International Science Index
Influence of Build Orientation on Machinability of Selective Laser Melted Titanium Alloy-Ti-6Al-4V
Selective laser melting (SLM), a promising additive manufacturing (AM) technology, has a huge potential in the fabrication of Ti-6Al-4V near-net shape components. However, poor surface finish of the components fabricated from this technology requires secondary machining to achieve the desired accuracy and tolerance. Therefore, a systematic understanding of the machinability of SLM fabricated Ti-6Al-4V components is paramount to improve the productivity and product quality. Considering the significance of machining in SLM fabricated Ti-6Al-4V components, this research aim is to study the influence of build orientation on machinability characteristics by performing low speed orthogonal cutting tests. In addition, the machinability of SLM fabricated Ti-6Al-4V is compared with conventionally produced wrought Ti-6Al-4V to understand the influence of SLM technology on machining. This paper is an attempt to provide evidence to the hypothesis associated that build orientation influences cutting forces, chip formation and surface integrity during orthogonal cutting of SLM Ti-6Al-4V samples. Results obtained from the low speed orthogonal cutting tests highlight the practical importance of microstructure and build orientation on machinability of SLM Ti-6Al-4V.
Study of Mechanical Properties of Aluminium Alloys on Normal Friction Stir Welding and Underwater Friction Stir Welding for Structural Applications
Friction stir welding is the new-fangled and cutting-edge technique in welding applications; it is widely used in the fields of transportation, aerospace, defense, etc. For thriving significant welding joints and properties of friction stir welded components, it is essential to carry out this advanced process in a prescribed systematic procedure. At this moment, Underwater Friction Stir Welding (UFSW) Process is the field of interest to do research work. In the continuous assessment, the study of UFSW process is to comprehend problems occurred in the past and the structure through which the mechanical properties of the welded joints can be value-added and contributes to conclude results an acceptable and resourceful joint. A meticulous criticism is given on how to modify the experimental setup from NFSW to UFSW. It can discern the influence of tool materials, feeds, spindle angle, load, rotational speeds and mechanical properties. By expending the DEFORM-3D simulation software, the achieved outcomes are validated.
Experimental Study on Thermomechanical Properties of New-Generation ODS Alloys
By using a combination of new technologies together with an unconventional use of different types of materials, specific mechanical properties and structures of the material can be achieved. Some possibilities are enabled by a combination of powder metallurgy in the preparation of a metal matrix with dispersed stable particles achieved by mechanical alloying and hot consolidation. This paper explains the thermomechanical properties of new generation of Oxide Dispersion Strengthened alloys (ODS) within three ranges of temperature with specified deformation profiles. The results show that the mechanical properties of new ODS alloys are significantly affected by the thermomechanical treatment.
Numerical Simulation of Bio-Chemical Diffusion in Bone Scaffolds
Previously, some materials like solid metals and their alloys have been used as implants in human’s body. In order to amend fixation of these artificial hard human tissues, some porous structures have been introduced. In this way, tissues in vicinity of the porous structure can be attached more easily to the inserted implant. In particular, the porous bone scaffolds are useful since they can deliver important biomolecules like growth factors and proteins. This study focuses on the properties of the degradable porous hard tissues using a three-dimensional numerical Finite Element Method (FEM). The most important studied properties of these structures are diffusivity flux and concentration of different species like glucose, oxygen, and lactate. The process of cells migration into the scaffold is considered as a diffusion process, and related parameters are studied for different values of production/consumption rates.
Process Optimisation for Internal Cylindrical Rough Turning of Nickel Alloy 625 Weld Overlay
Nickel-based superalloys are generally known to be difficult to cut due to their strength, low thermal conductivity, and high work hardening tendency. Superalloy such as alloy 625 is often used in the oil and gas industry as a surfacing material to provide wear and corrosion resistance to components. The material is typically applied onto a metallic substrate through weld overlay cladding, an arc welding technique. Cladded surfaces are always rugged and carry a tough skin; this creates further difficulties to the machining process. The present work utilised design of experiment to optimise the internal cylindrical rough turning for weld overlay surfaces. An L27 orthogonal array was used to assess effects of the four selected key process variables: cutting insert, depth of cut, feed rate, and cutting speed. The optimal cutting conditions were determined based on productivity and the level of tool wear.
