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Influence of scanning speed on the intermetallic produced in-situ in laser metal deposited TiC/Ti6Al4V composite

Effect of weight per meter of reinforced bar on mechanical properties and microstructure

  • Authors: Musonda, V. , Akinlabi, Esther Titilayo , Jen, T.C.
  • Date: 2017
  • Subjects: Billets , Hot rolling , Microstructure
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/241963 , uj:24945 , Citation: Musonda, V., Akinlabi, E.T. & Jen, T.C. 2017. Effect of weight per meter of reinforced bar on mechanical properties and microstructure.
  • Description: Abstract: Reinforced bars (rebars) are Thermo-mechanically treated (TMT) bars hot rolled from steel billets produced from scrap melted in an Electric Arc Furnace (EAF) at a temperature of about 1600 ℃ (usually 1580℃). Weight per meter of a low carbon steel rebar is one aspect which has been neglected by some steel producers during the tensile testing in the rod mill. Determination of weight per metre is explicitly required for a TMT rebar. Any reduction in mass will mean a lowering in capacity of the steel reinforcing bar. A series of “heat” numbers or batches of molten steel from an EAF for the production of steel sample A, (Y10 and Y 12 rebars), were observed at a Steel plant to investigate the effect of weight per meter of reinforced bar on the mechanical properties and microstructure. The rolling speed range was 3m/s to 14 m/s for different “heats”. Two other steel samples B and C were sourced from the local market to compare with Sample A. Samples collected from different sources on the local market, however, showed lower values of weight per meter different from the prescribed standards. This did not only affect the ultimate tensile strengths which were higher than normal but also the microstructure which deviated from the standard for this material. Sample A, did not only show a good combination of tensile strength and yield stress of 450MPa and a maximum tensile strength of 650MPa but also a standard pearliteferrite microstructure, while sample B and C exhibited excessive high strengths and brittle behaviour and can be prone to failure.
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Microstructural and mechanical properties of spark plasma sintering of Ni2 Cr11Al powders synthesized by mechanical alloying for thermal barrier coating

Influence of tool rotational speed on microstructure and joint strength of friction stir spot welded pure copper

The influence of scanning speed and number of scans on the properties of laser formed steel

Characterization of surface roughness of laser deposited Titanium alloy and copper using AFM

  • Authors: Erinosho, M. F. , Akinlabi, Esther Titilayo , Johnson, O. T.
  • Date: 2017
  • Subjects: AFM , LMD , Microstructure
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/251627 , uj:26211 , Citation: Erinosho, M. F., Akinlabi, E. T. & Johnson, O. T. 2017. Characterization of surface roughness of laser deposited Titanium alloy and copper using AFM.
  • Description: Abstract: Laser Metal Deposition (LMD) is the process of using the laser beam of a nozzle to produce a melt pool on a metal surface usually the substrate and metal powder is been deposited into it thereby creating a fusion bond with the substrate to form a new material layer against the force gravity. A good metal laminate is formed when the wettability between the dropping metal powder and the substrate adheres. This paper reports the surface roughness of laser deposited titanium alloy and copper (Ti6Al4V + Cu) using the Atomic Force Microscopy (AFM). This AFM is employed in order to sense the surface and produce different manipulated images using the micro-fabricated mechanical tip under a probe cartridge of high resolution. The process parameters employed during the deposition routine determines the output of the deposit. A careful attention is given to the laser deposited Ti6Al4V + Cu samples under the AFM probe because of their single tracked layers with semi-circular pattern of deposition.
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Microstructural characterization and hardness properties of magnesium alloy processed by high pressure torsion

Gas flow rate and powder flow rate effect on properties of laser metal deposited Ti6Al4V

