Mohammed Almomani

Effect of Processing Parameters on Friction Stir Welded Aluminum Matrix Composites Wear Behavior

In the present work, the aluminum matrix composites reinforced with both SiC and graphite particles are joined using a friction stir welding (FSW) process. The wear characteristics of the welded joints were investigated at constant load of 50 N and a rotational speed of 1,000 rpm using a pin-on-disk wear testing apparatus. This study focuses on the influences of the FSW processing parameters (tool geometry, rotational speed, and welding speed) on the wear characteristics of the welded joint of the considered hybrid aluminum matrix composite under dry sliding conditions. The experimental results indicate that the wear resistance of the joint increases at high welding speeds (>45 mm/min) and/or low value of rotational speeds. Different tool pin profiles (square, octagonal, and hexagonal) are developed to perform the welding process, and the effects of the tool pin profile on the weldments were studied. It is found that joints welded with square pin profile have better wear resistance compared to the other pin profiles. The results demonstrate that the FSW processing parameters greatly affect on the wear resistance of the welded joints due to various microstructural modifications during welding that cause an improvement in the welded zone hardness and wear properties.

Pitting corrosion protection of stainless steel by sputter deposited hafnia, alumina, and hafnia-alumina nanolaminate films

316L stainless steel coated with sputter deposited HfO2, Al2O3, and HfO2–Al2O3 nanolaminate films were subjected to direct current cyclic potentiodynamic polarization (DCP) in Hanks’ balanced salt solution electrolyte. Postexposure morphology was characterized by scanning electron microscopy (SEM) with in situ energy dispersive spectroscopy (EDS). SEM/EDS data show that bare steel and steel coated with single-layer HfO2 develop pits with perforated covers. These pits become autocatalytic, consistent with an observed positive DCP hysteresis. On the other hand, SEM/EDS data show that steel coated with Al2O3 and HfO2–Al2O3 nanolaminate films does not develop autocatalytic pits, consistent with an observed negative DCP hysteresis. However, Al2O3 splinters upon polarization whereas the HfO2–Al2O3 nanolaminate remains intact. The areas of worst damage in the nanolaminate correspond to pit cover rupture before autocatalysis, allowing pit and bulk electrolyte to mix and the newly exposed steel surface to repassivate. The films’ diverse behavior is discussed in terms of a model for perforated pit growth that requires occlusion until an autocatalytic geometry is established. The authors conclude that the key property a film must have to arrest autocatalytic geometry development is the ability to rupture locally at an early stage of pit growth.316L stainless steel coated with sputter deposited HfO2, Al2O3, and HfO2–Al2O3 nanolaminate films were subjected to direct current cyclic potentiodynamic polarization (DCP) in Hanks’ balanced salt solution electrolyte. Postexposure morphology was characterized by scanning electron microscopy (SEM) with in situ energy dispersive spectroscopy (EDS). SEM/EDS data show that bare steel and steel coated with single-layer HfO2 develop pits with perforated covers. These pits become autocatalytic, consistent with an observed positive DCP hysteresis. On the other hand, SEM/EDS data show that steel coated with Al2O3 and HfO2–Al2O3 nanolaminate films does not develop autocatalytic pits, consistent with an observed negative DCP hysteresis. However, Al2O3 splinters upon polarization whereas the HfO2–Al2O3 nanolaminate remains intact. The areas of worst damage in the nanolaminate correspond to pit cover rupture before autocatalysis, allowing pit and bulk electrolyte to mix and the newly exposed steel surface to repassiv...

Preventive maintenance planning using group technology

Purpose – The purpose of this paper is to develop a preventive maintenance (PM) model that encounters the problems of traditional methods of conducting PM within high component/machine variety environments.Design/methodology/approach – A new platform to conduct planning of the PM actions by using clustering based on the Group Technology concept to create PM virtual cells of equipment/machines is introduced. A real case study at Arab Potash Company was used to illustrate the model. The component/machine variety that requires PM at the considered company is in thousands of items.Findings – PM for high component/machine environments are not enough addressed in the literature. The concept of clustering and similarity coefficient was used and found very useful to model this situation.Practical implications – The proposed procedure will assist maintenance managers/engineers in too many ways. It will help to optimize the inventory of the spare parts, and to create standard process plan for executing the preventi...

