its surface. Due to this property, the alloy is found applicable for biomedical implants. Copper shows an excellent antimicrobial property and has been found to stabilize the immune system. In this study, laser metal deposition of Ti6Al4V powder and Cu powder on Ti6Al4V substrates were conducted by varying the laser power between 600 W and 1800 W while the scanning speed, the powder flow rate and the gas flow rate were kept constant. The surface behaviour and the morphologies of the composites were evaluated under the microscope and the SEM after soaking for 4 hours, 5 days and 2 weeks respectively. The simulated body fluid (hank’s solution) was maintained at normal body temperature of about 37±1oC. The surfaces showed fracture topography with porous bone-like structures and some trivial pitting were observed.
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Characterization of aluminium and titanium carbide metal matrix composites produced via friction stir welding

  • Authors: Abegunde, Olayinka Oluwatosin
  • Date: 2015
  • Subjects: Friction stir welding , Titanium alloys
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/212716 , uj:21011
  • Description: Abstract: The Friction Stir Welding (FSW) process was invented and developed at The Welding Institute of United Kingdom in the year 1991 for solid state joining of aluminum and its alloys. Subsequently, this welding process has been used for joining other materials like magnesium, titanium and copper alloys, stainless steels and thermoplastics. In this research work, ample study was conducted on the material characterization of aluminium (Al) and titanium carbide (TiC) metal matrix composites produced via friction stir welding. Different process parameters were employed for the welding process. Rotational speeds of 1600 rpm to 2000 rpm at an interval of 200 rpm and transverse speeds of 100 to 300 mm/min at an interval of 100 mm/min were employed for the welding on an Intelligent Stir Welding for Industry and Research (I-STIR) Process development System (PDS) platform. The process parameters were carefully selected to represent low, medium and high for the rotation and the translation of the tool. The characterizations carried out include optical microscopy and the scanning electron microscopy analyses combined with Energy Dispersive Spectroscopy (SEM/EDS) techniques to investigate the particle distribution, microstructural evolution and the chemical analysis of the welded samples. Vickers microhardness tests was used to determine the hardness distribution of the welded zone and tensile testing was conducted to quantify the strength of the welded area to the base metal in order to establish the optimal process parameters. Based on the results obtained from the characterization analysis, it was found that the process parameters played a major role in the microstructural evolution. Homogenous distribution of the TiC particles was observed at high rotational speed of 2000 rpm and low transverse speed of 100 mm/min. The highest hardness value was measured at the stir zone of the weld due to the presence of the TiC reinforcement particles. The tensile strength also increased as the rotational speed increased and 92% joint efficiency was found in a sample produced at 2000 rpm and 100 mm/min. The EDS analysis revealed that Al, Ti and C made up the composition formed at the stir zone. The optimum process parameter setting was found to be at 2000 rpm and 100 mm/min and can be recommended. , M.Ing. (Mechanical Engineering Science)
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Characterizing the effect of laser power on laser beam formed titanium sheets

  • Authors: Akinlabi, Esther Titilayo
  • Date: 2014
  • Subjects: Laser beam formation , Titanium alloys
  • Type: Article
  • Identifier: uj:4751 , ISSN 978-93-81505-62-5 , http://hdl.handle.net/10210/11737
  • Description: Laser forming is a new advanced technology in manufacturing for the bending of sheet metals and the joining of metallic components in automobile, microelectronics and the aerospace industries. In the laser forming process, various factors such as the laser parameters and the material properties need to be considered in order to achieve optimum properties after laser forming. This paper reports the effects of the laser power on the resulting curvatures of the laser beam formed Titanium sheets. The laser formed samples were characterized through the microstructure and the mechanical properties. The results obtained during the microscopic evaluation of the specimen showed that the grain sizes of the formed samples increases and is proportional to the laser power employed to form the samples. It was also found that the Vickers microhardness is directly proportional to the laser power and the radius of curvature increases with a decrease in the Laser power. Hence, the grain size is also directly proportional to the Vickers microhardness of the sample
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Effect of constitutive modeling during finite element analysis of machining-induced residual stresses in Ti6Al4V