Flexural Properties of Halloysite Nanotubes-Polyester Nanocomposites Exposed to Aggressive Environment
This study aimed to investigate the effect of aggressive environment on the flexural properties of halloysite nanotubes-polyester nanocomposites. Results showed that the addition of halloysite nanotubes into polyester matrix was found to improve flexural properties of the nanocomposites in dry condition and after water-methanol exposure. Significant increase in surface roughness was also observed and measured by Alicona Infinite Focus optical microscope.
Process Modeling of Electric Discharge Machining of Inconel 825 Using Artificial Neural Network
Electrical discharge machining (EDM), a non-conventional machining process, finds wide applications for shaping difficult-to-cut alloys. Process modeling of EDM is required to exploit the process to the fullest. Process modeling of EDM is a challenging task owing to involvement of so many electrical and non-electrical parameters. This work is an attempt to model the EDM process using artificial neural network (ANN). Experiments were carried out on die-sinking EDM taking Inconel 825 as work material. ANN modeling has been performed using experimental data. The prediction ability of trained network has been verified experimentally. Results indicate that ANN can predict the values of performance measures of EDM satisfactorily.
Nanocharacterization of PIII Treated 7075 Aluminum Alloy
Nitrogen implantation in aluminum and its alloys is acquainted for the difficulties in obtaining modified layers deeper than 200 nm. The present work addresses a new method to overcome such a problem; although, the coating with nitrogen and oxygen obtained by plasma immersion ion implantation (PIII) into a 7075 aluminum alloy surface was too shallow. This alloy is commonly used for structural parts in aerospace applications. Such a layer was characterized by secondary ion mass spectroscopy, electron microscopy, and nanoindentation experiments reciprocating wear tests. From the results, one can assume that the wear of this aluminum alloy starts presenting severe abrasive wear followed by an additional adhesive mechanism. PIII produced a slight difference, as shown in all characterizations carried out in this work. The results shown here can be used as the scientific basis for further nitrogen PIII experiments in aluminum alloys which have the goal to produce thicker modified layers or to improve their surface properties.
High Temperature Oxidation of Cr-Steel Interconnects in Solid Oxide Fuel Cells
Solid Oxide Fuel Cell (SOFC) is a promising solution for the energy resources leakage. Ferritic stainless steel becomes a suitable candidate for the SOFCs interconnects due to the recent advancements. Different steel alloys were designed to satisfy the needed characteristics in SOFCs interconnect as conductivity, thermal expansion and corrosion resistance. Refractory elements were used as alloying elements to satisfy the needed properties. The oxidation behaviour of the developed alloys was studied where the samples were heated for long time period at the maximum operating temperature to simulate the real working conditions. The formed scale and oxidized surface were investigated by SEM. Microstructure examination was carried out for some selected steel grades. The effect of alloying elements on the behaviour of the proposed interconnects material and the performance during the working conditions of the cells are explored and discussed. Refractory metals alloying of chromium steel seems to satisfy the needed characteristics in metallic interconnects.
Effect of Gas-Diffusion Oxynitriding on Microstructure and Hardness of Ti-6Al-4V Alloys
The commercially available titanium alloy, Ti-6Al-4V, was oxynitrided in the deoxygenated nitrogen gas at high temperatures followed by cooling in oxygen-containing nitrogen in order to analyze the influence of oxynitriding parameters on the phase modification, hardness, and the microstructural evolution of the oxynitrided coating. The surface microhardness of the oxynitrided alloy increased due to the strengthening effect of the formed titanium oxynitrides, TiNxOy. The maximum microhardness was obtained, when TiNxOy had near equiatomic composition of nitrogen and oxygen. It could be attained under the optimum oxygen partial pressure and temperature-time condition.
