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A359/SiC/xxp

Basic Description:

A359 Al alloy reinforced with irregularly shaped SiC particles

 

 

Matrix:

A359

Composition

aluminum cast alloy - A359

 

 

 

   

Reinforcement:

 

 

   

Type:

particulate

Volume content

10%, 20%

Composition:

SiC

 

 

 

   

Production route:

composite for gravity casting

 

 

 

 

 

Supplier:

DURALCAN

General information - Mr. Jean Richard / Mr. Gerald Tougas

 

Phone

(418) 699-4797

 

 

 

e-mail

gerald_tougas@alcan.com

 

 

 

 

 

 

 

Data dependent on:

 

 

 

 

 

 

 

   

Product Form:

foundry ingot

1.MMC-processing (synth.)& recycling

DURALCAN

GRAVITY CASTING

 

 

 

 

 

 

     

Microstructure

 

Fig. 1 - Mcrostructure o f a stir cast DURALCAN ingot of AlSi7Mg/SiC/15p with some defects: pores between touching particles, graines with low particle concentration (denuded zones) (click on the picture to enlarge)

Fig. 2 - The PRM DURALCAN casting alloys can be extruded at reduced extrusion speed. Example of cross section of an extrusion bar of AlSi7Mg/SiC/20p with high probability of fractured bigger SiC particles and fine distribution of the eutectic Si. (click on the picture to enlarge)

   

2.Working, final shaping

DURALCAN

 

 

 

 

 

 

 

 

 

 

 

ARC WELDING GUIDELINES

http://bricad.com/aluminium/dur/guides/awg/index.html

 

 

 

 

 

 

 

 

FOUNDARY GUIDELINES

 

 

 

Typical GMA weld of sand-cast DURALCAN F3S.20S. Note that there is no more porosity in the weld metal than in the base composite.

MACHINING GUIDELINES

 

 

 

Machining of a DURALCAN F3S.20S-T71 brake rotor during a suppliers proof-of-manufacturing trial.

   

 

 

   
Microstructure Examples

 

 

 

(a)

(b)

(c)

   
 

Examples of microstrucures of castings of DURALCAN AlSi7Mg/SiC/15p: (a) distribution of SiC particles (dark) and eutectic Si (grey), (b) coarsening of eutectic Si after remelting, (c) particle pushing effect in castings of slow cooling rate (taken from a feeder). (Click on the pictures to enlarge)

   

3.Metallography, quantitative

 
For more information see volume 3: "Metallographic Preparation of Metal Matrix Composites"
 

Metallographic Preparation

POLISHING CONDITIONS
Automatic polishing machine1) consists of:
a rotating polishing disk, RotoPol-22
a rotating specimen holder, RotoForce-4
a Multidoser
Grinding, polishing disc, cloths and diamond pastes1)

 

 

 

 

 

   
 

 

(click on the table to enlarge)

   
  1) STRUERS (http://www.struers.dk)
   
 

   
 

For more information contact:

          yi.lin.liu@riso.dk

          helmer.nilsson@risoe.dk

   
   

4.Bonding, interface formation

   
Interfacial reaction While silicon carbide is in theory thermodynamically stable when in contact with solid aluminium, the formation of aluminium carbide has been shown to occur in thermal treatments above 650C and also for prolongued treatment at 610C [1] The same reaction proceeds also readily with molten aluminium to form aluminium carbide and silicon [2] [3] [4]. The kinetic of that reaction has been reported [5]. The thermodynamic approaches of the reaction has been reviewed [1]. 

Even though this reaction enhances the wettability of SiC by the aluminium matrix [6], the formation of aluminium carbide is detrimental to composite properties because it reacts with water and and also indesirable in melt process because it increases the melt viscosity.

Aluminium carbide formation can be prevented by adjustment of the matrix, or by coating SiC particles with a physical barrier (Al2O3, TiO2,TiB2, SiO2, TiC, TiN, Ta, ...) or a sacrificial layer (Ni, Cu...) [7]. For example: 

  saturating the aluminium matrix with Si [8].

  surface preoxydation of the SiC into SiO2 at 1200-1300C in air. The SiO2 layer leads to the formation of Al2O3, for pure Al, and MgO and MgAl2O3, for AlMg alloys. And prevents the formation of carbide [9] [10].

  Minimising the contact time with the melt: a fast method such squeeze casting allows the infiltration of SiC by pure Al without carbide formation however, in the latter case the presence of as little as 1%Mg, leads to the formation of Mg2Si and concomitant formation of aluminium carbide [1].

