processing of carbon fiber reinforced aluminium (7075 ... · international journal of advanced...

International Journal of Advanced Chemical Science and Applications (IJACSA)

_______________________________________________________________________________________________

_______________________________________________________________________________________________

ISSN (Print):2347-7601, ISSN (Online): 2347-761X, Volume -5, Issue -2, 2017

6

Processing of Carbon fiber reinforced Aluminium (7075) metal matrix

composite

1Madhuri Deshpande,

2Rahul Waikar,

3Ramesh Gondil,

4S.V.S Narayan Murty,

5T.S.Mahata

1,2,3 Production Engineering Dept, Vishwakarma Institute of Technology, Pune, India

4Material Characterization Division, Vikram Sarabhai Space Centre, Thiruvanantapuram, India

5Powder Metallurgy Division, Bhabha Atomic Research Centre, Vashi Complex, India

Email: [email protected]; [email protected]; [email protected];

[email protected]; [email protected]

[Received:15th Jun.2017; Accepted:30th Jun.2017]

Abstract : Carbon fiber reinforced Al metal matrix

composites are potential materials for aerospace and

electronic industries. Various manufacturing methods that

would give uniform distribution of carbon fibers are

adopted to manufacture this composite. In the present

work, Powder Metallurgy route was used to make

composite using uncoated (UnCf) and coated milled pitch

based carbon fibers (NiCf) and AA7075 as matrix with

different volume contents of carbon fibers. Uncoated and

Ni coated carbon fibers were mixed with AA7075

aluminium alloy powder and subsequently hot pressed. Hot

pressing was carried out using single action and double

action vacuum assisted hot press and its effect on

densification was studied. Effect of contents of uncoated

carbon fibers and coated carbon fibers on hardness was

studied. Optical and Scanning electron microscopic

examination was carried out.

The fabricated composites exhibited uniform distribution

of carbon fibers and also good bonding between fibers and

matrix. Results of X-ray diffraction (XRD) revealed that

Al4C3 formation was absent. In case of uncoated carbon

fibers, as the amount of carbon fiber content increased,

hardness decreased. However, with coated carbon fibers,

increase in hardness values was observed as amount of

coated fibers increased.

Keywords—metal matrix composite, carbon fiber, hot

pressing

I. INTRODUCTION

Metal-Matrix composites (MMCs) consist of a metal or

alloy as the continuous matrix and a reinforcement

which may be particulate, short fiber or continuous fiber.

In light MMCs, important metal matrices are Aluminium

alloys, Titanium alloys, Copper, Magnesium alloys etc.

In case of light weight metal matrix composite,

most of the researche works done so far, revolves

around Aluminium MMCs. Aluminium alloy metal

matrix (AMCs) composites find applications mainly

in automobile, defense, transport and aerospace sectors.

These composites are also used as thermal

management materials in electronic industries. In

this category, matrices that are tried mainly are pure

Aluminium, and various Al-Si alloys [1,2], Al6061 [3, 4,

5], Al2024 [6], Al7075 [7-8] etc. 7XXX series of Al

alloys are widely used in aerospace industry, in transport

applications including marine and auto due to their high

strength/ductility ratio [9] yet it is not a very commonly

used matrix for AMCs.

The most commonly used reinforcement materials

for metal matrix composite are Alumina, B4C, and SiC

etc. Carbon fibers are also used as reinforcing

material in milled, chopped or in continuous form,

in metallic, ceramic or in polymer matrix also, due to its

high specific strength and specific modulus, light

weight, low coefficient of thermal expansion, high

thermal and electrical conductivities [5].

Polyacrilonitrile (PAN) based carbon fibers improve

mechanical properties [5, 2, 10, 11] while Pitch base

fibers improve thermal properties [12,

13]. Depending upon requirement, suitable type of

carbon fibers is used as reinforcement. In the current

research, attempts are made towards making AMC with

AA7075 as matrix and milled pitch based carbon fibers

as reinforcing material.

Carbon fibers exhibit high reactivity with Al and its

alloys forming undesirable interfacial reaction product

as Al4C3 which limits the development of such kind of

composites [14-16, 3, 12]. Carbon fibers and Aluminium

have poor wetability [17]. So, surface modification of

carbon fibers is essential to improve the wetability

and to prevent formation of interfacial reactions.