  • Authors: Pityana, Sisa , Mahamood, Rasheedat M. , Akinlabi, Esther Titilayo , Shukla, Mukul
  • Date: 2013
  • Subjects: Gas flow rate , Microhardness , Microstructure , Powder flow rate , Laser metal deposition , Additive manufacturing technology
  • Type: Article
  • Identifier: uj:4849 , http://hdl.handle.net/10210/12516
  • Description: Tracks of Ti6Al4V powder were deposited on Ti6Al4V substrate using Laser Metal Deposition (LMD) process, an Additive Manufacturing (AM) manufacturing technology, at a laser power and scanning speed maintained at 1.8 kW and 0.005 m/s respectively. The powder flow rate and the gas flow rate were varied to study their effect on the physical, metallurgical and mechanical properties of the deposits. The physical properties studied are: the track width, the track height and the deposit weight. The mechanical property studied is the Microhardness profiling using Microhardness indenter at a load of 500g and dwelling time of 15 μm. The metallurgical property studied is the microstructure using the Optical microscopy. This study revealed that as the powder flow rate was increased, the track width, track height and the deposit weight were increased while as the powder flow rate was increased, the track width, track height and the deposit weight decreased. The results are presented and discussed in detail.
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Effect of water flow rate on the yield strength of a reinforced bar

  • Authors: Musonda, Vincent , Akinlabi, Esther Titilayo , Jen, Tien-Chien
  • Date: 2017
  • Subjects: Hot rolling , Microstructure , Rebar
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://ujcontent.uj.ac.za8080/10210/370699 , http://hdl.handle.net/10210/243763 , uj:25198 , Citation: Musonda, V., Akinlabi, E.T. & Jen, T.C. 2017. Effect of water flow rate on the yield strength of a reinforced bar. Advances in Engineering Research (AER), volume 102, Second International Conference on Mechanics, Materials and Structural Engineering (ICMMSE 2017).
  • Description: Abstract: High strength requirement of Thermo-mechanically treated (TMT) rebars is crucial in the construction of flyovers, bridges and high rise buildings because of the good combination of the mechanical properties. The yield strength is expected to be between 450 MPa and 550 MPa after the hot rolling process depending on prescribed standards. A series of experimental trials during a hot rolling process were carried out in a steel plant in which parameters such as the water flow rate and the processing time were varied to study their effect on the evolving mechanical properties of the rebars. Four “heats”(A “heat” is a batch of molten steel, referred to as tap to tap cycle and involves furnace charging with scrap, melting, deslagging, tapping molten steel and furnace turn-around. Furnace turn-around is the period following completion of tapping until the furnace is recharged for the next “heat”) were done to produce Y 12 mm reinforced bars (rebars). For every “heat” done, tensile tests were carried out on the samples every after 15 minutes to establish the yield strength of the rebar. At least eight samples were tested in every “heat”. It was observed that some samples showed low values of yield strength (< 450 MPa) which falls short of the minimum guaranteed yield strength. It was further noted that the water flow rate in the water cooling chamber was far below 600 m􀬷⁄h for this size of rebar in some cases. A series of these tests were conducted and the water flow rate adjusted in order to arrive at the optimum flow rate corresponding to the expected yield strength and microstructure. The quenching time in the water cooling chamber was in the range 0.1 to 0.5 seconds and the results obtained both for the tensile tests and microstructure after several adjustments to the flow rate in particular yielded optimum results consistent with prescribed standards.
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Microstructure evolution and mechanical characterization of friction stir welded titanium alloy Ti–6Al–4V using lanthanated tungsten tool

Laser surface modification of Ti6Al4V-Cu for improved microhardness and wear resistance properties

  • Authors: Erinosho, Mutiu F , Akinlabi, Esther Titilayo , Pityana, Sisa , Owolabi, Gbadebo
  • Date: 2017
  • Subjects: Dry sliding wear , Laser metal deposition , Microstructure
  • Language: English
  • Type: Articles
  • Identifier: http://hdl.handle.net/10210/241797 , uj:24925 , Citation: Erinosho, M.F. et al. 2017. Laser surface modification of Ti6Al4V-Cu for improved microhardness and wear resistance properties.
  • Description: Abstract: The light weight of Ti6Al4V as a titanium alloy is been amongst the properties that have been tailed for the aerospace and other industrial applications. To modify the properties of this alloy, Cu has been added to host an antimicrobial effect in the revised alloy for marine application. The LMD process on the Ti6Al4V alloy and Cu was been investigated for surface modification in order to combat the problem of biofouling in the marine industry. The investigations focused on the microstructural observations, micro-hardness measurements and dry sliding wear in the presence of 3 and 5 weight percents of Cu. The microstructure results showed that Widmanstätten microstructures were formed in all the samples and lose their robustness towards the fusion zone as a result of the transition of heat sink towards the substrate. The microhardness values of Ti6Al4V-3Cu and Ti6Al4V-5Cu alloys were greatly improved to 547±16 VHN0.5 and 519±54 VHN0.5 respectively. In addition, the behaviour of wear loss on the surface of the Ti6Al4V-Cu alloys exhibited great improvement as compared with the parent...
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Experimental and numerical analysis of geometrical properties of laser metal deposited titanium

