Engineering and Technology Journal

Brazing fillers for joining applications are essential to advanced material design and fabrication. Several types of brazing fillers have been developed in recent decades to join similar or different engineering materials. Important parts of automotive and aircraft components, including steel, are often joined by brazing. In this study, Similar samples of martensitic stainless steel were welded by the brazing method, using effective silver-based metal alloys. The brazing welding is done in inert gas atmosphere furnaces, by placing the samples in a special container filled with argon gas during the welding period and at a flow rate (10 to 15 minutes) inside a cylindrical furnace. Three types of metal alloys (silver, copper, and titanium) with different weight ratios of Ag, Cu, and Ti were used with a fixed welding time (10 minutes) at an appropriate temperature for each joint. A set of examinations and tests were conducted to find out the microscopic structure of the bonding site and the extent of the binder overlapping with the base material.  Optical microscopy was used to study the microstructure of the weld joint. Optical and scanning electron microscopy (SEM) is used to study the joint microstructure. All joints of samples exhibited continuous bonding between the base metal and the filler metal, good wetting between the surfaces, and it was also noticed that the higher the proportion of titanium, the better the wetting between the surfaces., the greater the percentage of diffusion of the filler elements and the strength of the bonding with the base metal. The use of titanium-containing fillers in brazing is good for bonding in turbine blades of martensitic steel.

The goal of this research is to study the microstructural analysis and mechanical properties of an aluminum matrix reinforced with different amounts of nano Fe3O4 at (2, 4, 6, 8, and 10wt. %). Al/ Fe3O4 nanocomposites specimens were prepared using the powder metallurgy route. Many examinations, including Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD) analysis, were performed on the specimens in this study to determine the microstructure and phases of the nanocomposites. Mechanical tests, such as compressive, microhardness, and wear tests, were also performed to assess the mechanical properties of the nanocomposites. The results of this study show that Fe3O4 nanoparticles have been homogeneously dispersed in the Al matrix by FESEM and XRD examination. While the mechanical tests show improving the compressive strength at 6 wt.% by 5.36%, the highest microhardness was at 10% by 101.6% compared with the pure Al, and improving the wear rate.

In this paper, study the effects of magnetite nanomaterial Fe3O4 on the mechanical properties of epoxy. Dispersion of Fe3O4 nanoparticles in the epoxy resin was performed by ultrasonication. The samples of the nanocomposites were prepared using the casting method. The nanocomposites contain epoxy resins as a matrix material incorporated by different weight percentages of magnetite Fe3O4 that varies from 0wt.% to 15wt.% as a reinforcing material. The epoxy with the additive reinforcement materials Fe3O4 was slowly mixed in a sonication bath for 15 minutes, then the mixture poured into silicon molds. Field Emission Scanning Electron Microscopy FESEM and X-ray diffraction spectra XRD were used to characterize the morphological and structural properties of preparing samples and the distribution of Fe3O4 nanoparticles to the epoxy resin. Mechanical testing consists of tensile, hardness shore, and three-point flexural tests were performed on the samples at room temperature according to ASTM standards. The results showed that reinforcement by 15wt.% of Fe3O4 nanoparticles maximizes these mechanical properties of nanocomposites compared with pure epoxy except for the young modulus's preferred weight at 9 wt.%, this is due to aggregation of the additives nanomaterials in epoxy resin above 9 wt.%.

Aluminum – based metal matrix composite are widely used in industrial applications compared with conventional and unreinforced alloy. The composite materials usually exhibit a higher strength both at elevated and ambient temperature, as well as wear resistance. The production of composite materials which contain different weight percentage of ZrO2 (0.5, 1.5 and 2.5wt %) by stir casting process. The mechanical properties of the base alloy and composite were evaluated by using tensile and hardness tests. The microstructure inspection by optical microscopy, scanning electron microscope and energy dispersive spectroscopy (EDS) were utilized to study the fracture surface topography. The results represent that the hardness, strength of yield and tensile strength increased with increasing the weight % of ZrO2 to 2.5 % while the elongation decreased. The microstructure inspection by optical microscope shows that the dendrites structure and the particles distribution in matrix without any voids. Furthermore, the grain size refining with the weight percentage of weight reinforcement elevated.

This study presents an appropriate filler metal or welding electrode to join aluminum alloy (AA2024-T3) sheet of 3.2 mm thickness with a square butt joint using Gas Tungsten Arc Welding (GTAW) process. This process was carried out at three different welding currents with three various filler metals: ER4047 (12% Si), ER4043 (5% Si), and ER5356 (5% Mg). Experiments were conducted to investigate the microstructure and the mechanical properties. The effect of various filler metals upon the weld joints quality were analyzed via an X-ray radiographic and tensile test. Hardness test, microstructures, SEM, and XRD also conducted to the welded specimens. It was found that the best result was at 100 Ampere with using filler metal (ER5356) which produced the highest strength of 240 MPa in comparison with welded joints with utilizing fillers (ER4043) and (ER4047) having values of 235 MPa and 225 MPa, correspondingly. The hardness results showed that the highest hardness values were at the weld metal for ER4047 and ER4043, then decreased to HAZ and increased in the base metal. While in the case of ER5356, the highest hardness was in HAZ and decreased in the weld metal. The fractography of the fracture surface of the welded joints after the tensile test was analyzed using SEM

