Processing of Al-based MMCs by Indirect Squeeze Infiltration of Ceramic
Preforms on a Shot-Control High Pressure Die Casting Machine
S. Long, O. Beffort, G.Moret and Ph.Thevoz
The feasibility study on the production of Al-based metal matrix composites via indirect
squeeze pressurised liquid metal infiltration of ceramic preforms on a shot-control commercial die
casting machine and the related processing optimisation are briefly summarised. It has been
demonstrated that under optimised processing conditions high quality composite castings can be
The criteria for the selection of optimal processing parameters are the same as those
previously established for direct squeeze casting. That is, preform preheat and melt superheat should
be adjusted to preclude premature melt solidification before and during infiltration; infiltration
speed should be controlled to avoid permanent deformation of the ceramic preform; the maximum
pressure available on the die caster should be deployed to minimise non-infiltration defects; the
gating system should be designed to ensure feeding of the solidification shrinkage in the composite
Metal matrix composites (MMCs) of metallic alloys reinforced with ceramic particles and
fibres are designed to offer high specific mechanical properties and tailorable physical properties
that are highly desirable in various applications but not available in the parent monolithic materials.
Among the MMC fabrication technologies developed, liquid metal infiltration of particulate and/or
fibrous preforms by various casting techniques features a high potential of producing net-shape
composite structures. Among the casting techniques adaptable for the fabrication of Al-based
composites, the high pressure die casting technique keeps attracting research and commercial
interest due to its high productivity, high degree of automation, high surface quality and geometrical
flexibility. However, the repeatable production of composite structures with a high quality
microstructure and desirable properties presents a great challenge to composite engineering.
High pressure die casting has been widely used to produce monolithic Al- and Mg-based
alloy castings with high surface quality and complex geometries at high production rates, but also at
the expense of inferior microstructure soundness and mechanical properties due to the nature of
encouraging spontaneous solidification in process design. Thus, this technique is usually suitable for
monolithic castings with a near eutectic composition, thin and uniform thickness and moderate
requirement on mechanical properties. Although infiltration trials by high pressure die casting have
been reported previously [Jar.92. Kau.94, Kan.95], it remains to be exploited how to repeatably
produce composite castings with desired microstructures and satisfactory performance.
In the present study, the feasibility of the fabrication of Al-based MMC castings by indirect
squeeze pressurised infiltration of ceramic preforms on a Bühler shot-control (SC) die casting
machine was comprehensively examined and the optimal processing conditions were identified. The
obtained composite microstructures were characterised and their mechanical properties were
compared with those of identical composites produced by direct squeeze casting and with those
predicted by composite mechanics.
2. Description of the Processing Feasibility Study
Die casting possesses the high pressure required to achieve liquid metal infiltration of
ceramic preforms. However, as pointed-out previously [Lon.96, Lon.97a], the pre-requirements for
high quality composite castings via pressurised infiltration techniques are as follows in accordance
with the processing sequence:
1. No melt solidification before the beginning of infiltration
2. No melt solidification during preform infiltration
3. No preform deformation during processing
4. Pressurised feeding of melt solidification shrinkage
To obtain high quality composites by indirect squeeze pressurised infiltration on a
commercial high pressure die casting machine, the optimal processing conditions must be identified
to meet the above pre-requirements via experimental infiltration of ceramic preforms, infiltration
hydrodynamic analysis, and numerical optimisation of the gating system to:
1. Determine the optimal thermal parameters, namely: melt superheat and preform preheat
2. Identify the suitable range of the hydrodynamic parameters, i.e., infiltration speed and
infiltration pressure, with consideration of melt chemistry and the geometrical features of the
ceramic phases in the preforms
3. Obtain a desired solidification sequence and eliminate matrix shrinkage voids.
2-1. Component Materials of Composite Castings
In the first step, an age-hardenable AlCu4MgAg alloy [Bef.95] and Saffil chopped fibre
preforms of different fibre volume fractions (10-30 vol.%) were used for the feasibility study and
processing optimisation. The Saffil preforms with the dimension 120x80x15 mm3 were infiltrated
via the 120x80 mm2 surface, as illustrated in Fig. 2. In a second step, under optimised processing
conditions, ceramic preforms of continuous Altex fibres and SiC particles with volume fractions of
50% and 65%, respectively, were infiltrated with pure Al or the AlCu4MgAg alloy for the
characterisation of the microstructure and the mechanical performance. The details of the
reinforcements and matrix alloys are summarised in Table 1.