Influence of Maximum Fatigue Load on Probabilistic Aspect of Fatigue Crack Propagation Life at Specified Grown Crack in Magnesium Alloys
The principal purpose of this paper is to find the influence of maximum fatigue load on the probabilistic aspect of fatigue crack propagation life at a specified grown crack in magnesium alloys. The experiments of fatigue crack propagation are carried out in laboratory air under different conditions of the maximum fatigue loads to obtain the fatigue crack propagation data for the statistical analysis. In order to analyze the probabilistic aspect of fatigue crack propagation life, the goodness-of fit test for probability distribution of the fatigue crack propagation life at a specified grown crack is implemented through Anderson-Darling test. The good probability distribution of the fatigue crack propagation life is also verified under the conditions of the maximum fatigue loads.
Performance Study of Neodymium Extraction by Carbon Nanotubes Assisted Emulsion Liquid Membrane Using Response Surface Methodology
The high purity rare earth elements (REEs) have been vastly used in the field of chemical engineering, metallurgy, nuclear energy, optical, magnetic, luminescence and laser materials, superconductors, ceramics, alloys, catalysts, and etc. Neodymium is one of the most abundant rare earths. By development of a neodymium–iron–boron (Nd–Fe–B) permanent magnet, the importance of neodymium has dramatically increased. Solvent extraction processes have many operational limitations such as large inventory of extractants, loss of solvent due to the organic solubility in aqueous solutions, volatilization of diluents, etc. One of the promising methods of liquid membrane processes is emulsion liquid membrane (ELM) which offers an alternative method to the solvent extraction processes. In this work, a study on Nd extraction through multi-walled carbon nanotubes (MWCNTs) assisted ELM using response surface methodology (RSM) has been performed. The ELM composed of diisooctylphosphinic acid (CYANEX 272) as carrier, MWCNTs as nanoparticles, Span-85 (sorbitan triooleate) as surfactant, kerosene as organic diluent and nitric acid as internal phase. The effects of important operating variables namely, surfactant concentration, MWCNTs concentration, and treatment ratio were investigated. Results were optimized using a central composite design (CCD) and a regression model for extraction percentage was developed. The 3D response surfaces of Nd(III) extraction efficiency were achieved and significance of three important variables and their interactions on the Nd extraction efficiency were found out. Results indicated that introducing the MWCNTs to the ELM process led to increasing the Nd extraction due to higher stability of membrane and mass transfer enhancement. MWCNTs concentration of 407 ppm, Span-85 concentration of 2.1 (%v/v) and treatment ratio of 10 were achieved as the optimum conditions. At the optimum condition, the extraction of Nd(III) reached the maximum of 99.03%.
Experimental Analyses of Thermoelectric Generator Behavior Using Two Types of Thermoelectric Modules for Marine Application
Thermal power technology such as the TEG (Thermo-Electric Generator) arouses significant attention worldwide for waste heat recovery. Despite the potential benefits of marine application due to the permanent heat sink from sea water, no significant studies on this application were to be found. In this study, a test rig has been designed and built to test the performance of the TEG on engine operating points. The TEG device is built from commercially available materials for the sake of possible economical application. Two types of commercial TEM (thermo electric module) have been studied separately on the test rig. The engine data were extracted from a commercial Diesel engine since it shares the same principle in terms of engine efficiency and exhaust with the marine Diesel engine. An open circuit water cooling system is used to replicate the sea water cold source. The characterization tests showed that the silicium-germanium alloys TEM proved a remarkable reliability on all engine operating points, with no significant deterioration of performance even under sever variation in the hot source conditions. The performance of the bismuth-telluride alloys was 100% better than the first type of TEM but it showed a deterioration in power generation when the air temperature exceeds 300 °C. The temperature distribution on the heat exchange surfaces revealed no useful combination of these two types of TEM with this tube length, since the surface temperature difference between both ends is no more than 10 °C. This study exposed the perspective of use of TEG technology for marine engine exhaust heat recovery. Although the results suggested non-sufficient power generation from the low cost commercial TEM used, it provides valuable information about TEG device optimization, including the design of heat exchanger and the types of thermo-electric materials.
