Investigation of the Mechanical Properties of A356 alloy Reinforced AlTiB/SiCp Composite with Semi Solid Stir Casting Method

1. Natalino F.D.S. Guterres
by
MECHANICAL ENGINEERING DILI INSTITUTE OF
TECHNOLOGI - TIMOR LESTE

2.  Introduction
 Research Methods
 Results and Discussions
 Conclusion

3. AMC
APLICATION
Eurocopter Blade Sleeves
SELECTION CRITERIA:
- high specific strength
- High stiffness
- high fatigue life
- good fracture toughness
MATERIAL:
2009/SiC/15p-T4 P/M
(replaces Ti-6Al-4V)
Fan Exit Guide Vanes
SELECTION
CRITERIA:
-excellent erosion
-impact resistance
-high specific stiffness
MATERIAL:
6092/SiC/17.5p
(replaces
graphite/epoxy or Ti)
F-16 Fuel Access Door Covers
SELECTION CRITERIA:
-high specific strength
-good stiffnes
MATERIAL:
6092/SiC/17.5p wrought P/M
(replaced 2024 Al doors)

4. ALUMINUM
Advantages:
Mild
Corrosion
Resistant
Ductile
Disadvantage:
Less strong
Less hard
Less rigid
APPLICATIONS
Automotive industry,
Combat vehicles,
Aviation Industry
Material properties:
Lightweight, Strong,
Tough, Stiff
MAKING MMCS
Matrix : A356/Al7Si
Reinforced : SiCP
Method : Stir Casting
PROBLEMS
Homogeneous dispersion of
SiCP is bad.
 Less wettability
 Mixing of the Matrix & SiC is
difficult
ALTERNATIVE
SOLUTIONS
 Semi Solid Stir
Casting
 The addition of TiB
(wt%) and SiCP to
well

5.  The experiment of composite Al7Si1Mg/SiCp and
Al7Si1Mg1,5TiB/SiCp was made by employing the semi solid stir
casting method.
 In this case, the alloy A356 / Al7Si played a role as matrix.
Besides, Mg 1 wt.% was to incerase the wettability. Then, TiB 1,5
wt.% was to refine the grains on the matrix.
 The SiCp played a role as the reinforcement on the matrix Al7Si.
The variations of SiCp employed are 10, 15, 20 wt.%.

6. Basic material matrix AlSi (A356)
Tensile Strength 172-262 Mpa
% EL (elongation) 2-5%
Hardness 60-75 HB
(27.5 -42 HRB)
Modulus Elastisity 72.4 GPa
Melting temperature 615 oC
temperature Solid 555 oC
Thermal conductivity 167 W/m.K
Materials
Chemical composition (%)
Al Si SiCp Fe Ti B Mg Mn Other
Al7Si / A356
(ingot)
Mg (ingot)
AlTiB (ingot)
SiCp (powder)
92.39
0.022
93
0.03
7.26
0.013
0.16
-
-
-
-
98.6
0.147
0.003
0.16
0.1
-
-
5.00
-
-
-
0.98
-
0.07
99.93
-
0.03
0.008
0.012
-
-
0.125
0.02
0.05
1.24

7. Particles Reinforced SiCP
Consideration of use SiC :
 Density SiCP is similar to Al (3.2 g/cm3
and 2.7 g/cm3)
 Wettability with molten aluminum has
better
 Is good mechanical properties
 Hardness 2800 kg / mm2 (Knoop)
 Bending strength of 380 Mpa
 Modulus of elasticity 430 GPa
Materials
Chemical composition (%)
Al Si Fe Mg Mn Other
SiCP (powder) 0.03 98.6 0.1 0.03 - 1.24

8.  Used as the grain refinement.
 Could increase the hardness
and the grain refinement.
 The propagation of dislocation
which may occur would be
smaller.
Function TiB
AlTiB as an comparator element
Materials
Chemical composition (%)
Al Si Fe Ti B Other
AlTiB (ingot) 93 0.16 0.16 5.00 0.98 0,05