  • Authors: Akinlabi, Esther Titilayo , Tayob, Mohammed A. , Pietra, Francesco
  • Date: 2016
  • Subjects: Ansys , Heat-Affected zone , Laser metal deposition , Microhardness , Microstructure , Porosity , Powder flow rate , Titanium
  • Language: English
  • Type: Conference proceedings
  • Identifier: http://hdl.handle.net/10210/93300 , uj:20330 , Citation: Akinlabi, E.T., Tayob, M.A. & Pietra, F. 2016. Experimental and numerical analysis of geometrical properties of laser metal deposited titanium.
  • Description: Abstract: Laser metal deposition (LMD) is a manufacturing process, which can be used to manufacture a complete, fully functional part by building it up layer-by-layer using the data from a Computer-Aided-Design (CAD) file. The layer-by-layer addition can also be used to rebuild worn-out sections of existing parts, as well as to deposit protective coatings to protect parts in surface engineering. The process involves laser heating a substrate, on which a metal powder is deposited. The powder solidifies, when mixed with the substrate, thereby creating a metallurgical bond. In order to produce parts with high geometrical tolerances and desirable material properties, the process parameters have to be carefully controlled. Since the LMD process requires the interaction of parameters, it is not always easy to predict the output geometry. In this paper, the laser metal deposition process was modelled in ANSYS Parametric- Design-Language (APDL), using a transient thermal analysis, in order to determine the geometrical properties of the clad, that is, the width and the height of the resulting clad. The simulated results were then compared experimentally by depositing Commercially Pure (CP) titanium powder onto a Ti-6Al-4V substrate, in order to verify the simulation. The varying parameter in the experimental process was the powder flow rate, which was varied between 0.5-2.5g/min. In addition to the geometrical properties, the microstructure, microhardness; and the porosity levels of the deposited clads were also analyzed, in order to better determine the clad quality and integrity. The model showed good agreement in predicting both the height and the width of the clads. Porosity was noticed in all the samples with the exception of the clad deposited at the lowest powder flow rate setting of 0.5 g/min. An increase in the powder flow rate also led to a smaller fusion zone, due to a lower laser-material interaction period, which was the result of the increase in the quantity of powder causing attenuation of the beam, and less laser power being absorbed by the substrate. The smaller fusion zone meant that the clads could not bond to the substrate properly, which led to the clad in the sample produced with the highest powder flow rate falling off the substrate. There was a significant increase in the microhardness of the clad zone, which was due to a combination of alloying with Ti- 6Al-4V and a change in the microstructure to an acicular alpha martensite microstructure; while the Heat-Affected-Zone (HAZ) in the substrate only showed a slight increase in microhardness.
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Laser metal deposition of Ti6Al4V : a study on the effect of laser power on microstructure and microhardness