Metallic coatings improve the wetting behavior of

carbon fibers with aluminium leading to improved

uniform distribution of carbon fibers in the matrix

with reduced interfacial reactions [2,14]. Wetability can

also be improved by addition of Mg to the matrix

material[18]. Among all the aerospace and automotive

materials, Al and its alloys have been very popular

matrices for development of high strength, ultra low

weight and superior tribological properties with metallic

coated carbon fibers as reinforcement [19, 20].

mailto:[email protected]






_______________________________________________________________________________________________

_______________________________________________________________________________________________


7

Manufacturing methods of MMC can be broadly divided

into two categories: One is Liquid Metallurgy and

second is Solid state process.

Many researchers have adopted Liquid Metallurgy route

like Stir casting [5], Liquid infiltration [20] and Squeeze

casting [21] to process the Al based carbon fiber

reinforced composites due to its ease and simplicity of

processing. [2, 4, 5, 22].

Although Liquid Metallurgy is an easier and simpler

method of composite manufacturing. The main problems

encountered in this technique of manufacturing the

Aluminium/Carbon fiber Composites are

1) Poor wettability between the reinforcement

and matrix material.

2) Formation of interfacial reaction product (Al4C3)

which is detrimental to mechanical as well as

thermal properties.

3) Volume of reinforcement is limited in the matrix.

4) Surface modification of the reinforcement

material is essential to avoid the interfacial reactions.

Due to the above mentioned problems encountered in

Liquid Metallurgy route, Aluminium alloy (AA7075)

matrix composites with pitch based carbon fiber

reinforcement were prepared by Powder Metallurgy

route.

Powder Metallurgy is very widely used by the

researchers [13, 22, 23, 24] for the manufacturing of

fiber/particulate reinforced composites. Major

advantages of this method are ability to process wide

variety of matrix metals, control of fiber orientation and

high volume fraction of reinforcement. As PM processes

are carried out in solid state, this minimizes the reactions

between reinforcement and matrix which reduces the

risk of brittle interfacial reactions.

II. EXPERIMENTAL

A. Raw Materials

Aluminium alloy (AA7075) powder having spherical

shape with average particle size of 35m was selected as

matrix material which was supplied by AMPAL, INC

(Table1 shows chemical composition of AA7075) and

the reinforcement material used was pitch based milled

uncoated carbon fibers (10µm diameter and 200 µm

length) supplied by MITSUBISHI PLASTICS, INC and

the same fibers were subjected to electroless nickel

coating as described in our earlier works after

pretreatment [25]. Fig No.1 shows the surface

morphology of the uncoated carbon fiber (a), AA7075

powder (b) and uniformly Ni coated carbon fiber (c & d)

respectively . Fig.No.2 shows the EDS analysis of the Ni

coated carbon fiber.

Fig. No.1a SEM images of as received Pitch based

carbon fiber

Fig. No. 1b SEM image of as received AA7075 alloy

powder

Fig. No. 1c SEM image of nickel coated carbon fiber


_______________________________________________________________________________________________

_______________________________________________________________________________________________


8

Fig. No. 1d SEM image of nickel coated carbon fiber

Fig. No. 2 EDS Analysis of electroless nickel plated

Carbon fiber

Table No.1 Chemical composition of AA7075 powder

Element Cu Mg Zn Si Fe Ti Mn Cr Al

Wt% 1.2-2 2.1-2.9 5.1-6.1 0.4 0.5 0.2 0.3 0.2-0.3 Rest

B. Fabrication of the composite

Aluminium alloy (7075) matrix composites with

pitch based uncoated carbon fiber and Ni coated carbon

fiber reinforcement were prepared by powder metallurgy

route. Fabrication of the composites was carried out in

two major steps.

1. Mixing: To obtain homogeneous powder

mixtures containing 5 to 50 volume % of uncoated

carbon fibers and AA7075 powder, laboratory mixer

was used. Mixtures were also formed by using Nickel

coated carbon fibers up to 30vol%.

