Assessment of the Impact of Age-Hardening on the ...paper.uscip.us/ajmst/ajmst.2016.1002.pdf · materials (ASM, 1990; Machler, 1991; Chee and Mohamad, ... aggregates in light and

Columbia International Publishing American Journal of Materials Science and Technology (2016) Vol. 5 No. 1 pp. 11-29 doi:10.7726/ajmst.2016.1002

Research Article

______________________________________________________________________________________________________________________________ *Corresponding e-mail: [email protected] , 1 Federal University of Technology Akure, Nigeria.

11

Assessment of the Impact of Age-Hardening on the Mechanical Properties of As-Cast Aluminium Composites

based on Palm Kernel Shell Ash Oladele Isiaka Oluwole and Okoro Avwerosuoghene Moses Received: 6 June 2016; Published online 19 November 2016 © The author(s) 2016. Published with open access at www.uscip.us

Abstract

In a bid to improve the mechanical properties of PKS ash reinforced as-cast aluminium composites, recycled aluminum alloy from cylinders of automotive engine blocks were cleansed of its grease by using premium motor spirit (PMS) also known as petrol, washed thoroughly with soap and water and then sun dried for 5 days. The palm kernel shell was screened of dirt and other unwanted foreign materials before being roasted in furnace. The ash was further pulverized by laboratory ball mill machine followed by sieving to obtain particle sizes of 100 µm and divided into two parts. One portion was treated with NaOH solution while the other part was left as untreated before they are been added to the molten aluminum alloy in predetermined proportions. The newly developed composites were divided into two parts from where one part was subjected to age-hardening process to improve the mechanical properties of the developed composites and various tests such as hardness, impact and tensile were carried out on them. The tests were carried out to ascertain the effect of the heat treatment process on the mechanical properties of the developed composite samples. The results indicate that the hardness of the developed composites was immensely improved. Keywords: Age-hardening; Aluminum; Mechanical properties; Palm kernel shell ash; Composite

1. Introduction The essential need for aluminium (Al) grows tremendously over the past years because of its unique synergy of properties which makes it one of the most versatile engineering and structural materials (ASM, 1990; Machler, 1991; Chee and Mohamad, 2009). The optimum desired properties of aluminium are achieved by alloying and heat treatments. These promote the formation of coherent precipitates which obstruct with the motion of dislocations and enhance its mechanical properties (Smallman, 1985; Lavernia et al., 1990; Sanctis, 1991; White et al., 1991). Aluminium

mailto:[email protected]

Oladele Isiaka Oluwole and Okoro Avwerosuoghene Moses

/ American Journal of Materials Science and Technology (2016) Vol. 5 No. 1 pp. 11-29