  • Authors: Oosthuizen, Gert A. , Laubscher, Rudolph F. , Styger, Gary
  • Date: 2014
  • Subjects: Residual stresses , Titanium alloys , Finite element method , Machining
  • Type: Article
  • Identifier: uj:5028 , http://hdl.handle.net/10210/13547
  • Description: Residual stress is an important surface integrity descriptor that may have a marked effect on the functional performance of machined alloy parts. This paper describes a finite element evaluation of the effect of different constitutive models on machining induced residual stresses for Ti6Al4V titanium alloy. A two dimensional orthogonal turning process is modelled and the results compared to experimental data. Residual stress is evaluated with respect to different elastic-viscoplastic constitutive models at certain cutting speeds and feeds. The general-purpose finite element code MSC Marc@ was used with comparisons with experimental data made relative to residual stress, cutting force and temperature. The magnitude and extent (depth) of the residual stress field is evaluated with regards to the different material models and compared with experimental data.
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Effect of laser power on the microstructure and microhardness property of hybrid fabricated Ti6Al4V based metal matrix composite

  • Authors: Ochonogor, O. F. , Akinlabi, Esther Titilayo , Nyembwe, Didier
  • Date: 2016
  • Subjects: Titanium alloys , Laser treatment
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/93318 , uj:20333 , Citation: Ochonogor, O.F., Akinlabi, E.T. & Nyembwe, D. 2016. Effect of laser power on the microstructure and microhardness property of hybrid fabricated Ti6Al4V based metal matrix composite.
  • Description: Abstract: Several surface coatings on Ti-6Al-4V alloy using laser treatment technique have been investigated in this paper. A hybrid Ti-6Al-4V based metal matrix composites system was also successfully fabricated. This was possible using three hoper system which contained 3.8 vol. % of Ti-6Al-4V and a small amount 0.1 B4C and 0.1 BN respectively. Two different laser powers “2000 W and 1400 W with scanning speed of 1.0 were employed. The idea of these powder coatings and reason for investigating the different Laser power is to evaluate the influence of laser power on the surface morphology and hardness property of Ti-6Al-4V/B4C/BN alloy systems. The hardness result of experimental showed a general improvement. The hardness revealed that the Ti-6Al- 4V/B4C/BN system fabricated at 2000W showed a hardness improvement as high as 640.4 HVO.5 compared to the as receive Ti-6Al-4V substrate Hardness value of about 357.3 HVO.5 and that of 1400W recorded a hardness value of 886 HVO.5. The percentage increase from the as received Ti-6Al-4V alloy was 147.9% and 79.2% respectively. Problems to be solved and the prospective application of laser modification of the hybrid titanium alloy formed were also highlighted.
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Effect of number of laser scans on the corrosion behavior of laser formed titanium alloy

Effect of powder density variation on premixed Ti-6Al-4V and Cu composites during laser metal deposition

Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy

  • Authors: Franklin, Ochonogor O. , Akinlabi, Esther Titilayo , Nyembwe, Kasongo D. , Pityana, Sisa , Shongwe, Mxolisi Brendon
  • Date: 2016
  • Subjects: Heat treatment , Titanium alloys
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/214859 , uj:21334 , Citation: Franklin, O.O. et al. 2016. Effect of rapid cooling of high temperature laser fabricated Ti/B4C/BN coating on Ti-6AL-4V alloy.
  • Description: Abstract: A hybrid Ti-6Al-4V based metal matrix composites characterized of martensitic structure was formed using three hoper system. Different volume percentages used were as follows: 3.0 vol. % of Ti-6Al-4V, 3.2 vol. % of Ti-6Al-4V and 3.4 vol. % of Ti-6Al-4V respectively while an equal amount of BN and B4C mixed with the Ti-6Al-4V powder particle was fed through the hoper systems at a constant laser power 2000 W and scanning speed of 1.0 m/s. The influence of rapid cooling and varied powder particle at constant coating temperature on the surface morphology and hardness property of Ti-6Al- 4V/B4C/BN alloy systems was however investigated. The hardness result of experimental showed a general improvement. Further result showed that the Ti-6Al- 4V/B4C/BN system fabricated at 3.0 Ti Vol. percent had a hardness improvement as high as 986.9 HVO.5 compared to the as receive Ti-6Al-4V substrate Hardness value of about 357.3 HVO.5. 3.2 Ti Vol. percent systems recorded a hardness value of 723.4 HVO.5 and 3.2 Ti Vol. percent system recorded a hardness value of 609.6 HVO.5. Optical microscope (OM) Scanning electron microscope (SEM) was also carried out for microstructural evaluation and Energy Dispersive Spectroscopy (EDS) to confirm the elemental composition of coating when necessary.
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Effects of thermal processing of blended and roll compacted Ti6Al4V strips on microstructure and properties

