ENCYCLOPÉDIE DE LA RECHERCHE SUR L’ALUMINIUM AU QUÉBEC 2013 | Page 49

NOUVEAUX PRODUITS ET MATÉRIAUX À BASE D'ALUMINIUM
NEW ALUMINIUM BASED PRODUCTS AND MATERIALS

47

FRITTAGE DE POUDRES D’ALLIAGES D’ALUMINIUM EN FLACONS PAR LE PROCÉDÉ SPS
SINTERING OF AL ALLOY FLAKE POWDERS BY THE SPS PROCESS – COMPACTION STUDY
Bamidele Akinrinlola1, Raynald Gauvin1 et Mathieu Brochu1
1

Mining and Materials Engineering Department, McGill University, Montreal QC

Results

Introduction
In the design of advanced engineering materials there
has been a pursuit of improved strength and hardness,
properties often gained at the expense of the material’s
toughness. However, many biological materials possess
remarkable property combinations; in particular nacre,
where high hardness and toughness co-exist. These
unique properties have been attributed to the hierarchical
structures found in the material, over many length
scales. Interfacial processes also play an important role
in the deformation behavior and contribute to the
toughening mechanisms exhibited by nacre.

2c

Figure 5. (From left) Morphology of 5083 flakes; TEM image
of microstructure in milled powder with SAED pattern

1,50E-07

Pore height,
h (m)

A n Aluminum nacre-like structure is explored by the SPS
sintering of Aluminum flake powders. Diffusion bonding
theory, applicable to the joining of nominally flat
interfaces, has been used to understand the sintering
mechanisms at the flake interfaces. Previously, the
Figure 1. Microstructure in nacre;
bonding process, monitored by pore evolution, was
Stacking of aragonite tablets with
examined by a diffusion bonding model. Here some of nano-asperities at the interfaces [1]
the inconsistencies between the model and material
behavior are examined.

525°C - 15 sec
525°C - 1 min
525°C - 5 min
525°C - 1 hr
model - final pore

1,00E-07

5,00E-08

- Evaluate the bonding process in the flake compacts
- Determine sources of differences between material behaviour and model prediction

Figure 6. Microstructure of a flake compact after a
15 second hold at 525 C under 10 MPa

750
700
650
Bending
Strength, 600
MPa
550
500

0,00E+00
0,00E+00

Objectives

2h

450

1,00E-07
Pore width, c (m)

Figure 7. Evolution of pore structure with time,
experimental and model results

Experimental Procedure

350

0

20
40
Hold time , min

60

Figure 8. Change in the bending strength of flake
compacts with hold time

C

400

C

450

C

500

C

SPS
Joule heating
Pulsed current
100 C/min
Vacuum, 10 MPa

Attrition Milling
Liquid Nitrogen
-196 C, 6 hours

Figure 2. (Left) Schematic of Attrition milling from [2];
(Right) Schematic of SPS sintering process from [3].

Diffusion Bonding Model
Solid-state, low pressure joining process with processing temperatures in the
range of 0.5 – 0.8Tm
Figure 9. Microstructure of flake compacts during ramp to 525

Initial model parameters defined by the surface roughness
- asperity height (h) and wavelength (λ = 2b)

800,00

Current
Graphite Sheets (4R)

600,00

Figure 4. Neck formation due to
diffusion and creep processes;
0 – plastic yielding,
1 - surface diffusion,
2 – volume diffusion,
3 – evaporation-condensation,
4 – grain boundary diffusion,
5 – volume diffusion,
6 – power-law creep [4]

Table 1. Density of flake compacts during ramp

Bending
strength, 400,00
MPa

Figure 3. Schematic of assumed surface condition taken from [4]

Temperature (°C)
350
400
450
500
525

200,00
2

0 &6
1

3

4

5

0,00

C, 15 second holds at each temperature

300

350

400
450
Temperature, °C

500

Current
0.81
0.88
0.92
0.96
0.96

Graphite sheets
(4R)
0.81
0.89
0.92
0.99
0.99

Bamidele Akinrinlola
Raynald Gauvin
Mathieu Brochu
Département de génie
des mines et des matériaux,
Université McGill

550

Figure 10. Bending strength of flake compacts during ramp to
525 C, under current application (Current) and with increased
resistance (Graphite sheets (4R))

Acknowledgements

Conclusions

The authors would like to thank the members of the NAIN lab group, Nicolas Brodusch, and David Liu at
McGill for their contributions to this work. Also FQRNT, REGAL and MEDA for financial support.

References
[1] R. Wang and H.S. Gupta, Annu. Rev. Mater. Res. 41, 41-73 (2011)
[2] Maisano, A.J. (2006) . Masters Thesis. Virginia Polytechnic Institute and State University.
[3] Aalund, R. (2008, May 1). Ceramic Journal. Retrieved from
www.ceramicindustry.com/Articles/Feature_Article/BNP_GUID_9-5-2005_A_10000000000000_321084
[4] A. Hill and E.R. Wallach, Acta Metall. 37(9), 2425-2437 (1989)

Diffusion bonding mechanisms could be applicable to the flake bonding process. However, SPS consolidation
involves considerable compaction effects which are not accounted for in the model. The current also seems to
play a role i