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Fabrication of AlDiamond Particles FunctionallyGraded Materials by Centrifugal Sintered-CastingMethodTo cite this article Yoshimi Watanabe et al 2013 J Phys Conf Ser 419 012002

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Fabrication of AlDiamond Particles Functionally Graded

Materials by Centrifugal Sintered-Casting Method

Yoshimi Watanabe1 Masafumi Shibuya and Hisashi Sato

Department of Engineering Physics Electronics and Mechanics

Nagoya Institute of Technology Gokiso-cho Showa-ku Nagoya 466-8555 Japan

E-mail yoshiminitechacjp

Abstract The continuous graded structure of functionally graded materials (FGMs) can be

created under a centrifugal force Centrifugal sintered-casting (CSC) method proposed by the

authors is one of the fabrication methods of FGM under centrifugal force This method is

a combination of the centrifugal sintering method and centrifugal casting method In this study

Aldiamond particle FGM was fabricated by the proposed method

1 Introduction

The continuous graded structure of the functionally graded materials (FGMs) can be created by a

centrifugal force As one of fabrication methods of FGM under the centrifugal force centrifugal

mixed-powder method was developed [1 2] However the mixed powder moves along the flow of

the molten matrix metal when the molten metal is poured into the spinning mold To overcome this

problem novel FGM fabrication method centrifugal sintered-casting (CSC) method is proposed The

schematic illustration of CSC method is shown in figure 1 At first ring-shaped metal-matrix preform

including dispersion particles is produced by centrifugal sintering Powder mixture of dispersion

particles and matrix metal particles is inserted into a spinning mold as shown in figure 1 (a)

Subsequently the powder mixture is sintered under the centrifugal force as shown in figure 1 (b)

Then the molten matrix metal is poured into the fabricated preform by centrifugal casting as shown in

figure 1 (c) As a result the molten matrix metal penetrates into the space between the particles by

the pressure due to the centrifugal force At the same time matrix metal particles are melted by the

heat from molten matrix Finally an FGM ring with dispersion particles such as abrasive grains

distributed on its surface can be obtained as shown in figure 1 (d) In this study Aldiamond particle

FGM has been fabricated by the CSC method

Figure 1 The schematic illustration of the centrifugal sintered-casting (CSC) method

1 To whom any correspondence should be addressed

FGM 2012 IOP PublishingJournal of Physics Conference Series 419 (2013) 012002 doi1010881742-65964191012002

Published under licence by IOP Publishing Ltd 1

2 Experimental Procedure

Pure Al particles (purity 9999 diameter 106 to 180 m) pure Mg particles (purity 995 mean

diameter 180 m) Al-15massSi particles (mean diameter 125 m) and diamond particles (270 to

325 mesh) were used as primary materials Three types of mixed powder with pure Al Al-05Mg

and Al-15Si particles are prepared and they are named as P1 P2 and P3 samples respectively The

mixed powder was set in the cylindrical mold having rotation axis with 20 mm in diameter and 30 mm

in length respectively Then the mixed powder was sintered in the spinning cylindrical mold under

the centrifugal force of 280 G at 655 oC 640

oC and 570

oC for P1 P2 and P3 samples respectively

for 3 h in vacuum Here G is the ratio of centrifugal force to gravity (G number) The centrifugal

sintering conditions of each fabricated preform are listed in table 1

Table 1 Summary of the centrifugal sintering

Pure Al ingot and obtained cylindrical preform were placed in compact vacuum centrifugal casting as

shown in figure 2 The Al ingot was melted by heating coil and then molten Al was poured into the

mold with the preform by applied centrifugal force of 34 G or 78 G at casting temperature of 900 -

