Abstract: Aluminum alloy has an extensive range of industrial application due to its consistent mechanical properties and structural integrity. The heat treatment by precipitation technique affected the Magnesium, Silicon Manganese and copper crystals dissolved in the Aluminum alloy. The crystals dislocated to precipitate on the crystal’s boundaries of the Aluminum alloy when given a thermal energy increased its hardness. In this project various times and temperature were varied to find out the best combination of these variables to increase the precipitation of the metals on the Aluminum crystal’s boundaries which will lead to get the highest hardness. These specimens are then tested for their hardness and tensile strength. It is noticed that when the temperature increases, the precipitation increases and consequently the hardness increases. A threshold temperature value (264C0) of Aluminum alloy should not be reached due to the occurrence of recrystalization which causes the crystal to grow. This recrystalization process affected the ductility of the alloy and decrease hardness. In addition, and while increasing the temperature the alloy’s mechanical properties will decrease. The mechanical properties, namely tensile and hardness properties are investigated according to standard procedures. In this research, different temperature and time have been applied to increase hardening.The highest hardness at 100°c in 6 hours equals to 207.31 HBR, while at the same temperature and time the lowest elongation equals to 146.5.
Abstract: Wetting characteristics of reactive (Sn–0.7Cu solder)
and non– reactive (castor oil) wetting of liquids on Cu and Ag plated
Al substrates have been investigated. Solder spreading exhibited
capillary, gravity and viscous regimes. Oils did not exhibit noticeable
spreading regimes. Solder alloy showed better wettability on Ag
coated Al substrate compared to Cu plating. In the case of castor oil,
Cu coated Al substrate exhibited good wettability as compared to Ag
coated Al substrates. The difference in wettability during reactive
wetting of solder and non–reactive wetting of oils is attributed to the
change in the surface energies of Al substrates brought about by the
formation of intermetallic compounds (IMCs).
Abstract: End milling process is one of the common metal
cutting operations used for machining parts in manufacturing
industry. It is usually performed at the final stage in manufacturing a
product and surface roughness of the produced job plays an
important role. In general, the surface roughness affects wear
resistance, ductility, tensile, fatigue strength, etc., for machined parts
and cannot be neglected in design. In the present work an
experimental investigation of end milling of aluminium alloy with
carbide tool is carried out and the effect of different cutting
parameters on the response are studied with three-dimensional
surface plots. An artificial neural network (ANN) is used to establish
the relationship between the surface roughness and the input cutting
parameters (i.e., spindle speed, feed, and depth of cut). The Matlab
ANN toolbox works on feed forward back propagation algorithm is
used for modeling purpose. 3-12-1 network structure having
minimum average prediction error found as best network architecture
for predicting surface roughness value. The network predicts surface
roughness for unseen data and found that the result/prediction is
better. For desired surface finish of the component to be produced
there are many different combination of cutting parameters are
available. The optimum cutting parameter for obtaining desired
surface finish, to maximize tool life is predicted. The methodology is
demonstrated, number of problems are solved and algorithm is coded
in Matlab®.
Abstract: The optical properties of InGaN/GaN laser diode based on quaternary alloys stopper and superlattice layers are numerically studied using ISE TCAD (Integrated System Engineering) simulation program. Improvements in laser optical performance have been achieved using quaternary alloy as superlattice layers in InGaN/GaN laser diodes. Lower threshold current of 18 mA and higher output power and slope efficiency of 22 mW and 1.6 W/A, respectively, at room temperature have been obtained. The laser structure with InAlGaN quaternary alloys as an electron blocking layer was found to provide better laser performance compared with the ternary AlxGa1-xN blocking layer.
