Materials Engineering Dept.,

In this research, the effect of ethanol as gasoline additive has been investigated into metal corrosion of a fuel delivery system. Corrosion tests have been performed in gasoline with different percentages of ethanol, using weight loss (immersion test) and electrochemical impedance stereoscopy (EIS) procedures. Surface of test specimens were checked by scanning electron microscopy (SEM) after 144 days of immersion in test solution. Also corroded components were analyzed using energy-dispersive X-ray analysis (EDAX) method. Test results, investigations, and analyses, altogether show more corrosion with the increase in ethanol percentage and water content in gasoline. Test results show that among different materials in fuel delivery system, aluminum alloys and hard soldering alloys have less corrosion than the others. Also chloride and sulfide were recognized as the main compound of corrosion products; therefore, the control of these two elements in fuel delivery system is a must in case of using ethanol as fuel additive in near future.

Due to its attractive characteristics, thin wall ductile iron (TWDI), has been increasingly considered as a preference for reducing material consumption in order to save energy and contribute less environment pollutions as well as decreasing costs. In this research, the effect of two mould runner gating systems and mould coating on graphite nodule characteristics and hardness value of TWDI casting was studied. Strip samples with various thicknesses of 2.3, 3.3, 4.5, 5.4, 6.5, 7.5 and 8.5 mm were cast into CO 2 silicate mould designed with two different stepped and tapered runners. Half of the moulds were coated by graphite-based zircon material to investigate the effect of mould coating on the graphite nodule qualities and quantities. Optical microscope and image analyzer were used to evaluate graphite nodule count, roundness and diameter of the TWDI cast samples. Hardness value of all the samples was measured by Brinell hardness testing. The results showed that roundness and count of graphite nodules decreased in microstructure of the samples produced by stepped runner uncoated mould, whilst diameter of graphite nodules showed an opposite behaviour. In addition, molten metal experienced a superior fluidity in coated moulds. Moreover, the TWDI samples achieved a significant improvement in the value of hardness.

Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments (TMTs). For the first TMT, after solution treated at the temperature of 380 • C for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 • C and 250 • C for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 • C for 20 h, underwent 2% cold worked and quenched in water of 0 • C. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 • C and 250 • C for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β-phase (Mg 17 Al 12 ) in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 • C whereas, in the second TMT, aging at 250 • C exhibited the best hardness values.

Binary Mg-1Ca alloy has been considered as a potential material for implant applications due to its nontoxic and biodegradable properties. However, the high corrosion tendency of the alloy, as a serious drawback, limited its practical efficiency. In this study, the effect of hot rolling on biodegradability of Mg-1Ca was investigated as a process to improve the microstructure and corrosion resistance of the alloy in simulated body fluid. The as-cast alloy was rolled to various reduction levels at different temperatures. Optical and scanning electron microscopy together with energy dispersive X-ray spectroscopy and X-ray diffraction analysis were used characterize the microstructure of the as-cast and rolled samples. Immersion and potentiodynamic polarization tests were performed to examine the electrochemical and corrosion behavior of the samples in simulated body fluid. The results showed that the high corrosion tendency of as-cast Mg-1Ca was remarkably reduced by the hot rolling process due to the microstructure refinement. It was found that the corrosion rate of the samples which experienced higher reduction percentages decreased to some extent. However, the weight loss results indicated that the rolling process at higher temperatures caused more corrosion products to emerge on the surface of the samples. It can be associated with the accumulation and growth of Mg 2 Ca phase at the grain boundaries.

The performance of Mg-1Ca alloy, a biodegradable metallic material, may be improved by hot working in order that it may be of use in bone implant applications. In this study, Mg-1Ca cast alloy was preheated to different temperatures before undergoing forging process with various forging speeds. Macro-and microstructure of the samples were examined by stereo and scanning electron microscopes (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), respectively. To determine the mechanical properties of the alloy, hardness value and plastic deformation ability of the samples were measured. To investigate the corrosion behaviour of the alloy, immersion and electrochemical tests were performed on the samples in simulated body fluid and the corrosion products were characterized by SEM/EDS. The results showed that increasing forging temperature decreased grain size led to improved hardness value and plastic deformation ability of the alloy, whereas no significant effect was observed by changing forging speed. Moreover, forging at higher temperatures led to an increase in the amount of Mg 2 Ca phase at grain boundaries resulted in higher corrosion rates. It can be concluded that although forging process improved the mechanical properties of the alloy, it does not satisfy the corrosion resistance criteria required for bone healing.

Biodegradable implant is an alternative to metallic implant and has the advantage of not being necessary to remove once the fracture has healed. Magnesium is particularly desirable since it is biocompatible and has a modulus of elasticity closer to bone. In addition, it shows ability to biodegrade in situ, when used as an implant material. In this research, different percentages of calcium were added to magnesium during melting of the alloy. A selected alloy was forged at different parameters. Both as cast and forged alloys were subjected to polarization test performed in Kokubo simulated body fluid. Immersion test in the fluid was conducted for 96 hours to investigate the formation, growth and morphology of the hydroxyapatite on the surface of the alloys. The results showed that similar electrochemical behaviour took place in the alloys regardless of the calcium content. However, an increase in corrosion rate was observed with increasing calcium content. It was also observed that forging process decreased the corrosion resistance of the alloy. Furthermore, increasing calcium content accelerated the growth of bone-like apatite in the alloy.