1100 oC Table 2 summarizes the centrifugal casting conditions with fabricated preforms For ideal

processing centrifugal direction in centrifugal casting should correspond to the one in centrifugal

sintering However this centrifugal casting machine was used as a convenient means because of

machine performance in this study The microstructural observations of the fabricated preforms and

cast samples were carried out with a scanning electron microscope (SEM) Area fractions of diamond

abrasive grains in Al matrix were evaluated from SEM photographs

Figure 2 Schematic illustrations of compact vacuum centrifugal machine (left) and mold (right) The

shape of products by this machine is rod

Table 2 Summary of the centrifugal casting

Preform sample name P1 P2 P3

Amount of matrix particles

Al (g) 435 432 Mg (g) 002

Al-15Si (g) 425 Amount of diamond particles (g) 063

Volume fraction of diamond (vol) 10 Sintering temperature (

oC) 655 640 570

G number 280

Cast sample name C1 C2 C3 C4

Used preform sample P3 Amount of Al ingot (g) 35

Casting temperature (oC) 900 1200 1100

G number 34 78 Atmosphere Vacuum Ar

FGM 2012 IOP PublishingJournal of Physics Conference Series 419 (2013) 012002 doi1010881742-65964191012002

2

2 Experimental Procedure

Pure Al particles (purity 9999 diameter 106 to 180 m) pure Mg particles (purity 995 mean

diameter 180 m) Al-15massSi particles (mean diameter 125 m) and diamond particles (270 to

325 mesh) were used as primary materials Three types of mixed powder with pure Al Al-05Mg

and Al-15Si particles are prepared and they are named as P1 P2 and P3 samples respectively The

mixed powder was set in the cylindrical mold having rotation axis with 20 mm in diameter and 30 mm

in length respectively Then the mixed powder was sintered in the spinning cylindrical mold under

the centrifugal force of 280 G at 655 oC 640

oC and 570

oC for P1 P2 and P3 samples respectively

for 3 h in vacuum Here G is the ratio of centrifugal force to gravity (G number) The centrifugal

sintering conditions of each fabricated preform are listed in table 1

Table 1 Summary of the centrifugal sintering

Pure Al ingot and obtained cylindrical preform were placed in compact vacuum centrifugal casting as

shown in figure 2 The Al ingot was melted by heating coil and then molten Al was poured into the

mold with the preform by applied centrifugal force of 34 G or 78 G at casting temperature of 900 -

1100 oC Table 2 summarizes the centrifugal casting conditions with fabricated preforms For ideal

processing centrifugal direction in centrifugal casting should correspond to the one in centrifugal

sintering However this centrifugal casting machine was used as a convenient means because of

machine performance in this study The microstructural observations of the fabricated preforms and

cast samples were carried out with a scanning electron microscope (SEM) Area fractions of diamond

abrasive grains in Al matrix were evaluated from SEM photographs

Figure 2 Schematic illustrations of compact vacuum centrifugal machine (left) and mold (right) The

shape of products by this machine is rod

Table 2 Summary of the centrifugal casting

Preform sample name P1 P2 P3

Amount of matrix particles

Al (g) 435 432 Mg (g) 002

Al-15Si (g) 425 Amount of diamond particles (g) 063

Volume fraction of diamond (vol) 10 Sintering temperature (

oC) 655 640 570

G number 280

Cast sample name C1 C2 C3 C4

Used preform sample P3 Amount of Al ingot (g) 35

Casting temperature (oC) 900 1200 1100

G number 34 78 Atmosphere Vacuum Ar

FGM 2012 IOP PublishingJournal of Physics Conference Series 419 (2013) 012002 doi1010881742-65964191012002

2

3 Results and Discussion

Upper and lower figures of figure 3 (a) show the macro photograph and SEM micrograph of P1

sample respectively It is seen from these figures pure Al particles cannot be sintered even though

the sintering was carried out at high temperature (5 oC lower than melting point of Al) This is

because the Al particles are covered by Al oxide and higher sintering temperature is necessary for

sintering of the Al oxide To avoid this phenomenon Mg particles were added into the mixed powder

because it has strong reduction ability and P2 sample was fabricated The results of P2 sample are

shown in figure 3 (b) Although intermetallic compound was formed good sintering of P2 sample

was not found Alternatively Al-15Si alloy particles with lower melting point were used and macro

photograph of P3 perform and its SEM micrograph are shown in figure 3 (c) Ring-shaped Al-

15Sidiamond particles preform has been successfully fabricated using centrifugal sintering method