12

used for structural and automobile applications are known to possess attractive properties such as low density, high strength, ductility, toughness and resistance to fatigue (Heinz and Haszler, 2000; Williams and Starke, 2003; Clark et al., 2005; Li and Peng, 2008). These Al has been extensively utilized in aircraft structural parts and other highly stressed parts (Woei-Shyan and Wu-Chung, 2000; Lin et al., 2003; Shwe et al., 2008; Zhao and Jiang, 2008; Mohammad and Esmaeil, 2010). It has been discovered that during age-hardening or precipitation hardening of aluminium alloys, a very high specific strength is achieved in the Al alloy which may be as a result of the precipitates which are formed in the alloy that may eventually act as an obstacle to the movement of dislocation in the metal. .Most wrought aluminium alloys are strengthened by age hardening. The precipitation processes from which this hardening is derived are well known to be sensitive to the presence of selected trace element additions or microalloying, which can change the process and/or kinetics of precipitation in many age hardenable alloys (Polmear,1998; Mukhopadhyay et al., 1991). Precipitation in commercial aluminium alloys usually starts from the formation of GP zones, which may be regarded as fully coherent metastable precipitates. Subsequent evolution of the microstructure involves the replacement of the GP zones with more stable phases. This occurs primarily because GP zones are isomorphous with the matrix and, therefore, have a lower interfacial energy than intermediate or equilibrium precipitate phases that possess a distinct crystal structure. As a result, the nucleation barrier for GP zones is significantly smaller (Ringer and Hono, 2000). Research had shown that the mechanical and physical properties of aluminum alloys are affected by working temperature. Aluminium matrix composites (AlMC) are new trendy materials that possess excellent mechanical and physical properties and they’ve been comfortably applied in various applications such as automobile, aerospace, building structures etc. Most of their recent applications are in aviation, ground transportation, electronics and sports industries. The usage of AlMCs was over 3.5 million kg in the year 2004 and is increasing at an annual growth rate of over 6 %. AlMC are Al reinforced with other materials such as other metals, ceramics, fibres or organic compounds. They are made by dispersing the reinforcements in the metal matrix. Reinforcements are utilized to improve the properties of the base metal like strength, stiffness, conductivity and many more. Aluminium and its alloys have attracted most attention as base metal in metal matrix composites (McDanels, 1985). A number of reinforcements had been utilized in enhancing the properties of aluminium such as zirconia, titania, silica but they are quite costly and not easy to process. However, since the emerging concern of resource depletion and global pollution has motivated researchers and engineers to seek and develop new materials depending on renewable resources. These include the use of by-products and waste materials in construction. Many of these by-products are utilized as fillers for the production of desirable mix design. With the global economic recession in addition to the market inflationary trends, the constituent materials used for these mix design had led to the increase in cost of construction. Hence, researchers in material science and engineering are committed to having local materials to partially or fully replace these costly conventional ones (Nwaobakata and Agunwamba, 2014). Several breakthrough have been made in these regards and this subject is attracting attentions due to the functional advantages of waste reusability and sustainable development. Reduction in construction costs and the ability to produce adequate mix are added advantages (Muhamad, et al., 2010; Ndoke, 2006).To assessed the performance of palm kernel shells as a partial replacement for coarse aggregate in asphalt concrete, various investigations had been carried out to ascertain the suitability of palm kernel shells as aggregates in light and dense concrete for structural and non-structural purposes (Falade, 1992). Other similar efforts in the direction of waste management strategies include structural performance of concrete using oil palm shell (OPS) as lightweight aggregate. In addition, other



13

materials explored in partial replacement for concrete aggregates include cow bone ash, palm kernel shells, fly-ash, rice husk, and rice straw as pozzolanic materials. The use of coconut husk ash, corn cob ash and peanut shell ash as cement replacement has also been investigated (Kandahl, 1992; Nimityongskul and Daladar, 1992). However, this research was carried out to examine the effects of age-hardening process on the mechanical properties of palm kernel shell ash reinforced as-cast aluminium composites.

2. Materials and Method Materials for this work include; cylinders of engine blocks, palm kernel shells, sodium hydroxide pellets and distilled water. 2.1 Preparation of Materials 2.1.1 Aluminium alloy

As-received cylinders of an automobile engine block was degreased by using PMS and then washed thoroughly with soap and water followed by sun drying for 5 days. Before use, composition analysis was carried out as shown in Table1. 2.1.2 Spark Test Spark Test was carried out on the As – Received aluminium samples by placing the sample in an ionization chamber containing Argon and then sparked. A spectrum reader indicates the composition using a spectrometer; this is then interpreted to reveal the composition of the As- Received Sample as shown in Table 1. Table 1 Chemical Composition of As- Received Aluminium Alloy (Wt. %)

Elements Si Fe Cu Mn Mg Cr Ni Zn Ti Al

Composition (%) 6.52 4.43 3.88 0.5 0.29 0.01 0.01 0.46 0.15 91.5

2.1.3 Observation The Spark test result shows Al-Si Eutectic Composition. This was as a result of Silicon having the highest wt.% after aluminium from among the alloying elements. The presence of copper with about 3.8 wt. % helps in enhancing the strength and hardness. It also promote the ease of machinability and resistance to hot tear during solidification process. Also, Magnesium with about 0.29 wt,% aids strengthening and hardening of aluminium castings due to the formation of Mg2Si

when heat treatment is carried out. Titanium are used to refine primary aluminium grains while manganese and chromium changes the morphology of the iron Al5FeSi phase from its typical platelets/acicular form to a more cubic Al5(MnFe)3Si2 form that is less harmful to ductility. Nickel, as minor element, serves aid the improvement of the corrosion resistance.