Because of the unique properties, Ni-Ti based shape memory alloys (SMAs) are increasingly attractive for a wide variety of engineering applications such as actuators, biomedical, or robot coupling. In this work, a third alloying element, namely nanoparticles of Ag (which is insoluble in Ni-Ti matrix), is added by powder technology to the Ni-Ti alloy to produce a Ni-Ti-Ag alloy. The Nanoparticles of the Ag element are added at 3, 5, 7, and 10 wt. % to produce four alloy specimens with different mixtures .The mixing process was done by a horizontal mixer for 120 min with a speed of 350 rpm, and then the mixture was compacted by using a compacting pressure of 600 MPa. Afterward, the compacted specimens were sintered at 600 /min for 6 hrs. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to evaluate the microstructure and phases of the products. DSC examination was used to characterize the phase transformation temperatures in heating and cooling. Wear behavior was defined by using the pin-on-disc technique, and the hardness of the samples was calculated using Vickers's hardness apparatus. The results of this work showed that the nano-Ag added at 7 and 10 wt. % were distributed homogeneously in the Ni-Ti matrix, and that Ag slightly decreased hardness and increased the wear rate. The value of shape memory effect (SME) for the produced alloy was about 89.9% and the phase transformation in heating was at a temperature of about 186.48 and in cooling of about 140.3 for the specimen that contains 10 wt.% Ag nanoparticles.

The aim of this study is to find an alternative quenching medium for the ordinary nitrate mixture that is cheaper and more available in Iraqi markets. So to obtain the suitable medium , the  effect of different quenching mediums used in martempering treatment on the microstructure and mechanical properties of  high chromium white cast iron was studied  . This type of cast iron is used in mining ,crushing and cement plants as mill liners so it is subjected to extreme conditions of wear and impact that eventually cause failure . In this study, two types of quenching mediums were used in martempering treatment: (50% Sodium hydroxide + 50 % potassium hydroxide) mixture and (50% Sodium nitrate + 50 % potassium nitrate) mixture with different quenching intervals. It is  also found that both of the quenching mediums produce higher hardness values at 350°C martempering temperature for 4 hr quenching time ,but there were several advantages and disadvantages associated with using these two different mediums

Analysis using scanning electron microscope (SEM) at high magnification showed that the microstructure of the nano composites exhibited uniform distribution of SiC particles and less porosity. The experimental results revealed that adding Nano Reinforcement to 7075Al alloy improve the electrical conductivity for the metal matrix composites with 3, 6, 9 wt. % SiC were adopted in this work. The maximum enhancements were observed at 9wt. %SiC of 5200(Ω. m) -1 compared with the metal base of 35 (Ω. m) -1.

Friction stir processing (FSP) is an innovative technique of varying the metallic features by intense, local plastic deforming. Accordingly, materials are stirred with no altering the phase via melting or otherwise to produce a microstructure with equiaxed and fine grains. This method enhances the microstructural features of metals. In This study the microstructure and the mechanical features including (tensile strength and microhardness), and radiographic inspection results are studied. All specimens of pure copper use in the (FSW) and (FSP) have variable rotating speed (900, 1200, and 1600 rpm) with constant feed speed (40 mm/min). The most remarkable results, the ultimate tensile strength for FSW and FSP at (1200 RPM and 40 mm/min) with the values of 250.4 MPa for FSW and 261..2 MPa for FSP and the efficiency reached 92.7% and 96.3% for FSP and FSW, respectively. The high hardness in the same sample was 118 HV for FSW and 135 HV for FSP. The microstructure at welding zones, specially nugget zone, is improved by the friction stir processing. Radiographic examination showed incomplete fusion of welding joint without defect.

In this study five compositions of CoNiAl alloy with fixed Al content were prepaid to investigate the effect of chemical composition on the microstructure and phase volume fractions. It was found that by increasing Co the volume fraction of β phase increases and by increasing the β phase the grain size will be increased. This increase will be reflected on increasing the hardness of this alloy. Further investigations for the corrosion resistance in simulated body environment were done. It was found that phase volume fractions increased corrosion rate by increasing the volume fraction of β phase.

In recent years there has been an increasing demand to recycle wastes produced by the agricultural and industrial processing. The aim of this paper is to investigate the suitability of date palm (Phoenix dactylifera) as lignocellulosic materials for the production of wood-cement composite boards, in addition to enhance their compatibility with cement using physical pretreatment processes and accelerated carbonation curing.
Experiments were performed to assess the physical properties (as density, flexural strength, toughness and E-modulus), and micro structural properties (as determined by scanning electron microscopy) of the produced cement boards. The results show an improvement in the physical and microstructural properties of cellulosic fiber-cement composites by using accelerated CO2 curing method. In addition, excessive carbonation rate associated with pure gas carbonation does not necessarily lead to high strength and even detrimental strength development was found, which was shown by cement paste.

