Squeeze casting is one of the widely used processing method for Metal Matrix Composites (MMC's) after stir casting. This presentation gives an overall idea of process, its parameter and case study of Aluminum MMC's.
HRISHIKESH D. GHEWADE
(ROLL NO. 212215011)
M.Tech (Material Science and Engg.) 1st Year
COMPOSITION OF MMC
MMC’s are made by dispersing a reinforcing material into a metal matrix. The
reinforcing surface can be coated to prevent a chemical reaction with metal matrix.
For example: Carbon fibres are commonly used in aluminium matrix to synthesize
A matrix is usually a lighter metals such as Aluminium, Magnesium or Titanium and
provides a compliant support for the reinforcement.
The reinforcement can be a continuous or discontinuous.
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• Before understanding the mechanism of any processing method, it is
necessary to take a prior knowledge of some concepts such as;
1) Interfaces (Wettability, Type of bonding, etc)
2) Preform Preparation
3) Infiltration Process
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A. Adsorption and Wetting:
Good wettability is needed to generate a strong interface that will
allow transfer and distribution of load from the matrix to the
dispersed phase, without premature
Adsorption– It is a surface reaction which is dependent on
concentration, temperature, and diffusivity. The greater the
adsorption, the more the solute tends to lower the surface energy.
B. Surface treatment of the reinforcement
The reinforcement surfaces are coated with suitable materials to
improve wettability and adhesion and also to prevent any adverse
chemical reactions at elevated temperature.
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Example - 1. Coatings of SiC on boron fibre for Al matrices.
2. B4C coating on boron fibres for Titanium matrices.
C. Matrix Modification:
It is done by modifying the matrix alloy composition.
Example- Alloying the Al matrix with Lithium promotes the
wetting of polycrystalline Al2O3 fibres. The Lithium is believed to
react with alumina to form a lithium aluminate which is more
readily wetted by aluminium.
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INTRODUCTION TO SQUEEZE CASTING
Squeeze casting is the combination of the casting and forging
processes that can be done with help of high pressure when it is
applied during melt solidification.
It is a metal-forming process, which combines permanent mould
casting with die forging into a single operation.
Referred by many names as “pressure infiltration”, “liquid metal
forging”, ``extrusion casting”, “liquid pressing'', ``pressure
crystallization”, ``squeeze forming”.
Employs low die filling velocity, with minimum turbulence and high
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• Applying pressure on the solidification of molten metal could
change melting point of alloys which enhances the
• Moreover it refines the micro and macrostructure; it is helpful
to minimize the gas and shrinkage porosities of the castings.
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Direct Squeeze Casting
Indirect Squeeze Casting
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DIRECT SQUEEZE CASTING
The pressure for the infiltration of the prefabricated preforms is
applied directly to the melt.
The die is thereby part of the mold, which simplifies the structure of
the tools substantially.
- The volume of the melt must be determined exactly
- The appearance of oxidation products formed in the cast part
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INDIRECT SQUEEZE CASTING
The metal is injected into the die cavity by a small diameter piston
Pressure is transmitted from the hydraulic source to the metal in a
cavity through a runner system.
It is designed to combine the net shape advantage of high
pressure die casting with the internal structural advantages of squeeze
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Squeeze Casting Infiltration process has the following steps:
• A preform of dispersed phase (particles, fibers) is placed into the
lower fixed mold half.
• A molten metal in a predetermined amount is poured into the lower
• The upper movable mold half (ram) moves downwards and forces the
liquid metal to infiltrate the preform.
• The infiltrated material solidifies under the pressure.
• The part is removed from the mold by means of the ejector pin.
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List of variables and parameters
Molten metal pouring temperature;
Melt quality and quantity;
Preform preheating temperature;
Applied squeeze pressure;
Pressure applied duration;
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Theoretical background: Effect of
pressure on solidification behaviour
• The application of pressure during solidification would be
expected to affect phase relationships in an alloy system. This
may be deduced by considering the Clausius-Clapeyron equation,
where Tf is the equilibrium freezing temperature, Vl and Vs are the
specific volumes of the liquid and solid, respectively, and ΔHf is
the Latent heat of fusion.