   
   
 

Al-4Cu-2Mg-0.5Ag/SiC/60p. The presence of Mg produces Mg2Si and enhance the formation of Al4C3 While no interfacial reaction if found when pure aluminium is used. (squeeze cast) [1]
     
 

Al/SiC/60p. The presence of Mg produces Mg2Si and enhance the formation of Al4C3 While no interfacial reaction if found when pure aluminium is used. (squeeze cast) [1]

   
   
 

 

Minimum Si content to prevent aluminium carbide formation as a function of the temperature [8]

   
   
 

   

 

 
 

Chemical interaction at 727 C between Al and a-SiC single crystals: (a) average depth on which SiC is decomposed at the Si and C faces as a function of the square root of the reaction time; (b, c) surface morphology of these faces after 150 h reaction (Al and Al4C3 have been chemically etched) [11].

     
   
Interfacial  precipitation Silicon release in presence of Mg generates new Si based phases such as Mg2Si.
   
Comments, processing considerations Up to 40 wt% SiC both powder and liquid state processing are possible

Over 40 wt% SiC only liquid state processing are possible.

   
References

 

 

[1] Cayron C., EMPA report Nr 250, Thun, Switzerland (2001).

[2] Viala, J.C.;Bosselet, F.; Laurent, V. ,Lepetitcorps, Y., J.Mater.Sci.1997, 28, 1544.

[3] Bermudez, V.M.,Appl. Phys.Lett.1983, 42, 70.

[4] Viala, J.C.; Foretier, P. ;Bouix, J., J.Mater.Sci. 1990, 25, 1842.

[5] Lloyd D. J.,Jin I., in Comprehensive Composite Materials, Vol. 3: Metal Matrix Composites, Chap 21 p 5. Clyne, T.W. (ed.), , Elsevier, Amsterdam (2000).

[6] Han, D. S.; Jones, H.; Atkinson H. G., J. Mater. Sci. 1993, 28, 2654.

[7] Gheorghe, I., Rack, H.J., in Comprehensive Composite Materials, Vol. 3: Metal Matrix Composites, Chap 25 pp.1-21. Clyne, T.W. (ed.), , Elsevier, Amsterdam (2000).

[8] Lloyd, D. J., Compos. Sci. Technol.1989, 35, 159.

[9] Lloyd D. J.,Jin I., in Comprehensive Composite Materials, Vol. 3: Metal Matrix Composites, Chap 21 pp.1-21. Clyne, T.W. (ed.), , Elsevier, Amsterdam (2000).

[10] Lee, J.-C, Ahn, J.-P., Shi, Z., Shim, J.-H., Lee, H.-I, Metall. Mater: Trans. , 2001, 32A, 1541.

[11] Viala, J.-C; Peronnet, M.; Bosselet F. ; Bouix J. Proc., 12th Internat. Conf. Compos. Mater. (ICCM12) Paris 1999, Paper No739.

   

5.Modelling, Simulation

   

comments:

no data available

   

6.Static/dynamic mechanical testing (ambient+elev.T)

DURALCAN

 

 

 

 

 

 

 

F3S.10S-T6

F3S.20S-T6

Ultimate Strength

[MPa]

338

359

Yield Strength

[MPa]

303

338

Elongation

[%]

1,2

0,4

Elastic Modulus

[GPa]

86,2

98,6

Rockwell Hardness

[HRB]

73

77

 

 

   

 

Plane Straion Fracture Toughness KIC

[MPa.m1/2]

17,4

15,9

 

 

 

 

 

 

High Temperature Tensile Properties

F3K.10S-T5

F3K.20S-T5

 

 

 

   

 

at 22C

 

 

   

 

Ultimate Strength

[MPa]

269

283

Yield Strength

[MPa]

248

269

Elongation

[%]

0,3

0,2

 

 

 

   

 

at 260C

 

 

   

 

Ultimate Strength

[MPa]

124

159

Yield Strength

[MPa]

90

124

Elongation

[%]

1,7

1,0

 

 

 

   

 

at 371C

 

 

   

 

Ultimate Strength

[MPa]

55

76

Yield Strength

[MPa]

41

62

Elongation

[%]

4,3

2,7

 

 

 

 

 

 

comments

high temperature tensile properties, axial fatigue, fatigue-crack growth rate, creep -> 

7.Thermophys.& thermomech.properties

DURALCAN

 

 

 

F3S. 10Sa

F3S. 20Sa

Density (g/cm)

 

2,71

2,77

Electrical Conductivity (%IACS):

22C

34,2

26,4

Thermal Conductivity (cal/cmsK):

22C

0.360b

0.442b

Specific Heat (cal/gK):