  • Authors: Mahamood, Rasheedat M. , Akinlabi, Esther Titilayo , Shukla, Mukul , Pityana, Sisa
  • Date: 2013
  • Subjects: Laser metal deposition process , Laser power , Ti6Al4V , Macroscopic banding , Microhardness , Microstructure
  • Type: Article
  • Identifier: uj:4896 , http://hdl.handle.net/10210/12610
  • Description: The effect of laser power on the resulting microstructure and microhardness of laser metal deposited Ti6Al4V powder on Ti6Al4V substrate has been investigated. The tracks were deposited using 99.6 % pure Ti6Al4V powder of particle size ranging between 150 - 200 μm on 99.6% Ti6Al4V substrate. The laser power was varied between 0.8 - 3.0 kW while the scanning speed, powder flow rate and the gas flow rate were kept at the values of 0.005 m/sec, 1.44 g/min and 4 l /min respectively. The microstructure and the microhardness were studied using the optical microscope and the Vickers hardness tester respectively. Layer band or macroscopic banding was observed in all the samples which is phenomenon as it was only reported in the literature for multi-layer deposits. The literature attributed re-melting of the previous layers by the succeeding layers as being responsible for their formation. This study has revealed that this band could be as a result of shrinkage happening in the fusion zone as a result of the interaction of the deposited powder and the melt pool created by the substrate material. This study also reveals the relationship between the microstructure, the average microhardness and the laser power which are comprehensively discussed. The higher the laser power, the lower the density of columnar prior beta grain structure. Also the average microhardness increases as the laser power increases.
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Influence of multi-pass friction stir processing on microstructure and mechanical properties of die cast Al-7Si-3Cu aluminium alloy

Influence of laser power on improving the wear properties of laser deposited Ti-6Al-4V+B4C composite

  • Authors: Erinosho, Mutiu F. , Akinlabi, Esther Titilayo
  • Date: 2018
  • Subjects: Laser metal deposition , Microstructure , Wear measurement
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/273312 , uj:29114 , Citation: Erinosho, M.F. & Akinlabi, E.T. 2018. Influence of laser power on improving the wear properties of laser deposited Ti-6Al-4V+B4C composite.
  • Description: Abstract: Titanium and its alloys have possessed outstanding properties such as high specific strength, good oxidation and corrosion resistance; which have made them extensively suitable for use in the aeronautical, medical, automobile, marine and chemical industries. This paper presents the impact of laser power on the microstructure and the wear properties of titanium matrix Ti-6Al-4V+B4C composites. The laser powers were varied between 0.8 kW and 2.2 kW while keeping other contributing parameters constant. The microstructural effects were characterised with increasing α-Ti lamella and coarse Widmanstettan structures as the laser power was increased; alongside with the inclusion of 20 wt % of B4C. The mechanical action during wear test has created a loop shape with inner and outer radii on the surface of the laser deposited composites. The wear thickness, depth and COF were taken into cognisance; with sample C deposited at a laser power of 1.8 kW and scanning speed of 1 m/min having the lowest wear loss of 0.119 mm3. The substrate exhibited the shallowest wear depth and the reason is attributed the compressive nature of the material. The interlace of B4C in the titanium matrix has improved the properties the laser formed composites.
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Effect of starting powder particle size and heating rate on spark plasma sintering of Fe- Ni alloys

  • Authors: Shongwe,M.B. , Ramakokovhu, M.M. , Diouf, S. , Durowoju, M.O. , Obadele, B.A. , Sule, R. , Olubambi, P.A , Sadiku, E.R.
  • Date: 2016
  • Subjects: Densification , Sintering , Microstructure
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/123446 , uj:20792 , Citation: Shongwe,M.B. et al. 2016. Effect of starting powder particle size and heating rate on spark plasma sintering of Fe- Ni alloys.
  • Description: Abstract: The effect of starting powder particle size and heating rate on spark plasma sintering of Fe-Ni alloys was investigated, with the particle powder size varying from 3 to 70 μm and heating rate from 50 to 150 °C/min. The effect of the starting powder particle size was more obvious when comparing 3-FeNi and 70-FeNi at all heating rates, with the former having better density and hardness than the latter. Sintered densities close to theoretical (≥ 99%) were achieved for a heating rate of 50°C/min for the different starting particle size powders, and decreased with increasing heating rate. The average grain size of alloys sintered at 150°C/min was ~34% smaller than those sintered at 50°C/min. The porosity content of the sintered samples increased with increasing heating for the same particle size. The shrinkage rate depends on both heating rate and particle size. At a particle size of 3 μm and a heating rate of 50oC/min, three peaks were observed indicative of the phenomena responsible for good densification. As the heating rate increases, only two peaks and one peak are observed at heating rates of 100 and 150oC/min, respectively. This suggests that, unlike high heating rates, the longer processing time at low heating rate allows the three phenomena to take place. The hardness measurement revealed a steady decrease with increasing heating rate. At a heating rate of 150°C/min the particles were well packed but no typical dimple structure of a ductile material was observed. However, for samples sintered at 50 and 100°C/min a typical dimple fracture morphology was observed.
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Forming behaviour of steel sheets after mechanical and laser beam forming