Abstract: The steam cracking reactions are always accompanied with the formation of coke which deposits on the walls of the tubular reactors. The investigation has attempted to control catalytic coking by the applying aluminum, zinc and ceramic coating like aluminum-magnesium by thermal spray and pack cementation method. Rate of coke formation during steam cracking of naphtha has been investigated both for uncoated stainless steel (with different alloys) and metal coating constructed with thermal Spray and pack cementation method with metal powders of Aluminum, Aluminum-Magnesium, zinc, silicon, nickel and chromium. The results of the study show that passivating the surface of SS321 with a coating of Aluminum and Aluminum-Magnesium can significantly reduce the rate of coke deposition during naphtha pyrolysis. SEM and EDAX techniques (Philips XL Series) were used to examine the coke deposits formed by the metal-hydrocarbon reactions. Our objective was to separate the different stages by identifying the characteristic morphologies.
Abstract: This work is focused on the numerical prediction of the fracture resistance of a flat stiffened panel made of the aluminium alloy 2024 T3 under a monotonic traction condition. The performed numerical simulations have been based on the micromechanical Gurson-Tvergaard (GT) model for ductile damage. The applicability of the GT model to this kind of structural problems has been studied and assessed by comparing numerical results, obtained by using the WARP 3D finite element code, with experimental data available in literature. In the sequel a home-made procedure is presented, which aims to increase the residual strength of a cracked stiffened aluminum panel and which is based on the stochastic design improvement (SDI) technique; a whole application example is then given to illustrate the said technique.
Abstract: In the Lost Foam Casting process, melting point
temperature of metal, as well as volume and rate of the foam
degradation have significant effect on the mold filling pattern.
Therefore, gas generation capacity and gas gap length are two
important parameters for modeling of mold filling time of the lost
foam casting processes. In this paper, the gas gap length at the liquidfoam
interface for a low melting point (aluminum) alloy and a high
melting point (Carbon-steel) alloy are investigated by the
photography technique. Results of the photography technique
indicated, that the gas gap length and the mold filling time are
increased with increased coating thickness and density of the foam.
The Gas gap lengths measured in aluminum and Carbon-steel,
depend on the foam density, and were approximately 4-5 and 25-60
mm, respectively. By using a new system, the gas generation
capacity for the aluminum and steel was measured. The gas
generation capacity measurements indicated that gas generation in
the Aluminum and Carbon-steel lost foam casting was about 50 CC/g
and 3200 CC/g polystyrene, respectively.
Abstract: In this study, Friction Stir Processing (FSP) a recent grain refinement technique was employed to disperse micron-sized (2 *m) SiCp particles into aluminum alloy AA6063. The feasibility to fabricate bulk composites through FSP was analyzed and experiments were conducted at different traverse speeds and wider volumes of the specimens. Micro structural observation were carried out by employing optical microscopy test of the cross sections in both parallel and perpendicular to the tool traverse direction. Mechanical property including micro hardness was evaluated in detail at various regions on the specimen. The composites had an excellent bonding with aluminum alloy substrate and a significant increase of 30% in the micro hardness value of metal matrix composite (MMC) as to that of the base metal has observed. The observations clearly indicate that SiC particles were uniformly distributed within the aluminum matrix.
Abstract: Titanium alloys like the modern alloy Ti 6Al 2Sn 4Zr 6Mo (Ti-6246) combine excellent specific mechanical properties and corrosion resistance. On the other hand,due to their material characteristics, machining of these alloys is difficult to perform. The aim of the current study is the analyses of wear mechanisms of coated cemented carbide tools applied in orthogonal cutting experiments of Ti-6246 alloy. Round bars were machined with standard coated tools in dry conditions on a CNC latheusing a wide range of cutting speeds and cutting depths. Tool wear mechanisms were afterwards investigated by means of stereo microscopy, optical microscopy, confocal microscopy and scanning electron microscopy. Wear mechanisms included fracture of the tool tip (total failure) and abrasion. Specific wear features like crater wear, micro cracks and built-up edgeformation appeared depending of the mechanical and thermal conditions generated in the workpiece surface by the cutting action.
Abstract: This research was conducted to develop a correlation
between microstructure of HSLA steel and the mechanical properties
that occur as a result of both laser and mechanical forming processes
of the metal. The technique of forming flat metals by applying laser
beams is a relatively new concept in the manufacturing industry.