25C

0,210

0,200

 

100C

0,224

0,218

 

150C

0,235

0,228

Average CTE (10-6/K)

50-100C

20,7

17,5

 

50-300C

24,7

21,1

 

50-500C

24,8

21,4

 

 

 

 

 

 

comments

a)F temper for electrical conductivity and specific heat; T6 temper for CTE

 

b)T6 temper

 

 

 

 

 

 

comments

 

 

 

 

 

 

 

8.Surface Treatment & Corrosion resistance

DURALCAN

Corrosion of Various Materials Neutral Salt Spray Test:

 

ASTM B-117

 

 

 

 

 

 

 

 

 

 

comments

 

 

 

 

 

 

 

9.Quality control, non destructive testing

Internal Stress measurement by Neutron Diffraction

Internal stress in MMCs

Internal stresses in MMCs can be introduced thermally, mechanically and thermomechanically due to differences in thermal expansion coefficient (CTE), elastic constant and yield stress between matrix and reinforcement. The effects of the internal stress on properties of composites can roughly be divided into two groups: 1) those relating to the local pattern of stress, for example the onset of micro-flow and the initiation of voiding, and 2) those more dependent on the average stresses in each phase, such as composite stiffness and macro-flow.

  Techniques of measuring internal stress

Neutron diffraction is a powerful non-destructive technique for the measurements of lattice strains in crystalline materials. Neutrons are directed towards the volume to be measured where they are diffracted from the lattice planes of the crystallites (Fig. 1). The scattering angle, 2q, depends on the wavelength of the incident neutron beam, l, and the spacing between the lattice planes, dhkl, through Bragg's Law,

l = 2 dhkl sin(q)

By measuring the intensity of diffracted neutrons as a function of scattering angles and fitting the data with a Gaussian function, the mean scattering angle q of each diffraction peak can be measured. Hence, values of dhkl can be determined. When lattice is stressed the lattice spacing changes and so does the scattering angle q (see Fig. 1). By correlating observed variations in the lattice spacing with a strain-free reference level, d0, a measure of the lattice elastic strain, ehkl, can be obtained.

ehkl = (dhkl - d0) / d0

The advantage of the neutron diffraction technique as compared to the X-ray diffraction technique is the greater penetration power of neutrons, which allows for the determination of average bulk strains. The penetration and spatial resolution of the different techniques in aluminium are shown in the following table.

   

Fig. 1 A schematic drawing of an X-ray diffractometer. Bragg's law is satisfied for lattice planes in some grains.

 
 

Technique

Penetration

Spatial resolution

X-ray

diffraction

Cu Ka X-ray (15 keV)

0.14 mm

surface

synchrotron X-ray (80 keV)

18 mm

5x5x50 mm3

Neutron diffraction

97 mm

1x1x1 mm3

 

 

Table 1 Penetration and spatial resolution of different techniques in aluminium

   
  The development of lattice strains during thermal loading or thermomechanical loading can be measured in-situ by mounting a small oven, or a loading device with heating elements in the grips (see Fig. 2) into the neutron spectrometer.
   

Fig. 2 Experimental configuration for in-situ neutron diffraction measurements during uniaxial loading. Only those grains (marked by arrows) with their reflection planes perpendicular to the loading direction are monitored, and the longitudinal lattice strain component is measured.

 
  Applications of neutron diffraction for MMCs

Neutron diffraction has been used to study the build-up and relaxation of internal strains introduced by thermal, or mechanical, or thermomechanical processes. The following are some examples.

Measurements of residual lattice strains after fabrication by a powder route, and subsequent unloading after room-temperature uniaxial plastic deformation to 10% in three Al-SiCw composites (containing 5, 10, 15 vol%SiCw, respectively). The results are shown in Fig. 3. The aluminium lattice (a) is in a state of residual tension after fabrication and brought to a state of residual compression by a plastic elongation of 10%. The SiCw lattice (b) behaves in an opposite manner. It is initially in compression and brought to tension by plastic deformation.

   
 
 

Fig. 3 Residual lattice strains (a) in aluminium matrix, and (b) in SiCw after fabrication and subsequent unloading after uniaxial deformation to 10% in three Al-SiCw composites containing 5, 10, 15 vol%SiCw, respectively(click on the pictures to enlarge).