  • Authors: Muchavi, Noluntu Skhumbuzo
  • Date: 2019
  • Subjects: Titanium - Processing , Titanium - Metallurgy , Titanium alloys
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/297356 , uj:32415
  • Description: Abstract: Titanium and titanium alloys are considered to be one of the most significant advanced materials used in the aerospace, structural, chemical, marine, oil and gas, petrochemical, medical and other industries today. This can be attributed to its comprehensive properties such as excellent corrosion resistance, high heat resistance, specific strength and fracture toughness, good low temperature toughness and low density. Due to the high cost of producing titanium metal through the conventional way of using Ingot Metallurgy (IM), alternative cost effective methods of such as Powder Metallurgy (PM) have been developed. There are several forms of powder metallurgy processes but the process that was used for the research work is that of Direct Powder Rolling (DPR). This process uses powder as a feedstock for a roll compaction mill. The rolling mill consolidates the feedstock into a green strip that has some form of ductility. DPR of Ti and titanium alloy powder has been successfully demonstrated by CSIRO as well ADMA Incorporated using different processing techniques which contain multiple fabrication stages. The proposed research work was aimed at evaluating an alternative DPR processing route containing far less fabrication stages which leads to a further reduction in cost whilst achieving mechanical properties equivalent to those of wrought materials. The aim of this work was to produce roll compacted Ti6Al4V strips though roll compaction and sintering as well as to study the effect of thermal processing of the strips on density, microstructure and mechanical properties. The objectives of this work were therefore to define roll compaction parameters that will achieve green strips of 85 ±2% theoretical density of Ti6Al4V, define sintering parameters that will produce a perfectly homogeneous strip with a high final sintered density of ≥99% theoretical density and to achieve mechanical properties equivalent to those of Ti6Al4V sheets as per ASTM B265-15 standard specification for Ti and Ti alloy strip, sheet and plate. The roll compacted strips were sectioned and characterised for density using the volumetric density determination method. The strips were sintered at temperatures of 1200, 1300 and 1400°C with holding times of 2, 3 and 4 hours in a Carbolite tube... , M.Tech. (Engineering Metallurgy)
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Effects of wire electrical discharge machining on fracture toughness of grade 5 titanium alloy

  • Authors: Madyira, Daniel M. , Akinlabi, Esther Titilayo
  • Date: 2014
  • Subjects: Titanium alloys , Electrical discharge machining , Fracture toughness , Compact tension
  • Type: Article
  • Identifier: uj:4752 , ISSN 2078-0958 , http://hdl.handle.net/10210/11738
  • Description: Grade 5 titanium (Ti6Al4V) is considered as the workhorse material when it comes to automotive and aerospace applications. It is widely referred to as an aerospace alloy and is relatively a new engineering material. The main attraction of this material is its high strength to weight ratio when compared to such common engineering materials such as steel and aluminum alloys. One of the major challenges in the use of this aerospace material is its machinability. Its high strength which is maintained at elevated temperatures, low thermal conductivity, low elastic modulus and high reactivity with oxygen is a perfect recipe for machining challenges. This leads to high tool wear and long production times. Such challenges are sometimes overcome by electrical discharge machining (EDM). Given that titanium is usually applied to mission critical components (gears, shafts, wing sections), it is important to understand the possible effect of wire EDM on their structural performance. One of the structural integrity indicators in such applications is fracture toughness. Fracture toughness is widely used for damage tolerance analysis of aerospace components in which critical crack sizes are computed for given loading conditions to arrive at safe inspection and maintenance intervals. It is therefore the purpose of this paper to conduct a study on the effect of wire EDM on the fracture toughness of this aerospace material. Standard test procedure using compact tension (CT) specimen is used to measure the fracture toughness. Four specimens are produced using wire EDM. This includes the pre-crack which is usually produced by fatigue cycling. Obtained results indicate a slight decrease in fracture toughness compared to that reported in literature. In addition, it can also be concluded that wire EDM can be used as an alternative to fatigue pre-cracking in fracture toughness testing of titanium alloys.
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Enhancing the integrity of machined titanium alloy

