Advanced technologies / Manufacturing of metal matrix composites /
Pressure assisted liquid metal infiltration
Pressure assisted liquid metal infiltration is one of the cheapest and most easily applicable technologies for the production of metal matrix composites (MMCs).
Principle of operation
Pressure assisted liquid metal infiltration is performed in autoclave where matrix metal is melted in graphite or steel crucible under vacuum. The molten metal is forced by the pressurized gas (up to 15 MPa) to penetrate into a porous ceramic or fibrous preform. External force has to be applied because most of liquid metals that are used for MMCs production do not wet the preforms sufficiently.
General steps of pressure assisted liquid metal infiltration
During infiltration the porous preform is held in the molten metal in an approximate holder. After infiltration samples are either pulled out from the melt or held in the molten matrix metal throughout the cooling cycle. Finally the infiltrated preform has to be machined-out form the metal volume.
Pressure assisted liquid metal infiltration makes the preparation of 3D composite parts possible. Limitations are given by the autoclave size and available heating. Various preforms can be prepared with different porosities. This determines the volume fractions of metal and reinforcing phase in the resulting composite.
The process is well manageable through main processing parameters i.e. temperature, gas pressure and time.
The technique has been successfully applied for the preparation of:
- copper matrix/graphite composites for sliding contacts in electrical vehicles
- copper matrix/alumina composites for break discs in automotive
- NiAl composites for intermetallic valves
- copper matrix/high modulus C fibres for heat sinks with high thermal conductivity
- aluminum matrix/high modulus C fibres for heat sinks with high thermal conductivity
- magnesium matrix/ C fibres for ultralight structural applications
- MgLi matrix/saffil composites for ultralight structural applications
- MgLi matrix /C fibres composites for ultralight structural applications
- Aluminum matrix/Al2O3 particles composites