However, the effects of laser energy on the stability of metal alloy
phases have not yet been elucidated in terms of phase
transformations and microhardness. In this work, CO2 laser source
was used to irradiate the surface of a flat metal then the
microstructure and microhardness of the metal were studied on the
formed specimen. The extent to which the microstructure changed
depended on the heat inputs of up to 1000 J/cm2 with cooling rates of
about 4.8E+02 K/s. Experimental results revealed that the irradiated
surface of a HSLA steel had transformed to austenitic structure
during the heating process.
Abstract: The present study aims at determining the effect of ageing on the impact toughness and microstructure of 2024 Al-Cu - Mg alloy. Following the 2 h solutionizing treatment at 450°C and water quench, the specimens were aged at 200°C for various periods (1 to 18 h). The precipitation stages during ageing were monitored by hardness measurements. For each specimen group, Charpy impact and hardness tests were carried out. During ageing the impact toughness of the alloy first increased, and then, following a maxima decreased due to the precipitation of intermediate phases, finally it reached its minimum at the peak hardness. Correlations between hardness and impact toughness were investigated.
Abstract: Conventionally the selection of parameters depends
intensely on the operator-s experience or conservative technological
data provided by the EDM equipment manufacturers that assign
inconsistent machining performance. The parameter settings given by
the manufacturers are only relevant with common steel grades. A
single parameter change influences the process in a complex way.
Hence, the present research proposes artificial neural network (ANN)
models for the prediction of surface roughness on first commenced
Ti-15-3 alloy in electrical discharge machining (EDM) process. The
proposed models use peak current, pulse on time, pulse off time and
servo voltage as input parameters. Multilayer perceptron (MLP) with
three hidden layer feedforward networks are applied. An assessment
is carried out with the models of distinct hidden layer. Training of the
models is performed with data from an extensive series of
experiments utilizing copper electrode as positive polarity. The
predictions based on the above developed models have been verified
with another set of experiments and are found to be in good
agreement with the experimental results. Beside this they can be
exercised as precious tools for the process planning for EDM.
Abstract: Nanocrystals (NC) alloyed composite CdSxSe1-x(x=0
to 1) have been prepared using the chemical solution deposition
technique. The energy band gap of these alloyed nanocrystals of
approximately the same size, have been determined by scanning
tunneling spectroscopy (STS) technique at room temperature. The
values of the energy band gap obtained directly using STS are
compared to those measured by optical spectroscopy. Increasing the
molar fraction ratio x from 0 to 1 causes clearly observed increase in
the band gap of the alloyed composite nanocrystal. Vegard-s law was
applied to calculate the parameters of the effective mass
approximation (EMA) model and the dimension obtained were
compared to the values measured by STM. The good agreement of
the calculated and measured values is a direct result of applying
Vegard's law in the nanocomposites.
Abstract: Recycling of aluminum alloys often decrease fluidity,
consequently influence the castability of the alloy. In this study, the
fluidity of Al-Zn alloys, such as the standard A713 alloy with and
without scrap addition has been investigated. The scrap added was
comprised of contaminated alloy turning chips. Fluidity
measurements were performed with double spiral fluidity test
consisting of gravity casting of double spirals in green sand moulds
with good reproducibility. The influence of recycled alloy on fluidity
has been compared with that of the virgin alloy and the results
showed that the fluidity decreased with the increase in recycled alloy
at minimum pouring temperatures. Interestingly, an appreciable
improvement in the fluidity was observed at maximum pouring
temperature, especially for coated spirals.
Abstract: This paper reports the fatigue crack growth behaviour
of gas tungsten arc, electron beam and laser beam welded Ti-6Al-4V
titanium alloy. Centre cracked tensile specimens were prepared to
evaluate the fatigue crack growth behaviour. A 100kN servo
hydraulic controlled fatigue testing machine was used under constant
amplitude uniaxial tensile load (stress ratio of 0.1 and frequency of
10 Hz). Crack growth curves were plotted and crack growth
parameters (exponent and intercept) were evaluated. Critical and
threshold stress intensity factor ranges were also evaluated. Fatigue
crack growth behaviour of welds was correlated with mechanical
properties and microstructural characteristics of welds. Of the three
joints, the joint fabricated by laser beam welding exhibited higher
fatigue crack growth resistance due to the presence of fine lamellar
microstructure in the weld metal.