14

2.1.4 Palm kernel shell The palm kernel shell was screened of dirt and other unwanted foreign materials and roasted in the roasting furnace. The ash produced was further pulverized using laboratory ball mill machine and sieved to obtain particle sizes of 100 µm. The PKS ash was divided into two parts and one part was treated with 1 M NaOH solution while the other half was left and used as untreated. 2.1.5 Chemical Treatment of Palm Kernel Shell Ash The palm kernel shell ash was mercerized using 1 M NaOH solution in a shaker water bath

maintained at 50 ºC for 4 hours. The process was carried out by dissolving 50 grams of NaOH

pellets in 1dm3 of distilled water. Then the palm kernel shell ash was added to the NaOH solution and maintained at the stated conditions. 2.1.6 X-Ray Diffraction Test A focus X-ray beam is shot at the sample at a specific angle of incidence. The X-ray deflects or diffracts in various ways depending on the crystal structure (inter-atomic distance) of the sample. The locations (angle) and intensity of the diffracted rays are measured. Various compounds have a unique diffraction pattern. In order to identify a substance, the diffracted x-rays are compared with that of the data base. The Chemical Composition of As- Received Palm Kernel Shell Ash (%) is shown in Table 2. Table 2 Chemical Composition of As- Received Palm Kernel Shell Ash (%)

Compound SiO2 Al2O3 Fe2O3 P2O5 CaO TiO2 MgO Na2O K2O Cl MnO C

Composition (%) 31.73 3.46 1.78 2.57 20.27 12.39 1.01 1.38 1.51 0.08 1.27 12.55

2.1.7 Observation From the X-Ray diffraction of palm kernel ash result, the presence of compounds like SiO2, CaO, TiO2 and Al2O3 as well as C in higher proportions will aid the strengthening potential expected from the PKSA. These compounds also support the reason why the PKSA has a slightly refractory property. 2.1.8 Mould Preparation Tensile test mould with dump bell shape was produced from cast iron into which the molting metal was poured. Cast iron was selected based on its higher melting point than that of aluminium and since metal mould usually gives better surface finish for the cast products. 2.2 Composites Development The composites were developed by blending the materials in predetermined proportions. The



15

aluminium alloy based cylinder engine block was melted using diesel fuel burner furnace. Chemically treated and untreated palm kernel ash is being added at varying percentages of; 5, 10 and 15 respectively to the molten aluminium alloy after which it was properly stirred for 5 minutes before being poured into the metal mould. After the casting, the composites were allowed to solidify before being removed from the mould. The mould contains 6 cavities from where 6 samples were produced for each composition. 2.3 Composites Formulation For the production of the composites, the formulation consists of seven series of various samples which are; 5U, 5T, 10U, 10T, 15U and 15T while the neat sample was denoted as CS. T- denotes Treated Palm Kernel Shell Ash, while U- denotes Untreated Palm Kernel Shell Ash. The compositions are shown in Table 3. Table 3 Formulation Table for the Developed Composites

Samples Aluminium Alloy Matrix (%) Palm Kernel Shell Ash (%)

CS 100 -

5U 95 5 5T 95 5

10U 90 10 10T 90 10

15U 85 15 15T 85 15

2.4 Artificial Aging Process

The aging process was carried out in a muffle furnace, solution heat treatment was done at 500 ºC

for 1 hour after which it was quenched in water, and then aged at 170 ºC for 8 hours, after which it was allowed to cool in the furnace. The aged samples where denoted as shown in Table 4. Table 4 Description of the Aged samples Aged Samples Aluminium Alloy Matrix (%) Palm Kernel Shell Ash (%)

