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Osprey® CE6F SiAl alloy

Osprey® CE13F is an Aluminium Silicon (AlSi) Alloy with controlled thermal expansion and high specific stiffness. It is used in applications where low weight, high stiffness or controlled thermal expansion (CTE) is required.

Typical applications

Examples include space optics applications where Osprey® CE13F is a close CTE match to electroless nickel which is used for optical surfaces. Osprey® CE13F is also widely used for semi-conductor pick and place applications where high specific stiffness improves speed and accuracy.

Characteristics of Osprey® CE13F AlSi alloy

  • Offers improved CTE matching to electronic circuit boards when compared to aluminium or copper
  • In some use cases, a reliable carrier for most ceramic substrates and device materials, including alumina and GaAs
  • One third the weight of Copper
  • Weldable, machinable and plateable
  • Lower cost to machine than Osprey® alloys CE11F, CE9F, CE7F or CE6F

Mechanical properties

Mechanical properties, typical values
CE17F CE17MF CE13F CE11F CE9F CE7F CE6F
Composition Al-27%Si Al-27%Si Al-42%Si Al-50%Si Si-40%Al Si-30%Al Si-20%Al
Tensile strength, ultimate ≥160  175-3123) 205 193  181 ≥100  N/A
Yield strength, MPa  100 282 147  189 - - N/A
Bend strength (three point), Mpa - - 300  300  300  270 3191)
Young's modulus, GPa  91.8  91.82)  101.9  121.4 118 129.2  130
Rigidity modulus, GPa  35.8  35.82)  42.22)  48.6 46  51.6 N/A
Poisson's ratio  0.28 0.282)  0.272)  0.29 0.29 0.26  N/A
Density, g/cc  2.6 2.6  2.55   2.51 2.47  2.43  2.352)
Hardness, Hv  60  75–1323) 90 - 230 - N/A

1) Test pieces 4 mm x 3 mm x 40 mm
2) Calculated values
3) Depending on heat treatment condition

Thermal expansion

Coefficient of thermal expansion, ppm/ºC (typical values)
CE17F CE17MF CE13F CE11F CE9F CE7F
Composition1) Al-25%Si Al-27%Si Al-42%Si Al-50%Si Si-40%Al Si-30%Al
100K–200K - - - 7.8 - -
200K–300K - - - 10.6 - -
100K–300K - - - 9.2 - -
-60–200ºC - - - 11.6 - 7.6
Room temp. 15.3 15.3 12.2 11.4 9.1 7.2
25–200ºC 17.1 17.1 13.7 12.3 10.2 8.3
25–300ºC 18.1 18.1 14.6  12.9 10.9  8.8 
25–400ºC  18.7 18.7 15.2 13.4 11.3 9.2
25–500ºC  19 19 15.5 13.7 11.4 9.7

* Calculated values

Thermal conductivity

Thermal conductivity, W/m.K (typical values)
CE17F CE17MF CE13F CE11F CE9F CE7F
Composition1) Al-25%Si Al-27%Si Al-42%Si Al-50%Si Si-40%Al Si-30%Al
At -100ºC - - - - - 180
At -50ºC - - - - 1292) 140
At -0ºC - - - - - 135
At 25ºC 177.4 146.8 145 132 121 120
At 50ºC - - - - - 110
At 100ºC - - - - 125* 110
At 200ºC 151.2 146.5 - - 108* 100
At 300ºC - - - - 98* 88
At 400ºC - - - - 90* 80
At 500ºC - - - - 85* 75
Specific heat, J/kgºC 846.3 767.25 857* 754* 780* 785*

* Calculated values

Microstructure

Microstructure of CE alloys

In the molten state Si and Al are mutually soluble, whereas in the rapidly solidified condition there is minimal solubility of Si in Al (< 0.3%) and even less solubility of Al in Si. The products are true alloys rather than metal-matrix composites (such as AlSiC) as all the phases present originate from an homogeneous melt.

The Al phase is continuous up to ~ 85%Al. Over approximately 40% Si, the Si phase also becomes continuous, offering a co-continuous duplex alloy (similar to AlBe alloys).

The continuous Si phase produces a stiff alloy with low thermal expansion and low internal stresses, whereas the continuous Al phase enhances thermal conductivity and toughness and lowers electrical resistance.

Consequently, as the Al content is increased, electrical conductivity, thermal conductivity, strength, toughness, CTE and machinability are also increased. For these reasons, it is best to choose the highest Al content alloy that is acceptable for the application.

Although Sandvik can supply machined components with Si contents as high as 85% Si (i.e. CE5), the relative brittleness of this composition means whenever feasible it is often better to compromise on the exact expansion match required and use a lower Si content alloy. For example, Kovar* packages (with a CTE of ~ 7ppm/°C) have been successfully replaced with CE9, CE11 and even CE13.

* Kovar is a trademark of Carpenter Technology Corporation

Machinability