Effect of Impurities in the Chlorination Process of TiO2
With the increasing interest on Ti alloys, the extraction process of Ti from its typical ore, TiO2, has long been and will be important issue. As an intermediate product for the production of pigment or titanium metal sponge, tetrachloride (TiCl4) is produced by fluidized bed using high TiO2 feedstock. The purity of TiCl4 after chlorination is subjected to the quality of the titanium feedstock. Since the impurities in the TiCl4 product are reported to final products, the purification process of the crude TiCl4 is required. The purification process includes fractional distillation and chemical treatment, which depends on the nature of the impurities present and the required quality of the final product. In this study, thermodynamic analysis on the impurity effect in the chlorination process, which is the first step of extraction of Ti from TiO2, has been conducted. All thermodynamic calculations were performed using the FactSage thermodynamical software.
An Experimental Study on the Effect of Operating Parameters during the Micro-Electro-Discharge Machining of Ni Based Alloy
Ni alloys have managed to cover wide range of applications such as automotive industries, oil gas industries, and aerospace industries. However, these alloys impose challenges while using conventional machining technologies. On the other hand, Micro-Electro-Discharge machining (micro-EDM) is a non-conventional machining method that uses controlled sparks energy to remove material irrespective of the materials hardness. There has been always a huge interest from the industries for developing optimum methodology and parameters in order to enhance the productivity of micro-EDM in terms of reducing machining time and tool wear for different alloys. Therefore, the aims of this study are to investigate the effects of the micro-EDM process parameters, in order to find their optimal values. The input process parameters include voltage, capacitance, and electrode rotational speed, whereas the output parameters considered are machining time, entrance diameter of hole, overcut, tool wear, and crater size. The surface morphology and element characterization are also investigated with the use of SEM and EDX analysis. The experimental result indicates the reduction of machining time with the increment of discharge energy. Discharge energy also contributes to the enlargement of entrance diameter as well as overcut. In addition, tool wears show reduction with the increase of discharge energy. Moreover, crater size is found to be increased in size along with the increment of discharge energy.
Investigation of a Hybrid Process: Multipoint Incremental Forming
Multi-point forming (MPF) and asymmetric incremental forming (ISF) are two flexible processes for sheet metal manufacturing. To take advantages of these two techniques, a hybrid process has been developed: The Multipoint Incremental Forming (MPIF). This process accumulates at once the advantages of each of these last mentioned forming techniques, which makes it a very interesting and particularly an efficient process for single, small, and medium series production. In this paper, an experimental and a numerical investigation of this technique are presented. To highlight the flexibility of this process and its capacity to manufacture standard and complex shapes, several pieces were produced by using MPIF. The forming experiments are performed on a 3-axis CNC machine. Moreover, a numerical model of the MPIF process has been implemented in ABAQUS and the analysis showed a good agreement with experimental results in terms of deformed shape. Furthermore, the use of an elastomeric interpolator allows avoiding classical local defaults like dimples, which are generally caused by the asymmetric contact and also improves the distribution of residual strain. Future works will apply this approach to other alloys used in aeronautic or automotive applications.