  • Authors: Mathoho, Ipfi
  • Date: 2017
  • Subjects: Titanium alloys , Mechanical alloying , Milling (Metal-work) , High-speed machining , Surfaces (Technology)
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/269763 , uj:28661
  • Description: M.Phil. (Mechanical Engineering) , Abstract: Titanium alloys have proved to be the working horse in industries, such as aerospace, chemical and biomedical; and especially Ti-6Al-4V alloy owing to their excellent weight-to-strength ratio, corrosion resistance and biocompatibility. Such properties define a material that is required for engineering purposes; and therefore, this justifies the use of titanium alloys extensively nowadays. However, titanium alloys are known to be hard to machine materials, due to their low thermal conductivity, poor modulus of elasticity, chemical reactivity and strain hardening. Milling is a machining process, which is known to be a flexible process – with the ability to generate different three-dimensional shapes; and it makes use of a multi-point cutting tool that rotates during milling. It is known that milling parameters (feed rate, cutting speed/spindle speed and depth of cut) and machining conditions play a critical role in determining the operational efficiency of the workpiece. The current research project successfully milled Ti-6Al-4V 100x100x7 mm plates, using a vertical-milling machine; while varying the spindle speed (120, 150, and 180 rev/min), depth of cut (1, 1.5, and 2 mm) and keeping the feed rate constant at 4.6 mm/min. Milling was conducted by making use of a tungsten carbide cutting tool; and for each parameter, a new cutting tool was inserted to elude the effect of tool wear; since there are limited research studies on the milling of Ti-6Al-4V, which does not elude the effect of tool wear on the outcome of the milling operation. Furthermore, milling was conducted under dry conditions and flood conditions – using a synthetic soluble cutting fluid...
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Experimental investigation and CFD modelling of laser metal deposited hybrid coating on grade five titanium alloy

  • Authors: Gharehbaghi, Rezvan
  • Date: 2018
  • Subjects: Titanium alloys , Metal coating , Pulsed laser deposition , Computational fluid dynamics
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/284286 , uj:30697
  • Description: M.Ing. (Mechanical Engineering) , Abstract: The aim of this research project is to investigate the effect of laser deposited hybrid coatings (Al-Cu-Fe) on the physical, mechanical and metallurgical properties of titanium alloy (Ti-6Al-4V) by experimental techniques and numerical analysis. Laser Additive Manufacturing is relatively new in the manufacturing industry. Laser metal deposition (LMD) can be used to manufacture freeform shapes, to produce parts from graded porous to fully dense solid structures as well as to directly create various surface coatings on a part. This investigation also enhances the mechanical and corrosion properties of hybrid coatings of Al-Cu-Fe on Ti-6Al-4V alloy applicable in the aerospace industry through LMD technique. Icosahedral Al-Cu-Fe as quasicrystals are a relatively new class of materials which exhibit unusual atomic structure with useful physical and chemical properties. Ti6Al4V/Al-Cu-Fe composites were analysed using optical microscopy, scanning electron microscopy (SEM) with energy dispersive microscopy (EDS), indentation testing, x-ray diffraction (XRD) analysis. The hardness and wear resistance performances of the laser coatings were examined by high diamond dura scan microhardness tester and CERT UMT-2 reciprocating sliding machine. The anti-corrosion performances were evaluated by linear polarization technique in 3.5 M NaCl. It was found that the geometrical properties (deposit width and height, heat affected zone (HAZ) height), dilution rate, aspect ratio and powder efficiency of each sample remarkably increased with increasing laser power due to the laser-material interaction. However, the geometrical properties decrease with increasing scanning speed. Solidification began with formation of some large particles such as Al and Fe. The atomic migration of Cu into Ti lattice resulted in the formation of β-Ti phase during cooling and travels a longer distance in the Ti lattice than other elements which opens more crystallographic structure of the β matrix. It was observed that there was higher number of titanium and aluminium presented in the composite as per the theoretical expectation. The indentation testing reveals that Ti6Al4V/Al-Cu-5Fe composite has the highest mean hardness value and it decreases with increasing laser power at scanning speed of 0.8 m/min and 1 m/min. The corrosion and wear resistance of titanium alloy was improved by depositing Al-Cu-Fe quasicrystalline coating. The results obtained from numerical simulation using CFD analysis demonstrated that Ti6Al4V/Al-Cu-10Fe has the highest dilution rate, aspect ratio and HAZ height, and this corresponded with the experimental results. Finally, it was found that Ti6Al4V/Al-Cu-Fe composite have useful mechanical, physical and...
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Experimental investigation of laser beam forming of titanium and statistical analysis of the effects of parameters on curvature