Table 1 Component Materials and Their Mechanical Properties
Reinforcement Reinforcement Tenisle Ceramic E Matrix Alloy Tensile
Name Geometry Strength Modulus (wt.%) Strength
γ- Al2O3-based Continuous Fibres, 1800(MPa) 210 (GPa) Al 99.99 40(MPa)
Altex Fibres d=15 µm
δ-Al2O3-based Chopped Fibre, d=3 µm, 2100(MPa) 300 (GPa) Al-4Cu-1Mg- 450 (MPa)
Saffil Fibres aspect ratio= 50-100 0.4Ag (T6)
SiC Particles Norton F500S; Sharp n.a. n.a. Al-4Cu-1Mg- 450 (MPa)
shape, d =12 µm 0.4Ag (T6)
2-2. Facility Set-up
The Bühler 53D SC-Series die casting machine, as shown in Fig. 1, was used for
experimental investigations. The geometry of the casting with the gating system and the positions of
the thermocouples for temperature measurements is shown in Fig. 2. The dimensions of the die
cavity were 120x80x25 mm3.
Fig. 1 The SC die casting machine used for indirect squeeze pressurised liquid metal infiltration for
MMC casting production in Bühler AG, Uzwil.
Fig. 2 Schematic of the composite casting with the gating system and the four thermocouples for
measurement of melt temperature change during die filling. (The thermocouple positions:
T1--20 mm beneath the die cavity in the gating system, T2, T3 and T4 are 40 mm,
80 mm and 120 mm above T1, respectively) [Lon.99a].
2-3. Infiltration Processing
Before infiltration, the preforms and the melt of the matrix alloy were preheated to the pre-
selected temperatures, and the die and injection chamber were preheated to 280 °C.
Fig. 3 Processing procedure of indirect squeeze infiltration of the Saffil preforms. a) the inserted
preform in the die cavity, b) the ejected composite casting from the die cavity after solidification.
1. Die Filling
3. Solidification Pressurisation 4. Casting Ejection
1200 2. Preform Infiltration 160
P (bar) Plunger Speed
& D (mm)
0 5 10 15 20 25 30 35 40 45
Fig. 4 A typical indirect squeeze casting cycle on Bühler SC-series caster, where a high
die filling speed of 140 mm/s, but a slow infiltration speed of 25 mm/s were used. Note
the pressure change during infiltration similar to that of direct squeeze infiltration [lon.99a].
During composite casting, the following actions sequentially take place: placing the preform
into the die chamber as shown in Fig. 3a, pouring the melt into the injection chamber (the so-called
shot sleeve), moving the plunger to drive the melt to fill the die cavity and to infiltrate the preform
at the pre-selected plunger speed. Once the maximum pressure is achieved, this value is maintained
until the complete solidification of the casting. Post solidification, the casting is ejected from the
die, as shown in Fig. 3b, followed by the preparation for the next infiltration cycle.
The thermal and hydrodynamic processing parameters were continuously recorded
throughout the processing cycles. The record of a typical casting cycle is given in Fig. 4.
To study the processing feasibility and to identify the optimal processing conditions, the
main processing variables, namely, melt superheat Tm, preform preheat Tf, maximum pressure Pmax,
infiltration speed in terms of plunger speed Vp, were varied within the ranges as specified in Table
2. Throughout the whole experimental investigations, the plunger speed for die filling and the die
temperature are 80 mm/s and 280 °C, respectively. The effect of processing conditions on
infiltration quality was examined by optical microscopy.
