Recently, an increase of interest in new class of composite materials, which has been termed as interpenetrating phase composites (IPCs) has been observed. This results in a material with better mechanical characteristics, because of two phases with significantly different properties such as strength, strain which can be optimised in the composite material.
In this paper different methods for infiltration of porous ceramic performs by cast aluminium alloy are reported. As a result ceramic-metal composites of two interpenetrating phases are obtained. A pressure-vacuum infiltration on the Degussa press (T=7200C, p=15 MPa, t=15’) and gas-pressure infiltration (GPI) in an autoclave (T=7000C, p=4 MPa, t=5’) were applied for infiltration of porous Al2O3 ceramics by EN AC- AlSi12CuMgNi (AK12) cast aluminium alloy. Effect of the method of infiltration on mechanical properties and microstructure of ceramic-metal composites, was studied.
Ceramic preforms were formed by method of copying the cellular structure of the polymer matrix. Volume fraction of the aluminum alloy phase was up to 72 vol.%, while the pore sizes of the ceramic preforms were varied from 300 to 1000 µm. The results of the X-ray tomography proved very good infiltration of the pores by the metal for each method.
Compression tests for the obtained composites were carried out and Young’s modulus was measured by the application of the DIC (Digital Image Correlation) method. Moreover, Brinell hardness tests were performed. Gas-pressure infiltration (GPI) allowed to fabricate composites with higher value of mechanical properties.
The composites microstructure was studied using scanning electron microscopy (SEM). SEM investigations showed that the pores are almost fully filled by the aluminium alloy. The chemical composition of separated phases observed in the microstructures of composites were examined using the EDS method. The results of STEM studies confirmed diffusion of silicon phases from aluminium alloy to substrate of Al2O3 ceramics.
The obtained microstructure with percolation of ceramic and metal phases gives the composites high mechanical properties together with the ability to absorb the strain energy.