The mixer was rotated at standard rpm of 20, while the

total mixing time was set to 45±5 minutes.

2. Compaction: The hot pressing of the

composites was carried out using single action and

double actionpress. The homogenous mixture of

AA7075 powder and carbon fibers was filled in the

high density graphite die and consolidated by hot

pressing. At the bottom and top surface of the powder

mixture, circular graphite sheet of 0.5mm thick was

placed in order to prevent the adhesion between punch

and hot pressed specimen.

After that the die-punch-powder assembly was placed

into the vacuum chamber. A thermocouple was then

attached to the assembly to read out the temperature of

the system as well as that of graphite die. Once the

required temperature, vacuum and pressure were

reached (listed in Table 2), pressing of powder

mixture was started, which was maintained during the

remainder of the process. After completion of hot

pressing, the whole assembly was cooled down to room

temperature. Then specimen was removed from the die

and the graphite sheets were removed from the hot

pressed specimen. The entire hot pressing process for

each composition took around 3 hours.

Parameters used for single action and double action

pressing are summarized in Table 2

Table 2 Hot Pressing Parameters

Parameters Single action press Double action press

Pressure 35Mpa 50Mpa

Temperature 560±20°C 580±10°C

Vacuum 0.25bar 1.8×10-3

bar

Pressing

Time

30 Min 1.5 Hrs

Heating rate 14°C/min 8°C/min

Cooling rate 10°C/min. 12°C/min.

C. Characterization of composites

After hot pressing, specimens were cut into two pieces

along the longitudinal and perpendicular direction of hot

pressing, ground and polished for metallographic

studies. Microstructures were examined using optical

microscope and Zeiss scanning electron microscope

(SEM) equipped with EDS facility.

The densities of the composites were determined using

Archimedes principle. Theoretical density of the

composites was calculated using rule of mixtures

(ROM). The mechanical property of the composites was

evaluated by hardness test. The samples were polished

and made flat and smooth, for Brinell hardness

measurements. A minimum of 6 readings were taken

for each specimen. Brinell hardness of the composites

was measured using 31.25 kg load and 2.5mm diameter

ball indentor.

III. RESULTS AND DISCUSSION

A. Density of the composites

Theoretical and measured density of the composites

decreases as uncoated carbon fiber content increases

(listed in Table 3) because of the low density of carbon

fiber compared to matrix alloy. But, as the Ni coated


_______________________________________________________________________________________________

_______________________________________________________________________________________________


9

carbon fiber content increases, the theoretical and

measured density of composite (listed in Table No.4)

increases because of the high density of nickel. A

reduction in the density of the composites with uncoated

carbon fiber has been observed as reported in Table 3.

A maximum of 11% reduction in density is observed for

50Vol% Cf Composite compared to cast

AA7075. Fig.No.3 shows the comparison of

densification of composites fabricated using single

action and double action pressing.

Table 3 Density values of Al/Cf Composites

Content of

carbon fibres

Density

by ROM

Density

obtained

(single

action)

Density

obtained

(double

action)

Vol% g/cm3 g/cm3 g/cm3

(Pure 7075) 2.81 2.72 2.76

5 2.78 2.68 2.72

10 2.75 2.64 2.68

15 2.72 2.6 2.64

20 2.69 2.55 2.61

25 2.66 2.51 2.56

30 2.63 2.47 2.52

35 2.60 2.43 2.49

40 2.57 2.37 2.44

45 2.54 2.33 2.40

50 2.51 2.29 2.37

Table 4 Density values of Ni coated Carbon fiber

Composites

Specimen

No.

Content of Ni

coated carbon

fibers

Density

by

ROM

Density

obtained (single

action)

Vol% g/cc g/cc

1 5 2.92 2.81

2 10 3.02 2.89

3 15 3.13 2.96

4 20 3.24 3.02

5 25 3.35 3.10

6 30 3.45 3.11

Fig No.3 Effect of carbon fiber content on densification

of Al/Cf Composites

B. Hardness

Brinell hardness test results are listed in Table 5.

