Engineering and Technology Journal

To increase the erosion resistance of 2024 Al alloys, plasma nitriding surface treatment was used. Nitrogen and argon gases are injected into an evacuated chamber until the pressure reaches 15 Pa. The process requirements for normal plasma nitriding were heating at 440˚C for 8 hours, low voltage of 650 V, current of 25 mA, low gas consumption, and no air pollution. A continuous nitriding layer of AlN was formed. The microhardness reached a maximum value of 170 HV, about 3 times higher than that Al melts at, is transported upward through voids and capillaries in the AlN structures, and reacted with N plasma in the melt surface. The growth of the AlN structures promotes this transport of un-nitride alloy subjected to the same heat treatments. As a result, the erosion rate of the nitrided samples decreased by 10% when compared to the ones that are not nitrided.

The purpose of this study is to study the ultrasonic peening influence upon the mechanical properties of the welded joints of 3 mm AA 7075-T73. Friction stir welding (FSW) was carried out by using milling machine and cylindrical tool with tapered pin. The used welding parameters were 710 rpm , 35 mm min for rotational and travel speed , respectively .Tensile tests results showed that the welding efficiency was about 60% for welded samples , and this value increased by using one and two lines ultrasonic peening treatment to 74% , and 71% , respectively , this improvement is due to generating compressive stresses along the surface of welded joints. The microhardness of the welded samples showed that there were fluctuations across the welded centerline and minimum hardness occur in the heat affected zone (HAZ).

Asymmetric rolling refers to the conditions wherein velocities or diameters of two work rolls are different. Compared to symmetrical rolling, asymmetric rolling is more effective on microstructure modification and texture evolution. Intense shear deformation can be introduced into asymmetric rolling to enhance the ductility and formability of aluminum alloy and this is the aim of current research. The process of the asymmetrical rolling was done on specimens with different reductions (10%,15%, and 20% reductions). Then the tensile test was conducted at room temperature at the strain rate range between 0.33×10-3s-1 - 3.33×10-3s-1 to study the ductility property of the asymmetric rolling-deformed samples and also compared with as-received samples. The results show that the as-received specimen gave the highest elongation of 42.7%, while the lowest elongation of 22.4% was obtained by the (20%) thickness reduction specimen. Also, the as-received sample at an initial strain rate of 3.33×10-3s-1 gives the highest tensile strength value equal to 550MPa.

Ultrasonic peening is an innovative surface improvement process used to increase the resistance of aircraft metals and enhance high cycle fatigue life. The process creates residual compressive stresses deep into part surfaces. These compressive surface stresses inhibit the initiation and propagation of fatigue cracks. Aluminum alloys are relatively new materials used in aerospace, marine, automobile, and bridges due to low weight, which has significant advantages compared to the other materials. A major concern in the design of Aluminum alloys subjected to variable loads is fatigue strength and life. In this paper mechanical properties, fatigue strength, fatigue life and A.C.. electrical conductivity were studied for AA6061-T6 to assess the effects of ultrasonic peening (UP) on mechanical properties, fatigue at room temperature (RT), creep-fatigue (CF) at 250 ^ͦC and A.C.. electrical conductivity. Test results showed that after UP, the mechanical properties; ultimate tensile strength (UTS) and yield stress (Ys) were noticeably improved. The improvements in UTS and Ys were enhanced by 5.7% and 1.5% respectively while the ductility was reduced from 16.5% to 15.7%. Fatigue strength was enhanced by 8.37% compared to strength at RT. The results of UT before creep-fatigue CF showed increasing in fatigue strength 147 MPa at CF 250 ^̊C and improved to153 MPa after applying UP, indicating 4% improvement in strength. The fatigue life was improved after UP for both RT and CF. It was found that the A.C. electrical conductivity increase as the frequency increase for all the cases above.

This research presents microstructural characterization of the CoNi Al shape memory alloy with focus on understanding the significant properties as well as the relation between the physical properties and microstructure of this alloy. Melting technique were used to prepare Co Al Ni shape memory alloys, where scanning electron microscope, light optical microscopy and x-ray diffraction investigations showed that structure of this alloy is polycrystalline double phase (β and γ) structure, and it found that the grain size and phase fraction of β phase was ranged from 9 to 16 μm and (50-80) % respectively. It was found that by increasing the heat treatment time the phase fraction of hard β phase increased and phase fraction of ductile γ phase decreased, and consequently the grain size and the hardness of β phase increased. Differential Scanning Calorimeter results showed that transformation temperature decreased by increasing Al/Co, that Co content affected on transformation temperature. Tafel Curves showed the corrosion behavior in simulation body fluid, where the corrosion rate was ranged from 0.13 to 0.47 mpy and increased with each of increasing the annealing time and Co content, and from cyclic curves, the pitting corrosion possibility is not observed due to the formation of a protective layerthat formed by Al element.According to these properties and behavior, it was found that this alloy could be a good choice to be used for biomedical applications, especially in surgical, catheter tools and medical instruments.