  • Authors: Akinlabi, Esther Titilayo , Shukla, M. , Akinlabi, S. A. , Kanyanga, S. B. , Chizyuka, C. M.
  • Date: 2014
  • Subjects: Laser beam forming , Mechanical forming , Microhardness , Microstructure , Tensile testing , Steel plates - Mechanical properties
  • Type: Article
  • Identifier: http://ujcontent.uj.ac.za8080/10210/379024 , uj:4998 , http://hdl.handle.net/10210/13136
  • Description: This paper reports the influencing factors and the characteristic behaviour of steel plates during both the mechanical forming and laser beam forming processes. Samples of the steel sheets were mechanically bent to 120 mm curvatures using a 20 ton capacity eccentric mechanical press at room temperature and also with the laser beam using a 4.4 kW Nd: YAG laser system at a scan speed of 1.9 m/min, beam diameter of 12 mm, laser power of 1.7 kW at 25% beam overlap using argon for cooling the irradiated surfaces. The chemical composition of both the as-received material and the formed samples were analysed by emission spectroscopy to quantify the changes in the elemental composition. The result shows a percentage increase in the carbon after the mechanical and laser forming processes when compared to the parent material. This can be attributed to the enhancement resulting from the forming processes. The formed samples were further characterized through microstructure, microhardness and tensile tests. The microstructural characterisation of the samples revealed that the grains of the mechanically formed and laser formed components are elongated, it was also observed that there is an increase in the pearlite grains of the laser formed components resulting from the thermal heating during the laser process. The microhardness profiles of the formed components showed that there is a significant percentage increase in the Vickers microhardness values of the laser formed samples when compared to the mechanically formed samples and with respect to the parent material. The laser beam forming process can be considered a more appropriate forming process in terms of the resulting material properties in this regard.
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Microstructure and microhardness of 17-4 ph stainless steel made by laser metal deposition

Effect of heat treatment on microstructure and mechanical properties of magnesium alloy

Characterising the effect of laser power on laser metal deposited titanium alloy and boron carbide

  • Authors: Erinosho, M. F. , Akinlabi, Esther Titilayo
  • Date: 2017
  • Subjects: Ti6Al4V-B4C composites , Laser metal deposition , Microstructure
  • Language: English
  • Type: Article
  • Identifier: http://hdl.handle.net/10210/241349 , uj:24845 , Citation: Erinosho, M.F. & Akinlabi, E.T. 2017. Characterising the effect of laser power on laser metal deposited titanium alloy and boron carbide.
  • Description: Abstract: Titanium alloy has gained acceptance in the aerospace, marine, chemical and other related industries due to its excellent combination of mechanical and corrosion properties. In order to augment its properties, a hard ceramic, boron carbide has been laser cladded with it at varying laser powers between 0.8 kW and 2.4 kW. This paper presents the effect of laser power on the laser deposited Ti6Al4V-B4C composites through the evolving microstructures and microhardness. The microstructures of the composites exhibit the formation of α-Ti phase and β-Ti phase and were elongated towards the heat affected zone. These phases were terminated at the fusion zone and globular microstructures were found growing epi! taxially just immediately after the fusion zone. Good bondings were formed in all the deposited composites. Sample A1 deposited at a laser power of 0.8 kW and scanning speed of 1 m/min exhibits the highest hardness of HV 432±27 while sample A4 deposited at a laser power of 2.0 kW and scanning speed of 1 m/min displays the lowest hardness of HV 360±18. From the hardness results obtained, ceramic B4C has improved the mechanical properties of the primary alloy.
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