Influence of Boron Doping and Thermal Treatment on Internal Friction of Monocrystalline Si1-xGex(x≤0,02) Alloys
The impact of boron doping on the internal friction (IF) and shear modulus temperature spectra of Si1-xGex(x≤0,02) monocrsytals has been investigated by reverse torsional pendulum oscillations characteristics testing. At room temperatures, microhardness and indentation modulus of the same specimens have been measured by dynamic ultra microhardness tester. It is shown that boron doping causes two kinds effect: At low boron concentration (~1015 cm-3) significant strengthening is revealed, while at the high boron concentration (~1019 cm-3) strengthening effect and activation characteristics of relaxation origin IF processes are reduced.
Enhancement of Tribological Behavior for Diesel Engine Piston of Solid Skirt by an Optimal Choice of Interface Material
Shear stresses generate frictional forces thus lead to the reduction of engine performance due to the power losses. This friction can also cause damage to the piston material. Thus, the choice of an optimal material for the piston is necessary to improve the elastohydrodynamical contacts of the piston. In this study, to achieve this objective, an elastohydrodynamical lubrication model that satisfies the best tribological behavior of the piston with the optimum choice of material is developed. Several aluminum alloys composed of different components are studied in this simulation. An application is made on the piston 60 x 120 mm Diesel engine type F8L413 currently mounted on Deutz trucks TB230 by using different aluminum alloys where alloys based on aluminum-silicon have better tribological performance.
Influence of Titanium Addition on Wear Properties of AM60 Magnesium Alloy
This study aimed for improving wear resistance of AM60 magnesium alloy by Ti addition (0, 0.2, 0.5, 1wt%Ti). An electric resistance furnace was used to produce alloys. Pure Mg together with Al, Al-Ti and Al-Mn were melted at 750 0C in a stainless steel crucible under controlled Ar gas atmosphere and then poured into a metal mould preheated at 250 0C. Microstructure characterizations were performed by light optical (LOM) and scanning electron microscope (SEM) after the wear test. Wear rates and friction coefficients were measured with a pin-on-disk type UTS-10 Tribometer test device under a load of 20N. The results showed that Ti addition altered the morphology and the amount of b-Mg17Al12 phase in the microstructure of AM60 alloy. b-Mg17Al12 phases on the grain boundaries were refined with increasing amount of Ti. An improvement in wear resistance of AM60 alloy was observed due to the alteration in the microstructure by Ti addition.
Microstructure and Mechanical Properties of Mg-Zn Alloys
Effect of Zn addition on the microstructure and
mechanical properties of Mg-Zn alloys with Zn contents from 6 to 10
weight percent was investigated in this study. Through calculation of
phase equilibria of Mg-Zn alloys, carried out by using FactSage® and
FTLite database, solution treatment temperature was decided as
temperatures from 300 to 400oC, where supersaturated solid solution
can be obtained. Solid solution treatment of Mg-Zn alloys was
successfully conducted at 380oC and supersaturated microstructure
with all beta phase resolved into matrix was obtained. After solution
treatment, hot rolling was successfully conducted by reduction of
60%. Compression and tension tests were carried out at room
temperature on the samples as-cast, solution treated, hot-rolled and
recrystallized after rolling. After solid solution treatment, each alloy
was annealed at temperatures of 180 and 200oC for time intervals from
1 min to 48 hrs and hardness of each condition was measured by
micro-Vickers method. Peak aging conditions were deduced as at the
temperature of 200oC for 10 hrs. By addition of Zn by 10 weight
percent, hardness and strength were enhanced.
The Effect of the Weld Current Types on Microstructure and Hardness in Tungsten Inert Gas Welding of the AZ31 Magnesium Alloy Sheet
In this study, the butt welding of the commercial AZ31 magnesium alloy sheets have been carried out by using Tungsten Inert Gas (TIG) welding process with alternative and pulsed current. Welded samples were examined with regards to hardness and microstructure. Despite some recent developments in welding of magnesium alloys, they have some problems such as porosity, hot cracking, oxide formation and so on. Samples of the welded parts have undergone metallographic and mechanical examination. Porosities and homogeneous micron grain oxides were rarely observed. Orientations of the weld microstructure in terms of heat transfer also were rarely observed and equiaxed grain morphology was dominant grain structure as in the base metal. As results, fusion zone and few locations of the HAZ of the welded samples have shown twin’s grains. Hot cracking was not observed for any samples. Weld bead geometry of the welded samples were evaluated as normal according to welding parameters. In the results, conditions of alternative and pulsed current and the samples were compared to each other with regards to microstructure and hardness.