Laser peening (LP) is a surface treatment technology for metallic materials. LP has shown agreat improvement in the fatigue strength and life.A study of fatigue under constant rotating bending stress programs has been conducted on 7049 AL alloy at a stress ratio (R=-1) and room temperature using laser peening technique .Four groups of tests have been designed.The first group (15 specimens) tested under unpeened condition. The second group (15 specimens) tested under air laser peening (ALP) while the third group (15 specimens) tested under water laser peening (WLP). The last group was designed to examine the fatigue behavior under black paint laser peening (BPLP). All the above groups were designed to establish the S-N curve. The results show no effect of laser peening LP at higher stresses (above 300 MPa), while this effect appears clearly at low stresses (200 and 250 MPa). The results alsoindicated that the WLP is more effective than the ALP. The fatigue life improvement factor (FLIF%) was 39, 18.9 and 4.65 under WLP for 200 MPa, 250 MPa and 300 MPa stress levels respectively.while a clear effect was observed for black paint laser peening (BPLP),it was found that the FLIF % was 93.25 at 300 MPa , 103.24 at 250 MPa and 116 at 200 MPa compared to unpeened data .

In present paper the fatigue life of aluminum alloy 7075 T73 under constant amplitude loading is predicted using ANN and ANFIS models. Many neural networks models are used for this purpose and also different neuro-fuzzy models are built for predict fatigue life.Theclassical power law formula ismost common used to find fatigue behaviors of materials. In present study, two techniques are used to find coefficients of the formula linear and nonlinear regression. Forcomparison the fatigue life curves of soft computing methods are plotted together with two conventionalmethods. The neural network and neuro-fuzzy models give good results compared with two conventional methods. Also it is shown thatneural network model which is trained using Levenberg-Marquardt algorithm is best neural network modelscompared with other NNS models.Also, it is foundANFIS models with input trapezoidal membership function is best performance from other membership function types to predict fatigue life. It can be stated that neuro-fuzzy models are better models than neural network and conventional methods to predict fatigue life of the maintained alloy.

An Investigation of estimated Mechanical Properties of AL-Alloys 6061-T6, which is one of the most commonly used in industrial applications, has been established experimentally. A new novel Plasma Peening techniques had been applied to the whole surfaces of the material by CNC-Plasma machine for 48 specimens, and then a new investigation were takeover to figure the amount of change in mechanical properties and estimated fatigue life. It was found that the improvement was showing a nonlinear behavior, according to peening duration time, speed, peening distance, peening number, and amount of effected power on the depth of the material thickness. The major improvement was at medium speed long duration time normal peening distance. Which shows up to 4 times improvements than the other cases. It was found that reducing in elongation of about 25% from references for 1x plasma peening for the most techniques used while a reduction in elongation of 31% for the two time plasma peening, on the other hand increment of 10% in elongation for 2x plasma peening and 5% of the increment for peening with 5kW of plasma power. These results illustrated in both tables and figures. Further study may established for other AL-Alloys to study the effects of plasma peening on it and to find the most effected one of them for the completely nine AL family.

In this study, the influence of bothheat treatment and cold working (rolling) on the tensile properties andhardness of6061 aluminum alloy sheets was investigated. The solution heat treatment is first performed at about 520°C 1 hr followed by rolling to(40% and 60%). Artificial aging is obtained by heating to about 180 °C for 1/2hr and 2 hr.Theexperimental work has revealed that when two strengthening mechanism(cold work and aging)are combined, the values of the mechanical properties are come up.Increasing the aging time from ½ hrto 2hr with redaction in area was causing increase in the values of the strength and hardness and dropping the elongation. In the other hand, increasing the redaction in area from (40%) to (60%) with aging was rising the value of the strength and hardness and dropping the elongation. The changes in mechanical properties were discussed as a result of increasing the dislocation density(result of rolling) and formation of precipitation(effect of aging) which are interface with the motion of dislocation and causes hindering of dislocation.