Abstract: The study of effect of laser scanning speed on
material efficiency in Ti6Al4V application is very important because unspent powder is not reusable because of high temperature oxygen
pick-up and contamination. This study carried out an extensive study
on the effect of scanning speed on material efficiency by varying the
speed between 0.01 to 0.1m/sec. The samples are wire brushed and
cleaned with acetone after each deposition to remove un-melted
particles from the surface of the deposit. The substrate is weighed before and after deposition. A formula was developed to calculate the
material efficiency and the scanning speed was compared with the
powder efficiency obtained. The results are presented and discussed.
The study revealed that the optimum scanning speed exists for this study at 0.01m/sec, above and below which the powder efficiency
will drop
Abstract: Minor problems arising from optimizations by
welding of fixed prostheses frameworks can be identified by
macroscopic and microscopic visual inspection. The purpose of this
study was to highlight the visible discontinuities present in the laser
welds of dental Ni-Cr alloys. Ni-Cr base metal alloys designated for
fixed prostheses manufacture were selected for the experiments.
Using cast plates, preliminary tests were conducted by laser welding.
Macroscopic visual inspection was done carefully to assess the
defects of the welding rib. Electron microscopy images allowed
visualization of small discontinuities, which escapes visual
inspection. Making comparison to Ni-Cr alloys taken in the
experiment and laser welded, after visual analysis, the best welds
appear for Heraenium NA alloy.
Abstract: This study shows the effect of carbon towards
molybdenum carbide alloy when exposed to Microwave. This
technique is also known as Microwave Induced Alloying (MIA) for
the preparation of molybdenum carbide. In this study ammonium
heptamolybdate solution and carbon black powder were
heterogeneously mixed and exposed to microwave irradiation for 2
minutes. The effect on amount of carbon towards the produced alloy
on morphological and oxidation states changes during microwave is
presented. In this experiment, it is expected carbon act as a reducing
agent with the ratio 2:7 molybdenum to carbon as the optimum for
the production of molybdenum carbide alloy. All the morphological
transformations and changes in this experiment were followed and
characterized using X-Ray Diffraction and FESEM.
Abstract: A group of Stellite alloys are studied in consideration
of temperature effects on their hardness and wear resistance. The
hardness test is conducted on a micro-hardness tester with a hot stage
equipped that allows heating the specimen up to 650°C. The wear
resistance of each alloy is evaluated using a pin-on-disc tribometer
with a heating furnace built-in that provides the temperature capacity
up to 450°C. The experimental results demonstrate that the hardness
and wear resistance of Stellite alloys behave differently at room
temperature and at high temperatures. The wear resistance of Stellite
alloys at room temperature mainly depends on their carbon content and
also influenced by the tungsten content in the alloys. However, at high
temperatures the wear mechanisms of Stellite alloys become more
complex, involving multiple factors. The relationships between
chemical composition, microstructure, hardness and wear resistance of
these alloys are studied, with focus on temperature effect on these
relations.
Abstract: This presentation reviews recent advances in superalloys and thermal barrier coating (TBC) for application in hot sections of energy-efficient gas-turbine engines. It has been reviewed that in the modern combined-cycle gas turbines (CCGT) applying single-crystal energy materials (SC superalloys) and thermal barrier coatings (TBC), and – in one design – closed-loop steam cooling, thermal efficiency can reach more than 60%. These technological advancements contribute to profitable and clean power generation with reduced emission. Alternatively, the use of advanced superalloys (e.g. GTD-111 superalloy, Allvac 718Plus superalloy) and advanced thermal barrier coatings (TBC) in modern gas-turbines has been shown to yield higher energy-efficiency in power generation.