  • Authors: Akinlabi, Stephen A. , Akinlabi, Esther Titilayo
  • Date: 2013
  • Subjects: Laser beam forming , Titanium alloys
  • Type: Article
  • Identifier: uj:4746 , ISSN 2078-0966 , http://hdl.handle.net/10210/11732
  • Description: Laser beam forming, a non-contact manufacturing process has become a viable manufacturing process for shaping metallic components. The capability of laser beam forming and bending demands more experimental studies to identify an optimized parameter setting and the likely parameters influencing the formed curvature. This paper investigates experimental laser beam forming of Ti6Al4V titanium alloy using a 4.4 kW Nd: YAG laser and studied the effects of the process parameters on the formed curvature. It was established that an increase in both the laser beam power and the number of scan tracks reduces the radius of curvature in the formed sheets having a more dome shape. The scan speed on the other hand, achieved the same good curvature at a slower or reduced scan speed to allow enough laser – material interaction. Furthermore, both the ANOVA and the regression analysis confirmed the repeatability of the experimental data. A simple regression model was developed based on the known active parameters to determine approximate curvatures instead of running a series of experiments.
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Laser additive manufacturing technology for crack repairs in titanium alloy components

  • Authors: Marazani, Tawanda
  • Date: 2016
  • Subjects: Laser welding , Welded joints - Cracking , Manufacturing processes , Titanium alloys
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://ujcontent.uj.ac.za8080/10210/366385 , http://hdl.handle.net/10210/213019 , uj:21067
  • Description: Abstract: Laser additive technology (LAT) uses a laser beam which locally melts the target material surface. The technology has been widely used for high value and critical components mainly in the aerospace and the biomedical industries. Due to its favourable properties, titanium has become a workhorse metal, particularly the grade 5 titanium alloy (Ti-6Al-4V). Recent years have seen increased research and development studies on the application of the laser additive technology in the production of Ti-6Al-4V components. These ranged from free form fabrication, materials processing, manufacturing, maintenance and repairs. Attempts to use the laser additive technology for the repair of cracks in Ti alloy components have been recently reported where V-grooves have been recommended. Further attempts to use narrow U-grooves for crack repairs were not successful and hence not widely adopted. There is limited published work on the use of narrow rectangular grooves for crack repairs in Ti-6Al-4V.There is therefore a need to further investigate the potential repairing of U-cracks using LAT. This research work established through experimental design, mechanical and metallographic characterization, a process that was used for the laser additive repair of cracks in Ti-6Al-4V components. The preliminary repairs were made without laser re-melting. They were analysed for defects using the optical microscopy (OM) and their macrographs revealed lack of sidewall fusion, lack of interlayer fusion, lack of intralayer fusion, unmelted powder and porosity. The matrix used for the preliminary repairs was then optimised using the observations made during the preliminary phase. It was from this preliminary phase optimization that the final experimental matrix of the research was developed. Controlled laser re-melting, reduction of the spot size diameter and lowering of the scanning speed were introduced as main process parameters of the optimized matrix. The optimized repairs were further characterized using the optical microscopy (OM) and the scanning electron microscopy (SEM). The optimized repairs were observed to have very limited defects. The energy dispersive spectroscopy (EDS) analyses revealed that the deposits were dominated by Ti, Al and V which were the main compositions of the material. The Vickers microhardness tests, microhardness-tensile strength correlations and the Charpy impact tests obtained results confirmed mechanically sound repairs with good evolving microstructural properties... , M.Ing. (Mechanical Engineering)
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Laser metal deposition of functionally graded Ti6Al4V/TiC

  • Authors: Mahamood, R. M. , Akinlabi, Esther Titilayo
  • Date: 2015-06-20
  • Subjects: Functionally graded materials , Laser metal deposition , Titanium alloys
  • Type: Article
  • Identifier: uj:5119 , ISSN 02641275 , http://hdl.handle.net/10210/14077
  • Description: Functionally graded materials (FGMs) are advanced materials with improved properties that enable them to withstand severe working environment which the traditional composite materials cannot withstand. FGM found their applications in several areas which include: military,medicine and aerospace. Various manufacturing processes are used to produce functionally graded materials that include: powder metallurgy, physical vapour deposition, chemical vapour deposition process and laser metal deposition process. Laser metal deposition (LMD) process is an additive manufacturing process that can be used to produce functionally graded material directly from the three dimensional (3D) computer aided design (CAD) model of the part in one single process. LMD process is a fairly new manufacturing process and a highly non-linear process. The process parameters are of great importance in LMD process and they need to be optimized for the required application. In this study, functionally graded titanium alloy composite was produced using optimized process parameters for each material combination as obtained through a model that was developed in an initial study and the FGM was characterized throughmetallurgical, mechanical and tribological studies. The results showthat the produced FGM has improved properties when compared to those produced at constant processing parameters for all material combinations.
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