Hardness variation with volume content of carbon fibers

for coated and uncoated carbon fibers is graphically

represented in Fig.8

Fig. 8 Effect of uncoated and coated fiber on vol. % of

fiber on hardness of composites

Table 5 Hardness of the Composites

Vol % of Carbon

fiber

0 5 10 15 20 25 30 35 40 45 50

UnCf_MMC

(Double action

pressing)

Hard

ness,

BHN

116

102

97

80

73

68

63

66

58

52

46

UnCf_MMC (Single

action pressing)

101

75

71

69

65

61

60

56

51

48

45

NiCf MMC (Single

action

pressing)

101

116

124

130

139

134

127

C. Microstructures of composites

SEM micrographs of uncoated carbon fiber reinforced

aluminium alloy composites (parallel section) are shown

in Fig.No.4 (a-d and g). Fig.4 e shows the SEM image of

40 vol% composite (cross section) Fig.4 (f) shows the

SEM micrograph of Nickel-coated carbon fibers

composite. Fig.5 (a and b) are SEM images of parallel


_______________________________________________________________________________________________

_______________________________________________________________________________________________


10

section of 15Vol% uncoated carbon fibers MMC near

the bottom of the punch and away from the punch

respectively. Microstructures of composites containing

different volume % of uncoated carbon fibers are shown

in Fig. 6 .Figs 6 (a-c and d-f) show the parallel section

and cross section images respectively. Fig.7 represents

XRD analysis of Al/Cf Composites containing 10, 20

and 30 Vol% Cf.

Fig. 4a. SEM image parallel section of 10Vol uncoated

carbon fiber MMC

Fig. 4b. SEM image parallel section of 20Vo uncoated

carbon fiber MMC

Fig. 4c. SEM image parallel section of 40Vol% uncoated

carbon fiber MMC

Fig. 4d. SEM image parallel section of 50Vol%

uncoated carbon fiber MMC

Fig. 4f. SEM image parallel section of 10Vol% Ni

coated carbon fiber MMC


_______________________________________________________________________________________________

_______________________________________________________________________________________________


11

Fig. 4e. SEM image cross section of 40Vol% uncoated

carbon fiber MMC

Fig. 4g. SEM image parallel section of 50Vol%


Fig. 5a. SEM image parallel section of 15Vol%

uncoated carbon fiber MMC showing good bonding

Fig. 5b. SEM image parallel section of 15Vol%

uncoated carbon fiber MMC showing porosity

Fig. 6a. Microstructure image parallel section of

10Vol% uncoated carbon fiber MMC

Fig. 6b. Microstructure image parallel section of



_______________________________________________________________________________________________

_______________________________________________________________________________________________


12

Fig. 6c. Microstructure image parallel section of


Fig. 6d. Microstructure image cross section of 10Vol%


Fig. 6e. Microstructure image cross section of 20Vol%


Fig. 6f. Microstructure image cross section of 50Vol%


Composite properties

It is observed that the composites developed with

uncoated carbon fiber exhibit lower values of hardness

as compared with Pure AA7075 hot pressed specimen.

This decrease in hardness is due to increase of non

metallic phase (uncoated carbon fibers) in the matrix.

Whereas the Ni coated carbon fiber composites show the

increase in hardness up to 20Vol% and then it decreases.

The enhancement in the bulk hardness of the Ni coated

carbon fiber composite (20Vol% Cf) is 19% as

compared to pure AA7075 hot pressed specimen. This

may be due to the formation of hard intermetallic

compound of Al3Ni and coating also improves the

interfacial bonding between the carbon fiber and

AA7075 alloy. Drop in hardness for composites

with 25 and 30 Vol% carbon fiber content is attributed to

lower densification.

Fig. 7 XRD Analysis of Al/Cf Composites containing

10, 20 & 30Vol% Cf

Processing

It is important to consider the type of press used for hot

compaction of such composites when the specimen size

is big. Hot pressing by single action or double action is

reflected not only in densification but in density


_______________________________________________________________________________________________

_______________________________________________________________________________________________


13

gradient as well. Composites which were hot

pressed in single action press show density gradient

along the thickness of the developed composites. Fig. 5a

shows the top portion of the composite (15Vol% Cf)

which was near the punch and it shows good

densification. Fig. 5b shows the bottom portion of the

same composite having porosity because of poor

compaction. Higher densification with no porosity and

no density gradient along the thickness of composites

were observed in composites which were prepared by

using double action hot press. Due to high pressure and

pressing from both the ends, better densification was

observed (Table 3).