The present work encompasses the development of microstructure by using cooling plate casting process. This process consists of pouring the molten metal at temperature close to the liquidus line in an inclined cooling plate. The mould and the slope plate unit were manufactured by the researcher. Pouring temperature and inclination angles have effect on microstructure, tensile strength, and on the macro hardness for both Al-1.6%Mg, Al-0.46%Mg.
The following variables have been used in this work: pouring temperatures of (750,800,850ᵒC), tilt angles of (30ᵒ, 40ᵒ, 50ᵒand 60ᵒ), and Mg additive of (1.6%, 0.46%) with constant cooling length (380mm). Tensile results reveal that (750,800 and 850ᵒC) especially for (30ᵒ, 40ᵒ, 50ᵒ) for 1.6%-Mg, and 0.46%Mg have a high value. Vickers macro hardness has a gradual increasing value for Al-0.46%Mg, but for Al-1.6%Mg rheocast alloy it has a fluctuated value, the higher value is for small angles (30ᵒ, 40ᵒ, and 50ᵒ) and small value for high angle (60ᵒ).

The objective of the present paper is to investigate the effect of surface roughness on mechanical properties of aluminum alloy 2024-T4. This paper describes the effect of surface roughness at values of ( 0.1 , 3.5 , 8 ) μm on hardness and yield strength and also estimate the effect of shot peening on the yield strength at period time of ( 5 , 10 , 15 , 20 , 25 ) min. The obtained results show that the low roughness improved the mechanical properties by 15.7% and also the low roughness is better than the shot peening treatments by 5.3% because the low roughness make surface more coherent. Empirical equations are formulated based on the experimental results to evaluate the yield strength with the surface roughness and the hardness.

Sy= 394.3 ( Ra + 1.35 ) -0.1356
Sy = 1 / 2.2227(10)-2 - 1.32(10)-4 HV

This study has been conducted to investigate the effect of welding process parameter on the mechanical properties and microstructure of aluminum alloy 6061, using friction stir welding (FSW) and Tungsten inert gas welding (TIG). Different friction stir welded specimens were produced by employing variable welding speed from 10 to 40 mm/min, and constant rotation speed at 900 rpm. Different mechanical tests and microstructure examination were performing to evaluate the joints. The experimental results indicate that the welding process parameters have significant effect on mechanical properties of the joints, the best result of the (FSW) weld achieve at 30 mm/min welding speed which give tensile strength 189 MPa, and 55% joint efficiency of the ultimate tensile strength of parent metal. Tungsten inert gas welded (TIG) give tensile strength 124 MPa with 37% efficiency of the ultimate tensile strength of parent metal. The profile of micro hardness tests is shown variation in the hardness through the welding zones the lowest value at heat affected zone which is 60 HB and the highest value at the nugget zone which is 80HB, but in the case of Tungsten inert gas welded (TIG) the micro hardness profile is constant though the welded zones and the value of the hardness is very low about 43. The microstructure examinations of the friction stir – welded (FSW) are shown three welded zones, first fine equated crystalline in the nugget zone, second highly elongated grain with very small cells in thermo mechanical affected zone and third slightly elongated coarse grain in heat affected zone. For Tungsten inert gas welding (TIG) the microstructure contain dendrite structure with black eutectic regions and significant amount of aluminum and silicon.

There is a general interest in increasing the fatigue life of materials. Shot peening is the process commonly used in order to increase the fatigue strength and life of 7075-T651. The effect of a combination of processes, fatigue-creep interaction and shot peening has not been thoroughly investigated so far. The aim of the present investigation was whether further improvements can be achieved by a comb/*ination of the two treatments. Two level experiments (cumulative fatigue damage programe) were used in order to determine the optimal set of process. It was found that the combination of shot peening and fatigue-creep interaction could be applied successfully in order to increase fatigue life for some specimens. Results of variable loading test clearly indicate that Miner rule does not give accurate and reliable predictions on fatigue lives.

In this paper the effect of the springback on the bending operation of different
materials and alloys have been studied. Dies were designed and constructed in
different shape ( U-die , V-die) for several sheet’s thickness. Two types of alloys
were used; Aluminum Alloy 7020 T6 and Brass Alloy. These alloys have different
sheet thickness (2, 4, 6 and 8) mm. Aluminum alloys are heated to 270 °C and
330°C with cooling in the furnace for 90 min. while the brass alloys heated to 300,
320, 340 and 420 °C with cooling for 2 hours in furnace. Bending was done by
using the press of 80 ton. The springback is calculated by published equation. It
can be concluded that, the springback phenomenon caused to enlarge the external
dimensions when releasing the load and thick material have less springback due to
the enlarge of the plastic deformation. It’s found that the die’s shapes have great
effect on the springback, and when the temperature of the specimen is increased,
caused decreased in the springback.