Table 2 The Investigated Processing Parameter Ranges for the AlCu4MgAg /Saffil MMCs
Tm (C°) Tf (C°) Pmax (MPa) Vp (mm/s) Vf (%)
700-850 400-800 10-100 20-90 10-30
3. Processing Feasibility and Processing Optimisation
3-1 Optimisation of Thermal Parameters
3-1-1 Melt Superheat
Due to the large temperature difference between the superheated melt and the die
temperature, the melt flow is expected to be subjected to an intensive heat loss. Fig 5 shows the
temperature loss of a AlCu4MgAg melt superheated to different temperatures during pouring and
As the curves show, an extensive temperature loss of about 100 °C appears during the period
from the beginning of melt pouring until the melt reaches the first thermocouple, which takes ∼7-10
seconds. When the melt successively passes the next three thermocouples in the die cavity, the
extent of the melt temperature decreases successively due to the shortened time duration and the
reduced temperature difference between the melt flow and the die cavity. The temperature loss
ranges from a few degrees up to more than 30 °C according to the degree of the melt superheat
Tm = 750 °C
Tm = 800 °C
800 Tm = 830 °C
T (°C) T1
650 Melt Liquidus
0 50 100 150 200 250 300
Melt Flow Distance (mm)
Fig. 5 Temperature changes of an AlCu4MgAg melt during die filling in the
indirect squeeze casting process for different melt superheats [Lon.99a].
It has been understood that the employment of low melt superheat (Tm) will induce
undesirable premature melt solidification during die filling and preform infiltration [Lon.97a], but
the employment of an excessively high melt superheat is likely to raise difficulties in preparation of
a high quality melt in foundry practice and adversely prolongs the melt-ceramic contact time. The
temperature curves in Fig. 5 show that, with a melt superheat of ∼800 °C, the AlCu4MgAg melt
temperature remains a few degrees above the liquidus of pure Al (660 °C) after the die filling. These
few degrees superheat are sufficient to prevent premature melt solidification but not excessively
high to prolong melt-reinforcement contact time to a large extent. Noting that Al-based alloys
generally have a lower liquidus temperature than pure Al, a melt superheat of 800 °C is
recommended as the optimal temperature for the production of Al-based composites under similar
3-1-2. Preform Preheat
After die filling, the melt contacts the preform and starts to penetrate into the interspaces
between the ceramic phases in the preform. Due to the microscopic scale of the interspaces, the heat
exchange between the melt flow and the ceramic phase is intensive if a temperature difference exists
between them. Therefore, the preform preheat constitutes one of the most important thermal
parameters for pressurised infiltration free of premature melt solidification during infiltration.
Tf=400 °C Tf=800 °C
Tf=400°C Tf=800 °C
0.2 mm 0.2 mm
Fig. 6 Solidification structure (a) of 15%Saffil/ Fig. 7 Solidification structure (a) of 15%Saffil/
AlCu4MgAg cast at Tm=800 °C, Pmax=100 MPa, AlCu4MgAg cast at Tm=800 °C, Pmax=100 MPa,
and VP=30 mm/s, and Tf=400 °C; and the and VP=30 mm/s, and Tf=800 °C; and the
microstructure at the preform bottom (b). microstructure at the preform bottom (b).
Microscopical investigation of the cross sections of two 15 vol.% Saffil/AlCu4MgAg
composites produced with preform preheats of 400 and 800 °C, a constant melt superheat of 800 °C
and a plunger speed of 30 mm/s reveal that, a severe preform deformation and a defect rich zone at
the preform bottom were induced by premature melt solidification before and during infiltration
when the preform preheat was ∼400 °C, as shown in Fig. 6. With a preform preheat of 750-800 °C,
the preform deformation and the defect rich zone were eliminated, as shown in Fig. 7.
It was also made clear that the appearance of premature melt solidification will adversely
induce non-uniformity of matrix phase constitution and variation of matrix-ceramic binding strength
along the infiltration direction due to the partition of the alloying elements during solidification and
the change in melt-fibre contact condition [Lon.97a]. The employment of a preform preheat
between 750-800 °C is desirable to eliminate the premature melt solidification. Obviously, the
demand of such high preform preheat and melt superheat stems from the intensive heat loss of the
preform and melt to the cold environment during preform transfer and melt pouring.
3-2 Effect of Hydrodynamic Parameters
3-2-1 Squeeze Infiltration Hydrodynamics
In liquid metal infiltration of a ceramic preform, there are two hydrodynamic parameters
associated with infiltration quality: infiltration speed (Vinf.) and infiltration pressure (Pinf.).