CSA 100 - 5UA 95 5 5TA 95 5

10UA 90 10 10TA 90 10 15UA 85 15 15TA 85 15



16

2.5 Mechanical Testing of Samples Representative Samples of the materials were tested in various machines for tensile, impact and hardness tests as well as metallographic examination of the fractured surfaces. 2.5.1 Tensile Test Tensile Test was carried out using Instron Universal tensile testing machine which has a 100 KN load frame, a variety of specimen fixtures, several strain gauge extensometers and a software for data collections and analysis. Three (3) samples were tested for each composition from where the average value was taken to be the representative value. 2.5.2 Impact Test The developed composites were machined to impact test specimen with a notch at the middle. The samples were tested using the impact testing machine by applying sudden energy so as to break the sample. Three (3) samples were tested for each composition from where the average value was taken to be the representative value. 2.5.3 Hardness Test Hardness of the samples was determined by cutting out part of the samples and using Rockwell hardness testing machine. The machine measures the ability of the sample to resist penetration by measuring the depth of indention. Three (3) samples were tested for each composition from where the average value was taken to be the representative value. 2.6 Metallographic Examination Microstructure of the developed composites were examined after the samples have been grounded using Abrasive Paper from the coarse to the finest grit sizes, the 240, 320, 400 and 600 were used to smoothen the surfaces followed by polishing using velvet cloth with micron alumina paste and, finally using a diamond paste. The samples were etched using 2 % NaOH to reveal the grain structure of the aluminium alloy when viewed.

3. Results and Discussion 3.1 Hardness Test One of the major mechanical test carried out on the developed and aged composite samples is hardness test. This was done because the material in service will be exposed to wear. Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance of a material to indentation, and it is determined by measuring the permanent depth of the indentation. In this research, Rockwell hardness tester was utilized to analyze the hardness of the produced composite. The Rockwell test method can be used on all metals except in conditions where the test metal condition would introduce too many variations: where the indentation will be large for the application or the sample size or sample shape prohibit it use. This method measures the permanent



17

depth of indentation produced on the sample. The results were as shown in Figure1 and discussed below.

0

50

100

150

200

250

300

350

400

450

500

5U 5UA 5T 5TA 10U 10UA 10T 10TA 15U 15UA 15T 15TA CS CSA

HA

RDN

ESS

(HRA

)

SAMPLES

Fig. 1. Hardness Properties of the Control, Developed and Aged Composite Samples Figure 1 shows the hardness results for the samples. From the results, it was observed that sample 10UA with composition (90:10) weight percent has the highest hardness with a value of 477 HRA. This was followed by sample 10TA with composition (90:10) weight percent and value 444 HRA. Neat sample CS which has aluminium alloy alone was with a hardness value of 309 HRA but the value increase to 312 after age-hardening. With these results, it is obvious that the addition of treated PKSA to the aluminium alloy is the best for the development of good and strong composites and also, age-hardening process enhanced the hardness of the developed composite samples for automobile application. Also from the result, it was observed that the untreated PKSA reinforced the Al-matrix phase have betters hardness values after age-hardening treatment was carried out on them than the treated one which may be as result of the greater number of precipitate were formed which eventually act as an obstruction to the motion of dislocation. 3.2 Impact Test This method is used for ascertaining the behavior of material subjected to shock loading in bending, tension, or torsion. The quantity usually measured is the energy absorbed in breaking the specimen in a single blow, as in the Charpy Impact Test, Izod Impact Test, and Tension Impact Test. In this research, izod impact test was used to determine the impact strength of the produced composites.