To The aim of this research is to study the effect of 5 wt % Al2O3
addition Al- base alloy on sliding wear resistance under dry sliding
conditions using pin- on- disc machine . Wear test was conducted
after squeeze casting under different pressure ( 30 , 60 , 90) Mpa.
The results show that wear rate for Al- base alloy composites
increases with increasing applied load but decreases with increasing
sliding speed conditions . The composites which casting at 90 Mpa
pressure represents lower wear rate than those which cast at 30, 60 Mpa
pressure and the base alloy . The results also observed that the
coefficient of friction increasing with increasing sliding time but reaches to the steady state after 200 sec. The microhardness and ultimate tensile strength increases with increasing squeeze casting pressure.

The present work concerns with study of extrusion behavior of aluminum alloy-Al2014 comparing with pure aluminum-Al1050, using different die angles (á=15, 30 and 75°) and different billet lengths (20, 28, 40 and 52mm). Results showed that the extrusion load increase when billet length increases for aluminum alloy (Al-2014) and pure aluminum (Al-1050). The results also showed that small die angles required higher extrusion load than large die angles. The Brinell hardness values showed that aluminum alloy (Al-2014) undergoes higher work
hardening due to the presence of copper compared with the pure aluminum (Al-1050), in addition to formation of dead metal zone which resists the metal flow through the die opening.

The present work is aimed to study the friction stir welding and process for the
aluminum alloy 2024-T3, a threaded pin with a diameter of 6 mm and a concaved
shoulder of 18 mm welding tool was used. The single pass friction stir welding
(FSW) process was performed with clockwise tool rotation at different speeds and
variable feeding speeds. The specimens were tested to determine the best ultimate
tensile strength ( ult) and compared with the as received metal. In addition to friction
stir welding (FSW), another phase of welding named friction stir process (FSP) was
used. The best condition out of the FSW variables was selected in order to examine
the double pass welding processes. It was found that the best result is in forward
welding travel and counterclockwise tool rotation. The maximum tensile strength
achieved at friction stir welding process was 72% of the base metal and didn’t
improve in the FSP process. On the other hand, the fatigue endurance limit was
improved for FS weld ment when followed by FSP, where the reduction in fatigue
endurance limit for FSW specimen was 36% while for FSP specimen was 15% of the
base metal.

This paper presents an experimental study on the effect of shot peening on
mechanical properties and residual stresses of 2024-T351 Aluminum alloy. Under the
effects of shot peening time SPT the results show that the existence of SPT can
improve the mechanical properties and fatigue life up to a limit value of SPT. The 15
minutes SPT gave the highest value of (σu, σy) which is about 6.7 % for (σu) and 11.7
% for (σy). Empirical equations were proposed to evaluate the SPT with the
endurance limit stress and the residual stresses.

In this study the fatigue behavior of an aluminum alloy designated 2024 – T3
under constant and variable amplitude of stresses is considered. The applied load
adopted is a rotating bending one, the cross Section of the laboratory samples is
circular with a diameter of (6.74mm). All tests were carried out under a stress ratio
of R = - 1 and at room temperature condition. The study consists of two parts
experimental and theoretical. The experimental part includes carrying out
laboratory tests on two groups of specimens the first group was tested under
constant stress amplitude to establish the S-N curve of the specimen's material,
while the second group was tested under variable amplitude of stress to assess the
effects of the accumulated fatigue damage. The theoretical part of the study
includes a review of previous literature adopted to derive a theoretical and
mathematical model depending upon the variation of the stresses obtainedby
some previous theories, taking into consideration low and high stress levels, and
even post yield.
The derived model is denoted as elastic-plastic model for the evaluation of life
time of machinery parts. The linear theory of Miner and the theory of Elastic
Cracks Propagation are also studied throughout the theoretical part of the study.
In order to assess the capability of the two theories with the derived model: a
comparison is held between the experimented results and the results obtained by
applying the two theories.
It is noted that results obtained by applying the two theories are lower
(underestimates) than those obtained from the experimental study and that results
obtained by the suggested derived model are in better agreement than those
obtained by the two theories.