According to the established infiltration hydrodynamics [Lon.95], the effect of Vinf. and Pinf. during
unidirectional infiltration of a preform can be correlated to the physicochemical nature of the melt-
fibre contact system (melt surface tension σmg, melt viscosity µ and the contact angle of the melt
flow to the fibres θ) and the geometrical features of the porous preform as follows:
σ mg cosθ 40 µVinf
P =2 + Z + Pback
3G p (1 − V f )
inf Req. max
where, Vf is the ceramic volume fraction of the preform, Req.max is the equivalent radius of the
largest interspaces between the ceramic phase in the preform, Gp is the geometrical constant of the
preform, representing the orientation and size distribution of the interspaces in the preform.
According to the model, the infiltration starts when the external pressure exceeds the
minimum capillary resistance of the preform to the melt penetration, followed by a stable infiltration
stage featured by the linear pressure-time relationship until the melt penetrates through the preform.
The infiltration is terminated when the pressure reaches its pre-selected maximum value at the end
of the air compression stage. The variation of the pressure during infiltration is schematically shown
in Fig. 8. For a prescribed preform-melt system the infiltration pressure is a hydrodynamic response
to the resistance of the preform to the melt penetration at a constant flux.
Maximum Infiltration Pressure
Infiltration Stable Entrapped Air
Initiation Infiltration Compression
Fig. 8. The Time-Pressure relationship during unidirectional infiltration of a ceramic
preform at a constant speed. Note the three stages of the infiltration.
3-2-2 Effect of Infiltration Speed
The infiltration speed determines not only the time required to achieve full infiltration, but
also the infiltration pressure gradient, penetrating-through pressure and the saturation degree of the
infiltrated preform. Therefore, the infiltration speed affects the infiltration quality via:
1. inducing preform deformation and preform delamination when the infiltration pressure exceeds
the elastic compression strength of the ceramic preform [Lon.95].
2. determining the amount of the air entrapped in the infiltrated preform and the associated non-
infiltration defects [Lon.97b].
As the pressure-time curves during infiltration of a 15% Saffil preform with AlCu4MgAg
melt in Fig. 9 indicate, within the pre-selected plunger speed range, an increase in infiltration speed
shortens the time for the melt to penetrate through the preform, and increases the penetrating-
through pressure as predicted by the model. For a Saffil preform with a fibre volume fraction of
15% the penetrating-through pressure at the maximum plunger speed of 90 mm/s is about ∼1.5
MPa, slightly lower than the quasi-elastic preform compression strength of a 1.7 MPa [Lon.99a].
Therefore, no preform deformation is observed in the castings provided that the infiltration is free of
melt solidification. However, it is obvious that if the plunger speed is further raised, the penetrating-
through pressure will become higher than the strength of the preform, resulting in permanent
preform deformation as reported previously [Kann.95] during infiltration of preforms at a speed of
V=90 V=60 V=40 V=20
2 2.5 3 3.5 4 4.5
Fig. 9. Pressure-Time curves for infiltration of 15% Saffil preform with different plunger
Speeds and Tf=750 °C, Tm=800 °C, TD=280 °C. Note the increase of the pressure
gradient and the penetrating-through pressure with increasing infiltration speed [Lon.99a].
3-2-3 Effect of Maximum Pressure
As mentioned above, infiltration pressure is a hydraulic response to the resistance of the
preform to the melt infiltration. It can reach a few MPa for the infiltration of the preforms of various
types of ceramic reinforcement. Once the melt penetrates through the preform, the pressure is used
to overcome the capillary resistance of the non-infiltrated small interspaces and to compress the air
entrapped there to achieve maximum saturation in the course of its rapid increase [Lon.95]. Die
filling and infiltration are performed under displacement control; the control mode is changed to
pressure control at a preset value after completion of infiltration. The subsequently sustained
pressurisation at the maximum value is necessary to feed the solidification shrinkage of the melt in
the composite casting.
In the light of achieving a maximum degree of preform saturation, the use of the maximum
pressure available from the hydraulic system of the die casting machine is recommended. With
regard to the effect of pressure on the solidification shrinkage, the employment of insufficiently high
pressure will induce shrinkage voids in the composite castings. Previous infiltration practice on a
direct squeeze caster [Zhu.94] and the present indirect squeeze infiltration indicate that a pressure of
≥15-20 MPa is high enough to deform the peripherally solidified matrix shell to feed the
solidification shrinkage in the central part of the casting. However, an effective feeding of the
solidification shrinkage during indirect squeeze casting on a die casting machine relies on the
employment of an optimal gating system, as highlighted in the following section. The use of a
gating system designed for conventional high pressure die casting will inevitably lead to the
formation of shrinkage voids despite of a pressurisation exceeding 100 MPa, as shown in Fig. 10.