Microstructures of Composites

It is seen from the microstructures that carbon fibers are

uniformly distributed in the aluminium matrix for all

compositions. The optical micrographs of composites

containing different volume % of fibers show no pores

in the composites. In all the specimens, good bonding is

seen between carbon fibers and matrix. Fig.7 shows

XRD analysis of composites containing 10, 20 and 30

vol % carbon fibers, from which, it appears that Al4C3

has not formed. In Powder Metallurgy route, pool of

liquid metal is absent and hence there is no reaction

between molten Aluminium and carbon fibers due to

which Al4C3 formation is prohibited.

IV. CONCLUSION

1. Pitch based carbon fiber reinforced Al matrix

composites are successfully fabricated by the Powder

Metallurgy (PM) route.

2. The fabricated composites show good bonding

between the fibers and Aluminium alloy matrix with

uniform distribution of carbon fibers in the matrix even

with high volume fraction of reinforcement.

3. The application of electroless nickel coating on the

fiber surface enhances the interfacial bonding which

results in increased hardness of the composite.

4. Fabrication of Carbon fiber reinforced Aluminium

matrix composites by PM route eliminates interfacial

reaction and thus the formation of Al4C3 which is

detrimental to mechanical and thermal properties of

composite.

5. Double action hot pressing gives better

densification and does not show density gradient in the

composite.

6. Therefore PM route possesses a great potential to

fabricate the short/milled carbon fiber reinforced

Aluminium matrix composites.

V. ACKNOWLEDGMENT

Authors gratefully acknowledge the financial support

of ISRO UoP Space Technology cell,SPPU, Pune and

support of BARC, Vashi complex, for providing their

double action hot pressing facility.

REFERENCES

[1] R. Prieto, J.M.Molina, J. Narciso, E. Louis,

“Thermal conductivity of graphite flakes–SiC

particles/metal composites”, Composites: Part

A, 42(2011) pp1970–1977

[2] H. Naji, S. M. Zebarjad, S.a. Sajjadi, “The effects

of volume percent and aspect ratio of carbon

fiber on fracture toughness of reinforced

aluminum matrix composites” Materials Science

and Engineering, 486 (1-2) (2008) pp 413-419

[3] Yiping Tang, Lei Liu, Weiwei Li, Bin Shen,

Wenbin Hu, “Interface characteristics and

mechanical properties of short carbon fibers-

Aluminium composites with different coatings”,

Applied Surface Science 255(2009), 4393-4400.

[4] M. Sanchez,J. Rams, a. Urena,

“Fabrication of Aluminium composites

reinforced with carbon fibers by centrifugal

infiltration process”, Composites Part A 41

(2010) 1605-1611

[5] B. Bhav Singh, M. Balasubramanian, “Processing

and properties of copper-coated carbon fiber

reinforced aluminium alloy composites”, Journal

of Materials Processing technology, 209 (2009)

pp2104–2110

[6] E. Hajjari, M. Divandari, H. Mirhabibi, “The

effect of applied pressure on fracture surface

and tensile properties of nickel coated continuous

carbon fiber reinforced aluminum composites

fabricated by squeeze casting.”, Materials and

Design, 31(2010) pp 2381–2386.

[7] V. Balaji, N. Sateesh, M. Manzoor Hussain,

“Manufacture of Aluminium metal matrix

composites (Al7075-Sic) by Stir Casting

technique”, Materials Today Proceedings 2

(2015) 3403-3408

[8] Woel-Shyan Lee, Wu-Chung sue, Chi-Feng Lin,

“ The effects of temperature and strain rate on the

properties of carbon-fiber- reinforced 7075

aluminum alloy metal-matrix composite”,

Composites Science and Technology 60 (2000)