   
  In-situ measurements of lattice strain evolution during axial plastic deformation in Al-10vol%SiCw. The longitudinal lattice strain component of the two phases as a function of the applied stress is shown in Fig. 4 (a). The same results are also presented as a function of the macroscopic strain in Fig. 4 (b). In these two figures the initial points represent the thermal residual lattice strains resulting from the fabrication process, i.e. +0.6x10-3 in the aluminium matrix and -1.4x10-3 in the SiCw. Upon deformation the elastic response of the aluminium matrix initially is more compliant than the SiCw. But above an applied stress of about 100 MPa the lattice strain of the matrix is saturated at a level of 1.4x10-3, and further elastic straining is not possible. The SiCw, however, sustains elastic strains well beyond the capacity of the aluminium matrix. The lattice strain of the SiCw increases monotonically with the applied stress reaching a level of 2.8x10-3 at an applied stress of 200 MPa.
   
 
 

Fig. 4 Lattice strain response of the aluminium matrix and the SiCw as a function of (a) the applied stress, and (b) the total macroscopic strain.

   
  Measurements of lattice strain evolution during room-temperature progressive axial deformation and after unloading in A359-20%SiCp. The results are given in Fig. 5 where the total macroscopic strain is also superimposed. It indicates that the aluminium lattice is brought to a state of residual compression as compared to its initial value (to be set arbitrarily to zero) as a consequence of plastic elongation to 2% and unloading. The residual compressive lattice strain is 3.5x10-4 and subsequent deformation to 4 and 6.8% has no further effect. The residual tensile lattice strain in the SiCp is 3x10-4 and is also independent of the macroscopic strain in the range studied.
   
 
 

Fig. 5 Aluminium lattice strain (open circle) in A359-20% SiCp measured at room temperature with progressive deformation to 2, 4 and 7% and unloading. The solid line indicates the total macroscopic strain.

   
  Measurements of lattice strain evolution during multiple elevated-temperature deformation in A359-20%SiCp. The process consists of heating (to 100oC)-deform-heating (to 250oC)-deform- cooling (to 100oC)-deform-heating (to 350oC)-cooling (to 250oC)-deform. The measured lattice strains in the aluminium matrix and SiCp are shown in Fig. 6. This work shows that the change in lattice strain resulting from axial plastic deformation is dependent on thermomechanical history. The maximum axial residual strains introduced in the composite due either to CTE effects or to plastic deformation are very small: in the order of 2x10-4
   
 
 

Fig. 6 Overview of lattice strains of (a) aluminium, and (b) SiCp in A359-20% SiCp measured at different temperatures and with progressive deformation. The solid line indicates the total macroscopic strain.

   
References 1. A.J. Allen, M. Bourke, S. Dawes, M.T. Hutchings and P.J. Withers, "The analysis of internal strains measured by neutron diffraction in Al/SiC MMCs", Acta Met. Mat., 40, 1992, 2361-2373.

2. P.J. Withers, H. Lilholt, D. Juul Jensen and W.M. Stobbs, "An examination of diffusional stress relief in metal matrix composites", In Proc. 9th Ris Int. Symp. on Materials Science, eds. S.I. Andersen et al., 1988, Ris National Laboratory, Roskilde, Denmark, p. 503-510.

3. T. Lorentzen and N.J. Srensen, "A new device for in-situ loading of samples during neutron diffraction strain measurements", In Proc. 12th Ris Int. Symp. on Materials Science, eds. N. Hansen et al., 1991, Ris National Laboratory, Roskilde, Denmark, p. 489-496.

4. T. Lorentzen, H. Lilholt and Y. L. Liu, "Generation and relaxation of thermal stresses in metal matrix composites", In Proc. 10th Int. Conf. on Composite Materials, ICCM-10, 1995, Woodhead Publishing Ltd., Cambridge, UK, Vol. 2, p. 629-636.

5. T. Lorentzen, N.J. Srensen and Y.L. Liu, "A comparison of numerical predictions and in-situ neutron diffraction measurements of MMC phase response", In Proc. 15th Ris Int. Symp. on Materials Science, eds. S.I. Andersen et al., 1994, Ris National Laboratory, Roskilde, Denmark, p. 405-412.

6. T. Lorentzen and A.P. Clarke, "Thermomechanical induced residual strains in Al/SiCp metal-matrix composites", Composites Science and Technology, 58, 1998, 345-353.

   

10.Existing/Potential Applications

DURALCAN

The New Lupo from Volkswagen uses DURALCAN brake applications

 

 

 

 

 

 

 

Brake discs, drums, calipers or back-plate applications are found in automotive braking systems. Other suitable applications are found in engine and gearbox parts. Bike and golf components are also developing rapidly.

 

 

 

 

 

 

 

Pictures:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11.Pros and cons, Assessment

comments

no data available

   

Last update: 06.03.07 by Guillermo Requena / MMC-Assess Webteam