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• Substituting the appropriate thermodynamic equation for volume, the
effect of pressure on freezing point may roughly be estimated as
• where P0, ΔHf and R are constants. Therefore, Tf should increase with
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ALUMINUM METAL MATRIX
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Among all the MMC’s Aluminum metal matrix composites are
finding increased applications, because of their improved mechanical
and tribological properties.
Matrix- Aluminum metal and Reinforcement- SiC Particles
1) Squeeze Pressure:
- Of the order of 100 MPa
- Improves wettability and bonding force
- Results in large undercooling and hence high nucleation rate-
refinement change in structure.
- A primary α (Al rich) phase seen as light dendritic areas and eutectic
matrix of the α phase and silicon particles (darker areas)
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1) the decrease of grain size
2) Decreasing SDAS
3) Reduction of porosity
4) increase in heat transfer coefficient
5) preventing Al4C3
6) Microstructural refinement, 10% increase in tensile strength
2) Casting (melt) / Preform preheat / Die temperature:
- Best melt temperature is either 690°C or 660°C , at 630°C, the formation of
very fine and uniform equiaxed grains.
- SiC preform is preheated to 600°C- forms SiO2 layer
- Die preheating temperature of 200°C-250°C, it shows increase in tensile
strength and elongation.
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3) Solidification Rate:
- Very high
- The relation between the grain size “d” and the cooling rate
“R” is written as:
where, K and d are constants. ‘a’ is factor which depends on type of composites. (0.34-0.39)
- the grain size increased when the cooling rate decreased
- The shorter the solidification time, the higher is the value of the property
- The interface heat transfer coefficients were found to increase with the increase
in applied pressure.
4) Reinforcement Particle Size:
• When the particle size is smaller, the spacing between the particles is reduced.
The smaller particles will exert more constraint on grain growth during cooling
and more restriction on plastic flow during deformation, which can also contribute
to increase in the strength.
• Optimum reinforcement particle grain size of SiC in the range of 15-30 μm
• The higher particle size which reduces the nucleation sites during the solidification
and a weaker the bond strength which becomes the crack initiation sites in the
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5) Porosity and Mechanical properties:
• The applied pressure increases the volume fraction of the Al-rich α-phase, and
decreases in the size of the primary Al-rich dendrites.
• High applied pressure finer microstructure increasing the freezing point
increases nucleation frequency finer grain size structure low or no porosity
• Increase in tensile properties, hardness, flexural strength
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1. The optimum pressure used in the squeeze casting of Aluminium
alloys and composites, which gives a better microstructural refinement
and increase in the mechanical properties, is 100 MPa.
2. The selection of the reinforcement particle size also influences the
strength of the material in the squeeze casting process. The smaller the
grain size the better the improvement in the properties.
3. The suggested melt and die temperature during the squeeze casting of
Aluminium alloys and composites are 600°C to 700°C and around
4. There is a refinement in the microstructure with the combined effect
of undercooling and a higher cooling rate, due to the high pressure level
in the squeeze casting process.
5. The mechanical properties are enriched for both the alloys and the
composites when fabricated through the squeeze casting technique,
under controlled process parameters.
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Elimination of porosity and shrinkage
100% casting yield
Attainment of greater part details
Good surface finish, good dimensional accuracy
High strength to weight ratio
Improved wear resistance, higher corrosion resistance, resistance to high temperature
Improved fatigue and better creep strength3/18/2016 Squeeze casting 26
Costs are very high due to complex tooling.
No flexibility as tooling is dedicated to specific components
Process needs to be accurately control which slows the cycle time down and
increases process cost
High costs mean high production volumes are necessary to justify equipments
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1. M.R. Ghomashchi, A. Vikhrov, “Squeeze casting: an overview”,
Journal of Materials Processing Technology 101 (2000) 1-9
2. M. Dhanashekara, V. S. Senthil Kumar, “Squeeze Casting of
Aluminium Metal Matrix Composites- An Overview”, 12th global
congress on manufacturing and management, GCMM 2014,
procedia Engineering 97 ( 2014 ) 412 – 420
3. Krishnan K. Chawla, “ Composite Materials- Science and
Engineering”, Springer Publication
4. T.R. Vijayaram, S. Sulaiman, A.M.S. Hamouda ∗, M.H.M. Ahmad,
“Fabrication of fiber reinforced metal matrix composites by squeeze
casting technology”, Journal of Materials Processing Technology
178 (2006) 34–38
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