Fig. 10. The as-cast microstructure of the central part of a 15 vol.% Saffil/AlCu4MgAg composite
casting produced on a Bühler SC die casting machine with a conventional
gating system under 100 MPa maximum pressure. Note the shrinkage voids.
3-2-4 Effect of the Preform-Melt Infiltration System
According to the infiltration hydrodynamics, the preform-melt system influences the
infiltration kinetics via altering the melt viscosity, the wettability of the melt to the preform and the
size and numerical distribution of the interspaces between the fibres that act as melt flow ducts in
V (m m /s)
P (10% )
P (20% )
P (30% )
D (m m )
P (MPa) & V (mm/s)
3 3.3 3.6 3.9 4.2 4.5 4.8
Fig. 11 Effect of fibre volume fraction of preforms on the infiltration kinetics [Lon.99a].
In general, melt alloying manifests its influence on the infiltration via the change in melt
viscosity and the change in melt wettability to the preform by melt-preform interfacial chemical
reaction. Therefore, it has been widely believed that the addition of the elements chemically reactive
to the preform or/and encouraging the formation of eutectic phases is able to facilitate infiltration.
However, alloying melt within the practical range changes the melt viscosity to a limited extent, and
the wetting promotion via melt-preform interfacial chemical reaction requires a period of contacting
time much longer than the practical infiltration time which is less than one second. Therefore, melt
alloying imposes no considerable influence on the kinetics of solidification free infiltration
The influence of the geometrical characteristics of the preform on the infiltration kinetics is
demonstrated in Fig. 11. As predicted by the model (eq. 1), with increasing fibre volume fraction,
the threshold pressure for the initiation of infiltration, the penetrating-through pressure and the
pressure gradient are raised due to the inverse decrease of the preform interspaces.
As far as the solidification free infiltration is concerned, the geometrical factor of the
preform plays a much more dominant role in infiltration quality control than melt alloying. To
prevent preform damage, the infiltration speed must be selected to ensure that the penetrating-
through pressure is lower than the elastic compression strength of the preform.
3-3 Gating System Optimisation
In foundry practice, a proper gating system design is crucial to obtain sound castings, but its
importance in producing sound composite castings on a die casting machine has been largely
To visualise the sensitiveness of matrix void formation to the geometry of the gating system,
the solidification behaviour of a composite casting with a gating system for conventional monolithic
die casting (DG) and with a gating system optimised for composite casting (CG) have been
numerically simulated and empirically verified [Lon.99a].
Fig. 12 shows the solidification behaviour of the composite castings with different gating
systems (a and d) and the castings produced with the respective gating systems (b and c) under the
optimal processing conditions.
As illustrated by the solid-liquid volume fraction map of Fig.12a, with the narrow gating
system for conventional monolithic die casting, the melt solidification completes first in the gating
system, which isolates the partially solidified composite casting from the pressurised melt reservoir
in the injection chamber. Consequently, the casting surface is seamed due to the resultant
depressurisation, as shown in Fig. 12b, and internal shrinkage voids form, as shown in Fig. 10,
despite of the use of a 100 MPa infiltration pressure. In contrast, as shown in Fig. 12d, when the
gating system is optimised to control the sequence of the solidification completion from the top of
the casting towards the melt reservoir in the injection chamber through the gating system, the
casting has a high quality surface, as shown in Fig. 12c, and is free of internal shrinkage voids, as
illustrated in Fig. 13b.
a b c d
Fig. 12 Solidification behaviour and corresponding surface appearance of the composite castings
with DG (a and b) and CG (d and c) gating system, respectively, in terms of solid fraction (where
the red colour refers to 100% solid metal and purple colour to 100% liquid.). Note the poor surface
quality in (b) due to de-pressurisation induced by early solidification of the DG gating system.
3-4 Processing Timing
As indicated by the strict requirement on the preform preheat and melt superheat, any
processing delay before the initiation of the infiltration will dramatically alter the actual preform and
melt temperatures from the optimal values and leads to the formation of undesirable microstructure
features as reported previously. Therefore, the importance of a strict processing timing will never be
over-emphasised during indirect squeeze casting of MMCs on a high pressure die casting machine
at the industrial scale.