Microstructure imaging interpretation of polished surface has become well established as a method for the study of cement and concrete microstructure. This paper is an attempt to provide micro-level examination to the microstructure of cement paste in concrete particularly the hydrated mineral admixture and interfacial transition zone, which received increasing attention due to their effect on the hardened concrete properties. Furthermore, illustrations are provided of the transition area of cement paste adjacent to the aggregate border as well as other cement paste areas. SEM images reveal that pozzolanic reaction is not the only benefit of using mineral admixture. Spherical shape of grains is important to improve the microstructure of cement paste particularly in the interfacial transition zone.

This paper presents the influence of carbon steel microstructure on the corrosion rates. Four types of microstructures have obtained by quenching and tempering and iso-thermal annealing. These microstructures are:
banded ferrite/pearlite microstructure, fine ferrite/pearlite microstructure, coarse ferrite/pearlite microstructure and tempered martensite microstructure.
General corrosion and localized corrosion (penetration rates) were determined via mass loss and optical microscopy. The different microstructures of steels investigated in this paper revealed corrosion rate variations of 0.8– 3.2 mm y-1 and 3.3–6.4 - mm y-1 for the general and localized forms, respectively. The corrosion stability of the various microstructures may arise from variations of phases within the steel. A banded ferrite/pearlite microstructures have worse general corrosion properties, while tempered martensite worse microstructures have localized pitting corrosion properties. Coarse ferrite/pearlite microstructures have better localized pitting corrosion resistances compared to others investigated microstructures This paper has demonstrated that, microstructure is an important consideration when selecting carbon steel for an industrial corrosion resistance application.

For semigroups of linear bounded operators on Hilbert spaces, the problem of
being in Cp , 0 Keywords

The present work is aimed to investigate the effect of heat treatment on corrosion resistance of Al-alloy 7020-T6 in sea water, the specimens which manufactured by (1.5*1.5*0.2) cm, according to ASTM (G31-72) [1] The heat treatment was carried out at 480°C and water quench after that artificial aging are implemented at temperature 150°C for (1, 4) hours. Microstructure and phase properties after heat treatment and corrosion test were investigated by optical microscope; X-ray diffraction and
computer potentiodynamic polarization technique have been used to study corrosion behavior in 3.5% NaCl. The results of corrosion resistance 7020-T6 decrease by solution heat treatment and, increase the holding time from 1- 4 hour would increase the corrosion rate, Intermetallics compounds containing zinc represent as the sacrificial anode and control pitting corrosion in 7020-T6 alloy also, the artificial
ageing time increase the precipitation of zinc and decrease pitting corrosion at 1 hour.

The microstructure and hardness of copper alloy after fatigue-creep interaction
testing have been investigated. Experiments were carried out in the temperature
range from room temperature to 300oC. Attention has been paid to the role of the
microstructure and hardness on the fatigue-creep strength of copper alloy. It has
been shown that, there is a little effect of microstructure in the cyclic response of
copper alloy, while the hardness has a significant effect on the fatigue-creep
strength. The relation between strength and hardness were described by the
following equation:
σE.L. = 5.345 H0.6217

In this research, composite materials of hypereutectic aluminum – silicon as a matrix reinforced with different volume fractions (2%, 4%, 6%, 8%) of Yttria particles with grain size between (50 - 75 μm) are prepared. The composites are prepared by vortex technique in which the particles were added to the melt then mixing it by mechanical stirrer then the mixture is poured in a metallic cylindrical molds. After that, the microstructure, Vickers hardness and wear rate were conducted. The results showed the existence of the reinforcement particles in
different amounts in the microstructure and an increase in the hardness for the prepared composites when compared with the unreinforced alloy. The results also showed a better particles distribution and higher hardness with increasing yttria volume fraction. The wear rate of the composites is reduced when compared with the unreinforced alloy due to the hardness increase. More reduction in wear rate was noticed with increasing the Yttria volume fraction, and the better added percent was (8%Y2O3).

A novel surface modifying technique, Friction Stir Processing, is used to
enhance mechanical properties of Al-Si / Al2O3 composite, through micro
structural refinement and homogenization. The effect of processing parameters on
resultant microstructure and wear rate is investigated in this work.
The Friction Stir Processing resulted in significant breakup of the coarse Si
and Al-dendrites and uniform distribution of Si and Al2O3 in the matrix with
significant micro structural refinement. These microstructures changes lead to
significant improvement in wear resistance of composite

This work is concerned with a study of dry sliding wear of α–Brass (70/30) with
addition of lead and tin(3%wt) for each one alloy. Three brass alloys were prepared by
melting and pouring in steel molds. A Pin -on-Disc technique was used. The effect of
applied loads and sliding times on wear rate were examined. The results show that the
wear rate increases with increasing applied loads and with increasing sliding time at
constant sliding speed (2.7m/s) while hardness of steel disc was 35 HRc .
The results also show that the brass alloy containing 3% tin has more
wear resistance than that of other brass alloys.