Lost foam casting is a relatively new process in commercial terms and is widely used to produce defect free castings owing to its advantages like producing complex shape and acceptable surface finish. In the present research, experimental investigations in lost foam casting of aluminium-silicon cast alloy, LM6, were conducted. The main objective of the study was to evaluate the effect of different sand sizes and pouring temperatures on the porosity of thin-wall castings. A stepped pattern was used in the study and the focus of the investigations was at the thinnest 3 mm section. A full 2-level factorial design experimental technique was employed to plan the experiment and subsequently identify the significant factors which affect the casting porosity. The result shows that increasing in the pouring temperature decreases the porosity in the thin-wall section of casting. Finer sand size is more favourable than coarse size for LFC mould making process.

Effect of calcium addition on microstructure, hardness value and corrosion behavior of five different Mg-xCa binary alloys (x = 0.7, 1, 2, 3, 4 wt. (%)) was investigated. Notable refinement in microstructure of the alloy occurred with increasing calcium content. In addition, more uniform distribution of Mg 2 Ca phase was observed in α-Mg matrix resulted in an increase in hardness value. The in-vitro corrosion examination using Kokubo simulated body fluid showed that the addition of calcium shifted the fluid pH value to a higher level similar to those found in pure commercial Mg. The high pH value amplified the formation and growth of bone-like apatite. Higher percentage of Ca resulted in needle-shaped growth of the apatite. Electrochemical measurements in the same solution revealed that increasing Ca content led to higher corrosion rates due to the formation of more cathodic Mg 2 Ca precipitate in the microstructure. The results therefore suggested that Mg-0.7Ca with the minimum amount of Mg 2 Ca is a good candidate for bio-implant applications.

In this research, the effect of ethanol as gasoline additive has been investigated into metal corrosion of a fuel delivery system. Corrosion tests have been performed in gasoline with different percentages of ethanol, using weight loss (immersion test) and electrochemical impedance stereoscopy (EIS) procedures. Surface of test specimens were checked by scanning electron microscopy (SEM) after 144 days of immersion in test solution. Also corroded components were analyzed using energy-dispersive X-ray analysis (EDAX) method. Test results, investigations, and analyses, altogether show more corrosion with the increase in ethanol percentage and water content in gasoline. Test results show that among different materials in fuel delivery system, aluminum alloys and hard soldering alloys have less corrosion than the others. Also chloride and sulfide were recognized as the main compound of corrosion products; therefore, the control of these two elements in fuel delivery system is a must in case of using ethanol as fuel additive in near future.

Magnesium alloys, due to their low density and excellent specific strength, are known as advanced materials for ultra light and low energy consumption purposes. The present study is to investigate the effect of using different covering flux compositions on mould-metal reaction during in-situ melting of AZ91D magnesium alloy. In this study the alloy in the form of granules was charged into a ceramic shell mould and heated up under argon atmosphere and the covering fluxes to different temperatures until it was melted and filled the mould at the possible lowest temperature. Thermal analysis was used to explore the melting behaviour of the granules during using in-situ melting technique. Results showed that employing covering flux is necessary to approach to a lower temperature for melting. In addition, it diminished the mould metal reaction which led to a higher quality casting surface. Moreover, the granules showed the characteristic temperatures similar to the bulk material melting.

The effect of multi-step tempering On retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated. Microstructural evolutions were characterized by optical microscope, X-ray diffraction, scanning electron microscope and Feritscope, while the mechanical properties were determined by hardness and tensile tests. The results revealed that the content of retained austenite decreased by about 2 % after multi-step tempering. However, the content of retained austenite increased from 3. 6 % to 5. 1% by increasing multi-step tempering temperature. The hardness and tensile strength increased as the austenitization temperature changed from 800 to 920 'C, while above 920 'C, hardness and tensile strength decreased. In addition, the maximum values of hardness, ultimate and yield strength were obtained via triple tempering at 520 ·c, while beyond 520 ·c, the hardness, ultimate and yield strength decreased sharply, Key words: cold back-up roll; retained austenite; mechanical property; austenite grain size In strength. A Abdollah-zadeh et al[5 J investigated Biography: Hamid Reza Bakhsheshi-Rad ( 1976-), Male, Doctor Candidate;

An experimental study on lost foam casting of an Al−Si−Cu alloy was conducted. The main objective was to study the effect of pattern coating thickness on casting imperfection and porosity percentage as well as eutectic silicon spacing of the alloy. The results showed that increasing slurry viscosity and flask dipping time influenced the casting integrity and microstructural characteristics. It was found that thinner pattern coating produced improved mould filling, refined microstructure and higher quality castings containing less porosity.

The quality of surface finish after machining is one of the most important parameters in ensuring the performance requirements of machined components during assembly. In this study the surface roughness of titanium alloy, Ti-6Al-4V was investigated during high speed end milling under dry condition. Evaluation was conducted using TiAlN+TiN PVD coated carbide tool under different cutting speeds and feed rates. Surface roughness was measured in two directions of feed and stepover. Results showed that increasing cutting speed led to a higher or better surface quality of the machined part. This behaviour was more significant when higher feed rate was employed. In contrast, lower feed rate at higher cutting speed caused appearance of lamellae defect on the machined surface resulting in comparatively poor surface finish. Overall results revealed that the best surface finish with 63 nm was obtained when employing cutting conditions of 300 m/min and 0.06 mm/tooth.