4. Microstructure and Mechanical Properties of the Composites
The microstructure and the mechanical properties of the Al-based metal matrix composites
of different types of reinforcement and different reinforcement volume fractions produced under
optimised conditions were characterised by microscopy and mechanical testing.
The typical microstructures of the composites are given in Fig. 13. Detailed microscopy of
the composites indicates that the die cast composites possess microstructural features similar to
those of identical composites produced by optimised direct squeeze casting in terms of
reinforcement distribution, interfacial structure, matrix precipitation states, and infiltration degree.
15 µm 15 µm
Microstructures of the peak-age hardened
F500S-SiCp/AlCu4MgAg composite (A), 15%
Saffil/AlCu4MgAg composite (B), and as-cast
Altex/Al composite (C) produced on a Bühler
SC die caster under optimal processing
parameters. Note the high infiltration quality.
The mechanical properties of the composite castings produced on a Bühler SC die casting
machine under optimal conditions are summarised in Table 3 in comparison with the properties of
identical composites produced on EMPA's direct squeeze caster under optimal conditions with 130
MPa maximum pressure. As the data indicate, the composites produced by industrial indirect
squeeze casting possess properties comparable to their counterparts produced by direct squeeze
casting in the laboratory.
Table 3 Mechanical Performance of Direct and Indirect Squeeze Cast MMCs
(σB: 3-pt. bending strength, σT: ultimate tensile strength)
Composite Type σB σT E Pressure
Reinforcement Vol-Fract. (MPa) (MPa) (GPa) (MPa)
indirect Squeeze Casting F500S-SiCp/AlCu4MgAg 730 470 198 100
(Bühler SC-die caster) 65%
direct Squeeze Casting F500S-SiCp/AlCu4MgAg 750 n.a. 201 130
indirect Squeeze Casting Altex/Al (UD) n.a. 899.4 120 100
(Bühler SC-die caster) 50%
direct Squeeze Casting Altex/Al (UD) n.a. 890.7 119.9 130
indirect Squeeze Casting Saffil/AlCu4MgAg n.a. 523 96 100
(Bühler SC-die caster) 15%
direct Squeeze Casting Saffil/AlCu4MgAg n.a. 514 95 130
Usually, the tensile strength of fibrous composites is well predicted by the modified Rule of
Mixtures (RoM) as follows:
σc = κσfVf+(1-Vf)σm (2)
where, σc, σf and σm refer to the strength of composite, fibre and matrix upon composite
failure, respectively; Vf referes to fibre volume fraction, κ=is the geometrical factor with
consideration of the interfacial binding behaviour. For Altex/Al composite under axial tension,
κ==1. For chopped fibrous composites, κ==0.27 or 0.375 has been used previously [Fuk.82, Bad.85]
to account for the random orientation and variation of aspect ratio of the fibres in the composite.
As compared with the prediction of the RoM, Altex/Al composite produces a strength very
close to the theoretical value of 930 MPa if the component strengths in Table 1 are used. Fig. 14
gives the strength of the peak-aged (T6) Saffil/AlCu4MgAg composite of variable fibre volume
fraction in comparison with the predictions of the modified RoM.
0.05 0.1 0.15 0.2 0.25 0.3 0.35
Fibre Volume Fraction (%)
Fig. 14 A comparison of the strength of Saffil/AlCu4MgAg with the theoretical predictions
of the modified Rule of Mixtures for discontinuous composites [Lon.99b].
As the figure shows, the properties of the die cast composite exceed the theoretical
predictions, which not only indicates the achievement of a high quality composite casting, but also
hints the need for a better understanding on the strengthening mechanisms of discontinuously
reinforced composite castings.
The present study demonstrates that the production of metal matrix composites via indirect
squeeze pressurised infiltration of ceramic preforms on a shot-control die casting machine is
feasible and that the produced composites possess the desired microstructural features and excellent
mechanical properties provided that the infiltration processing is conducted with the optimal
parameters as detailed hereafter:
In accordance with the criterion of solidification free infiltration, the main thermal
parameters--preform preheat and melt superheat--should be selected to avoid premature melt
solidification. In practice, 750-800 °C preform preheat and 800 °C melt superheat are recommended
for indirect squeeze casting with a 280-300 °C die temperature and a strict processing timing.