18

0

2

4

6

8

10

12

14

16

18

20


IMPA

CT T

EST

(Jou

le)

SAMPLES

Fig.2. Variation of Impact Strength with the Control, Developed and Aged Composite Samples

Figure 2 shows the impact strength for the samples. From the result it was observed that sample 15T shows the highest impact strength of 18.38 J with a composition of 15 wt% of treated PKSA added to Al-Si alloy. This was followed by 10T with impact strength of 13.22 J with a composition of 10 wt% of treated PKSA added to Al-Si alloy. Neat sample was observed to possess the lowest impact strength of 6.80 J. The results of the impact strength for the composites revealed that the impact strength of the composites increases as the weight fraction of the reinforcement was increased. Also, the result shows that treated PKSA reinforcement enhances the impact strength of the produced composite than the untreated reinforcement and this is as a result of the high force of adhesion between the treated palm kernel shell ash and the aluminium alloy matrix which eventually brought about the high impact strength of the produced composites. However, it was observed that age-hardening process only enhanced the impact strength of the neat and the samples with untreated and lowest volume of reinforcement which may be as a result of overcrowding and competition between the precipitates and the reinforcements at higher volume fractions. Comparing the response of the materials to both impact strength and hardness, it was observed that, the sample from among the developed composites with the best impact strength was the one with the least hardness while sample with the best hardness happened to be the one with the lower impact strength. This was in agreement with literatures. 3.3 Tensile Test A tensile test, which is also called tension test, is one of the most fundamental type of mechanical test you can perform on material. Tensile tests are simple, relatively inexpensive, and fully standardized. By pulling a material at both end, we will instantaneously determine how the material will react to forces being applied in tension. As the material is being pulled, you will find its strength along with how much it will elongate. During the course of this research, the tensile strain and stress at various point were examined to study the tensile properties of the developed composite. Figures 3-4 show the response the materials to tensile properties.



19

0

50

100

150

200

250

300

350

400


TEN

SILE

STR

ESS

AT P

EAK

(MPA

)

SAMPLES

Fig.3. Variation of Tensile Stress at Peak with the Control, Developed and Aged Composite Samples The response of the materials to tensile stress at peak was as shown in Figure 3 from where it was seen that sample 5U and CSA displayed same tensile strength at peak with a value of 359. 07 MPa which was the best result. This was followed by another aged sample, 10TA with a value of 286.31 MPa which marginally lead 5T and 10T that has values 263.62 MPa and 262.48 MPa Respectively. This behaviour was also an indication that the age-hardening process enhanced the tensile properties of the developed composites.

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09


Tens

ile S

trai

n at

Pea

k (m

m/m

m)

Samples

Fig.4. Variation of Tensile Strain at Peak with the Control, Developed and Aged Composite Samples The response of the materials to tensile strain at peak was displayed in Figures 4. The results showed that 5T has the best strain property with a value of 0.09 mm/mm with a composition of 5 wt% of treated palm kernel ash added to Al-Si alloy. This was followed by CSA with a value of 0.07 mm/mm and 10TA with a value of 0.06 mm/mm. This gave a lead to the control sample (CS) which has a value of 0.05 mm/mm. The tensile stress and strain properties results revealed that the use of 5 wt% and preferably from treated PKSA was the best for optimum performance.



20

0

5

10

15

20

25

30


MO

DU

LUS

OF

ELA

STIC

ITY

(GPa

)

SAMPLES

Fig.5. Variation of Modulus of Elasticity with the Control, Developed and Aged Composite Samples The response of the materials to modulus of elasticity was shown in Figures 5. The results showed that 10UA has the best modulus of elasticity property with a value of 25.36 MPa being developed from composition of 10 wt% of untreated PKSA blended with Al-Si alloy and age hardened. Next to this was sample denoted as CSA with a value of 23.22 MPa and sample denoted as 10TA with a value of 22.53 MPa. These samples, when compared to the unreinforced as-cast aluminium alloy with a value of 21.09 MPa correspond to high enhancement of the modulus of elasticity for the materials by the age hardened process. 3.4 Metallographic Examination Optical microscope was used to view the surface morphology of the samples from which the following different structures were observed. The structures aid the understanding of the reasons why the properties of the developed composites differ.