Statistical analysis of some mechanical properties of friction stir welded aluminium matrix composite

In this study, the effect of friction stir welding (FSW) parameters such as rotational speed, welding (transverse) speed, and the type of pin profile tool on some mechanical properties was statistically investigated. Plates of aluminium matrix composites fabricated by stir casting method were joined by friction stir welding process. The statistical analysis has shown that the most important factor affecting hardness and tensile strength is the welding (transverse) speed, while the rotational speed has a second ranking and pin profile tool geometry is the least. The rotational speed has no statistical significant influence on the wear rate. However, the nugget zone, which was welded by square pin profile tool, seemed to exhibit better mechanical properties compared to those obtained by other pin profile tools.

Corrosion investigation of zinc−aluminum alloy matrix (ZA-27) reinforced with alumina (Al2O3) and fly ash

ABSTRACT In this study, zinc−aluminum alloy (ZA-27) matrix composites reinforced by different weight fractions of fly ash or alumina (Al2O3) were produced using the traditional stir casting technique. The corrosion behaviors of both unreinforced alloy and reinforced composites were examined using direct current polarization (DCP) test in a simulated sea solution (3.5 wt.% NaCl). Scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) were used to examine the morphology of the composites’ surface before and after corrosion tests. The results of corrosion revealed that reinforcing ZA-27 alloy by fly ash or Al2O3 particles decreases its tendency to uniform corrosion due to the formation of weak microgalvanic couple between matrix and reinforcement particles. The fly ash and alumina (Al2O3) particles have protected the matrix material from pits formation at early stage of polarization. However, once these pits are formed, they grow faster. Positive hysteresis of the polarization curves implies that the salt layer breakdown and matrix dissolution overshadow surface passivation during the reverse scan. The electrochemical results are consistent with the pits’ morphology of the corroded composite. Composites with fly ash reinforcements have autocatalytic pits, whereas composites with alumina (Al2O3) reinforcements have shallow pits.

Tribological investigation of Zamak alloys reinforced with alumina (Al2O3) and fly ash

ABSTRACT In this study, zinc aluminum alloy (Zamak) (ZA-27) composites reinforced by different weight fractions of fly ash, alumina (Al2O3), or both particles were produced using compo-casting technique. The composites were subjected to hardness and wear tests. The hardness of the composites increases with increase of the weight fractions of reinforcements. In wear test, the composites were examined under dry sliding conditions using pin on disc apparatus. The wear results revealed that the wear resistance increases with increase of the weight fractions of reinforcements. However, the effect of fly ash particles on the wear resistance of the produced composites is more statistically significant than the effect of Al2O3 particles. The morphology of the composites was examined using scanning electron microscopy (SEM) after the test. The SEM images revealed the existence of adhesion and delamination wear mechanism.

Effect of process parameters on corrosion rate of friction stir welded aluminium SiC-Gr hybrid composites

Abstract In the present study, the influence of processing parameters of friction stir welding on the corrosion rate of the welded joints of aluminium SiC–Gr hybrid composites was investigated. The experimental results indicate that the corrosion resistance of the welded joints increases at high welding (traverse) speed and/or low values of rotational speed. These variations occur as a result of the changes in the joint microstructure, where fine grains are developed as a consequence of a relatively low heat input and fast cooling to room temperature by ambient air associated with low rotational speed and/or high welding speeds. The mixed electrode theory is used to explain these variations of the corrosion rate, where the area ratio of cathode/anode for the galvanic couple between the aluminium metal matrix and the reinforcement constituents becomes small for fine grains. Thus, the corrosion resistance of the welded joints is increased.

Applying ANOVA and DOE to study the effect of manganese on the hardness and wear rate of artificially aged Al-4.5wt%Cu alloys

Abstract The addition of manganese may constitute an important means for imparting the mechanical properties of Al-4.5wt%Cu alloys that have been artificially aged. The literature, however, comprises conflicting reports on the effect of manganese on these alloys. Thus, this work tries to reach results that are more conclusive by utilizing statistical approaches such as Design of Experiments and the Analysis of Variance. Accordingly, different percentages of manganese additions under different aging times were investigated in this study for their effect on hardness and wear rate. Manganese was added in concentrations of 0.2, 0.4, 0.6, 0.8 and 1wt%. Following the solution treatment, aging was applied for time durations of 1, 2 and 3 h. Aging temperature was held constant at 200 °C. Results showed that Mn concentration and aging time have significant effect on alloy hardness and wear rate.