1100 Al specimens were anodically oxidized in different concentrations of
tartaric acid-tartrate solution (pH=7) in 1, 1.75, 3.25 and 4 wt % at temperatures of
30, 37.5, 52.5 and 60 ºC by applying a range of potentials of 30, 37.5, 52.5 and 60
V at exposure times of 40, 47.5, 62.5 and 70 min.. These four variables are
manipulated through the experimental work using Box – Wilson experimental
design where second order polynomial model was proposed to correlate the studied
variables with the thickness of anodic film of aluminum alloy (1100) to estimate
the coefficients of the proposed polynomial adopted via statistica software.
Optimum conditions for achieving the maximum film thickness are obtained from
optimizing the above correlation and are found as follows: temp. = 44ºC, acid conc.
= 2.8 wt %, voltage = 43.6 V, time = 54.6 min.. Stagnate Solutions of 3, 5, 10 and
25 wt % Nacl at 25ºC have been investigated using polarization technique at
optimum conditions for anodizing. The most important feature achieved was the
great difference in behavior between the anodic polarization curves for bare and
anodized aluminum in different concentrations of Nacl solutions. The corrosion
rates for anodized specimens are lower than those for unanodized ones. The
polarization behavior of anodizing specimens shows that the breakdown potentials
are shifted to more noble direction than bare specimens which is more pronounced
in 25 wt % Nacl solution due to anodizing.

A series of constant and cumulative fatigue tests under the effect of shot peening were conducted for two aluminum alloys 2024 and 5052. Three unpeed specimens were tested for each alloy under low-high stress levels (120-280 MPa) for 2024 aluminum alloy and (40-90 MPa) for 5052 aluminum alloy at room temperature and stress ratio R= -1. Other specimens were exposed to shot peening with different blasting time before the cumulative fatigue testing. It is found for 2024 Al alloy that as the shot peening time increases the cumulative fatigue life is improved but above 10 min. the life is reduced. For 5052 Al alloy the cumulative fatigue life is reduced as shot peening time increases

In some applications, the aluminum alloy 2024 T4 may be subjected to an
interaction of fatigue and creep effects at high temperature. This paper investigates
the effect of this interaction by studying the effect of constant amplitude fatigue
(CAF) and creep separately, and then fatigue-creep interaction is introduced by
testing the alloy under constant amplitude with some holding time periods through
the test at high temperature (150 oC). The results showed that the life time of the
alloy decreases due to fatigue-creep interaction as compared to creep alone in
about 77%, and in about 80% as compared with fatigue alone. This is a result of
accumulated fatigue damage superimposed on creep damage. Creep allows more
free spaces for fatigue cracks paths that accelerate failure. A theoretical model to
calculate the time to failure due to fatigue-creep interaction has been proposed.
This theoretical interaction model predicts very close time to failure values to the
experimental results.

Aluminum alloy (6063) has been anodized using sulfuric acid as an
electrolyte. To study the characteristic of the anodic film, four variables, were
considered as the most dominant variables. These variables are: current density in the
range of 1- 4 A/dm2, electrolyte concentration in the range of 6 - 20 vol.%, electrolyte
temperature in the range of 10- 30oC and anodizing time between 12- 60 min.
These four variables are manipulated through the experimental work using Box –
Wilson experimental design where second order polynomial model was proposed to
correlate the studied variables with the thickness of anodic film of aluminum alloy
(6063) to estimate the coefficients of the proposed polynomial adopted via statistica
software.
The predicated models are found after statistically analyzing the significance as
follows:
Y= 27.7800 + 8.0737X1 - 0.8037X3 + 8.2078X4 - 0.6994X2
1 - 0.8882X2
2
- 1.5582X2
3 - 1.1231X1X2 + 2.6225X1X4 - 1.7931X2X3 - 1.6956X2X4
- 1.0581X3X4
where Y is the objective function (thickness of anodic film), X1 is the current density;
X2 is the electrolyte concentration; X3 is the temperature of electrolyte and X4 is the
anodizing time.
The study shows that the anodizing time and current density had shown positive
dependence of great significance on the anodic film thickness while the other two
studied variables (i.e. concentration and temperature of electrolyte) had shown small
dependence on the film thickness of aluminum alloy (6063).
Optimum conditions for achieving the maximum film thickness are obtained from
optimizing the above correlation and are found as follow: 4 A /dm2 Current
density, 6 vol. % Acid concentration, 19.5 oC Electrolyte temperature and 60 min.
time of anodizing.