Under the optimal thermal parameters, the maximum infiltration speed is controlled by the
geometrical features and the elastic compression strength of the preform. For a prescribed preform-
melt infiltration system, the infiltration speed should be selected in such a way that the penetrating-
through pressure is lower than the elastic compression strength of the preform to prevent preform
damage. For the infiltration of Saffil preforms, the infiltration speed should be inferior to 100 mm/s.
To minimise the non-infiltration defects associated with capillarity and air entrapment, employment
of the maximum pressure available on the die casting machine is recommended.
To eliminate shrinkage voids in the matrix, to which the properties of the composites are
sensitive, the gating system should be optimised to ensure a sequential solidification from the far
end of the composite casting to the melt reservoir in the injection chamber through the gating
This work was part of the project 2.1B "High Performance Aluminium Matrix Composites"
of the Swiss Priority Program on Materials Research (1995-1999) and supported by grants from the
Board of the Swiss Federal Institutes of Technology FIT Board.
Jar.92. P. Jarry, V. J. Michaud, A. Mortensen, A. Dubus, and R. Tirard-collet: Infiltration of fibre
preforms by an alloy: Part III. Die casting experiments, Metall. Trans., Vol. 23A (1992),
Kau.94. H. Kaufmann, R. Auer-Knöbl, and H. P. Degischer: Elevated temperature properties of
short-fibre reinforced AlSi9Cu3 produced by pressure die-casting, Z. Metallkd., vol. 85 (1994),
Kan.95. C. G. Kang, and K. S. Yun: The production of metal matrix composites by die casting
processes and its mechanical properties, in Proc. ICCM9, Vol. 1—Metal Matrix Composites,
Lon.96. S. Long: Cast Composites: Transfer Phenomena and Microstructure Formation, Ph.D.
thesis, Department of Materials, Imperial College, UK, June. 1996.
Lon.97a. S. Long, H. M. Flower and O. Beffort: Effects of premature melt solidification on
pressurised infiltration kinetics and infiltration quality, Solidification Processing 1997, ed. by J.
Beech and H. Jones, (Proc. of the 4th decennial International Conference on Solidification
Processing, 7-10 July, 1997, Sheffield, UK), pp92-96.
Bef.95. O. Beffort, C. Solenthaler, P. J. Uggowitzer, and M. O. Speidel: High toughness and high
strength spray-deposited AlCuMgAg-based alloys for use at moderately elevated temperatures,
Mater. Sci. Eng., Vol. 191A (1995), pp121-134.
Lon.99a. S. Long, O. Beffort, U. Müller, O. Greim, and G. Moret: Indirect Squeeze Infiltration of
ceramic Preforms on Die casting Machine for Composite Castings, Part I: Processing
Feasibility and Optimisation, in publication.
Lon.95. S. Long, Z. Zhang, and H. M. Flower: Characterisation of liquid metal infiltration of
chopped fibre preforms aided by external pressure. Part II: modelling of liquid metal infiltration
process, Acta Metall. Mater., Vol. 43 (1995), p3499-3509.
Lon.97b. S. Long, O. Beffort, L. Rohr, and H. M. Flower: Effect of infiltration speed on infiltration
quality and tensile properties of Saffil/Al-Cu-Mg-Ag, in Proc. of ICCM11, Vol. III: Metal
Matrix Composites and Physical Properties, ed. by Murray L. Scott, Australia Composite
Structures Society, 14-18, Sept. 1997, pp.274-283.
Zhu.94. Z. Zhang, S. Long, and H. M. Flower: Light Alloy Composite Production by Liquid Metal
Infiltration, Composites A, Vol. 25, No. 5, 1994, P379-392.
Fuk.82. H. Fukuda, and T. W. Chou, Mater. Sci., vol. 17 (1982), pp.1003-1007.
Bad.85. M. G. Bader, T. W. Clyne, G. R. Cappleman, and P. A. Hubert: Comp. Sci. Technol., vol.
23 (1985), pp287-301.
Lon.99b. S. Long, O. Beffort, and U. Müller: Indirect Squeeze Infiltration of Ceramic Preforms on
Die casting Machine for Composite Castings, Part II: Microstructure and Mechanical
Properties, in publication.