21

(a)

(b) Plate 1: show the Microstructure of As-Cast Al–Si Alloy (a) it age hardened structure CSA (b) The structure from Plate 1(a) shows that the Si phase in the Al alloy matrix is partially evenly distributed, revealing partial formation of Si at the grain boundaries. The effect of silicon in the aluminium matrix is to aid flowability during casting operation. It also improves alloy wear resistance while Plate 1(b) shows that the Silicon(Si) phase in the Al alloy is partially evenly distributed, revealing no formation of Silicon in the grain boundaries. Due to the heat treatment carried out in the alloy, there is possibility of the formation of hardening phase as a result of the combination of Silicon and Magnesium to form Mg2Si which aids strengthening of the alloy.

100µm

100µm



22

(a)

(b)

100µm

100µm



23

(c)

(d)

Plate 2: Shows the Microstructure of Sample 5U, 5UA, 5T and 5TA respectively In Plate 2, there is uniform distribution of the PKSA phase in the Al-matrix with the formation of well blended PKSA/Al structures. These structures were responsible for the good response in the mechanical properties of these composites in terms of hardness and tensile. These were made possible because the particles were able to aid the matrix in bearing the applied load. Also, plate 2(d) which indicate sample 5TA displayed the formation of hardening phase as a result of the combination of Silicon and Magnesium to form Mg2Si which aids hardness of the alloy.

100µm

100µm



24

(a)

(b)

100µm

100µm



25

(c)

(d) Plate 3: Shows the Microstructure of Sample 10U, 10UA, 10T and 10TA respectively Microstructures of 10 wt% untreated (a), aged untreated (b), treated (c) and aged treated (d) PKSA reinforced composites (640X) as shown in Plate 3, revealed the Microstructures of 10 wt% reinforced composites. From the micrographs, it was observed that, the particles were more present in the untreated PKSA reinforced Al-matrix than for the treated PKSA reinforced Al-matrix. This may be responsible for the weak performance from this sample because the particles forms too much clusters. However, for the treated PKSA reinforced composites, there is well dispersed formation of the particles in the Al-matrix which was responsible for the good impact strength property. Also the age-hardened process brought about the formation of hardened precipitates which eventually enhanced the stiffness and hardness of the developed composite.

100µm

100µm



26

(a)

(b)

(c)

100µm

100µm

100µm



27

(d) Plate 4: Microstructures of 15 wt% untreated (a), aged untreated (b), treated (c) and aged treated (d) PKSA reinforced composites (640X) Plate 4 Revealed the microstructures of 15 wt% reinforced composite. Tin these micrographs, there are uniform distribution of the PKSA phase in the Al- matrix with the formation of well blended PKSA/Al structures. These structures were responsible for the good response in the mechanical properties of these composites.

4. Conclusion

The results of the investigations on both the effect of age-hardening process and the influence of treated and untreated palm kernel shell ash on the mechanical properties of aluminium composites indicates that the applied methods to strengthened aluminium alloy has a potential value. Apart from using the combination of waste aluminium alloy engine blocks and palm kernel shell ash which is biodegradable and readily available materials that can be used as low cost reinforcing materials, it was observed that; The age-hardening process enhanced the mechanical properties of the developed composite and this paper also revealed that the addition of treated and untreated palm kernel shell ash has a great effect in enhancing the mechanical properties of already used engine blocks when recycled. While treatment of the palm kernel shell ash also enhances the impact strength, tensile strain and hardness, the untreated palm kernel shell ash improves the tensile and hardness properties. These shows that the combination of these selected environmentally friendly materials are promising materials for automobile applications.

100µm



28

Acknowledgements The authors appreciate the services of Mr. Akinwumi and Mr. Benson of the department of Metallurgical and Materials Engineering, Federal University of Technology Akure.