9. Mg (1%wt) as an enhancer element
Function Mg
To improve the wettability of
the particles of SiC matrix
Reduce the surface tension of
the liquid matrix
Trigger reaction liquid
matrix-SiC interface
Materials
Chemical composition (%)
Al Si Fe Mg Mn Other
Mg (ingot) 0.022 0.013 0.003 99.93 0.012 0.02

10. Variations in the composition of foundry
To the simplify process of mixing the composition settings. Each
ingredient is weighed to obtain mass composition according to the
variation.
Composition (wt.%)
Al7Si
(gram)
Mg
(gram)
AlTiB
(gram)
SiCp
(gram)
Total
(gram)
Al7Si1Mg/SiCp 0%
Al7Si1Mg/SiCp 10%
Al7Si1Mg/SiCp 15%
Al7Si1Mg/SiCp 20%
Al7Si1Mg1.5TiB/SiCp 0%
Al7Si1Mg1.5TiB/SiCp 10%
Al7Si1Mg1.5TiB/SiCp 15%
Al7Si1Mg1.5TiB/SiCp 20%
990
890
840
790
975
875
825
775
10
10
10
10
10
10
10
10
-
-
-
-
15
15
15
15
-
100
150
200
-
100
150
200
1000
1000
1000
1000
1000
1000
1000
1000

11. Stir Casting Equipments
Permanent mold
Heating processStir up to mixing
Specimen model

12. Semi Solid Stir Casting Process
Semi-solid chart stir casting process
0
100
200
300
400
500
600
700
800
900
0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96
TemperatureoC
Time (minute)
1) In the process of melt into the first electric
furnace, AlSi (A356) + Mg was heated to
800oC to achieve the perfect liquid state.
2) SiCP + Borax was heated before hand at
400oC in the oven.
3) The materials Mg-TiB-SiCP+Borax was
added into the electric furnace.
4) Temperature inside the electric furnace
was lowered to 590oC to attain the semi-
solid condition.
5) Furthermore, stirred by a mechanical
stirrer. The stirrer rotational speed was at
500 rpm and the stirring time was 180
seconds for a long time.
6) Heated again until the pouring
temperature was at 750oC.
7) Besides, the metal mold was heated to
300oC. After that the mold results were
cooled at the room temperature.
8) The last process specimen material was
cut to fit the specimen testing.
Casting results

13. The test results of density and porosity
Composites (wt. %)
ρactual
(g/cm3)
ρtheoretic
(g/cm3)
Porosity
Al7Si1Mg/SiCp 0%
Al7Si1Mg/SiCp 10%
Al7Si1Mg/SiCp 15%
Al7Si1Mg/SiCp 20%
Al7Si1Mg1.5TiB/SiCp 0%
Al7Si1Mg1.5TiB/SiCp 10%
Al7Si1Mg1.5TiB/SiCp 15%
Al7Si1Mg1.5TiB/SiCp 20%
2.63
2.65
2.66
2.69
2.64
2.65
2.67
2.70
2.66
2.71
2.72
2.76
2.68
2.73
2.76
2.78
1.50
2.58
2.57
2.89
1.49
2.19
2.22
2.51
2.58
2.6
2.62
2.64
2.66
2.68
2.7
2.72
0 10 15 20
Al7Si1Mg/SiCp
Al7Si1Mg1.5TiB/SiCp
0
0.5
1
1.5
2
2.5
3
3.5
0 10 15 20
Al7Si1Mg/SiCp
Al7Si1Mg1.5TiB/SiCp
The density graphic indicated that
composite komposit Al7Si1Mg/SiCp
underwent an increase averagely 1,2%.
Whereas, composite
Al7Si1Mg1.5TiB/SiCp went through a
decrease on the variation of SiCp (15
wt.%), and increased as much as 1.4%
on the variation of SiCp (20 wt.%).
The porosity of composite Al7Si1Mg/SiC
increased averagely as 28%. Whereas, the
composite Al7Si1Mg1.5TiB/SiCp decreased
on the variation of SiCp (15 wt.%), and then,
increased 10.9% on the variation of SiCp (20
wt.%).