Mechanism and Kinetic of Layers Growth: Application to Nitriding of 32CrMoV13 Steel
In this work, our goal is to optimize the nitriding treatment at a low-temperature of the steel 32CrMoV13 using gas mixtures of ammonia, nitrogen and hydrogen to improve the mechanical properties of the surface (good wear resistance, friction and corrosion), and of the diffusion layer of the nitrogen (good resistance to fatigue and good tenacity with heart). By limiting our work to the pure iron and to the alloys iron-chromium and iron-chromium-carbon, we have studied the various parameters which manage the nitriding: flow rate and composition of the gaseous phase, the interaction chromium-nitrogen and chromium-carbon by the help of experiments of nitriding realized in the laboratory by thermogravimetry. The acquired knowledge has been applied by the mastery of the growth of the γ' combination layer on the α diffusion layer in the case of the industrial steel 32CrMoV13.
Effect of T6 and Re-Aging Heat Treatment on Mechanical Properties of 7055 Aluminum Alloy
Heat treatable aluminum alloys such as 7075 and
7055, because of high strength and low density, are used widely in
aircraft industry. For best mechanical properties, T6 heat treatment
has recommended for this regards, but this temper treatment is
sensitive to corrosion induced and Stress Corrosion Cracking (SCC)
damage. For improving this property, the over-aging treatment (T7)
applies to this alloy, but it decreases the mechanical properties up to
30 percent. Hence, to increase the mechanical properties, without any
remarkable decrease in SCC resistant, Retrogression and Re-Aging
(RRA) heat treatment is used. This treatment performs in a relatively
short time. In this paper, the RRA heat treatment was applied to 7055
aluminum alloy and then effect of RRA time on the mechanical
properties of 7055 has been investigated. The results show that the
40-minute time is suitable time for retrogression of 7055 aluminum
alloy and ultimate strength increases up to 625MPa.
Effect of Injection Moulding Process Parameter on Tensile Strength Using Taguchi Method
The plastic industry plays very important role in the
economy of any country. It is generally among the leading share of
the economy of the country. Since metals and their alloys are very
rarely available on the earth. Therefore, to produce plastic products
and components, which finds application in many industrial as well
as household consumer products is beneficial. Since 50% plastic
products are manufactured by injection moulding process. For
production of better quality product, we have to control quality
characteristics and performance of the product. The process
parameters plays a significant role in production of plastic, hence the
control of process parameter is essential. In this paper the effect of
the parameters selection on injection moulding process has been
described. It is to define suitable parameters in producing plastic
product. Selecting the process parameter by trial and error is neither
desirable nor acceptable, as it is often tends to increase the cost and
time. Hence, optimization of processing parameter of injection
moulding process is essential. The experiments were designed with
Taguchi’s orthogonal array to achieve the result with least number of
experiments. Plastic material polypropylene is studied. Tensile
strength test of material is done on universal testing machine, which
is produced by injection moulding machine. By using Taguchi
technique with the help of MiniTab-14 software the best value of
injection pressure, melt temperature, packing pressure and packing
time is obtained. We found that process parameter packing pressure
contribute more in production of good tensile plastic product.
