Abstract
An interpenetrating aluminum–alumina composite is presented, based on a ceramic foam manufactured via a novel slurry‐based route resulting in a highly homogeneous preform microstructure in contrast to other preform techniques. The metal matrix composite (MMC) is produced by infiltrating the open‐porous ceramic preform with molten aluminum at 700 °C using a Argon‐driven gas pressure infiltration process. The resulting MMC and the primary ceramic foam are investigated both numerically and experimentally in terms of microstructural characteristics. In addition, the mechanical behavior of the material as well as the structural and material interactions on the microscale are investigated. To characterize the MMC regarding mechanical isotropy, elastic properties are determined experimentally via ultrasonic phase spectroscopy (UPS). A fast Fourier transform (FFT) formulation is used to simulate the complex 3D microstructure with reasonable effort based on image‐data gathered from high‐resolution X‐ray computed tomography (CT) scans of the ceramic foam as computational grid. Simulations prove that the material properties are, indeed, considered as highly homogeneous with respect to the material microstructure. A comparison with effective experimental investigations confirms these findings.
Highlights
An interpenetrating aluminum–alumina composite is presented, based on a to the matrix material class
A fast logically interconnected throughout the whole material volume, it is defined as an interpenetrating phase composite.[3]
Fourier transform (FFT) formulation is used to simulate the complex 3D microstructure with reasonable effort based on image-data gathered from highresolution X-ray computed tomography (CT) scans of the ceramic foam as computational grid
Summary
State-of-the-art manufacturing techniques of ceramic preforms for interpenetrating alumina–aluminum composites are freeze-casting,[13,14] pore-former processes with pyrolyzable placeholders,[5,10] suspension-based polyurethane system,[4,11,28] and sintering of (coarse) alumina powders to an open-porous ceramic.[8,9] Other methods to get interpenetrating MMCs directly are displacement reaction of silica-glass and molten aluminum[23] or sintering of a mixture of aluminum alloy and alumina powders.[29]. By mechanical stirring a stable ceramic foam suspension is produced. A ceramic foam as a MMC preform can be produced. Gas pressure infiltration is used to manufacture the interpenetrating composite. The ceramic preform is heated in an evacuated vacuum furnace at a residual pressure of 2 Â 10À2 mbar with an aluminum slab (AlSi10Mg) up to a maximum temperature of 700 C. During heating the pressure in the furnace is held between 2 Â 10À2 and 10À1 mbar. As soon as the maximum temperature is reached and the slab is molten, an external Argon gas pressure of 40 bar is applied onto the surface of the melt covering the previously evacuated preform and the molten aluminum is infiltrated into it. The infiltrated preform, i.e., the interpenetrating composite, is removed from the furnace for sample preparation
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