14. Tensile Test
0
20
40
60
80
100
120
140
160
0 10 15 20
Al7Si1Mg/SiCp
Al7Si1Mg1.5TiB/SiCp
SiCp (Wt.%)
σu(MPa)
0
20
40
60
80
100
120
140
0 10 15 20
Al7Si1Mg/SiCp
Al7Si1Mg1.5TiB/SiCp
0
0.5
1
1.5
2
2.5
3
3.5
0 10 15 20
Al7Si1Mg/SiCp
Al7Si1Mg1.5TiB/SiCp
σu(MPa)
SiCp (Wt.%)
%(EL)
SiCp (Wt.%)
The tensile strength of composite Al7Si1Mg/SiCp
was bigger than composite Al7Si1Mg1.5TiB/SiCp
with the difference of averagely 16,18%. The
strength of composite Al7Si1Mg1.5TiB/SiCp
increased on the variation of SiCp (10 wt.%) with
120 MPa
The biggest value of yield strength for the
composite Al7Si1Mg1.5TiB/SiCp; was 106 MPa.
The difference of the yield strength betwing
composite of Al7Si1Mg/SiCp and
Al7Si1Mg1.5TiB/SiCp i.e. 14 MPa.
The amount of force on the composite
Al7Si1Mg1.5TiB/SiCp was bigger than composite
Al7Si1Mg/SiCp

15. Impact test
0
1
2
3
4
5
6
0 10 15 20
Al7Si1Mg/SiCp
Al7Si1Mg1.5TiB/SiCp
SiCp (Wt.%)
Impact(J/Cm)
For the composite Al7Si1Mg1.5TiB/SiCp, with the variation of SiCp
as folow (10, 15, 20 wt.%) the value was increased averagely 4.74
J/cm2.
Then for the composite Al7Si1Mg/SiCp with the variations of SiCp
as folow (10, 15, 20 wt.%), the value was increased averagely 4,68
J/cm2.
The impact value of
composite
Al7Si1Mg1.5TiB/SiCp
was higher than
composite
Al7Si1Mg/SiCp.

16. Micro Structure
Agglomeration SiCP looked
irregularly shaped with a dark
gray color. SiC particles randomly
dispersed and relatively evenly
distributed in the composite
Al7Si1Mg1.5TiB/SiCp and
composite Al7Si1Mg/SiCp.
This is consistent with the
research of Hashim, et al (2001)
which states that the semi-solid
casting wheel will help improve
wettability and dispersion of
reinforcing particles
homogeneously.

17. The Results of the Morphology Test
Composite Al7Si1Mg1.5TiB/SiCpComposite Al7Si1Mg/SiCp.

18.  Porosity will increase with the increase in the number of heavy mass of SiCP. The
use of borax can lower porosity values, lowest porosity value of 2.10% which
contained in the composite Al7Si1Mg1.5TiB/SiCp variation10 wt.% SiCP. The
highest value of 2.38% porosity contained in the composite Al7Si1Mg/SiCp
variation 20 wt.% SiCP.
 The highest tensile strength of the composite Al7Si1Mg1.5TiB/SiCp variation 20
wt.% SiCP with value 106 MPa.
 The impact value has highest point in the composite Al7Si1Mg1.5TiB/SiCp
variation 20 wt.% SiCP of 5.63 J/cm2.
 The micro-structure of composite Al7Si1Mg/SiCp agglomeration contained on
the surface of the matrix. The addition of borax compounds composite
Al7Si1Mg1.5TiB/SiCp , SiCP particles spread more evenly.
 The morphology of SEM test results of composite Al7Si1Mg/SiCp and composite
Al7Si1Mg1.5TiB/SiCp between reinforcement and matrix particles can be fused
and well dispersed.
Results of the data analysis in this study can be concluded
as follows:

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21. ThankYou