Effect of Load Ratio on Probability Distribution of Fatigue Crack Propagation Life in Magnesium Alloys
It is necessary to predict a fatigue crack propagation
life for estimation of structural integrity. Because of an uncertainty
and a randomness of a structural behavior, it is also required to
analyze stochastic characteristics of the fatigue crack propagation life
at a specified fatigue crack size. The essential purpose of this study is to find the effect of load ratio
on probability distribution of the fatigue crack propagation life at a
specified grown crack size and to confirm the good probability
distribution in magnesium alloys under various fatigue load ratio
conditions. To investigate a stochastic crack growth behavior, fatigue
crack propagation experiments are performed in laboratory air under
several conditions of fatigue load ratio using AZ31. By Anderson-Darling test, a goodness-of-fit test for probability
distribution of the fatigue crack propagation life is performed. The
effect of load ratio on variability of fatigue crack propagation life is
Microstructure, Mechanical, Electrical and Thermal Properties of the Al-Si-Ni Ternary Alloy
In recent years, the use of the aluminum based alloys
in the industry and technology are increasing. Alloying elements in
aluminum have further been improving the strength and stiffness
properties that provide superior compared to other metals. In this
study, investigation of physical properties (microstructure,
microhardness, tensile strength, electrical conductivity and thermal
properties) in the Al-12.6wt.%Si-%2wt.Ni ternary alloy were
investigated. Al-Si-Ni alloy was prepared in vacuum atmosphere. The
samples were directionally solidified upwards with different growth
rate V (8.3−165.45 μm/s) at constant temperature gradient G (7.73
K/mm). The flake spacings (λ), microhardness (HV), ultimate tensile
strength (σ), electrical resistivity (ρ) and thermal properties (H, Cp,
Tm) of the samples were measured. Influence of the growth rate and
spacings on microhardness, ultimate tensile strength and electrical
resistivity were investigated and relationships between them were
obtained. According to results, λ values decrease with increasing V,
but HV, σ and ρ values increase with increasing V. Variations of
electrical resistivity (ρ) of solidified samples were also measured.
The enthalpy of fusion (H) and specific heat (Cp) for the alloy was
also determined by differential scanning calorimeter (DSC) from
heating trace during the transformation from liquid to solid. The
results in this work were compared with the previous similar
Effect of Aging Treatment on Mechanical Properties of Non-Flammable AZ91D Mg Alloy
Microstructure and mechanical properties of AZ91D
Mg alloys for nonflammable use, containing Ca and Y, were
investigated in this study. Solid solution treatment of AZ91D Mg alloy
with Ca and Y was successfully conducted at 420oC and
supersaturated microstructure with almost all beta phases resolved into
matrix was obtained. After solid solution treatment, the alloy was
annealed at temperatures of 180 and 200oC for time intervals from 1
min to 48 hrs and hardness of each condition was measured by
micro-Vickers method. Peak aging conditions were deduced from the
results as at the temperature of 200oC for 10 hrs. Hot rolling was also
carried out at 400oC by the reduction ratio of 0.6 through 5 passes
followed by recrystallization treatment. Tensile and compressive
properties were measured at room temperature on the specimens of
each process, i.e. as-cast, solution treatment, hot rolling, and
Bacteriological Quality of Commercially Prepared Fermented Ogi (Akamu) Sold in Some Parts of South Eastern Nigeria
Food poisoning and infection by bacteria are of public
health significance to both developing and developed countries.
