Mechanical Processing of Cu-graphite powders mixtures and subsequentconsolidation.

Barbara Lasio1*, Francesco Torre 1, Roberto Orrù1, Giacomo Cao1, Marcello Cabibbo2, Francesco Delogu1

1 Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, Italy2 Dipartimento di Ingegneria Industriale e Scienze Matematiche, Università Politecnica delle Marche, via Brecce Bianche 12, 60131 Ancona, Italy

*ba.lasio1@studenti.unica.it

Università degli Studi

di Cagliari

References:J.W. Kaczmar, K. Pietrzakb, W. Włosińskici, 2000, Journal of Materials Processing Technology, 106, Pp 58–67;F. Delogu, G. Gorrasi, A. Sorrentino, 2017, Progress in Materials Science, 86 Pp 75-126;

L.Y. Chen, J.Q. Xu, H. Choi, M. Pozuelo, X. Ma, S. Bhowmick, J. M. Yang, S. Mathaudhu, X. C. Li, 2015, Nature, 528 Pp. 539-549.S. Garroni, S. Soru, S. Enzo, F. Delogu, 2014, Scripta Materialia, 88, Pp 9–12;P. Baláž, M. Achimovičová, M. Baláž, P. Billik, Z. Cherkezova-Zheleva, J. M. Criado, F. Delogu, E. Dutková, E. Gaffet, F. J. Gotor, R. Kumar, I. Mitov, T. Rojac, M. Senna, A. Streletskiikl, K. Wieczorek-Ciurowam, 2013, Chemical Society Reviews, 42 Pp 7571-7637;http://multiphysics.lab.asu.edu/facilities.shtml; https://www.elvatech.com/en/catalog/materials/blending/good464?print=1; http://dir.indiamart.com/delhi/graphite-powder.html. Acknowledgements: Special thanks to Dr Roberta Licheri for the loving helpful support.

Results: Nanoindentation Mechanical Tests

Results: X-Ray Diffraction XRD

Results: TEM Micrographs

Fig.4 Nanoindentation test of MMCs sintered samples: a) hardness and b) elastic modulus of the samples with the addition of graphite during every step of BM, c) hardness and d) elastic

modulus variation of the sintered samples after four steps of BM and only one addition of graphite

Without addition of graphite in every step

With addition of graphite in every step

Fig.2 XRD of MMCs powders and sintered samples measured every step of milling and with the addition of graphite only at the first step: a) behaviour of crystalline size

compared to milling time b) XRD analysis of milled powders measured after every step of milling c)XRD analysis of bulk samples measured after every step of milling.

Fig.1 XRD of MMCs powders and sintered samples measured every step of milling with the addition of graphite during every step: a) behaviour of crystalline size

compared to milling time b) XRD analysis of milled powders measured after every step of milling c) XRD analysis of bulk samples measured after every step of milling.

Fig.3 TEM Micrographs of MMCs sintered samples a) after one step of milling and one addition of graphite, b) after two steps of milling and two additions of graphite and c) after three steps of milling and

three additions of graphite, d) after four steps of milling and four additions of graphite.

a) b) c)

a) b)

c) d)

30 40 50 60 70 80

I hkl Copper

X r

ay In

ten

sity / a

.u.

Scattering Angle / 2

Powder BM step 1+C3%

Powder BM step 2+C3%

Powder BM step 3+C3%

Powder BM step 4+C3%

30 40 50 60 70 80

Scattering Angle / 2

X r

ay Inte

nsity / a

.u.

I hkl Copper

BM step 1+C3%

BM step 2+C3%

BM step 3+C3%

BM step 4+C3%

10 15 20 25 30 35 40 45 5020

30

40

50

60

70

80

90

100

110

120

Cry

sta

llite

Siz

e / n

m

Ball Milling Time / h

CrySizeS

CriSizeP

a) b) c)

40 50 60 70 80

Scattering Angle / 2

BM Step1 +C 3 wt.%

BM Step2

BM Step3

BM Step4

X r

ay In

tensity / a

.u.

I hkl Copper

30 40 50 60 70 80

I hkl Copper

Scattering Angle / 2

X r

ay Inte

nsity / a

.u.

Powder BM step1+C3%

Powder BM step2

Powder BM step3

Powder BM step4

10 15 20 25 30 35 40 45 5020

30

40

50

60

70

80

90

Cry

sta

llite

Siz

e / n

m

Ball Milling Time / h

sintered

powdera) b) c)

Copper

Graphite(3 wt.%)

Ball MillingSPS

consolidation Bulk material

Experimental

Ball milling BMBall to powder ratio: 1,5:1

Milling Time: 12 h, 24 h, 36 h and 48 hRest Time: 30 min every hour

Spark Plasma sintering SPS:900°C

Thermal Ramp :100°C/minIsothermal Time:10 min

Cu+C 3% Samples+C 3%

First procedure: addition of graphite in every step

Second procedure: addition of graphite only in the first step

Samples+C 3%

Samples+C 3%

BM

SPS

BM

SPS

BM

SPS

BM

SPS

Cu+C 3% Samples Samples SamplesBM

SPS

BM

SPS

BM

SPS

BM

SPS

Experimental

The present research work addresses the fabrication of metal matrix composites (MMCs) by mechanical processing. In particular, Cu-graphite powder mixtures have been subjected to mechanical processing by ball milling under inert atmosphere to induce mutual

dispersion of the constituents. Then, powder has been consolidated by spark plasma sintering, and the obtained pellets subjected to nanoindentation to investigate the variation of mechanical properties with milling time and graphite content.

SampleH

AverageError

H

Asymptoticerror

Er

Averageerror

Er

Asymptoticerror

1 step

BM

+3%C

900°C

Sintered1.25 0.05 1.15 0.05 28 6 25 5

2 step

BM

900°C

Sintered1.15 0.05 0.95 0.1 26 4 15 5

3 step

BM

900°C

Sintered1.5 0.1 1.35 0.05 42 6 42 2

4 step

BM

900°C

Sintered1.5 0.1 1.35 0.05 45 5 40 2

SampleH

AverageError

H

Asymptoticerror

Er

Averageerror

Er

Asymptoticerror

1 step

BM

+3%C

900°C

Sintered

2.10.2 1.3 0.1 33 5 31 5

2 step

BM

+3%C

900°C

Sintered1.4 0.1 0.85 0.05 23 3 21 2

3 step

BM

+3%C

900°C

Sintered0.86 0.05 0.65 0.05 25 3 22 2

4 step

BM

+3%C

900°C

Sintered0.80 0.1 0.55 0.05 23 2 22 2

Without addition of graphite in every stepWith addition of graphite in every step

d)

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0.0

0.5

1.0

1.5

2.0

2.5

H average

H tendency

Ha

rdn

ess / G

Pa

20

22

24

26

28

30

32

34

Ela

stic m

od

ulu

s / G

Pa Er Average

Er Tendency

0.8

1.0

1.2

1.4

1.6

1.8

Ha

rdn

ess / G

Pa

HAverage

HTendency

10

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50

Ela

stic M

odu

lus / G

Pa ErAverage

ErTendency