Funding Source None

Conflict of Interest None

References American Society for Metals – ASM (1990). Handbook. Properties and selection. Nonferrous Alloys and

Special-Purpose Materials ASM International Handbook Committee; vol. 2, pp. 137-38. Chee, F.T. and Mohamad, R.S. (2009). Effect of Hardness Test on Precipitation Hardening Aluminium Alloy

6061-T6. Chiang Mai Journal of Science. 36(3), pp. 276-86. Clark, R. Coughran, B., Traina, I., Hernandez, A., Scheck, T., Etuk, C. (2005). On the correlation of mechanical

and physical properties of 7075-T6 Al alloy. Engineering Failure Analysis. 12, pp. 520-526. http://dx.doi.org/10.1016/j.engfailanal.2004.09.005 Esezobor, D.E., Adeosun, S. O. (2006). Improvement on the Strength of 6063 Aluminum Alloy by Means of

Solution Heat Treament. Materials Processing Challenges for the Aerospace Industry Organized By L.L. Shaw, S.L. Semiatin, R.F. Mignogna, and J.P. Singh Materials Science and Technology (MS&T): Processing.

Falade, F. (1992). The Use of Palm Kernel Shells as Coarse Aggregate in Concrete. Journal of Housing Science. 16(3), pp. 213-219.

Heinz, A. and Haszler, A. (2000). Recent Development In Aluminum Alloys For Aerospace Applications.

Materials Science and Engineering A., 280(1), pp.102-107. http://dx.doi.org/10.1016/S0921-5093(99)00674-7 Kandahl, P. (1992). Waste Materials in Hot Mix Asphalt', National Center for Asphalt Technology, NCAT

Report pp. 92–106. Lavernia, E.J., Rai, G. and Grant, N.J. (1990). Rapid solidification processing of 7xxx aluminium alloys: a review.

Materials Science and Engineering. vol. 79, pp. 211-212. http://dx.doi.org/10.1016/0025-5416(86)90406-4 Li, J.F and Peng, Z.W. (2008). Mechanical Properties, Corrosion Behaviors and Microstructures of 7075

Aluminium Alloy with Various Aging Treatments. Transactions of Nonferrous Metal Society of China. 18(4), pp. 755-762.

http://dx.doi.org/10.1016/S1003-6326(08)60130-2 Lin, G., Zhang, H., Zhang, X., Han, D., Zhang, Y. and Peng, D. (2003). Influences of Processing Routine on

Mechanical Properties and Structures of 7075 Aluminium Alloy Thick Plate. Transactions of Nonferrous Metal Society of China. 13(4), pp. 809-813.

Machler, R., Ugowitzer, P.J., Solenthaler, C., Pedrazzoli, R.M. and Spiedel, M.O. (1991) Structure, mechanical properties, and stress corrosion behaviour of high strength spray deposited 7000 series aluminium alloy.

http://dx.doi.org/10.1016/j.engfailanal.2004.09.005

http://dx.doi.org/10.1016/S0921-5093(99)00674-7

http://dx.doi.org/10.1016/0025-5416(86)90406-4

http://dx.doi.org/10.1016/S1003-6326(08)60130-2



29

Materials Science Technology. Vol.7, pp. 447-51. http://dx.doi.org/10.1179/mst.1991.7.5.447 Mohammad, T. and Esmaeil, E. (2010). Mechanical and Anisotropic Behaviors of 7075 Aluminum Alloy Sheets.

Materials and Design. 32(2), pp.1594-1599. McDanels D. L.(1985). Analysis of Stress-Strain, Fracture and Ductility Behaviour of Aluminium Matrix

Composites Containing Discontinuous SiC Reinforcement. Metallurgical and Materials Transaction A. 16, pp. 1105-1115.

http://dx.doi.org/10.1007/BF02811679 Muhamad, N.B., Amiruddin I. and Riza, R. (2010). Evaluation of Palm Oil Fuel Ash (POFA) on Asphalt Mixtures.

Australian Journal of Basic and Applied Sciences, 4(10), pp. 5456-5463, Mukhopadhyay, A. K., Shiflet, G. J. and Starke, E. A. (1991). The role of trace alloy additions on precipitation in

age hardenable aluminium alloys. In Morris E. Fine Symposium, P. K. Liaw, J. R. Weertman, H. L. Marcus, and J. S. Santner, eds., TMS, Warrendale, PA, pp. 283–293.