1975-198

[9] Ling-Mei Wu, Wen-Hsiung Wang, Yung-Fu

Hsu, Shan Trong, “Effects of microstructure on

the mechanical properties and stress corrosion of

an Al-Zn-Mg-Sc-Zr alloy by various temper

treatments”, Materials Transactions Volume 48

No.3 (2007) 600- 609

[10] Junjia Zang, Shichao Liu, Yingxin Zhang, Yong

Dong, Yiping Lu, Tingju Li, “Fabrication and

bending properties of carbon fibers reinforced

Al-alloys matrix composites”,Journal of

Materials Processing technology,231(2016) 366-

373

[11] Qiurong Yang, Jinxu Liu, Shukui Li, Fuchi Wang,

Tengteng Wu, “Fabrication and mechanical


_______________________________________________________________________________________________

_______________________________________________________________________________________________


14

properties of cu-coated woven carbon fibers

reinforced aluminium alloy composite”,Materials

and Design 57(2014)442-448

[12] Moonhee Lee, Yongbum Choi, Kenjiro Sugio,

kazuhiro Matsugi, Gen Sasaki, “Effect of

Aluminium Carbide on unidirectional Cf-Al

Composites fabricated by low pressure

infiltration process”, Composites Sciences and

Technology 97 (2014) 1-5.

[13] Jean Frank Silvain, Amelie Veillere, Yongfeng

Lu, “Copper-Carbon and Aluminum-Carbon

Composites Fabricated by Powder Metallurgy

Processes”, Journal of Physics: Conference

Series 525 (2014)

[14] H. Chen, A. T .Alpas, “Wear of aluminium

matrix composites reinforced with nickel-coated

carbon fibers”, Wear 1996;192:186–98.

[15] H. D. Steffens, B. Reznik, V. Kruzhanov, W.

Dudzinski, . “Carbideformation in aluminium–

carbon fibre-reinforced composites”, J MaterSci

1997;32:5413–7.

[16] Zhang Yun-he, Wu Gao-hui, “Interface and

thermal expansion of carbon fiber reinforced

aluminum matrix composites.” Trans. Nonferrous

Met. Soc. China, 20 (2010) pp 2148-2151

[17] J.Rams, A. Urena, M. D. Escalera, M. Sanchez,

“Electroless nickel coated short carbon fibers in

aluminium matrix composites”, Composites Part

A 38 (2007) 566-575

[18] B.C Pai, Geetha Ramani, R.M Pillai, K.G.

Satyanarayana, “Role ofmagnesium in cast

aluminium alloy matrix composites”, J Mater

Sci1995;30:1903–11.

[19] A. Urena, J.Rams, M. D.Escalera, M. Sánchez,

“Characterization of interfacial mechanical

properties in carbon fiber/aluminium matrix

composites by thenanoindentation technique”,

Compos Sci Technol 2005;65:2025–38.

[20] H. Chen, A.T. Alpas, “Wear of Aliuminium matrix

composite reinforced with nickel coated carbon

fibers.”, Wear 192(1996) pp186-198.

[21] T.Shalu, E. Abhilash, A. Joseph, “Development

and characterization of liquid carbon fiber

reinforced aluminium matrix composite”, Journal

of Materials Processing Technology 209 (2009)

4809-4813.

[22] E. Simancik, G. Jangg, H. Degischer “Short

carbon fibers- aluminium matrix composite

material prepared by extrusion of powder

mixtures”,Journal de Phsique IV,1993,03(C7)

1775-1780.

[23] J.K. Chen, I.S. Huang, “Thermal properties of

aluminum–graphite composites by powder

metallurgy.” Composites: Part B 44 (2013) pp

698–703.

[24] Hiroki Kurita, Takamichi Miyazaki, Akira

Kawasaki, Yongfeng Lu, Jean-Francois Silvain,

“Interfacial microstructure of graphite flake

reinforced aluminum matrix composites

fabricated via hot pressing”, Composites: Part

A 73 (2015) 125–131.

[25] Madhuri Deshpandel, R.A. Waikar, R. Gondil,

S.V.S. Narayan Murty, “Effect of Coating

Parameters on Coating Rate of Carbon Fibers by

Electroless Nickel Plating”, Materials Science

Forum, ISSN: 1662-9752, Vols. 830-831,(2015)

pp 635-638

processing of carbon fiber reinforced aluminium (7075 ... · international journal of advanced...

Documents