Samples of ogi (akamu) prepared from white and yellow variety of
maize sold in Uturu and Okigwe were analyzed together with the
laboratory prepared ogi for bacterial quality using the standard
microbiological methods. The analyses showed that both white and
yellow variety had total bacterial counts (cfu/g) of 4.0 ×107 and 3.9 x
107 for the laboratory prepared ogi while the commercial ogi had 5.2
x 107 and 4.9 x107, 4.9 x107 and 4.5 x107, 5.4 x107 and 5.0 x107 for
Eke-Okigwe, Up-gate and Nkwo-Achara market respectively. The
Staphylococcal counts ranged from 2.0 x 102 to 5.0 x102 and 1.0 x
102 to 4.0 x102 for the white and yellow variety from the different
markets while Staphylococcal growth was not recorded on the
laboratory prepared ogi. The laboratory prepared ogi had no Coliform
growth while the commercially prepared ogi had counts of 0.5 x103
to 1.6 x 103 for white variety and 0.3 x 103 to 1.1 x103 for yellow
variety respectively. The Lactic acid bacterial count of 3.5x106 and
3.0x106 was recorded for the laboratory ogi while the commercially
prepared ogi ranged from 3.2x106 to 4.2x106 (white variety) and 3.0
x106 to 3.9 x106 (yellow). The presence of bacteria isolates from the
commercial and laboratory fermented ogi showed that Lactobacillus
sp, Leuconostoc sp and Citrobacter sp were present in all the
samples, Micrococcus sp and Klebsiella sp were isolated from Eke-
Okigwe and ABSU-up-gate markets varieties respectively, E. coli
and Staphylococcus sp were present in Eke-Okigwe and Nkwo-
Achara markets while Salmonella sp were isolated from the three
markets. Hence, there are chances of contracting food borne diseases
from commercially prepared ogi. Therefore, there is the need for
sanitary measures in the production of fermented cereals so as to
minimize the rate of food borne pathogens during processing and
Enhancement of Hardness Related Properties of Grey Cast Iron Powder Reinforced AA7075 Metal Matrix Composites through T6 and T8 Heat Treatments
In present global scenario, aluminum alloys are
coining the attention of many innovators as competing structural
materials for automotive and space applications. Comparing to other
challenging alloys, especially, 7xxx series aluminum alloys have
been studied seriously because of benefits such as moderate strength;
better deforming characteristics and affordable cost. It is expected
that substitution of aluminum alloys for steels will result in great
improvements in energy economy, durability and recyclability.
However, it is necessary to improve the strength and the formability
levels at low temperatures in aluminum alloys for still better
applications. Aluminum–Zinc–Magnesium with or without other
wetting agent denoted as 7XXX series alloys are medium strength
heat treatable alloys. In addition to Zn, Mg as major alloying
additions, Cu, Mn and Si are the other solute elements which
contribute for the improvement in mechanical properties by suitable
heat treatment process. Subjecting to suitable treatments like age
hardening or cold deformation assisted heat treatments; known as low
temperature thermomechanical treatments (LTMT) the challenging
properties might be incorporated. T6 is the age hardening or
precipitation hardening process with artificial aging cycle whereas T8
comprises of LTMT treatment aged artificially with X% cold
deformation. When the cold deformation is provided after solution
treatment, there is increase in hardness related properties such as
wear resistance, yield and ultimate strength, toughness with the
expense of ductility. During precipitation hardening both hardness
and strength of the samples are increasing. The hardness value may
further improve when room temperature deformation is positively
supported with age hardening known as thermomechanical treatment.
It is intended to perform heat treatment and evaluate hardness, tensile
strength, wear resistance and distribution pattern of reinforcement in
the matrix. 2 to 2.5 and 3 to 3.5 times increase in hardness is reported
in age hardening and LTMT treatments respectively as compared to
as-cast composite. There was better distribution of reinforcements in
the matrix, nearly two fold increase in strength levels and up to 5
times increase in wear resistance are also observed in the present
Ni-B Coating Production on Magnesium Alloy by Electroless Deposition
The use of magnesium alloys is limited due to their
susceptibility to corrosion although they have many attractive
physical and mechanical properties. To increase mechanical and
corrosion properties of these alloys, many deposition method and
coating types are used. Electroless Ni–B coatings have received
considerable interest recently due to its unique properties such as
cost-effectiveness, thickness uniformity, good wear resistance,
lubricity, good ductility and corrosion resistance, excellent
solderability and electrical properties and antibacterial property. In
this study, electroless Ni-B coating could been deposited on AZ91
magnesium alloy. The obtained coating exhibited a harder and
rougher structure than the substrate.