Polmear, I. J. (1998). Control of precipitation processes and properties in aged aluminium alloys by trace element additions. Proc. 6th Intl Conf on Aluminium Alloys, ICAA6, Toyohashi, Japan, July 5–10, 1998, eds. T. Sato, S. Kumai, T. Kobayshi and Y. Murakami, The Japan Inst. of Light Metals, Tokyo, Japan, pp. 75–86.

Ndoke P. N. (2006). Performance of Palm Kernel Shells as a Partial Replacement for Coarse Aggregate in

Asphalt Concrete. Leonardo Electronic Journal of Practices and Technologies ISSN 1583-1078 Issue 9, July-December pp. 145-152

Nimityongskul P. and T. U. Daladar. (1995). Use of Coconut Husk Ash, Corn Cob Ash and Peanut Shell Ash as Cement Replacement. Journal of Ferrocement. 25(1), pp. 35-44.

Nwaobakata, C.I. and Agunwamba J. C. (2014). Effect of Palm Kernel Shells Ash as Filler on the Mechanical Properties of Hot Mix Asphalt. Archives of Applied Science Research, 6 (5), pp. 42-49.

Ringer, S. P. and Hono, K. (2000). Microstructural Evolution and Age Hardening in Aluminium Alloys: Atom Probe Field-Ion Microscopy and Transmission Electron Microscopy Studies. Materials Characterization 44, pp. 101–103.

http://dx.doi.org/10.1016/S1044-5803(99)00051-0 Sanctis, M.D. (1991). Structure and Properties of Rapidly Solidified Ultrahigh Strength Al-Zn-Mg-Cu Alloys

Produced by Spray Deposition. Materials Science and Engineering. A141:103-21. http://dx.doi.org/10.1016/0921-5093(91)90714-X Shwe, W.H.A, Kay, T.L. and Waing, K.K.O. (2008). The Effect of Ageing Treatment of Aluminum Alloys for

Fuselage Structure-Light Aircraft. World Academy of Science, Engineering and Technology. 46, pp. 696-699.

Smallman, R.E. (1985). Modern Physical Metallurgy. 4th ed. London: Butterworths & Co. pp.167-169 White, J., Mingard, K., Hughes, I.R. and Palmer, I.G. (1994). Aluminium Alloys with Unique Property

Combinations by Spray Casting. Powder Metallurgy. 37(2), pp. 129-32. http://dx.doi.org/10.1179/pom.1994.37.2.129 Williams, J.C. and Starke, J. A. (2003). Progress in Structural Materials for Aerospace Systems. Acta Materialia.

51(19), pp. 5775-5799. http://dx.doi.org/10.1016/j.actamat.2003.08.023 Woei-Shyan, L.S. and Wu-Chung, S. (2000). The Strain Rate and Temperature Dependence of the Dynamic

Impact Properties of 7075 Aluminum Alloy. Journal of Materials Process and Technology. 100, pp. 116-122.

http://dx.doi.org/10.1016/S0924-0136(99)00465-3 Zhao, T. and Jiang, Y. (2008). Fatigue of 7075-T651 aluminum alloy. International Journal of Fatigue.830, pp.

834-849. http://dx.doi.org/10.1016/j.ijfatigue.2007.07.005

http://dx.doi.org/10.1179/mst.1991.7.5.447

http://dx.doi.org/10.1007/BF02811679

http://dx.doi.org/10.1016/S1044-5803(99)00051-0

http://dx.doi.org/10.1016/0921-5093(91)90714-X

http://dx.doi.org/10.1179/pom.1994.37.2.129

http://dx.doi.org/10.1016/j.actamat.2003.08.023

http://dx.doi.org/10.1016/S0924-0136(99)00465-3

http://dx.doi.org/10.1016/j.ijfatigue.2007.07.005

Documents

Assessment of the Impact of Age-Hardening on the ...paper.uscip.us/ajmst/ajmst.2016.1002.pdf · materials (ASM, 1990; Machler, 1991; Chee and Mohamad, ... aggregates in light and