It is also found that homogeneous distribution of diamond particles was observed in the preform It is

interesting to note here that the microstructure of P3 sample still consists of the spherical-shaped Al

particles similar to those of primary Al-15Si particles without sintering However from magnified

SEM photograph it is found that these spherical-shaped Al has been connected each other Therefore

it is expected that perform of P3 sample is good for application of CSC method

Figure 3 Macro photographs of performs (upper) and their SEM micrographs (lower) (a) (b) and

(c) are P1 P2 and P3 samples respectively

Since the Al-15Sidiamond particles preform can be successfully fabricated using centrifugal

sintering method P3 sample will be used for centrifugal casting experiment Figures 4 upper (a) to

(d) show the cross sectional views of C1 to C4 samples respectively SEM photographs showing

microstructures around outer surface of C1 to C4 samples are also shown in figures 4 lower (a) to (d)

respectively Solid samples could not be obtained for the C1 and C2 samples which were fabricated

under vacuum condition with casting temperature of 900 oC or 1200

oC respectively as shown in

figures 4 upper (a) and (b) In our previous study [3] cooling rate distribution of the centrifugal

casting using the compact vacuum centrifugal casting machine shown in figure 2 is estimated by Al-

Al2Cu eutectic lamella structure It was shown that the casting atmosphere as well as casting

temperature and G number have affected the cooling rate distribution Since local cooling rate

strongly influences the local microstructure of the cast centrifugal casting is carried out under Ar gas

condition and the results are shown in figures 4 (c) and (d) It is seen that the solid samples could be

fabricated under Ar gas condition Moreover as seen in figure 4 lower (d) diamond particles are

distributed at only outer surface of C4 sample and volume fraction of diamond particles is 11 vol as

expected Therefore it is concluded that the CSC method is useful to fabricate the rod or ring shaped

FGM 2012 IOP PublishingJournal of Physics Conference Series 419 (2013) 012002 doi1010881742-65964191012002

3

FGMs with diamond particles located at outer surface of rod-shaped sample These rod or ring shaped

FGMs dispersed with diamond particles on its outer surface can be used as grading wheels for drilling

of carbon fiber reinforced plastic (CFRP) [4]

Figure 4 Macro photographs of cast samples (upper) and their SEM micrographs (lower) (a) C1 (b)

C2 (c) C3 and (d) C4 samples

4 Conclusions In this study Aldiamond particle FGM has been fabricated by the centrifugal sintered-casting (CSC)

method which is combination of sintering method and casting under the centrifugal force First three

types of performs are fabricated under the centrifugal force from mixed powder of pure Al Al-Mg and

Al-15Si alloy particles with diamond particles Among them it is found that preform can be

obtained from mixed powder of Al-15Si alloy particles with diamond particles Using this type of

preform FGM was fabricated by casting under the centrifugal force It is found that the diamond

particles are distributed at only outer surface of casting In this way Aldiamond particles FGM can

be successfully fabricated by CSC method This method has advantage of the good control ability of

diamond distribution

Acknowledgments

This research was supported by Regional Innovation Cluster Program (Global Type) ldquoTokai Region

Nanotechnology Manufacturing Clusterrdquo from the Ministry of Education Culture Sports Science and

Technology (MEXT) of Japan One of the authors YW acknowledges the financial support from The

Light Metal Educational Foundation Inc of Japan

References

[1] Watanabe Y Inaguma Y Sato H and Miura-Fujiwara E 2009 Materials 2 2510

[2] Watanabe Y and Sato H 2011 Review Fabrication of Functionally Graded Materials under a

Centrifugal Force Nanocomposites with Unique Properties and Applications in Medicine and

Industry ed J Cuppoletti (Rijeka Shanghai and New York InTech) chapter 7 pp 133-150

[3] Watanabe Y Hattori Y and Sato H 2012 unpublished data

[4] Watanabe Y Miura-Fujiwara E Sato H Takekoshi K Tsuge H Kaga T Bando N Yamagami

S Kurachi K and Yokoyama H 2011 Inter J Mater Prod Tech 42 29

FGM 2012 IOP PublishingJournal of Physics Conference Series 419 (2013) 012002 doi1010881742-65964191012002

4