Composite Material


Fabrication

The composite material has been fabricated using a standard powder metallurgy process. The Zirconia/Silica particles have a narrow size distribution with a mean diameter of 50 microns to reduce the particle size effect on damage in the material. The matrix is made of 99.9% pure aluminum powder 16 microns in diameter.


Powder metallurgy route.

Zirconia/Silica particles.

A core/shell design was created to have a better control on the material failure and therefore be able to follow the entire fracture process without stochastic failure. The core/shell is shematically shown below along with an optical micrograph of the core of the sample.


Schematics of the core/shell design.

Optical micrograph showing of the core showing
the Zirconia/Silica particles and the pure aluminum grains.

In-situ tensile test using x-ray micro-tomography

The samples were tested in-situ in an x-ray computed micro-tomography set-up in the synchrotron in France (ESRF) and in Japan (SPRing-8). Radiographs are recorded in real time during the tensile test to be able to visualize the material deformation while pulling on it. (see movies below) The test can then be stopped whenever interesting features are observed on a radiograph and a tomograph can be acquired for 3D reconstruction (a tomograph consists of a series of radiographs taken at different angles)


X-ray radiographs of an in-situ tensile test on the
metal matrix composite with core/shell design.
Uniform sample with 2% of particles in the core.

X-ray radiographs of an in-situ tensile test on the
metal matrix composite with core/shell design.
Notched sample with 10% of particles in the core.

Void nucleation, growth and localization (coalescence) events can be precisely captured on the radiographs (as shown in the images below). Void nucleation occurs by decohesion at the particle/matrix interface.

X-ray radiographs taken at the void nucleation event for various volume fractions of particles in the compostite core
(the arrows point at some nucleated voids).

Tomographic reconstruction of voids (red) nucleated at Zirconia/Silica particles (blue)
when the deformation is homogeneous (left) and localized (right).

X-ray radiographs taken at the void coalescence event for various volume fractions of particles in the compostite core
(the arrows point at coalescing voids).

Copyright ©2013 Arnaud Weck. All Rights Reserved