AlSr10 (EN 575)
Eutectic silicon modifier with 10% strontium. Transforms acicular Si into fibrous morphology for greater ductility.
AlSr10% is a master alloy containing 10% strontium in an aluminum matrix, used as a eutectic silicon modifier in Al-Si alloys. Without modification, eutectic silicon solidifies as acicular plates (needles) that act as stress concentrators and reduce ductility. Strontium modifies the eutectic Si morphology to a fine fibrous structure, dramatically improving elongation, impact resistance, and machinability. Equivalent effect to sodium modification but more stable and controllable.
Chemical Composition
| Element | Symbol | Percentage |
|---|---|---|
| Aluminum | Al | Balance (~90 %) |
| Strontium | Sr | 9.0–11.0 % |
| Iron | Fe | ≤ 0.20 % |
| Silicon | Si | ≤ 0.20 % |
Physical Properties
| Property | Value |
|---|---|
| Melting point | 660–700 °C |
| Density | ~2.60 g/cm³ |
| Form | Waffle o barra cortada |
Metallurgical Function
Eutectic silicon modification. Strontium is absorbed at the Si solidification front, inhibiting faceted growth and forcing a fibrous morphology that improves ductility, impact resistance, and machinability.
Dosage & Usage
Target residual level: 0.015–0.040% Sr in the liquid metal. Typical addition: 1.0–2.5 kg/ton. Add at 720–740 °C, wait 10–15 min for dissolution before pouring. Sr gradually oxidizes (fading in ~2–4 hours), re-dose if holding the melt.
Applications
- Modification of AlSi7 (A356), AlSi10 (A360) alloys
- Parts with elongation and impact resistance requirements
- Machinability improvement in cast parts
Industries
Automotive
Safety components requiring ductility: wheels, suspension, subframes
Aluminum Casting
Standard modification for hypoeutectic Al-Si alloys
Special Notes
Important: Strontium can increase hydrogen porosity tendency. Ensure proper degassing before or after addition. Do not use simultaneously with sodium modification. For hypereutectic alloys (Si >12%), strontium is not recommended — use phosphorus as primary Si refiner.
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