Advanced technologies /

Manufacturing of metal matrix composites



Pressure assisted liquid metal infiltration


General description

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
Gas pressure infiltration 1 
Gas pressure infiltration 2 
Gas pressure infiltration 3 
Gas pressure infiltration 4 

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.

Typical applications

The technique has been successfully applied for the preparation of:

Vacuum diffusion bonding


General description

Diffusion bonding is a solid state technique used for joining of metals or metals with ceramics, etc. It is widely used also for preparation of metal matrix composites (MMCs).

Principle of operation

Diffusion bonding operates on the principle of solid state diffusion where the atoms of two solid surfaces intersperse themselves over time. This is usually implemented by applying high pressure, in conjunction with necessarily high temperature, to the materials to be bonded. The process is typically accomplished in vacuum chambers with preheated pressing tools. The technique is widely used to bond preforms of alternating layers of thin metal foils and metal wires or ceramic fibres.

Monolayers of foils and wires are often prepared in advance using plasma spraying or diffusion bonding to fix the position of wires on the foil. In this case different orientation of fibres in 2D can be obtained.

The diffusion bonding is well manageable through main processing parameters i.e. temperature, pressure and time.
 
Vacuum chamberVacuum chamber for diffusion bonding
1 – vacuum chamber; 2 – lid, 3 – preheated pressing tool, 4 - composite perform, 5 – cooling water supply, 6 – vacuum pump connection
 
Preform of alternating layers Preform of alternating layers of thin metal foils and wires
 
Monolayer of Al foils with B fibresMonolayer of Al foils with B fibres prepared by diffusion bonding; 1 – B fibre, 2 – Al foil
 

Typical applications

The technique has been successfully applied for the preparation of
AlB compositeAluminium matrix/boron fibre composite
 
Al Fe maraging laminate detailAluminium matrix/steel wire composite
 

Equipment


Manufacturing of metal matrix composites - Powder based techniques